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Sample records for fatigue estimation due

  1. Estimates of thermal fatigue due to beam interruptions for an ALMR-type ATW

    SciTech Connect

    Dunn, F. E.; Wade, D. C.

    1999-11-12

    Thermal fatigue due to beam interruptions has been investigated in a sodium cooled ATW using the Advanced Liquid Metal mod B design as a basis for the subcritical source driven reactor. A k{sub eff} of 0.975 was used for the reactor. Temperature response in the primary coolant system was calculated, using the SASSYS- 1 code, for a drop in beam current from full power to zero in 1 microsecond.. Temperature differences were used to calculate thermal stresses. Fatigue curves from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code were used to determine the number of cycles various components should be designed for, based on these thermal stresses.

  2. System for estimating fatigue damage

    DOEpatents

    LeMonds, Jeffrey; Guzzo, Judith Ann; Liu, Shaopeng; Dani, Uttara Ashwin

    2017-03-14

    In one aspect, a system for estimating fatigue damage in a riser string is provided. The system includes a plurality of accelerometers which can be deployed along a riser string and a communications link to transmit accelerometer data from the plurality of accelerometers to one or more data processors in real time. With data from a limited number of accelerometers located at sensor locations, the system estimates an optimized current profile along the entire length of the riser including riser locations where no accelerometer is present. The optimized current profile is then used to estimate damage rates to individual riser components and to update a total accumulated damage to individual riser components. The number of sensor locations is small relative to the length of a deepwater riser string, and a riser string several miles long can be reliably monitored along its entire length by fewer than twenty sensor locations.

  3. Changes in bone fatigue resistance due to collagen degradation.

    PubMed

    Wynnyckyj, Chrystia; Willett, Thomas L; Omelon, Sidney; Wang, Jian; Wang, Zhirui; Grynpas, Marc D

    2011-02-01

    Clinical tools for evaluating fracture risk, such as dual energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS), focus on bone mineral and cannot detect changes in the collagen matrix that affect bone mechanical properties. However, the mechanical response tissue analyzer (MRTA) directly measures a whole bone mechanical property. The aims of our study were to investigate the changes in fatigue resistance after collagen degradation and to determine if clinical tools can detect changes in bone mechanical properties due to fatigue. Male and female emu tibiae were endocortically treated with 1 M KOH for 1-14 days and then either fatigued to failure or fatigued to induce stiffness loss without fracture. Partial fatigue testing caused a decrease in modulus measured by mechanical testing even when not treated with KOH, which was detected by MRTA. At high stresses, only KOH-treated samples had a lower fatigue resistance compared to untreated bones for both sexes. No differences were observed in fatigue behavior at low stresses for all groups. KOH treatment is hypothesized to have changed the collagen structure in situ and adversely affected the bone. Cyclic creep may be an important mechanism in the fast deterioration rate of KOH-treated bones, as creep is the major cause of fatigue failure for bones loaded at high stresses. Therefore, collagen degradation caused by KOH treatment may be responsible for the observed altered fatigue behavior at high stresses, since collagen is responsible for the creep behavior in bone.

  4. A survey of fatigue crack growth life estimation methodologies

    NASA Astrophysics Data System (ADS)

    Akyurek, T.; Bilir, O. G.

    1992-07-01

    In this study, three fatigue crack growth life estimation methodologies are reviewed and sample calculations are made using these methodologies. Comparisons of the results with respect to the methodologies are made. Three computer codes which represent these methodologies, CRACKS IV, FAST and FATIGUE, are selected for the analyses. The estimations are also correlated to the test results.

  5. Fatigue of LMFBR piping due to flow stratification

    SciTech Connect

    Woodward, W.S.

    1983-01-01

    Flow stratification due to reverse flow was simulated in a 1/5-scale water model of a LMFBR primary pipe loop. The stratified flow was observed to have a dynamic interface region which oscillated in a wave pattern. The behavior of the interface was characterized in terms of location, local temperature fluctuation and duration for various reverse flow conditions. A structural assessment was performed to determine the effects of stratified flow on the fatigue life of the pipe. Both the static and dynamic aspects of flow stratification were examined. The dynamic interface produces thermal striping on the inside of the pipe wall which is shown to have the most deleterious effect on the pipe wall and produce significant fatigue damage relative to a static interface.

  6. Fatigue life estimation procedure for a turbine blade under transient loads

    SciTech Connect

    Vyas, N.S. . Dept. of Mechanical Engineering); Rao, J.S. . Dept. of Mechanical Engineering)

    1994-01-01

    Fatigue analysis and consequent life prediction of turbomachine blading requires the stress load history of the blade. A blade designed for safe operation at particular constant rotor speeds may, however, incur damaging stresses during start-up and shut-down operations. During such operations the blade experiences momentary resonant stresses while passing through the criticals, which may lie in the speed range through which the rotor is accelerated. Fatigue due to these transient influences may accumulate to lead to failure. In this paper a technique for fatigue damage assessment during variable-speed operations is presented. Transient resonant stresses for a blade with nonlinear damping have been determined using a numerical procedure. A fatigue damage assessment procedure is described. The fatigue failure surface is generated on the S-N-mean stress axes and Miner's Rule is employed to estimate the accumulation of fatigue.

  7. Are pilots at risk of accidents due to fatigue?

    PubMed

    Goode, Jeffrey H

    2003-01-01

    There is concern in the aviation community that pilot schedules can lead to fatigue and increased chance of an aviation accident. Yet despite this concern, there is little empirical analysis showing the relationship between pilot schedules and commercial aviation accidents. This study attempts to demonstrate an empirical relationship between pilot schedules and aviation accidents. Data for human factors-related accidents and pilot work patterns were identified. The distribution of pilot work schedule parameters for the accidents was compared to that for all pilots using a chi-square test to determine if the proportions of accidents and length of duty exposure were the same. If the distributions are the same, then one could infer that pilot human factor accidents are not affected by work schedule parameters. The proportion of accidents associated with pilots having longer duty periods is higher than the proportion of longer duty periods for all pilots. There is a discernible pattern of increased probability of an accident as duty time increases for commercial aircraft pilots in the United States. The analysis suggests that establishing limits on duty time for commercial pilots would reduce risk. Such a rule is likely to be expensive and could substantially impact the commercial airlines. In return, there is likely to be a reduction in the risk of commercial aviation accidents due to pilot fatigue.

  8. Estimating mental fatigue based on electroencephalogram and heart rate variability

    NASA Astrophysics Data System (ADS)

    Zhang, Chong; Yu, Xiaolin

    2010-01-01

    The effects of long term mental arithmetic task on psychology are investigated by subjective self-reporting measures and action performance test. Based on electroencephalogram (EEG) and heart rate variability (HRV), the impacts of prolonged cognitive activity on central nervous system and autonomic nervous system are observed and analyzed. Wavelet packet parameters of EEG and power spectral indices of HRV are combined to estimate the change of mental fatigue. Then wavelet packet parameters of EEG which change significantly are extracted as the features of brain activity in different mental fatigue state, support vector machine (SVM) algorithm is applied to differentiate two mental fatigue states. The experimental results show that long term mental arithmetic task induces the mental fatigue. The wavelet packet parameters of EEG and power spectral indices of HRV are strongly correlated with mental fatigue. The predominant activity of autonomic nervous system of subjects turns to the sympathetic activity from parasympathetic activity after the task. Moreover, the slow waves of EEG increase, the fast waves of EEG and the degree of disorder of brain decrease compared with the pre-task. The SVM algorithm can effectively differentiate two mental fatigue states, which achieves the maximum classification accuracy (91%). The SVM algorithm could be a promising tool for the evaluation of mental fatigue. Fatigue, especially mental fatigue, is a common phenomenon in modern life, is a persistent occupational hazard for professional. Mental fatigue is usually accompanied with a sense of weariness, reduced alertness, and reduced mental performance, which would lead the accidents in life, decrease productivity in workplace and harm the health. Therefore, the evaluation of mental fatigue is important for the occupational risk protection, productivity, and occupational health.

  9. Fatigue life estimates for helicopter loading spectra

    NASA Technical Reports Server (NTRS)

    Khosrovaneh, A. K.; Dowling, N. E.; Berens, A. P.; Gallagher, J. P.

    1990-01-01

    Helicopter loading histories applied to notch metal samples are used as examples, and their fatigue lives are calculated by using a simplified version of the local strain approach. This simplified method has the advantage that it requires knowing the loading history in only the reduced form of ranges and means and number of cycles from the rain-flow cycle counting method. The calculated lives compare favorably with test data.

  10. Fatigue life estimates for helicopter loading spectra

    NASA Technical Reports Server (NTRS)

    Khosrovaneh, A. K.; Dowling, N. E.; Berens, A. P.; Gallagher, J. P.

    1989-01-01

    Helicopter loading histories applied to notch metal samples are used as examples, and their fatigue lives are calculated by using a simplified version of the local strain approach. This simplified method has the advantage that it requires knowing the loading history in only the reduced form of ranges and means and number of cycles from the rain-flow cycle counting method. The calculated lives compare favorably with test data.

  11. Residual fatigue life estimation using a nonlinear ultrasound modulation method

    NASA Astrophysics Data System (ADS)

    Piero Malfense Fierro, Gian; Meo, Michele

    2015-02-01

    Predicting the residual fatigue life of a material is not a simple task and requires the development and association of many variables that as standalone tasks can be difficult to determine. This work develops a modulated nonlinear elastic wave spectroscopy method for the evaluation of a metallic components residual fatigue life. An aluminium specimen (AA6082-T6) was tested at predetermined fatigue stages throughout its fatigue life using a dual-frequency ultrasound method. A modulated nonlinear parameter was derived, which described the relationship between the generation of modulated (sideband) responses of a dual frequency signal and the linear response. The sideband generation from the dual frequency (two signal output system) was shown to increase as the residual fatigue life decreased, and as a standalone measurement method it can be used to show an increase in a materials damage. A baseline-free method was developed by linking a theoretical model, obtained by combining the Paris law and the Nazarov-Sutin crack equation, to experimental nonlinear modulation measurements. The results showed good correlation between the derived theoretical model and the modulated nonlinear parameter, allowing for baseline-free material residual fatigue life estimation. Advantages and disadvantages of these methods are discussed, as well as presenting further methods that would lead to increased accuracy of residual fatigue life detection.

  12. A real time neural net estimator of fatigue life

    NASA Technical Reports Server (NTRS)

    Troudet, T.; Merrill, W.

    1990-01-01

    A neural net architecture is proposed to estimate, in real-time, the fatigue life of mechanical components, as part of the Intelligent Control System for Reusable Rocket Engines. Arbitrary component loading values were used as input to train a two hidden-layer feedforward neural net to estimate component fatigue damage. The ability of the net to learn, based on a local strain approach, the mapping between load sequence and fatigue damage has been demonstrated for a uniaxial specimen. Because of its demonstrated performance, the neural computation may be extended to complex cases where the loads are biaxial or triaxial, and the geometry of the component is complex (e.g., turbopump blades). The generality of the approach is such that load/damage mappings can be directly extracted from experimental data without requiring any knowledge of the stress/strain profile of the component. In addition, the parallel network architecture allows real-time life calculations even for high frequency vibrations. Owing to its distributed nature, the neural implementation will be robust and reliable, enabling its use in hostile environments such as rocket engines. This neural net estimator of fatigue life is seen as the enabling technology to achieve component life prognosis, and therefore would be an important part of life extending control for reusable rocket engines.

  13. Analysis of Vibration Exercise at Varying Frequencies by Different Fatigue Estimators.

    PubMed

    Xu, Lin; Rabotti, Chiara; Mischi, Massimo

    2016-12-01

    Vibration exercise (VE) has been suggested to improve muscle strength and power performance, due to enhanced neuromuscular demand. However, understanding of the most appropriate VE protocols is lacking, limiting the optimal use of VE in rehabilitation programs. In this study, the fatiguing effect of vibration at different frequencies was investigated by employing a force-modulation VE system. Twenty volunteers performed 12-s isometric contractions of the biceps brachii with a load consisting of a baseline force of 80% of their maximum voluntary contraction (MVC) and a superimposed sinusoidal force at 0 (control condition with no vibration), 20, 30, and 40 Hz. Mechanical fatigue was estimated by assessment of MVC decay after each task while myoelectric fatigue was estimated by analysis of multichannel electromyography (EMG) signals recorded during VE. EMG conduction velocity, spectral compression, power, and fractal dimension were estimated as indicators of myoelectric fatigue. Our results suggest vibration, in particular at 30 Hz, to produce a larger degree of fatigue as compared to control condition. These results motivate further research aiming at introducing VE in rehabilitation programs with improved training protocols.

  14. Fatigue life estimation procedure for a turbine blade under transient loads

    SciTech Connect

    Vyas, N.S.; Rao, J.S. Indian Inst. of Technology, New Delhi )

    1992-01-01

    A technique for fatigue damage assessment during variable speed operations is presented. Transient resonant stresses for a blade with nonlinear damping have been determined using a numerical procedure. A fatigue damage assessment procedure is described. The fatigue failure surface is generated on the S-N-mean stress axes, and Miner's rule is employed to estimate the cumulation of fatigue. 16 refs.

  15. Estimation of fatigue damage parameters using guided wave technique

    NASA Astrophysics Data System (ADS)

    Rathod, V. T.; Roy Mahapatra, D.

    2014-03-01

    In the present work we have considered the problem of monitoring a fatigue crack growth in a thin plate specimen. The problem is first solved analytically by modeling the structure with a cyclic plastic zone around the crack. The damaged region is modeled as a visco-elastic zone and other regions are modeled as elastic zones. Using the one-dimensional guided wave model, the reflected and transmitted energies of the guided waves from the fatigue crack and plastic zone are studied. Experimental study of the reflected and transmitted energies is done using guided waves generated and received by piezoelectric wafers. The reflected and transmitted energies are derived at various cycles of fatigue loading till the failure of the structure. Validation of the results from the analytical model is done by comparing the results obtained from the experiments. The reflected and transmitted energy is related to the size of crack size or the magnitude of loading. Using crack size and the nature of loading, a method is proposed to estimate the fatigue life using fracture mechanics approach.

  16. A real time neural net estimator of fatigue life

    NASA Technical Reports Server (NTRS)

    Troudet, T.; Merrill, W.

    1990-01-01

    A neural network architecture is proposed to estimate, in real-time, the fatigue life of mechanical components, as part of the intelligent Control System for Reusable Rocket Engines. Arbitrary component loading values were used as input to train a two hidden-layer feedforward neural net to estimate component fatigue damage. The ability of the net to learn, based on a local strain approach, the mapping between load sequence and fatigue damage has been demonstrated for a uniaxial specimen. Because of its demonstrated performance, the neural computation may be extended to complex cases where the loads are biaxial or triaxial, and the geometry of the component is complex (e.g., turbopumps blades). The generality of the approach is such that load/damage mappings can be directly extracted from experimental data without requiring any knowledge of the stress/strain profile of the component. In addition, the parallel network architecture allows real-time life calculations even for high-frequency vibrations. Owing to its distributed nature, the neural implementation will be robust and reliable, enabling its use in hostile environments such as rocket engines.

  17. A real time neural net estimator of fatigue life

    NASA Technical Reports Server (NTRS)

    Troudet, T.; Merrill, W.

    1990-01-01

    A neural network architecture is proposed to estimate, in real-time, the fatigue life of mechanical components, as part of the intelligent Control System for Reusable Rocket Engines. Arbitrary component loading values were used as input to train a two hidden-layer feedforward neural net to estimate component fatigue damage. The ability of the net to learn, based on a local strain approach, the mapping between load sequence and fatigue damage has been demonstrated for a uniaxial specimen. Because of its demonstrated performance, the neural computation may be extended to complex cases where the loads are biaxial or triaxial, and the geometry of the component is complex (e.g., turbopumps blades). The generality of the approach is such that load/damage mappings can be directly extracted from experimental data without requiring any knowledge of the stress/strain profile of the component. In addition, the parallel network architecture allows real-time life calculations even for high-frequency vibrations. Owing to its distributed nature, the neural implementation will be robust and reliable, enabling its use in hostile environments such as rocket engines.

  18. Residual stress relief due to fatigue in tetragonal lead zirconate titanate ceramics

    SciTech Connect

    Hall, D. A.; Mori, T.; Comyn, T. P.; Ringgaard, E.; Wright, J. P.

    2013-07-14

    High energy synchrotron XRD was employed to determine the lattice strain {epsilon}{l_brace}111{r_brace}and diffraction peak intensity ratio R{l_brace}200{r_brace}in tetragonal PZT ceramics, both in the virgin poled state and after a bipolar fatigue experiment. It was shown that the occurrence of microstructural damage during fatigue was accompanied by a reduction in the gradient of the {epsilon}{l_brace}111{r_brace}-cos{sup 2} {psi} plot, indicating a reduction in the level of residual stress due to poling. In contrast, the fraction of oriented 90 Degree-Sign ferroelectric domains, quantified in terms of R{l_brace}200{r_brace}, was not affected significantly by fatigue. The change in residual stress due to fatigue is interpreted in terms of a change in the average elastic stiffness of the polycrystalline matrix due to the presence of inter-granular microcracks.

  19. Fatigue

    MedlinePlus

    ... to help you find out what's causing your fatigue and recommend ways to relieve it. Fatigue itself is not a disease. Medical problems, treatments, and personal habits can add to fatigue. These include Taking certain medicines, such as antidepressants, ...

  20. Fatigue Level Estimation of Bill Based on Acoustic Signal Feature by Supervised SOM

    NASA Astrophysics Data System (ADS)

    Teranishi, Masaru; Omatu, Sigeru; Kosaka, Toshihisa

    Fatigued bills have harmful influence on daily operation of Automated Teller Machine(ATM). To make the fatigued bills classification more efficient, development of an automatic fatigued bill classification method is desired. We propose a new method to estimate bending rigidity of bill from acoustic signal feature of banking machines. The estimated bending rigidities are used as continuous fatigue level for classification of fatigued bill. By using the supervised Self-Organizing Map(supervised SOM), we estimate the bending rigidity from only the acoustic energy pattern effectively. The experimental result with real bill samples shows the effectiveness of the proposed method.

  1. The relationship between observed fatigue damage and life estimation models

    NASA Technical Reports Server (NTRS)

    Kurath, Peter; Socie, Darrell F.

    1988-01-01

    Observations of the surface of laboratory specimens subjected to axial and torsional fatigue loadings has resulted in the identification of three damage fatigue phenomena: crack nucleation, shear crack growth, and tensile crack growth. Material, microstructure, state of stress/strain, and loading amplitude all influence which of the three types of fatigue damage occurs during a dominant fatigue life fraction. Fatigue damage maps are employed to summarize the experimental observations. Appropriate bulk stress/strain damage parameters are suggested to model fatigue damage for the dominant fatigue life fraction. Extension of the damage map concept to more complex loadings is presented.

  2. Estimating Viscoelastic Deformation Due to Seasonal Loading

    NASA Technical Reports Server (NTRS)

    Sauber, Jeanne

    2015-01-01

    Scientists have been making summer-­-time geodetic measurements in south central Alaska for decades to estimate the rate at which a continental-­-ocean terrane is accreting to the North American continent. Southern Alaska has big earthquakes every century and large, rapidly changing glaciers. In the last decade, primarily as part of the EarthScope Plate Boundary Observatory project, continuous GPS measurements have recorded the response of sites such as the near-­-coastal geodetic site, AB35 to competing processes: uplift and movement to the northwest due to tectonic forces and the response of the solid Earth to seasonal and longer-­-term changes in the cryosphere (snow and ice) surrounding the site. Which process causes the largest displacements of the site? Figure 1 (Blewitt, Nevada Geodetic Lab, 2015) shows the Northward, Eastward, and Upward motion of AB35 between 2007 and 2015. The site is moving rapidly to the north and west reflecting the tectonic convergence of site toward interior Alaska but there is small wiggle on the North component reflecting seasonal displacements of the site associated with snow loading and unloading. However, the Up component, shows a large seasonal signal due to snow loading in the winter (down) and ice and snow melting in the warmer months (site goes up). Between 2007 and the present, the site position is slowly moving upward, due to tectonic forcing but probably associated with longer-­- term ice melting as well. We are using the CIG finite element modeling (FEM) program Pylith to estimate the surface displacements and stresses associated with seasonal loading changes (top figure and Figure 2 far right) for water year 2012, 2011.8 - 2012.8) and the longer-­-term retreat of the surrounding glaciers.

  3. Structural health monitoring of wind towers: residual fatigue life estimation

    NASA Astrophysics Data System (ADS)

    Benedetti, M.; Fontanari, V.; Battisti, L.

    2013-04-01

    In a recent paper (Benedetti et al 2011 Smart Mater. Struct. 20 055009), the authors investigated the possibility of detecting cracks in critical sites of onshore wind towers using a radial arrangement of strain sensors around the tower periphery in the vicinity of the base welded joint. Specifically, the strain difference between adjacent strain sensors is used as a damage indicator. The number of sensors to be installed is determined by the minimum crack size to be detected, which in turn depends on the expected extreme wind conditions and programmed inspection/repair schedule. In this companion paper, we address these issues by investigating possible strategies for residual fatigue life assessment and management of onshore wind towers once the crack has been detected. For this purpose, fracture mechanics tests are carried out using welded samples to quantify the resistance to fatigue crack growth as well as the elastic-plastic fracture toughness of the welded joint at the tower base. These material strength characteristics are used to estimate (i) the critical crack size for structural integrity on the basis of fracture toughness tests, elastoplastic finite element analyses and loading spectra under extreme wind conditions, (ii) the residual life before structural collapse, applying a frequency-domain method to typical in-service wind actions and wind directionality.

  4. Estimation of muscle fatigue by ratio of mean frequency to average rectified value from surface electromyography.

    PubMed

    Fernando, Jeffry Bonar; Yoshioka, Mototaka; Ozawa, Jun

    2016-08-01

    A new method to estimate muscle fatigue quantitatively from surface electromyography (EMG) is proposed. The ratio of mean frequency (MNF) to average rectified value (ARV) is used as the index of muscle fatigue, and muscle fatigue is detected when MNF/ARV falls below a pre-determined or pre-calculated baseline. MNF/ARV gives larger distinction between fatigued muscle and non-fatigued muscle. Experiment results show the effectiveness of our method in estimating muscle fatigue more correctly compared to conventional methods. An early evaluation based on the initial value of MNF/ARV and the subjective time when the subjects start feeling the fatigue also indicates the possibility of calculating baseline from the initial value of MNF/ARV.

  5. Thermal fatigue due to beam interruptions in a Lead-Bismuth cooled ATW blanket

    SciTech Connect

    Dunn, F.

    2000-11-15

    Thermal fatigue consequences of frequent accelerator beam interruptions are quantified for both sodium and lead-bismuth cooled blankets in current designs for accelerator transmutation of waste devices. Temperature response was calculated using the SASSYS-1 systems analysis code for an immediate drop in beam current from full power to zero. Coolant temperatures from SASSYS-1 were fed into a multi-node structure temperature calculation to obtain thermal strains for various structural components. Fatigue curves from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code were used to determine the number of cycles that these components could endure, based on these thermal strains. Beam interruption frequency data from a current accelerator were used to estimate design lifetimes for components. Mitigation options for reducing thermal fatigue are discussed.

  6. Fatigue failure in thin-film polysilicon is due to subcriticalcracking within the oxide layer

    SciTech Connect

    Alsem, D.H.; Muhlstein, C.L.; Stach, E.A.; Ritchie, R.O.

    2005-01-11

    It has been established that microelectromechanical systems (MEMS) created from polycrystalline silicon thin-films are subject to cyclic fatigue. Prior work by the authors has suggested that although bulk silicon is not susceptible to fatigue failure in ambient air, fatigue in micron-scale silicon is a result of a ''reaction-layer'' process, whereby high stresses induce a thickening of the post-release oxide at stress concentrations such as notches, which subsequently undergoes moisture-assisted cracking. However, there exists some controversy regarding the post-release oxide thickness of the samples used in the prior study. In this Letter, we present data from devices from a more recent fabrication run that confirm our prior observations. Additionally, new data from tests in high vacuum show that these devices do not fatigue when oxidation and moisture are suppressed. Each of these observations lends credence to the '''reaction-layer'' mechanism. Recent advances in the design of microelectromechanical systems (MEMS) have increased the demand for more reliable microscale structures. Although silicon is an effective and widely used structural material at the microscale, it is very brittle. Consequently, reliability is a limiting factor for commercial and defense applications. Since the surface to volume ratio of these structural films is very large, classical models for failure modes in bulk materials cannot always be applied. For example, whereas bulk silicon is immune to cyclic fatigue failure thin micron-scale structural films of silicon appear to be highly susceptible. It is clear that at these size scales, surface effects may become dominant in controlling mechanical properties. The main reliability issues for MEMS are stiction, fatigue and wear. Fatigue is important in cases where devices are subjected to a large number of loading cycles with amplitudes below their (single-cycle) fracture stress, which may arise due to vibrations intentionally induced in the

  7. Estimation of uncertainty for fatigue growth rate at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Nyilas, Arman; Weiss, Klaus P.; Urbach, Elisabeth; Marcinek, Dawid J.

    2014-01-01

    Fatigue crack growth rate (FCGR) measurement data for high strength austenitic alloys at cryogenic environment suffer in general from a high degree of data scatter in particular at ΔK regime below 25 MPa√m. Using standard mathematical smoothing techniques forces ultimately a linear relationship at stage II regime (crack propagation rate versus ΔK) in a double log field called Paris law. However, the bandwidth of uncertainty relies somewhat arbitrary upon the researcher's interpretation. The present paper deals with the use of the uncertainty concept on FCGR data as given by GUM (Guidance of Uncertainty in Measurements), which since 1993 is a recommended procedure to avoid subjective estimation of error bands. Within this context, the lack of a true value addresses to evaluate the best estimate by a statistical method using the crack propagation law as a mathematical measurement model equation and identifying all input parameters. Each parameter necessary for the measurement technique was processed using the Gaussian distribution law by partial differentiation of the terms to estimate the sensitivity coefficients. The combined standard uncertainty determined for each term with its computed sensitivity coefficients finally resulted in measurement uncertainty of the FCGR test result. The described procedure of uncertainty has been applied within the framework of ITER on a recent FCGR measurement for high strength and high toughness Type 316LN material tested at 7 K using a standard ASTM proportional compact tension specimen. The determined values of Paris law constants such as C0 and the exponent m as best estimate along with the their uncertainty value may serve a realistic basis for the life expectancy of cyclic loaded members.

  8. An estimation of fatigue life for a carbon fibre/poly ether ether ketone hip joint prosthesis.

    PubMed

    Akay, M; Aslan, N

    1995-01-01

    A fracture mechanics approach was applied to estimate the life of a prosthesis injection moulded from short carbon fibre reinforced poly ether ether ketone. Flexural modulus and strength, fracture toughness, fatigue endurance limit, fatigue crack growth rate and threshold stress intensity factor were determined. The dimensions of the test pieces were selected to yield fibre orientation and fibre length distributions similar to those obtained in the prosthesis. Stress levels generated in the prosthesis under different activities were estimated by conducting three-dimensional finite element analysis. It was shown by a fracture mechanics approach that a fatigue failure due to the propagation of an embedded elliptical slit, under these stresses, would be unlikely for a crack length smaller than 1.85 mm. However, the cement would fail under the same conditions, irrespective of the type of the prosthesis employed.

  9. Assessment of material degradation due to corrosion-fatigue using a backscattered Rayleigh surface wave.

    PubMed

    Kim, Young H; Song, Sung-Jin; Bae, D H; Kwon, Sung-Duk

    2004-04-01

    Material degradation due to corrosion-fatigue was evaluated nondestructively using backscattered Rayleigh surface wave. A corrosion-fatigue test was carried out for the specimens made of thermo-mechanically controlled process steel in 3.5 wt.% NaCl solution at 25 degrees C. The Backscattering profile, which is the amplitude variation of backscattered ultrasound according to the incident angle, of the specimens were measured in water at room temperature after the corrosion-fatigue test. The velocity of Rayleigh surface wave, determined from the incident angle at which the profile of the backscattered ultrasound became maximum, decreased for the specimen that had the large number of cycles to failure in the corrosion-fatigue test. This fact implies that the corrosion degradation occurred at specimen surface in this specific test is dominantly dependant on the time exposed to corrosion environment. The result observed in the present work demonstrates the high potential of backscattered Rayleigh surface wave as a tool for nondestructive evaluation of corrosion degradation of aged materials.

  10. Calculation of Local Stress and Fatigue Resistance due to Thermal Stratification on Pressurized Surge Line Pipe

    SciTech Connect

    Bandriyana, B.; Utaja

    2010-06-22

    Thermal stratification introduces thermal shock effect which results in local stress and fatigue problems that must be considered in the design of nuclear power plant components. Local stress and fatigue calculation were performed on the Pressurize Surge Line piping system of the Pressurize Water Reactor of the Nuclear Power Plant. Analysis was done on the operating temperature between 177 to 343 deg. C and the operating pressure of 16 MPa (160 Bar). The stagnant and transient condition with two kinds of stratification model has been evaluated by the two dimensional finite elements method using the ANSYS program. Evaluation of fatigue resistance is developed based on the maximum local stress using the ASME standard Code formula. Maximum stress of 427 MPa occurred at the upper side of the top half of hot fluid pipe stratification model in the transient case condition. The evaluation of the fatigue resistance is performed on 500 operating cycles in the life time of 40 years and giving the usage value of 0,64 which met to the design requirement for class 1 of nuclear component. The out surge transient were the most significant case in the localized effects due to thermal stratification.

  11. Characterization of microstructural damage due to low-cycle fatigue by EBSD observation

    SciTech Connect

    Kamaya, Masayuki

    2009-12-15

    Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess the damage due to cyclic or uniform strain. Samples of Type 316 stainless steel after fatigue and tensile tests were prepared for EBSD observation and the misorientation angle between neighboring points (local misorientation) was evaluated. It was shown that the local misorientation developed due to the cyclic and uniform strain and that its spatial distribution was not uniform. In fatigue samples, the area of large local misorientation tended to form clusters, whereas it localized to the grain boundaries in the tensile samples, and the magnitude of local misorientation and the degree of the localization increased with the strain amplitude. The degree of localization was quantified via statistical processing of the measured data. It was also shown that the source of damage (cyclic or uniform strain) and the loading direction could be deduced from the EBSD observations of the damaged sample.

  12. Estimation of the Residual Fatigue Life of Laminated Composites Under a Multistage Cyclic Loading

    NASA Astrophysics Data System (ADS)

    Strizhius, V.

    2016-11-01

    Problems on estimation of the residual fatigue life of laminated composites under a multistage regular cyclic loading (with a constant amplitude at each loading stage) are among the most frequently ones encountered in the practice of fatigue life estimations of laminated composites. There are several methods for solving these problems, but their use not always gives results of acceptable accuracy. To improve the accuracy of such estimations for the type of cyclic loading mentioned, a special model of nonlinear accumulation of fatigue damage is proposed.

  13. Metacognitions Are Associated with Subjective Memory Problems in Individuals on Sick Leave due to Chronic Fatigue

    PubMed Central

    Jacobsen, Henrik B.; Aasvik, Julie K.; Borchgrevink, Petter C.; Landrø, Nils I.; Stiles, Tore C.

    2016-01-01

    Background: Subjective cognitive impairments are frequent, but poorly understood in patients with chronic fatigue. We hypothesized that maladaptive metacognitive beliefs at baseline were associated with baseline subjective cognitive impairments, that they predict subjective cognitive impairments at treatment termination, and that a reduction in maladaptive metacognitive beliefs was associated with less subjective cognitive impairments at treatment termination, independent of changes in fatigue, pain, insomnia, depression, and anxiety. Methods: In this non-controlled study, patients (n = 137) on sick leave due to chronic fatigue received a 3.5-week inpatient RTW rehabilitation program. Of these patients 69 (50.4%) was referred with a ICPC-2 diagnosis of chronic fatigue. Patients completed questionnaires about metacognitive beliefs, somatic complaints, psychological complaints, and cognitive impairments before and after treatment. To test the hypotheses we performed paired t-tests of change, as well as seven hierarchical linear regressions. Results: Results showed that baseline maladaptive metacognitive beliefs were significantly associated with subjective cognitive impairments at baseline, controlling for symptoms. Score on baseline metacognitive beliefs did not predict impairments post-treatment. Testing specific maladaptive beliefs, pre-treatment scores on cognitive confidence were associated with subjective cognitive impairments both pre and post-treatment, controlling for symptoms. Post-treatment metacognitive beliefs and post-treatment cognitive confidence were associated with post-treatment subjective cognitive impairments, controlling for pre-treatment impairments and pre-treatment metacognitive beliefs, as well as pre and post-scores on symptom measures. Conclusion: This study reports associations between maladaptive metacognitive beliefs and subjective cognitive impairments in patients with chronic fatigue. Targeting metacognitive beliefs could prove an

  14. Evolution of mechanical properties of M50 bearing steel due to rolling contact fatigue

    NASA Astrophysics Data System (ADS)

    Allison, Bryan D.

    Current bearing life models significantly under predict the life of bearings made of modern ultra-clean steels. New life models that include the constitutive response of the material are needed. However, the constitutive response of bearing steel is known to change during bearing operation. In the current study, the evolution of the mechanical properties of M50 bearing steel due to rolling contact fatigue (RCF) was investigated. A combination of M50 balls and rods were subjected to RCF testing under various conditions (e.g. number of RCF cycles, applied Hertzian stress, and interacting material). Additionally, some of the balls tested went through a proprietary mechanical process to induce compressive residual stresses over the first several hundred microns into the depth of the ball prior to RCF testing. After RCF testing, the specimens were subjected to a number of tests. First, the residual stresses within the subsurface RCF affected region were measured via x-ray diffraction. The residual stresses within the mechanically processed (MP) balls were found to not significantly change due to RCF, while a linear relationship was found between the maximum residual stress with the RCF affected zone and the Hertzian stress for the unprocessed balls. Then, the specimens were sectioned, polished, and chemically etched to study the evolution of the microstructure due to RCF. A similar relationship was found between the size of the dark etching region (DER) and the Hertzian stress. Formation of a light etching region (LER) is demonstrated to not correlate with a decrease in material strength and hardness, but it does serve as a predictor for failure due to spall. Micro-indentation was performed within subsurface to estimate the local yield stress. Micro-indentation is not able to provide information about the stress-strain response, only the yield strength. Hence, a novel method to extract and test miniature compression specimens from within the RCF affected regions of

  15. A rapid estimation method of structural fatigue analysis for a 17k ton DWT oil tanker

    NASA Astrophysics Data System (ADS)

    Chen, Tuohan; Zheng, Jianli; Bae, Dong-Myung

    2012-06-01

    Fatigue cracks and fatigue damage have been important issues for ships and offshore structures for a long time. However, in the last decade, with the introduction of higher tensile steel in hull structures and increasingly large ship dimensions, the greater attention should be paid to fatigue problems. Most research focuses on how to more easily access the fatigue strength of ships. Also, the major classification societies have already released their fatigue assessment notes. However, due to the complexity of factors influencing fatigue performances, such as wave load and pressure from cargo, the combination of different stress components, stress on concentration of local structure details, means stress, and the corrosive environments, there are different specifications with varying classification societies, leading to the different results from different fatigue assessment methods. This paper established the Det Norske Veritas(DNV) classification notes "fatigue assessment of ship structures" that explains the process of fatigue assessment and simplified methods. Finally, a fatigue analysis was performed by use data of a real ship and the reliability of the result was assessed.

  16. Driver fatigue alarm based on eye detection and gaze estimation

    NASA Astrophysics Data System (ADS)

    Sun, Xinghua; Xu, Lu; Yang, Jingyu

    2007-11-01

    The driver assistant system has attracted much attention as an essential component of intelligent transportation systems. One task of driver assistant system is to prevent the drivers from fatigue. For the fatigue detection it is natural that the information about eyes should be utilized. The driver fatigue can be divided into two types, one is the sleep with eyes close and another is the sleep with eyes open. Considering that the fatigue detection is related with the prior knowledge and probabilistic statistics, the dynamic Bayesian network is used as the analysis tool to perform the reasoning of fatigue. Two kinds of experiments are performed to verify the system effectiveness, one is based on the video got from the laboratory and another is based on the video got from the real driving situation. Ten persons participate in the test and the experimental result is that, in the laboratory all the fatigue events can be detected, and in the practical vehicle the detection ratio is about 85%. Experiments show that in most of situations the proposed system works and the corresponding performance is satisfying.

  17. Mechanism and estimation of fatigue crack initiation in austenitic stainless steels in LWR environments.

    SciTech Connect

    Chopra, O. K.; Energy Technology

    2002-08-01

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figures I-9.1 through I-9.6 of Appendix I to Section III of the Code specify fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Existing fatigue strain-vs.-life ({var_epsilon}-N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. This report provides an overview of fatigue crack initiation in austenitic stainless steels in LWR coolant environments. The existing fatigue {var_epsilon}-N data have been evaluated to establish the effects of key material, loading, and environmental parameters (such as steel type, strain range, strain rate, temperature, dissolved-oxygen level in water, and flow rate) on the fatigue lives of these steels. Statistical models are presented for estimating the fatigue {var_epsilon}-N curves for austenitic stainless steels as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are presented. The influence of reactor environments on the mechanism of fatigue crack initiation in these steels is also discussed.

  18. X-43A Rudder Spindle Fatigue Life Estimate and Testing

    NASA Technical Reports Server (NTRS)

    Glaessgen, Edward H.; Dawicke, David S.; Johnston, William M.; James, Mark A.; Simonsen, Micah; Mason, Brian H.

    2005-01-01

    Fatigue life analyses were performed using a standard strain-life approach and a linear cumulative damage parameter to assess the effect of a single accidental overload on the fatigue life of the Haynes 230 nickel-base superalloy X-43A rudder spindle. Because of a limited amount of information available about the Haynes 230 material, a series of tests were conducted to replicate the overload and in-service conditions for the spindle and corroborate the analysis. Both the analytical and experimental results suggest that the spindle will survive the anticipated flight loads.

  19. Estimating Aircrew Fatigue: A Technique with Application to Airlift Operations

    DTIC Science & Technology

    1982-12-01

    most closely corresponds to how tired he feels at the time of checkcard administration. On this scale, the higher the number, the greater the subjective ... feeling of fatigue being reported. The 7-point scale appears to provide slightly greater sensitivity and reliability than the format used in the

  20. Fatigue Strength Estimation Based on Local Mechanical Properties for Aluminum Alloy FSW Joints

    PubMed Central

    Sillapasa, Kittima; Mutoh, Yoshiharu; Miyashita, Yukio; Seo, Nobushiro

    2017-01-01

    Overall fatigue strengths and hardness distributions of the aluminum alloy similar and dissimilar friction stir welding (FSW) joints were determined. The local fatigue strengths as well as local tensile strengths were also obtained by using small round bar specimens extracted from specific locations, such as the stir zone, heat affected zone, and base metal. It was found from the results that fatigue fracture of the FSW joint plate specimen occurred at the location of the lowest local fatigue strength as well as the lowest hardness, regardless of microstructural evolution. To estimate the fatigue strengths of aluminum alloy FSW joints from the hardness measurements, the relationship between fatigue strength and hardness for aluminum alloys was investigated based on the present experimental results and the available wide range of data from the references. It was found as: σa (R = −1) = 1.68 HV (σa is in MPa and HV has no unit). It was also confirmed that the estimated fatigue strengths were in good agreement with the experimental results for aluminum alloy FSW joints. PMID:28772543

  1. Fatigue Strength Estimation Based on Local Mechanical Properties for Aluminum Alloy FSW Joints.

    PubMed

    Sillapasa, Kittima; Mutoh, Yoshiharu; Miyashita, Yukio; Seo, Nobushiro

    2017-02-15

    Overall fatigue strengths and hardness distributions of the aluminum alloy similar and dissimilar friction stir welding (FSW) joints were determined. The local fatigue strengths as well as local tensile strengths were also obtained by using small round bar specimens extracted from specific locations, such as the stir zone, heat affected zone, and base metal. It was found from the results that fatigue fracture of the FSW joint plate specimen occurred at the location of the lowest local fatigue strength as well as the lowest hardness, regardless of microstructural evolution. To estimate the fatigue strengths of aluminum alloy FSW joints from the hardness measurements, the relationship between fatigue strength and hardness for aluminum alloys was investigated based on the present experimental results and the available wide range of data from the references. It was found as: σa (R = -1) = 1.68 HV (σa is in MPa and HV has no unit). It was also confirmed that the estimated fatigue strengths were in good agreement with the experimental results for aluminum alloy FSW joints.

  2. Models of multiaxial fatigue fracture and service life estimation of structural elements

    NASA Astrophysics Data System (ADS)

    Bourago, N. G.; Zhuravlev, A. B.; Nikitin, I. S.

    2011-12-01

    We study criteria and models of multiaxial fracture under the conditions of low-cycle fatigue (LCF). The model parameters are determined by using the data of uniaxial fatigue tests for different coefficients of the cycle asymmetry. A procedure for calculating the stress state of the compressor disk in a gas turbine engine (GTE) in the flight cycle of loading is outlined. The calculated stress state and models of multiaxial fatigue fracture are used to estimate the service life of the compressor disk. The results are compared with the observational data collected during the operation.

  3. FRACTURE MECHANICS APPROACH TO ESTIMATE FATIGUE LIVES OF WELDED LAP-SHEAR SPECIMENS

    SciTech Connect

    Lam, P.; Michigan, J.

    2014-04-25

    A full range of stress intensity factor solutions for a kinked crack is developed as a function of weld width and the sheet thickness. When used with the associated main crack solutions (global stress intensity factors) in terms of the applied load and specimen geometry, the fatigue lives can be estimated for the laser-welded lap-shear specimens. The estimations are in good agreement with the experimental data. A classical solution for an infinitesimal kink is also employed in the approach. However, the life predictions tend to overestimate the actual fatigue lives. The traditional life estimations with the structural stress along with the experimental stress-fatigue life data (S-N curve) are also provided. In this case, the estimations only agree with the experimental data under higher load conditions.

  4. Calculation of Local Stress and Fatigue Resistance due to Thermal Stratification on Pressurized Surge Line Pipe

    NASA Astrophysics Data System (ADS)

    Bandriyana, B.; Utaja

    2010-06-01

    Thermal stratification introduces thermal shock effect which results in local stress and fatique problems that must be considered in the design of nuclear power plant components. Local stress and fatique calculation were performed on the Pressurize Surge Line piping system of the Pressurize Water Reactor of the Nuclear Power Plant. Analysis was done on the operating temperature between 177 to 343° C and the operating pressure of 16 MPa (160 Bar). The stagnant and transient condition with two kinds of stratification model has been evaluated by the two dimensional finite elements method using the ANSYS program. Evaluation of fatigue resistance is developed based on the maximum local stress using the ASME standard Code formula. Maximum stress of 427 MPa occurred at the upper side of the top half of hot fluid pipe stratification model in the transient case condition. The evaluation of the fatigue resistance is performed on 500 operating cycles in the life time of 40 years and giving the usage value of 0,64 which met to the design requirement for class 1 of nuclear component. The out surge transient were the most significant case in the localized effects due to thermal stratification.

  5. Measures and Models for Estimating and Predicting Cognitive Fatigue

    NASA Technical Reports Server (NTRS)

    Trejo, Leonard J.; Kochavi, Rebekah; Kubitz, Karla; Montgomery, Leslie D.; Rosipal, Roman; Matthews, Bryan

    2004-01-01

    We analyzed EEG and ERPs in a fatiguing mental task and created statistical models for single subjects. Seventeen subjects (4 F, 18-38 y) viewed 4-digit problems (e.g., 3+5-2+7=15) on a computer, solved the problems, and pressed keys to respond (intertrial interval = 1 s). Subjects performed until either they felt exhausted or three hours had elapsed. Re- and post-task measures of mood (Activation Deactivation Adjective Checklist, Visual Analogue Mood Scale) confirmed that fatigue increased and energy decreased over time. We tested response times (RT); amplitudes of ERP components N1, P2, P300, readiness potentials; and amplitudes of frontal theta and parietal alpha rhythms for change as a function of time. For subjects who completed 3 h (n=9) we analyzed 12 15-min blocks. For subjects who completed at least 1.5 h (n=17), we analyzed the first-, middle-, and last 100 error-free trials. Mean RT rose from 6.7 s to 8.5 s over time. We found no changes in the amplitudes of ERP components. In both analyses, amplitudes of frontal theta and parietal alpha rose by 30% or more over time. We used 30-channel EEG frequency spectra to model the effects of time in single subjects using a kernel partial least squares classifier. We classified 3.5s EEG segments as being from the first 100 or the last 100 trials, using random sub-samples of each class. Test set accuracies ranged from 63.9% to 99.6% correct. Only 2 of 17 subjects had mean accuracies lower than 80%. The results suggest that EEG accurately classifies periods of cognitive fatigue in 90% of subjects.

  6. Baseline-free estimation of residual fatigue life using a third order acoustic nonlinear parameter.

    PubMed

    Amura, Mikael; Meo, Michele; Amerini, F

    2011-10-01

    Prediction of crack growth and fatigue life estimation of metals using linear/nonlinear acousto-ultrasound methods is an ongoing issue. It is known that by measuring nonlinear parameters, the relative accumulated fatigue damage can be evaluated. However, there is still a need to measure two crack propagation states to assess the absolute residual fatigue life. A procedure based on the measurement of a third-order acoustic nonlinear parameter is presented to assess the residual fatigue life of a metallic component without the need of a baseline. The analytical evaluation of how the cubic nonlinear-parameter evolves during crack propagation is presented by combining the Paris law to the Nazarov-Sutin crack equation. Unlike other developed models, the proposed model assumes a crack surface topology with variable geometrical parameters. Measurements of the cubic nonlinearity parameter on AA2024-T351 specimens demonstrated high sensitivity to crack propagation and excellent agreement with the predicted theoretical behavior. The advantages of using the cubic nonlinearity parameter for fatigue cracks on metals are discussed by comparing the relevant results of a quadratic nonlinear parameter. Then the methodology to estimate crack size and residual fatigue life without the need of a baseline is presented, and advantages and limitations are discussed.

  7. Estimation of Fatigue Damage for an Austenitic Stainless Steel (SUS304) Using Magnetic Methods

    SciTech Connect

    Oka, M.; Yakushiji, T.; Tsuchida, Y.; Enokizono, M.

    2007-03-21

    There are some fatigue damage estimation methods of the austenitic stainless steel that uses the martensitic transformation. For instance, they are the remanent magnetization method, the excitation method, and so on. Those two methods are being researched also in our laboratory now. In the remanent magnetization method, it is well known that the relation between fatigue damage and the remanent magnetization is simple, clear, and reproducible. However, this method has the disadvantage to need a special magnetizer. This method cannot be easily used on the site such as the factory. On the other hand, because the special magnetizer is unnecessary, the excitation method can use easily on the site. The output signal of this method is small. In this paper, two fatigue evaluation methods such as the remanent magnetization method and the excitation method are introduced. In addition, we report on the result of comparing the fatigue evaluation performances of two methods.

  8. Estimation of fatigue and extreme load distributions from limited data with application to wind energy systems.

    SciTech Connect

    Fitzwater, LeRoy M.

    2004-01-01

    An estimate of the distribution of fatigue ranges or extreme loads for wind turbines may be obtained by separating the problem into two uncoupled parts, (1) a turbine specific portion, independent of the site and (2) a site-specific description of environmental variables. We consider contextually appropriate probability models to describe the turbine specific response for extreme loads or fatigue. The site-specific portion is described by a joint probability distribution of a vector of environmental variables, which characterize the wind process at the hub-height of the wind turbine. Several approaches are considered for combining the two portions to obtain an estimate of the extreme load, e.g., 50-year loads or fatigue damage. We assess the efficacy of these models to obtain accurate estimates, including various levels of epistemic uncertainty, of the turbine response.

  9. Influence of Initial Inclined Surface Crack on Estimated Residual Fatigue Lifetime of Railway Axle

    NASA Astrophysics Data System (ADS)

    Náhlík, Luboš; Pokorný, Pavel; Ševčík, Martin; Hutař, Pavel

    2016-11-01

    Railway axles are subjected to cyclic loading which can lead to fatigue failure. For safe operation of railway axles a damage tolerance approach taking into account a possible defect on railway axle surface is often required. The contribution deals with an estimation of residual fatigue lifetime of railway axle with initial inclined surface crack. 3D numerical model of inclined semi-elliptical surface crack in railway axle was developed and its curved propagation through the axle was simulated by finite element method. Presence of press-fitted wheel in the vicinity of initial crack was taken into account. A typical loading spectrum of railway axle was considered and residual fatigue lifetime was estimated by NASGRO approach. Material properties of typical axle steel EA4T were considered in numerical calculations and lifetime estimation.

  10. Assessing Fatigue and Ultimate Load Uncertainty in Floating Offshore Wind Turbines Due to Varying Simulation Length

    SciTech Connect

    Stewart, G.; Lackner, M.; Haid, L.; Matha, D.; Jonkman, J.; Robertson, A.

    2013-07-01

    With the push towards siting wind turbines farther offshore due to higher wind quality and less visibility, floating offshore wind turbines, which can be located in deep water, are becoming an economically attractive option. The International Electrotechnical Commission's (IEC) 61400-3 design standard covers fixed-bottom offshore wind turbines, but there are a number of new research questions that need to be answered to modify these standards so that they are applicable to floating wind turbines. One issue is the appropriate simulation length needed for floating turbines. This paper will discuss the results from a study assessing the impact of simulation length on the ultimate and fatigue loads of the structure, and will address uncertainties associated with changing the simulation length for the analyzed floating platform. Recommendations of required simulation length based on load uncertainty will be made and compared to current simulation length requirements.

  11. Changes in lower extremity biomechanics due to a short-term fatigue protocol.

    PubMed

    Cortes, Nelson; Greska, Eric; Kollock, Roger; Ambegaonkar, Jatin; Onate, James A

    2013-01-01

    Noncontact anterior cruciate ligament injury has been reported to occur during the later stages of a game when fatigue is most likely present. Few researchers have focused on progressive changes in lower extremity biomechanics that occur throughout fatiguing. To evaluate the effects of a sequential fatigue protocol on lower extremity biomechanics during a sidestep-cutting task (SS). Controlled laboratory study. Laboratory. Eighteen uninjured female collegiate soccer players (age = 19.2 ± 0.9 years, height = 1.66 ± 0.5 m, mass = 61.6 ± 5.1 kg) volunteered. The independent variable was fatigue level, with 3 levels (prefatigue, 50% fatigue, and 100% fatigue). Using 3-dimensional motion capture, we assessed lower extremity biomechanics during the SS. Participants alternated between a fatigue protocol that solicited different muscle groups and mimicked actual sport situations and unanticipated SS trials. The process was repeated until fatigue was attained. Dependent variables were hip- and knee-flexion and abduction angles and internal moments measured at initial contact and peak stance and defined as measures obtained between 0% and 50% of stance phase. Knee-flexion angle decreased from prefatigue (-17° ± 5°) to 50% fatigue (-16° ± 6°) and to 100% fatigue (-14° ± 4°) (F2,34 = 5.112, P = .004). Knee flexion at peak stance increased from prefatigue (-52.9° ± 5.6°) to 50% fatigue (-56.1° ± 7.2°) but decreased from 50% to 100% fatigue (-50.5° ± 7.1°) (F2,34 = 8.282, P = 001). Knee-adduction moment at peak stance increased from prefatigue (0.49 ± 0.23 Nm/kgm) to 50% fatigue (0.55 ± 0.25 Nm/kgm) but decreased from 50% to 100% fatigue (0.37 ± 0.24) (F2,34 = 3.755, P = 03). Hip-flexion angle increased from prefatigue (45.4° ± 10.9°) to 50% fatigue (46.2° ± 11.2°) but decreased from 50% to 100% fatigue (40.9° ± 11.3°) (F2,34 = 6.542, P = .004). Hip flexion at peak stance increased from prefatigue (49.8° ± 9.9°) to 50% fatigue (52.9° ± 12.1

  12. Fatigue failure in polysilicon not due to simple stress corrosion cracking.

    PubMed

    Kahn, H; Ballarini, R; Bellante, J J; Heuer, A H

    2002-11-08

    In the absence of a corrosive environment, brittle materials such as silicon should be immune to cyclic fatigue. However, fatigue effects are well known in micrometer-sized polycrystalline silicon (polysilicon) samples tested in air. To investigate the origins of this phenomenon in polysilicon, we developed a fixed-grip fracture mechanics microspecimen but could find no evidence of static stress corrosion cracking. The environmental sensitivity of the fatigue resistance was also investigated under cyclic loading. For low-cycle fatigue, the behavior is independent of the ambient conditions, whether air or vacuum, but is strongly influenced by the ratio of compressive to tensile stresses experienced during each cycle. The fatigue damage most likely originates from contact stresses at processing-related surface asperities; subcritical crack growth then ensues during further cyclic loading. The lower far-field stresses involved in high-cycle fatigue induce reduced levels of fatigue damage. Under these conditions, a corrosive ambient such as laboratory air exacerbates the fatigue process. Without cyclic loading, polysilicon does not undergo stress corrosion cracking.

  13. Excitation, response, and fatigue life estimation methods for the structural design of externally blown flaps

    NASA Technical Reports Server (NTRS)

    Ungar, E. E.; Chandiramani, K. L.; Barger, J. E.

    1972-01-01

    Means for predicting the fluctuating pressures acting on externally blown flap surfaces are developed on the basis of generalizations derived from non-dimensionalized empirical data. Approaches for estimation of the fatigue lives of skin-stringer and honeycomb-core sandwich flap structures are derived from vibration response analyses and panel fatigue data. Approximate expressions for fluctuating pressures, structural response, and fatigue life are combined to reveal the important parametric dependences. The two-dimensional equations of motion of multi-element flap systems are derived in general form, so that they can be specialized readily for any particular system. An introduction is presented of an approach to characterizing the excitation pressures and structural responses which makes use of space-time spectral concepts and promises to provide useful insights, as well as experimental and analytical savings.

  14. Global effect on multi-segment physiological tremors due to localized fatiguing contraction.

    PubMed

    Chen, Yi-Ching; Yang, Jeng-Feng; Hwang, Ing-Shiou

    2012-03-01

    Physiological tremors within a limb are coupled, whereas between-limb tremors are thought to oscillate independently for a healthy subject. This study was undertaken to reinvestigate bilateral tremor relations and intra-limb tremor dynamics for a two-limb task after exhausting a single joint. Fifteen volunteers conducted prolonged tracking with the left (target) shoulder. Neuromuscular functions were monitored before and after the exercise-fatiguing intervention, including tracking displacement, muscle activity of the deltoid, and physiological tremors in the bilateral upper limbs. Localized fatiguing contraction degraded tracking accuracy and movement smoothness, accompanied by an increase in deltoid activation. Segment tremors in the bilateral limbs and inter-limb tremor coherences in 8-12 Hz increased, though coherence peaks in 5-8 Hz waned with fatigue response. Intra-limb tremor relations in the target and non-target limbs were also reorganized with unilateral fatiguing contraction. Tremor coupling in the arm-C7 complexes was enhanced, associated with tremor uncoupling in the forearm-arm and hand-forearm complexes. Tracking error in the pre- fatigue and post-fatigue conditions was predicted by different principal components that had high communalities with tremors of distal and proximal segments of the target limb, respectively. The adaptive changes in tremor dynamics were attributable to fatigue-induced enhancement of common central drive and decline in neural inputs of long-looped reflexes that diverge to contralateral segments.

  15. Accumulation of microstructural damage due to fatigue of high-strength aluminum alloys

    NASA Astrophysics Data System (ADS)

    Luévano, A. J.; Przystupa, M. A.; Zhang, J.

    1994-02-01

    The microstructural features of aluminum alloy 7050-T7451 in the vicinity of fatigue cracks and on the crack path were studied to determine which of these features influence fatigue crack propagation. The studies included characterization of the full spectrum of microstructural and fracture surface features— from the largest (e.g., roughness and grain type) to the smallest (e.g., second-phase particles and dislocations). Of all the features studied, only the second-phase particles were shown to have a definite influence by causing crack deflection. The number of particles encountered by the fatigue cracks were significantly higher than the expected average. The fatigue crack path was predominately transgranular, and there was no change in the dislocation and precipitation structures in the crack-affected zone.

  16. Accumulation of microstructural damage due to fatigue of high-strength aluminum alloys

    SciTech Connect

    Luevano, A.J.; Przystupa, M.A.; Zhang, J. . Dept. of Materials Science and Engineering)

    1994-02-01

    The microstructural features of aluminum alloy 7050-T7451 in the vicinity of fatigue cracks on the crack path were studied to determine which of these features influence fatigue crack propagation. The studies included characterization of the full spectrum of microstructural and fracture surface features--from the largest (e.g., roughness and grain type) to the smallest (e.g., second-phase particles and dislocations). Of all the features studied, only the second-phase particles were shown to have a definite influence by causing crack deflection. The number of particles encountered by the fatigue cracks were significantly higher than the expected average. The fatigue crack path was predominantly transgranular, and there was no change in the dislocation and precipitation structures in the crack-affected zone.

  17. Wireless Tri-Axial Trunk Accelerometry Detects Deviations in Dynamic Center of Mass Motion Due to Running-Induced Fatigue.

    PubMed

    Schütte, Kurt H; Maas, Ellen A; Exadaktylos, Vasileios; Berckmans, Daniel; Venter, Rachel E; Vanwanseele, Benedicte

    2015-01-01

    Small wireless trunk accelerometers have become a popular approach to unobtrusively quantify human locomotion and provide insights into both gait rehabilitation and sports performance. However, limited evidence exists as to which trunk accelerometry measures are suitable for the purpose of detecting movement compensations while running, and specifically in response to fatigue. The aim of this study was therefore to detect deviations in the dynamic center of mass (CoM) motion due to running-induced fatigue using tri-axial trunk accelerometry. Twenty runners aged 18-25 years completed an indoor treadmill running protocol to volitional exhaustion at speeds equivalent to their 3.2 km time trial performance. The following dependent measures were extracted from tri-axial trunk accelerations of 20 running steps before and after the treadmill fatigue protocol: the tri-axial ratio of acceleration root mean square (RMS) to the resultant vector RMS, step and stride regularity (autocorrelation procedure), and sample entropy. Running-induced fatigue increased mediolateral and anteroposterior ratios of acceleration RMS (p < .05), decreased the anteroposterior step regularity (p < .05), and increased the anteroposterior sample entropy (p < .05) of trunk accelerometry patterns. Our findings indicate that treadmill running-induced fatigue might reveal itself in a greater contribution of variability in horizontal plane trunk accelerations, with anteroposterior trunk accelerations that are less regular from step-to-step and are less predictable. It appears that trunk accelerometry parameters can be used to detect deviations in dynamic CoM motion induced by treadmill running fatigue, yet it is unknown how robust or generalizable these parameters are to outdoor running environments.

  18. Wireless Tri-Axial Trunk Accelerometry Detects Deviations in Dynamic Center of Mass Motion Due to Running-Induced Fatigue

    PubMed Central

    2015-01-01

    Small wireless trunk accelerometers have become a popular approach to unobtrusively quantify human locomotion and provide insights into both gait rehabilitation and sports performance. However, limited evidence exists as to which trunk accelerometry measures are suitable for the purpose of detecting movement compensations while running, and specifically in response to fatigue. The aim of this study was therefore to detect deviations in the dynamic center of mass (CoM) motion due to running-induced fatigue using tri-axial trunk accelerometry. Twenty runners aged 18–25 years completed an indoor treadmill running protocol to volitional exhaustion at speeds equivalent to their 3.2 km time trial performance. The following dependent measures were extracted from tri-axial trunk accelerations of 20 running steps before and after the treadmill fatigue protocol: the tri-axial ratio of acceleration root mean square (RMS) to the resultant vector RMS, step and stride regularity (autocorrelation procedure), and sample entropy. Running-induced fatigue increased mediolateral and anteroposterior ratios of acceleration RMS (p < .05), decreased the anteroposterior step regularity (p < .05), and increased the anteroposterior sample entropy (p < .05) of trunk accelerometry patterns. Our findings indicate that treadmill running-induced fatigue might reveal itself in a greater contribution of variability in horizontal plane trunk accelerations, with anteroposterior trunk accelerations that are less regular from step-to-step and are less predictable. It appears that trunk accelerometry parameters can be used to detect deviations in dynamic CoM motion induced by treadmill running fatigue, yet it is unknown how robust or generalizable these parameters are to outdoor running environments. PMID:26517261

  19. Changes in running pattern due to fatigue and cognitive load in orienteering.

    PubMed

    Millet, Guillaume Y; Divert, Caroline; Banizette, Marion; Morin, Jean-Benoit

    2010-01-01

    The aim of this study was to examine the influence of fatigue on running biomechanics in normal running, in normal running with a cognitive task, and in running while map reading. Nineteen international and less experienced orienteers performed a fatiguing running exercise of duration and intensity similar to a classic distance orienteering race on an instrumented treadmill while performing mental arithmetic, an orienteering simulation, and control running at regular intervals. Two-way repeated-measures analysis of variance did not reveal any significant difference between mental arithmetic and control running for any of the kinematic and kinetic parameters analysed eight times over the fatiguing protocol. However, these parameters were systematically different between the orienteering simulation and the other two conditions (mental arithmetic and control running). The adaptations in orienteering simulation running were significantly more pronounced in the elite group when step frequency, peak vertical ground reaction force, vertical stiffness, and maximal downward displacement of the centre of mass during contact were considered. The effects of fatigue on running biomechanics depended on whether the orienteers read their map or ran normally. It is concluded that adding a cognitive load does not modify running patterns. Therefore, all changes in running pattern observed during the orienteering simulation, particularly in elite orienteers, are the result of adaptations to enable efficient map reading and/or potentially prevent injuries. Finally, running patterns are not affected to the same extent by fatigue when a map reading task is added.

  20. Some observations on loss of static strength due to fatigue cracks

    NASA Technical Reports Server (NTRS)

    Illg, Walter; Hardrath, Herbert F

    1955-01-01

    Static tensile tests were performed on simple notched specimens containing fatigue cracks. Four types of aluminum alloys were investigated: 2024-T3(formerly 24S-T3) and 7075-T6(formerly 75S-T6) in sheet form, and 2024-T4(formerly 24S-T4) and 7075-T6(formerly 75S-T6) in extruded form. The cracked specimens were tested statically under four conditions: unmodified and with reduced eccentricity of loading by three methods. Results of static tests on C-46 wings containing fatigue cracks are also reported.

  1. Development of detection technique for fatigue crack due to thermal stratification phenomena in RCS piping

    NASA Astrophysics Data System (ADS)

    Lee, Sam Lai; Kim, Byoung Chul; Lim, Hyung Taik; Park, Chi Sung; Lee, Jong Po; Chang, Kee Ok

    1993-01-01

    Area highly vulnerable to crack generation has been chosen by calculating the stress and deformation using computer program ANSYS considering thermal stratification phenomena, and for weld area, stress distribution has been investigated in order to perform the intensive ISI. The manufacturing of specimens with inside natural cracks has been done and basic procedure to manufacture mechanical fatigue crack by implanting fatigue cracked specimen into parent metal has been set up. This is a distribution that meets the requirement of ASME code Sec.XI, App.VII and VIII (1989 edition).

  2. An investigation of fatigue phenomenon in the upper limb muscle due to short duration pulses in an FES system

    NASA Astrophysics Data System (ADS)

    Naeem, Jannatul; Wong Azman, Amelia; Khan, Sheroz; Mohd Mustafah, Yasir

    2013-12-01

    Functional Electrical Stimulation (FES) is a method of artificially stimulating muscles or nerves in order to result in contraction or relaxation of muscles. Many studies have shown that FES system has helped patients to live a better lives especially those who are suffering from physical mobility. Unfortunately, one of the main limitations of an FES system besides of its high cost is largely due to muscle fatigue. Muscle fatigue will affect the training duration which could delay patients' recovery rate. In this paper, we analyzed the occurrence of this fatigue phenomenon in terms of stimulator parameters such as amplitude, frequency, pulse width and pulse shape. The objective of this investigation is to identify other key features of the FES system parameters in order to prolong the training duration among patients. The experiment has been done on a healthy person for the duration of one minute and later the muscles response will be observed. Resultant muscle response is recorded as force using force resistive sensor. The experimental results show muscles will get fatigue at a different rate as the frequency increases. The experiment also shows that the duty cycle is reciprocal to the resultant force.

  3. Reducing muscle fatigue due to functional electrical stimulation using random modulation of stimulation parameters.

    PubMed

    Thrasher, Adam; Graham, Geoffrey M; Popovic, Milos R

    2005-06-01

    A major limitation of many functional electrical stimulation (FES) applications is that muscles tend to fatigue very rapidly. It was hypothesized that FES-induced muscle fatigue could be reduced by randomly modulating the pulse frequency, amplitude, and pulse width in a range of +/-15%. Seven subjects with spinal-cord injuries participated in this study. FES was applied to quadriceps and tibialis anterior muscles using surface electrodes. Isometric force was measured, and the time for the force to drop by 3 dB (fatigue time) was compared between trials. Four different modes of FES were applied in random order: constant stimulation, randomized frequency, randomized amplitude, and randomized pulse width. There was no significant difference between the fatigue-time measurements for the four modes of stimulation (P=0.329). Therefore, random modulation appeared to have no effect. Based on an observed correlation between maximum force measurements and trial order, we concluded that having 10-min rest periods between trials was insufficient.

  4. An electromyographic-based test for estimating neuromuscular fatigue during incremental treadmill running.

    PubMed

    Camic, Clayton L; Kovacs, Attila J; Enquist, Evan A; VanDusseldorp, Trisha A; Hill, Ethan C; Calantoni, Austin M; Yemm, Allison J

    2014-12-01

    The purposes of the present study were two fold: (1) to determine if the model used for estimating the physical working capacity at the fatigue threshold (PWCFT) from electromyographic (EMG) amplitude data during incremental cycle ergometry could be applied to treadmill running to derive a new neuromuscular fatigue threshold for running, and (2) to compare the running velocities associated with the PWCFT, ventilatory threshold (VT), and respiratory compensation point (RCP). Fifteen college-aged subjects (21.5 ± 1.3 y, 68.7 ± 10.5 kg, 175.9 ± 6.7 cm) performed an incremental treadmill test to exhaustion with bipolar surface EMG signals recorded from the vastus lateralis. There were significant (p < 0.05) mean differences in running velocities between the VT (11.3 ± 1.3 km h(-1)) and PWCFT (14.0 ± 2.3 km h(-1)), VT and RCP (14.0 ± 1.8 km h(-1)), but not the PWCFT and RCP. The findings of the present study indicated that the PWCFT model could be applied to a single continuous, incremental treadmill test to estimate the maximal running velocity that can be maintained prior to the onset of neuromuscular fatigue. In addition, these findings suggested that the PWCFT, like the RCP, may be used to differentiate the heavy from severe domains of exercise intensity.

  5. An engineering method for estimating notch-size effect in fatigue tests on steel

    NASA Technical Reports Server (NTRS)

    Kuhn, Paul; Hardrath, Herbert F

    1952-01-01

    Neuber's proposed method of calculating a practical factor of stress concentration for parts containing notches of arbitrary size depends on the knowledge of a "new material constant" which can be established only indirectly. In this paper, the new constant has been evaluated for a large variety of steels from fatigue tests reported in the literature, attention being confined to stresses near the endurance limit. Reasonably satisfactory results were obtained with the assumption that the constant depends only on the tensile strength of the steel. Even in cases where the notches were cracks of which only the depth was known, reasonably satisfactory agreement was found between calculated and experimental factors. It is also shown that the material constant can be used in an empirical formula to estimate the size effect on unnotched specimens tested in bending fatigue.

  6. Self-motion magnitude estimation during linear oscillation - Changes with head orientation and following fatigue

    NASA Technical Reports Server (NTRS)

    Parker, D. E.; Wood, D. L.; Gulledge, W. L.; Goodrich, R. L.

    1979-01-01

    Two types of experiments concerning the estimated magnitude of self-motion during exposure to linear oscillation on a parallel swing are described in this paper. Experiment I examined changes in magnitude estimation as a function of variation of the subject's head orientation, and Experiments II a, II b, and II c assessed changes in magnitude estimation performance following exposure to sustained, 'intense' linear oscillation (fatigue-inducting stimulation). The subjects' performance was summarized employing Stevens' power law R = k x S to the nth, where R is perceived self-motion magnitude, k is a constant, S is amplitude of linear oscillation, and n is an exponent). The results of Experiment I indicated that the exponents, n, for the magnitude estimation functions varied with head orientation and were greatest when the head was oriented 135 deg off the vertical. In Experiments II a-c, the magnitude estimation function exponents were increased following fatigue. Both types of experiments suggest ways in which the vestibular system's contribution to a spatial orientation perceptual system may vary. This variability may be a contributing factor to the development of pilot/astronaut disorientation and may also be implicated in the occurrence of motion sickness.

  7. HIV Due to Female Sex Work: Regional and Global Estimates

    PubMed Central

    Prüss-Ustün, Annette; Wolf, Jennyfer; Driscoll, Tim; Degenhardt, Louisa; Neira, Maria; Calleja, Jesus Maria Garcia

    2013-01-01

    Introduction Female sex workers (FSWs) are at high risk of HIV infection. Our objective was to determine the proportion of HIV prevalence in the general female adult population that is attributable to the occupational exposure of female sex work, due to unprotected sexual intercourse. Methods Population attributable fractions of HIV prevalence due to female sex work were estimated for 2011. A systematic search was conducted to retrieve required input data from available sources. Data gaps of HIV prevalence in FSWs for 2011 were filled using multilevel modeling and multivariate linear regression. The fraction of HIV attributable to female sex work was estimated as the excess HIV burden in FSWs deducting the HIV burden in FSWs due to injecting drug use. Results An estimated fifteen percent of HIV in the general female adult population is attributable to (unsafe) female sex work. The region with the highest attributable fraction is Sub Saharan Africa, but the burden is also substantial for the Caribbean, Latin America and South and Southeast Asia. We estimate 106,000 deaths from HIV are a result of female sex work globally, 98,000 of which occur in Sub-Saharan Africa. If HIV prevalence in other population groups originating from sexual contact with FSWs had been considered, the overall attributable burden would probably be much larger. Discussion Female sex work is an important contributor to HIV transmission and the global HIV burden. Effective HIV prevention measures exist and have been successfully targeted at key populations in many settings. These must be scaled up. Conclusion FSWs suffer from high HIV burden and are a crucial core population for HIV transmission. Surveillance, prevention and treatment of HIV in FSWs should benefit both this often neglected vulnerable group and the general population. PMID:23717432

  8. Low cycle fatigue numerical estimation of a high pressure turbine disc for the AL-31F jet engine

    NASA Astrophysics Data System (ADS)

    Spodniak, Miroslav; Klimko, Marek; Hocko, Marián; Žitek, Pavel

    This article deals with the description of an approximate numerical estimation approach of a low cycle fatigue of a high pressure turbine disc for the AL-31F turbofan jet engine. The numerical estimation is based on the finite element method carried out in the SolidWorks software. The low cycle fatigue assessment of a high pressure turbine disc was carried out on the basis of dimensional, shape and material disc characteristics, which are available for the particular high pressure engine turbine. The method described here enables relatively fast setting of economically feasible low cycle fatigue of the assessed high pressure turbine disc using a commercially available software. The numerical estimation of accuracy of a low cycle fatigue depends on the accuracy of required input data for the particular investigated object.

  9. Rate-dependent impairments in repetitive finger movements in patients with Parkinson's disease are not due to peripheral fatigue.

    PubMed

    Stegemöller, Elizabeth L; Allen, David P; Simuni, Tanya; MacKinnon, Colum D

    2010-09-20

    Performance of repetitive finger movements is an important clinical measure of disease severity in patients with Parkinson's disease (PD) and is associated with a dramatic deterioration in performance at movement rates near 2 Hz and above. The mechanisms contributing to this rate-dependent movement impairment are poorly understood. Since clinical and experimental testing of these movements involve prolonged repetition of movement, a loss of force-generating capacity due to peripheral fatigue may contribute to performance deterioration. This study examined the contribution of peripheral fatigue to the performance of unconstrained index finger flexion movements by measuring maximum voluntary contractions (MVC) immediately before and after repetitive finger movements in patients with PD (both off- and on-medication) and matched control subjects. Movement performance was quantified using finger kinematics, maximum force production, and electromyography (EMG). The principal finding was that peak force and EMG activity during the MVC did not significantly change from the pre- to post-movement task in patients with PD despite the marked deterioration in movement performance of repetitive finger movements. These findings show that the rate-dependent deterioration of repetitive finger movements in PD cannot be explained by a loss of force-generating capacity due to peripheral fatigue, and further suggest that mechanisms contributing to impaired isometric force production in PD are different from those that mediate impaired performance of high-rate repetitive movements.

  10. Changes of the balancing between anode and cathode due to fatigue in commercial lithium-ion cells

    NASA Astrophysics Data System (ADS)

    Kleiner, Karin; Jakes, Peter; Scharner, Sebastian; Liebau, Verena; Ehrenberg, Helmut

    2016-06-01

    The electrode balancing defines the state of charge (SoC) of a lithium-ion cell and is a crucial point considering lifetime and safe operation. The electrode balancing varies during fatigue which results in changes of the individual electrode potentials for fixed (dis-)charge voltages of the full-cell. Therefore the materials are cycled closer or beyond their electrochemical (meta-)stability window. This leads to accelerated degradation reactions or even to safety problems. The origin of the changes in the cell balancing is the limited amount of mobile lithium, which decreases during cycling due to the loss of lithiated active material a), the reduction of accessible lattice sites in the active materials b) and the loss of active lithium outside the electrodes c). In most of the commercial cells a) and b) can be attributed to the cathode, c) occurs due to reactions on the anode surface. Changes in the electrode balancing of three differently fatigued 7 Ah lithium-ion cells are investigated by electrochemical cycling of full- and half-cells, assembled from cell components of the fatigued 7 Ah cells. Based on these results the observed performance drop is assigned to a), b) or c) mentioned above and the capacity losses are quantified.

  11. Dynamic Elbow Flexion Force Estimation Through a Muscle Twitch Model and sEMG in a Fatigue Condition.

    PubMed

    Na, Youngjin; Kim, Jung

    2016-11-14

    We propose a joint force estimation method to compute elbow flexion force using surface electromyogram (sEMG) considering time-varying effects in a fatigue condition. Muscle fatigue is a major cause inducing sEMG changes with respect to time over long periods and repetitive contractions. The proposed method composed the muscle-twitch model representing the force generated by a single spike and the spikes extracted from sEMG. In this study, isometric contractions at six different joint angles (ten subjects) and dynamic contractions with constant velocity (six subjects) were performed under non-fatigue and fatigue conditions. Performance of the proposed method was evaluated and compared with that of previous methods using mean absolute value (MAV). The proposed method achieved average 6.7±2.8 %RMSE for isometric contraction and 15.6±24.7 %RMSE for isokinetic contraction under fatigue condition with more accurate results than the previous methods.

  12. Hydrological model uncertainty due to spatial evapotranspiration estimation methods

    NASA Astrophysics Data System (ADS)

    Yu, Xuan; Lamačová, Anna; Duffy, Christopher; Krám, Pavel; Hruška, Jakub

    2016-05-01

    Evapotranspiration (ET) continues to be a difficult process to estimate in seasonal and long-term water balances in catchment models. Approaches to estimate ET typically use vegetation parameters (e.g., leaf area index [LAI], interception capacity) obtained from field observation, remote sensing data, national or global land cover products, and/or simulated by ecosystem models. In this study we attempt to quantify the uncertainty that spatial evapotranspiration estimation introduces into hydrological simulations when the age of the forest is not precisely known. The Penn State Integrated Hydrologic Model (PIHM) was implemented for the Lysina headwater catchment, located 50°03‧N, 12°40‧E in the western part of the Czech Republic. The spatial forest patterns were digitized from forest age maps made available by the Czech Forest Administration. Two ET methods were implemented in the catchment model: the Biome-BGC forest growth sub-model (1-way coupled to PIHM) and with the fixed-seasonal LAI method. From these two approaches simulation scenarios were developed. We combined the estimated spatial forest age maps and two ET estimation methods to drive PIHM. A set of spatial hydrologic regime and streamflow regime indices were calculated from the modeling results for each method. Intercomparison of the hydrological responses to the spatial vegetation patterns suggested considerable variation in soil moisture and recharge and a small uncertainty in the groundwater table elevation and streamflow. The hydrologic modeling with ET estimated by Biome-BGC generated less uncertainty due to the plant physiology-based method. The implication of this research is that overall hydrologic variability induced by uncertain management practices was reduced by implementing vegetation models in the catchment models.

  13. The use of ultrasonic signals and optical method to estimate the damage of materials after fatigue loading

    NASA Astrophysics Data System (ADS)

    Mishakin, V. V.; Mitenkov, F. M.; Klyushnikov, V. A.; Danilova, N. V.

    2010-12-01

    The influence of fatigue load of steels on parameters of ultrasonic and microplastic characteristics has been studied. A phenomenological theory, which connects process of damage accumulation (before appearance of crack) under fatigue loading with acoustic parameters and microplastic parameters, has been developed. Experimental studies showed that the combination of nondestructive methods of control (acoustical and optical) allows one to estimate the state of materials at an early stage of destruction in both low-cycle and high-cycle areas.

  14. Bilateral Femoral Neck Fatigue Fracture due to Osteomalacia Secondary to Celiac Disease: Report of Three Cases.

    PubMed

    Selek, Ozgur; Memisoglu, Kaya; Selek, Alev

    2015-08-01

    Bilateral non traumatic femoral neck fatigue fracture is a rare condition usually occurring secondary to medical conditions such as pregnancy, pelvic irradiation, corticosteroid exposure, chronic renal failure and osteomalacia. In this report, we present three young female patients with bilateral femoral neck fracture secondary to osteomalacia. The underlying cause of osteomalacia was Celiac disease in all patients. The patients were treated with closed reduction and internal fixation with cannulated lag screws. They were free of pain and full weight bearing was achieved at three months. There were no complications, avascular necrosis and nonunion during the follow up period. In patients with bone pain, non traumatic fractures and muscle weakness, osteomalacia should be kept in mind and proper diagnostic work-up should be performed to identify the underlying cause of osteomalacia such as celiac disease.

  15. Probabilistic analysis and fatigue damage assessment of offshore mooring system due to non-Gaussian bimodal tension processes

    NASA Astrophysics Data System (ADS)

    Chang, Anteng; Li, Huajun; Wang, Shuqing; Du, Junfeng

    2017-08-01

    Both wave-frequency (WF) and low-frequency (LF) components of mooring tension are in principle non-Gaussian due to nonlinearities in the dynamic system. This paper conducts a comprehensive investigation of applicable probability density functions (PDFs) of mooring tension amplitudes used to assess mooring-line fatigue damage via the spectral method. Short-term statistical characteristics of mooring-line tension responses are firstly investigated, in which the discrepancy arising from Gaussian approximation is revealed by comparing kurtosis and skewness coefficients. Several distribution functions based on present analytical spectral methods are selected to express the statistical distribution of the mooring-line tension amplitudes. Results indicate that the Gamma-type distribution and a linear combination of Dirlik and Tovo-Benasciutti formulas are suitable for separate WF and LF mooring tension components. A novel parametric method based on nonlinear transformations and stochastic optimization is then proposed to increase the effectiveness of mooring-line fatigue assessment due to non-Gaussian bimodal tension responses. Using time domain simulation as a benchmark, its accuracy is further validated using a numerical case study of a moored semi-submersible platform.

  16. Estimation of operators' fatigue using optical methods for determination of pupil activity.

    PubMed

    Różanowski, Krzysztof; Bernat, Michał; Kamińska, Agnieszka

    2015-01-01

    The purpose of this study was to develop and initially validate an objective, yet quick, method for assessment of human fatigue. This aim can be achieved by the use of an optical, non-contact method of analysis of pupil activity. The study involved 2 phenomena typical for the behavior of the human pupil: pupillary reflex and pupillary movements. The 1st phenomenon is related to the pupillary light reflex (PLR), which presents the results of physiological adaptation mechanisms of the human eye. The pupillary unrest index (PUI) is an additional parameter referring to the tendency for instability of the pupil. Indicators of these 2 mechanisms were assessed under the same experimental laboratory conditions. Assessment was conducted on a group of volunteers (N = 10) during 4 controlled series of measurements performed at night. Pupillary reflex parameters associated with PLR and pupillary unrest index (PUI) were recorded using F²D Fit-For-Duty, a commercially available system made by AMTech Pupilknowlogy GmbH. Baseline pupil diameter, oscillations, reflex latency, maximum reaction time, pupil constriction time, pupil dilation time, and constriction amplitude were recorded. As a result of the study, we were able to demonstrate correlation and confirm the usefulness of PLR and PST methods in the assessment of sleep deprivation. Parameters of PLR that may indicate human fatigue were identified. The effect of light impulse sequences on the dynamics of pupillary reflex and the relationship between PUI (pupillary unrest index) measurement duration and sleepiness assessment validity, were assessed. The results of the pilot studies were sufficient to develop minimum requirements for a PLR sensor that would be capable of estimating the level of fatigue with accuracy of a PUI method, but at a 5 times faster rate. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

  17. Fatigue life estimation procedures for the endurance of a cardiac valve prosthesis: stress/life and damage-tolerant analyses.

    PubMed

    Ritchie, R O; Lubock, P

    1986-05-01

    Projected fatigue life analyses are performed to estimate the endurance of a cardiac valve prosthesis under physiological environmental and mechanical conditions. The analyses are conducted using both the classical stress-strain/life and the fracture mechanics-based damage-tolerant approaches, and provide estimates of expected life in terms of initial flaw sizes which may pre-exist in the metal prior to the valve entering service. The damage-tolerant analysis further is supplemented by consideration of the question of "short cracks," which represents a developing area in metal fatigue research, not commonly applied to data in standard engineering design practice.

  18. Genetic and Environmental Influences on Disability Pension Due To Mental Diagnoses: Limited Importance of Major Depression, Generalized Anxiety, and Chronic Fatigue.

    PubMed

    Narusyte, Jurgita; Ropponen, Annina; Alexanderson, Kristina; Svedberg, Pia

    2016-02-01

    Previous research indicates that liability to disability pension (DP) due to mental diagnoses is moderately influenced by genetic factors. This study investigates whether genetic contributions to the liability to DP due to mood and neurotic diagnoses overlap with the genetic influences on major depression (MD), generalized anxiety disorder (GAD), or chronic fatigue (CF). A prospective cohort study including 9,985 female twins born in Sweden 1933-1958. The presence of MD, GAD, and CF was assessed by computer-assisted telephone interviews conducted in 1998-2002. Data on DP due to mood and neurotic diagnoses were obtained from nationwide registers for the years 1998-2010. Common genetic and environmental influences on the phenotypes were estimated by applying structural equation modeling. The prevalence of MD/GAD was 30%, CF 8%, and DP due to mood and neurotic diagnoses 3% in 2010. Genetic effects on MD/GAD explained 31% of the total genetic variation in DP, whereas genetic contributions in common with CF were small and not significant. The majority of the total non-shared environmental variance in DP (85%) was explained by the factors that were unique to DP. Large proportions of genetic and non-shared environmental influences in DP due to mood and neurotic diagnoses were not explained by the contributions from MD/GAD or CF. The results suggest that the process leading to DP is complex and influenced by factors other than those related to the disorder underlying DP.

  19. Mental fatigue and working memory load estimation: interaction and implications for EEG-based passive BCI.

    PubMed

    Roy, Raphaelle N; Bonnet, Stephane; Charbonnier, Sylvie; Campagne, Aurelie

    2013-01-01

    Current mental state monitoring systems, a.k.a. passive brain-computer interfaces (pBCI), allow one to perform a real-time assessment of an operator's cognitive state. In EEG-based systems, typical measurements for workload level assessment are band power estimates in several frequency bands. Mental fatigue, arising from growing time-on-task (TOT), can significantly affect the distribution of these band power features. However, the impact of mental fatigue on workload (WKL) assessment has not yet been evaluated. With this paper we intend to help fill in this lack of knowledge by analyzing the influence of WKL and TOT on EEG band power features, as well as their interaction and its impact on classification performance. Twenty participants underwent an experiment that modulated both their WKL (low/high) and time spent on the task (short/long). Statistical analyses were performed on the EEG signals, behavioral and subjective data. They revealed opposite changes in alpha power distribution between WKL and TOT conditions, as well as a decrease in WKL level discriminability with increasing TOT in both number of statistical differences in band power and classification performance. Implications for pBCI systems and experimental protocol design are discussed.

  20. Simplified rotor load models and fatigue damage estimates for offshore wind turbines.

    PubMed

    Muskulus, M

    2015-02-28

    The aim of rotor load models is to characterize and generate the thrust loads acting on an offshore wind turbine. Ideally, the rotor simulation can be replaced by time series from a model with a few parameters and state variables only. Such models are used extensively in control system design and, as a potentially new application area, structural optimization of support structures. Different rotor load models are here evaluated for a jacket support structure in terms of fatigue lifetimes of relevant structural variables. All models were found to be lacking in accuracy, with differences of more than 20% in fatigue load estimates. The most accurate models were the use of an effective thrust coefficient determined from a regression analysis of dynamic thrust loads, and a novel stochastic model in state-space form. The stochastic model explicitly models the quasi-periodic components obtained from rotational sampling of turbulent fluctuations. Its state variables follow a mean-reverting Ornstein-Uhlenbeck process. Although promising, more work is needed on how to determine the parameters of the stochastic model and before accurate lifetime predictions can be obtained without comprehensive rotor simulations. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  1. Increased resistance to fatigue in creatine kinase deficient muscle is not due to improved contractile economy.

    PubMed

    ter Veld, Frank; Nicolay, Klaas; Jeneson, Jeroen A L

    2006-06-01

    There has been speculation on the origin of the increased endurance of skeletal muscles in creatine kinase (CK)-deficient mice. Important factors that have been raised include the documented increased mitochondrial capacity and alterations in myosin heavy chain (MyHC) isoform composition in CK-deficient muscle. More recently, the absence of inorganic phosphate release from phosphocreatine hydrolysis in exercising CK-deficient muscle has been postulated to contribute to the lower fatigueability in skeletal muscle. In this study, we tested the hypothesis that the reported shift in MyHC composition to slower isoforms in CK-deficient muscle leads to a decrease in oxygen cost of twitch performance. To that aim, extensor digitorum longus (EDL) and soleus (SOL) muscles were isolated from wild-type (WT) and knock-out mice deficient in the cytoplasmic muscle-type and sarcomeric mitochondrial isoenzymes of CK, and oxygen consumption per twitch time-tension-integral (TTI) was measured. The results show that the adaptive response to loss of CK function does not involve any major change to contractile economy of skeletal muscle.

  2. Fatigue failure kinetics and structural changes in lead-free interconnects due to mechanical and thermal cycling

    NASA Astrophysics Data System (ADS)

    Fiedler, Brent Alan

    the interface was found to be caused by dislocation pile-ups at the IMC when the plastic zone ahead of the crack tip reached this interface. In temperature cycling testing, strains arose within the interconnect due to CTE mismatch between the solder and IMC. The substrates had matched CTE for all specimens in this research. Because of this, all the temperature cycling cracks were observed at interfaces, generally between the solder and IMC. Additionally, real-time electrical resistance may be a useful non-destructive evaluation (NDE) tool for the empirical observation of fatigue cracking in ball-grid arrays (BGA) during both mechanical and temperature cycling tests.

  3. Accounting for reporting fatigue is required to accurately estimate incidence in voluntary reporting health schemes.

    PubMed

    Gittins, Matthew; McNamee, Roseanne; Holland, Fiona; Carter, Lesley-Anne

    2017-01-01

    Accurate estimation of the true incidence of ill-health is a goal of many surveillance systems. In surveillance schemes including zero reporting to remove ambiguity with nonresponse, reporter fatigue might increase the likelihood of a false zero case report in turn underestimating the true incidence rate and creating a biased downward trend over time. Multilevel zero-inflated negative binomial models were fitted to incidence case reports of three surveillance schemes running between 1996 and 2012 in the United Kingdom. Estimates of the true annual incidence rates were produced by weighting the reported number of cases by the predicted excess zero rate in addition to the within-scheme standard adjustment for response rate and the participation rate. Time since joining the scheme was associated with the odds of excess zero case reports for most schemes, resulting in weaker calendar trends. Estimated incidence rates (95% confidence interval) per 100,000 person years, were approximately doubled to 30 (21-39), 137 (116-157), 33 (27-39), when excess zero-rate adjustment was applied. If we accept that excess zeros are in reality nonresponse by busy reporters, then usual estimates of incidence are likely to be significantly underestimated and previously thought strong downward trends overestimated. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Fatigue life estimation program for Part 23 airplanes, `AFS.FOR`

    SciTech Connect

    Kaul, S.K.

    1993-12-31

    The purpose of this paper is to introduce to the general aviation industry a computer program which estimates the safe fatigue life of any Federal Aviation Regulation (FAR) Part 23 airplane. The algorithm uses the methodology (Miner`s Linear Cumulative Damage Theory) and the various data presented in the Federal Aviation Administration (FAA) Report No. AFS-120-73-2, dated May 1973. The program is written in FORTRAN 77 language and is executable on a desk top personal computer. The program prompts the user for the input data needed and provides a variety of options for its intended use. The program is envisaged to be released through issuance of a FAA report, which will contain the appropriate comments, instructions, warnings and limitations.

  5. The Dmax method is a valid procedure to estimate physical working capacity at fatigue threshold.

    PubMed

    Riffe, Joshua J; Stout, Jeffrey R; Fukuda, David H; Robinson, Edward H; Miramonti, Amelia A; Beyer, Kyle S; Wang, Ran; Church, David D; Muddle, Tyler W D; Hoffman, Jay R

    2017-03-01

    The purpose of this study was to determine the validity of the maximal distance-electromyography (Dmax-EMG) method for estimating physical working capacity at fatigue threshold (PWCFT ). Twenty-one men and women (age 22.9 ± 3.0 years) volunteered to perform 12 sessions of high-intensity interval training (HIIT) over 4 weeks. Before and after HIIT training, a graded exercise test (GXT) was used to estimate PWCFT using the Dmax method and the original (ORG) method. There was a significant increase in PWCFT for both ORG (+10.6%) and Dmax (+12.1%) methods, but no significant difference in the change values between methods. Further, Bland-Altman analyses resulted in non-significant biases (ORG-Dmax) between methods at pre-HIIT (-6.4 ± 32.5 W; P > 0.05) and post-HIIT (-4.2 ± 33.1 W; P > 0.05). The Dmax method is sensitive to training and is a valid method for estimating PWCFT in young men and women. Muscle Nerve 55: 344-349, 2017. © 2016 Wiley Periodicals, Inc.

  6. Vortex-induced vibration effect on fatigue life estimate of turbine blades

    NASA Astrophysics Data System (ADS)

    Lau, Y. L.; Leung, R. C. K.; So, R. M. C.

    2007-11-01

    An analysis of a turbine blade fatigue life that includes the physics of fluid-structure interaction on the high cycle fatigue (HCF) life estimate of turbine blades is carried out. The rotor wake excitation is modeled by rows of Karman vortices superimposed on an inviscid uniform flow. The vortex-induced vibration problem is modeled by a linear cascade composed of five turbine blades and the coupled Euler and structural dynamics equations are numerically solved using a time-marching boundary element technique. The analysis can be applied to any blade geometries; it is not limited to the blade geometry considered here. Two major design parameters have been identified; the ratio of blade spacing to blade chord length s/ c of the stator, and the normalized frequency parameter c/ d which is related to the wake passing frequency of the rotor. For a rigid cascade, it is found that aerodynamic resonance prevails at the resonant c/ d values corresponding to an isolated blade while s/ c is responsible for the level of the aerodynamic response. If the central blades were elastic, the parameter s/ c plays a different role in the fluid-structure interaction problem. With a c/ d that could lead to structural resonance for an isolated blade, changing s/ c would stabilize the aerodynamic and structural response of the elastic blade in a cascade. On the contrary, an improper choice of s/ c might turn the elastic blade response into structural resonance even though the oncoming c/ d is non-resonant. The results of the nonlinear effects of c/ d and s/ c could be used together with the Campbell diagram to obtain an improved HCF design of rotor-stator pair.

  7. Estimation of Reduction in Airspace Capacity Due to Convective Weather

    NASA Technical Reports Server (NTRS)

    Sheth, Kapil; Sridhar, Banavar; Namjoshi, Leena

    2006-01-01

    Severe convective weather routinely disrupts normal flow of air traffic in the United States' National Airspace System (NAS). Over the last decade, severe weather has been the most significant cause, accounting for over 70% of air traffic delays in the NAS. Flights incur modification in their nominal routes due to the presence of severe weather, and hence, suffer increased delays. These delays contribute to increased burden on airlines due to extra fuel costs and missed schedules for connecting flights. In this paper, the reduction in air space capacity and the associated air traffic delays due to severe convective weather will be investigated.

  8. Erasing Errors due to Alignment Ambiguity When Estimating Positive Selection

    PubMed Central

    Redelings, Benjamin

    2014-01-01

    Current estimates of diversifying positive selection rely on first having an accurate multiple sequence alignment. Simulation studies have shown that under biologically plausible conditions, relying on a single estimate of the alignment from commonly used alignment software can lead to unacceptably high false-positive rates in detecting diversifying positive selection. We present a novel statistical method that eliminates excess false positives resulting from alignment error by jointly estimating the degree of positive selection and the alignment under an evolutionary model. Our model treats both substitutions and insertions/deletions as sequence changes on a tree and allows site heterogeneity in the substitution process. We conduct inference starting from unaligned sequence data by integrating over all alignments. This approach naturally accounts for ambiguous alignments without requiring ambiguously aligned sites to be identified and removed prior to analysis. We take a Bayesian approach and conduct inference using Markov chain Monte Carlo to integrate over all alignments on a fixed evolutionary tree topology. We introduce a Bayesian version of the branch-site test and assess the evidence for positive selection using Bayes factors. We compare two models of differing dimensionality using a simple alternative to reversible-jump methods. We also describe a more accurate method of estimating the Bayes factor using Rao-Blackwellization. We then show using simulated data that jointly estimating the alignment and the presence of positive selection solves the problem with excessive false positives from erroneous alignments and has nearly the same power to detect positive selection as when the true alignment is known. We also show that samples taken from the posterior alignment distribution using the software BAli-Phy have substantially lower alignment error compared with MUSCLE, MAFFT, PRANK, and FSA alignments. PMID:24866534

  9. Ultrasonic Evaluation of Fatigue Damage

    NASA Astrophysics Data System (ADS)

    Bayer, P.; Singher, L.; Notea, A.

    2004-02-01

    Despite the fact that most engineers and designers are aware of fatigue, many severe breakdowns of industrial plant and machinery still occur due to fatigue. In effect, it's been estimated that fatigue causes at least 80% of the failures in modern engineering components. From an operational point of view, the detection of fatigue damage, preferably at a very early stage, is a critically important consideration in order to prevent possible catastrophic equipment failure and associated losses. This paper describes the investigation involving the use of ultrasonic waves as a potential tool for early detection of fatigue damage. The parameters investigated were the ultrasonic wave velocities (longitudinal and transverse waves) and attenuation coefficient before fatigue damage and after progressive stages of fatigue. Although comparatively small uncertainties were observed, the feasibility of utilizing the velocity of ultrasonic waves as a fatigue monitor was barely substantiated within actual research conditions. However, careful measurements of the ultrasonic attenuation parameter had demonstrated its potential to provide an early assessment of damage during fatigue.

  10. Estimating lake susceptibility to acidification due to acid deposition.

    Treesearch

    Dale S. Nichols

    1990-01-01

    Presents a graphical procedure for evaluating the same sensitivity of lakes to acidification due to acid deposition. The procedure is based on empirical relationships between sulfur (and in some cases nitrogen) deposition rates and lake pH, acid-neutralizing capacity, base cation concentrations, and the amount of runoff.

  11. A novel closure based approach for fatigue crack length estimation using the acoustic emission technique in structural health monitoring applications

    NASA Astrophysics Data System (ADS)

    Gagar, Daniel; Foote, Peter; Irving, Philip

    2014-10-01

    Use of Acoustic Emission (AE) for detecting and locating fatigue cracks in metallic structures is widely reported but studies investigating its potential for fatigue crack length estimation are scarce. Crack growth information enables prediction of the remaining useful life of a component using well established fracture mechanics principles. Hence, the prospects of AE for use in structural health monitoring applications would be significantly improved if it could be demonstrated not only as a means of detecting crack growth but also for estimation of crack lengths. A new method for deducing crack length has been developed based on correlations between AE signals generated during fatigue crack growth and corresponding cyclic loads. A model for crack length calculation was derived empirically using AE data generated during fatigue crack growth tests in 2 mm thick SEN aluminium 2014 T6 specimens subject to a tensile stress range of 52 MPa and an R ratio of 0.1. The model was validated using AE data generated independently in separate tests performed with a stress range of 27 MPa. The results showed that predictions of crack lengths over a range of 10 mm to 80 mm can be obtained with the mean of the normalised absolute errors ranging between 0.28 and 0.4. Predictions were also made using existing AE feature-based methods and the results compared to those obtained with the novel approach developed.

  12. High-Throughput Computation and the Applicability of Monte Carlo Integration in Fatigue Load Estimation of Floating Offshore Wind Turbines

    SciTech Connect

    Graf, Peter A.; Stewart, Gordon; Lackner, Matthew; Dykes, Katherine; Veers, Paul

    2016-05-01

    Long-term fatigue loads for floating offshore wind turbines are hard to estimate because they require the evaluation of the integral of a highly nonlinear function over a wide variety of wind and wave conditions. Current design standards involve scanning over a uniform rectangular grid of metocean inputs (e.g., wind speed and direction and wave height and period), which becomes intractable in high dimensions as the number of required evaluations grows exponentially with dimension. Monte Carlo integration offers a potentially efficient alternative because it has theoretical convergence proportional to the inverse of the square root of the number of samples, which is independent of dimension. In this paper, we first report on the integration of the aeroelastic code FAST into NREL's systems engineering tool, WISDEM, and the development of a high-throughput pipeline capable of sampling from arbitrary distributions, running FAST on a large scale, and postprocessing the results into estimates of fatigue loads. Second, we use this tool to run a variety of studies aimed at comparing grid-based and Monte Carlo-based approaches with calculating long-term fatigue loads. We observe that for more than a few dimensions, the Monte Carlo approach can represent a large improvement in computational efficiency, but that as nonlinearity increases, the effectiveness of Monte Carlo is correspondingly reduced. The present work sets the stage for future research focusing on using advanced statistical methods for analysis of wind turbine fatigue as well as extreme loads.

  13. Estimated incident cost savings in shipping due to inspections.

    PubMed

    Knapp, Sabine; Bijwaard, Govert; Heij, Christiaan

    2011-07-01

    The effectiveness of safety inspections of ships has been analysed from various angles, but until now, relatively little attention has been given to translate risk reduction into incident cost savings. This paper provides a monetary quantification of the cost savings that can be attributed to port state control inspections and industry vetting inspections. The dataset consists of more than half a million ship arrivals between 2002 and 2007 and contains inspections of port state authorities in the USA and Australia and of three industry vetting regimes. The effect of inspections in reducing the risk of total loss accidents is estimated by means of duration models, in terms of the gained probability of survival. The monetary benefit of port state control inspections is estimated to range, on average, from about 70 to 190 thousand dollars, with median values ranging from about 20 to 45 thousand dollars. Industry inspections have even higher benefits, especially for tankers. The savings are in general higher for older and larger vessels, and also for vessels with undefined flag and unknown classification society. As inspection costs are relatively low in comparison to potential cost savings, the results underline the importance of determining ships with relatively high risk of total loss. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. A fracture mechanics approach for estimating fatigue crack initiation in carbon and low-alloy steels in LWR coolant environments

    SciTech Connect

    Park, H. B.; Chopra, O. K.

    2000-04-10

    A fracture mechanics approach for elastic-plastic materials has been used to evaluate the effects of light water reactor (LWR) coolant environments on the fatigue lives of carbon and low-alloy steels. The fatigue life of such steel, defined as the number of cycles required to form an engineering-size crack, i.e., 3-mm deep, is considered to be composed of the growth of (a) microstructurally small cracks and (b) mechanically small cracks. The growth of the latter was characterized in terms of {Delta}J and crack growth rate (da/dN) data in air and LWR environments; in water, the growth rates from long crack tests had to be decreased to match the rates from fatigue S-N data. The growth of microstructurally small cracks was expressed by a modified Hobson relationship in air and by a slip dissolution/oxidation model in water. The crack length for transition from a microstructurally small crack to a mechanically small crack was based on studies on small crack growth. The estimated fatigue S-N curves show good agreement with the experimental data for these steels in air and water environments. At low strain amplitudes, the predicted lives in water can be significantly lower than the experimental values.

  15. Effects of fatigue due to contraction of evertor muscles on the ankle joint position sense in male soccer players.

    PubMed

    Mohammadi, Farshid; Roozdar, Arash

    2010-04-01

    The high incidence of ankle sprains that occur later in matches suggests that fatigue may contribute to altered neuromuscular control of the ankle. Moreover, deficits in ankle joint position sense (JPS) were seen in patients with a history of recurrent ankle sprains. It has been hypothesized that ankle sprains may be related to altered ankle JPS as a consequence of fatigue. To evaluate if fatiguing contractions of evertor muscles alter the ankle JPS. Controlled laboratory study. Thirty-six soccer players (age, 24.7 +/- 1.3 years; height, 183.7 +/- 8.2 cm; weight, 78.9 +/- 7.9 kg) were recruited. Subjects were asked to recognize 2 positions (15 degrees of inversion and maximal active inversion minus 5 degrees ) for 2 conditions: normal and fatigue. Muscular fatigue was induced in evertor muscles of the dominant leg by using isometric contractions. The average of the absolute and variable errors of 3 trials were recorded for both fatigue and nonfatigue conditions. A matched control group of 36 soccer players (age, 23.9 +/- 0.9 years; height, 181.2 +/- 6.9 cm; weight, 77.8 +/- 6.5 kg) was asked to recognize the same positions, before a soccer match and after 45 minutes of playing, and their same scores were recorded. Finally, results of the 2 groups were compared. There was significant decrease in subjects' ability to recognize passive and active repositioning of their ankle after a fatigue protocol (P <.001). Passive and active JPS were reduced after playing (P <.001). There was no significant difference between 2 groups in the results of JPS before and after the intervention (P > .1). The acuity of the ankle JPS is reduced subsequent to a fatigue protocol and after a soccer match. Evaluation of athletes' ankle JPS before returning to physical activity may prevent further injuries.

  16. Fatigue life estimation for different notched specimens based on the volumetric approach

    NASA Astrophysics Data System (ADS)

    Zehsaz, M.; Hassanifard, S.; Esmaeili, F.

    2010-06-01

    In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fatigue tests of mentioned specimens have been conducted on the 250kN servo-hydraulic Zwick/Amsler fatigue testing machine with the frequency of 10Hz. The fatigue lives of the specimens have also been predicted based on the available smooth S-N curve of Al2024-T3 and also the amounts of notch strength reduction factor which have been obtained from volumetric, Neuber and Peterson methods. The values of stress and strain around the notch roots are required to predict the fatigue life of notched specimens, so Ansys finite element code has been used and non-linear analyses have been performed to obtain the stress and strain distributions around the notches. The plastic deformations of the material have been simulated using multi-linear kinematic hardening and cyclic stress-strain relation. The work here shows that the volumetric approach does a very good job for predicting the fatigue life of the notched specimens.

  17. A Micromechanics-Based Method for Multiscale Fatigue Prediction

    NASA Astrophysics Data System (ADS)

    Moore, John Allan

    An estimated 80% of all structural failures are due to mechanical fatigue, often resulting in catastrophic, dangerous and costly failure events. However, an accurate model to predict fatigue remains an elusive goal. One of the major challenges is that fatigue is intrinsically a multiscale process, which is dependent on a structure's geometric design as well as its material's microscale morphology. The following work begins with a microscale study of fatigue nucleation around non- metallic inclusions. Based on this analysis, a novel multiscale method for fatigue predictions is developed. This method simulates macroscale geometries explicitly while concurrently calculating the simplified response of microscale inclusions. Thus, providing adequate detail on multiple scales for accurate fatigue life predictions. The methods herein provide insight into the multiscale nature of fatigue, while also developing a tool to aid in geometric design and material optimization for fatigue critical devices such as biomedical stents and artificial heart valves.

  18. [Estimation of fatigue state in patient with CFS using actigraph and R-R interval power spectrum analysis].

    PubMed

    Tajima, Seiki; Kuratsune, Hirohiko; Yamaguti, Kouzi; Takahashi, Ayumi; Takashima, Shoko; Watanabe, Yasuyoshi; Nishizawa, Yoshiki

    2007-06-01

    In this study, we try to estimate the fatigue state using actigraphy and R-R interval power spectrum analysis. Actigraphy analysis showed that mean awake activity was decreased and duration of sleep was prolonged in patients with chronic fatigue syndrome (CFS), significantly (p < 0.001). Both of sleep episodes in wake period and wake episodes in sleep period were significantly increased in CFS patients in comparison with healthy volunteers (p < 0.001) In autonomic nerve analysis, sleep/awake ratio of high frequency component was significantly decreased in patients with CFS (p < 0.05). The quality of sleep in patients with CFS was decreased because of increase of wake episodes in sleep period. Also the lack of parasympathetic activation during sleep period might be associated with the deterioration of sleep quality in patients with CFS.

  19. Non-destructive estimation of fatigue damage for steel by Barkhausen noise analysis

    SciTech Connect

    Tomita, Yasumitsu; Hashimoto, Kiyoshi; Osawa, Naoki; Inai, Hirohisa

    1993-12-31

    A magnetic Barkhausen noise signals are detected when magnetized domain walls move discontinuously in a ferromagnetic material. This non-uniform motion is sensitive to the microstructures of material which vary continuously with the increase of applied loading cycles. In this paper, the process of fatigue damage accumulation subjected to constant cyclic loading are explored by measuring the Barkhausen noise signal with the progress of loading cycles. The experimental results show the possibility to detect the progress of fatigue damage using the peak Barkhausen noise signal.

  20. Estimation of the mesoscopic thermoplastic dissipation in High-Cycle Fatigue

    NASA Astrophysics Data System (ADS)

    Charkaluk, Eric; Constantinescu, Andrei

    2006-06-01

    A series of High-Cycle Fatigue (HCF) criteria for polycrystalline materials is based on a multiscale interpretation, proposed initially by Dang Van, in which the principal concepts are a two scales model and a shakedown condition. The purpose of this Note is to extend the study of the different dissipative regimes during cyclic loading within this framework by using a self consistent homogenization scheme in coupled thermoplasticity. It is shown that the Sachs and Lin-Taylor schemes are not able to represent the thermal evolutions observed during fatigue tests. To cite this article: E. Charkaluk, A. Constantinescu, C. R. Mecanique 334 (2006).

  1. Three Dimensional Constraint Effects on the Estimated (Delta)CTOD during the Numerical Simulation of Different Fatigue Threshold Testing Techniques

    NASA Technical Reports Server (NTRS)

    Seshadri, Banavara R.; Smith, Stephen W.

    2007-01-01

    Variation in constraint through the thickness of a specimen effects the cyclic crack-tip-opening displacement (DELTA CTOD). DELTA CTOD is a valuable measure of crack growth behavior, indicating closure development, constraint variations and load history effects. Fatigue loading with a continual load reduction was used to simulate the load history associated with fatigue crack growth threshold measurements. The constraint effect on the estimated DELTA CTOD is studied by carrying out three-dimensional elastic-plastic finite element simulations. The analysis involves numerical simulation of different standard fatigue threshold test schemes to determine how each test scheme affects DELTA CTOD. The American Society for Testing and Materials (ASTM) prescribes standard load reduction procedures for threshold testing using either the constant stress ratio (R) or constant maximum stress intensity (K(sub max)) methods. Different specimen types defined in the standard, namely the compact tension, C(T), and middle cracked tension, M(T), specimens were used in this simulation. The threshold simulations were conducted with different initial K(sub max) values to study its effect on estimated DELTA CTOD. During each simulation, the DELTA CTOD was estimated at every load increment during the load reduction procedure. Previous numerical simulation results indicate that the constant R load reduction method generates a plastic wake resulting in remote crack closure during unloading. Upon reloading, this remote contact location was observed to remain in contact well after the crack tip was fully open. The final region to open is located at the point at which the load reduction was initiated and at the free surface of the specimen. However, simulations carried out using the constant Kmax load reduction procedure did not indicate remote crack closure. Previous analysis results using various starting K(sub max) values and different load reduction rates have indicated DELTA CTOD is

  2. Rate-Dependent Impairments in Repetitive Finger Movements in Patients with Parkinson’s Disease are not Due to Peripheral Fatigue

    PubMed Central

    Stegemöller, Elizabeth L.; Allen, David P.; Simuni, Tanya; MacKinnon, Colum D.

    2010-01-01

    Performance of repetitive finger movements is an important clinical measure of disease severity in patients with Parkinson’s disease (PD) and is associated with a dramatic deterioration in performance at movement rates near 2 Hz and above. The mechanisms contributing to this rate-dependent movement impairment are poorly understood. Since clinical and experimental testing of these movements involve prolonged repetition of movement, a loss of force generating capacity due to peripheral fatigue may contribute to performance deterioration. This study examined the contribution of peripheral fatigue to the performance of unconstrained index finger flexion movements by measuring maximum voluntary contractions (MVC) immediately before and after repetitive finger movements in patients with PD (both off- and on-medication) and matched control subjects. Movement performance was quantified using finger kinematics, maximum force production, and electromyography (EMG). The principal finding was that peak force and EMG activity during the MVC did not significantly change from the pre- to post- movement task in patients with PD despite the marked deterioration in movement performance of repetitive finger movements. These findings show that the rate-dependent deterioration of repetitive finger movements in PD cannot be explained by a loss of force-generating capacity due to peripheral fatigue, and further suggest that mechanisms contributing to impaired isometric force production in PD are different from those that mediate impaired performance of high-rate repetitive movements. PMID:20599591

  3. Study of an engineering method for fatigue life estimation and safety evaluation of well drilling string

    SciTech Connect

    Deng Zengjie; Zhang Yi; Li Helin; Li Zhonghua

    1995-12-31

    In this paper, an engineering method for calculating the loading capacity, predicting the residual life, making the safety evaluation of drilling pipe and connection joint based on fracture mechanics was presented. The stress intensity factors K{sub I}, K{sub II} and K{sub III} at the critical sections were calculated by means of 3D FEM, then the fracture toughness J{sub c} under mixed mode loading of drilling pipe steel 37Mn5 and 4340 was obtained. In addition, the tests of fatigue crack initiation under different stress concentration state and fatigue crack growth performance of the same steel were carried out, and corresponding expressive formulae were researched.

  4. An approach for developing a national estimate of waterborne disease due to drinking water and a national estimate model application.

    PubMed

    Messner, Michael; Shaw, Susan; Regli, Stig; Rotert, Ken; Blank, Valerie; Soller, Jeff

    2006-01-01

    In this paper, the US Environmental Protection Agency (EPA) presents an approach and a national estimate of drinking water related endemic acute gastrointestinal illness (AGI) that uses information from epidemiologic studies. There have been a limited number of epidemiologic studies that have measured waterborne disease occurrence in the United States. For this analysis, we assume that certain unknown incidence of AGI in each public drinking water system is due to drinking water and that a statistical distribution of the different incidence rates for the population served by each system can be estimated to inform a mean national estimate of AGI illness due to drinking water. Data from public water systems suggest that the incidence rate of AGI due to drinking water may vary by several orders of magnitude. In addition, data from epidemiologic studies show AGI incidence due to drinking water ranging from essentially none (or less than the study detection level) to a rate of 0.26 cases per person-year. Considering these two perspectives collectively, and associated uncertainties, EPA has developed an analytical approach and model for generating a national estimate of annual AGI illness due to drinking water. EPA developed a national estimate of waterborne disease to address, in part, the 1996 Safe Drinking Water Act Amendments. The national estimate uses best available science, but also recognizes gaps in the data to support some of the model assumptions and uncertainties in the estimate. Based on the model presented, EPA estimates a mean incidence of AGI attributable to drinking water of 0.06 cases per year (with a 95% credible interval of 0.02-0.12). The mean estimate represents approximately 8.5% of cases of AGI illness due to all causes among the population served by community water systems. The estimated incidence translates to 16.4 million cases/year among the same population. The estimate illustrates the potential usefulness and challenges of the approach, and

  5. [Auditory fatigue].

    PubMed

    Sanjuán Juaristi, Julio; Sanjuán Martínez-Conde, Mar

    2015-01-01

    Given the relevance of possible hearing losses due to sound overloads and the short list of references of objective procedures for their study, we provide a technique that gives precise data about the audiometric profile and recruitment factor. Our objectives were to determine peripheral fatigue, through the cochlear microphonic response to sound pressure overload stimuli, as well as to measure recovery time, establishing parameters for differentiation with regard to current psychoacoustic and clinical studies. We used specific instruments for the study of cochlear microphonic response, plus a function generator that provided us with stimuli of different intensities and harmonic components. In Wistar rats, we first measured the normal microphonic response and then the effect of auditory fatigue on it. Using a 60dB pure tone acoustic stimulation, we obtained a microphonic response at 20dB. We then caused fatigue with 100dB of the same frequency, reaching a loss of approximately 11dB after 15minutes; after that, the deterioration slowed and did not exceed 15dB. By means of complex random tone maskers or white noise, no fatigue was caused to the sensory receptors, not even at levels of 100dB and over an hour of overstimulation. No fatigue was observed in terms of sensory receptors. Deterioration of peripheral perception through intense overstimulation may be due to biochemical changes of desensitisation due to exhaustion. Auditory fatigue in subjective clinical trials presumably affects supracochlear sections. The auditory fatigue tests found are not in line with those obtained subjectively in clinical and psychoacoustic trials. Copyright © 2013 Elsevier España, S.L.U. y Sociedad Española de Otorrinolaringología y Patología Cérvico-Facial. All rights reserved.

  6. Fatigue damage estimate comparisons for northern European and US wind farm loading environments

    NASA Astrophysics Data System (ADS)

    Sutherland, H. J.; Kelley, N. D.

    Typical loading histories associated with wind turbine service environments in northern Europe and within a large wind farm in the continental US were recently compared by Kelley using the WISPER (Ten Have) loading standard and its development protocol. In this study, an equivalent load spectrum for a US wind farm was developed by applying the WISPER development protocol to representative service load histories collected from two adjacent turbines operating within a large wind farm in San Gorgonio Pass, California. The results of this study showed that turbines operating in the California wind farm experience many more loading cycles with larger peak-to-peak values for the same mean wind speed classification than their European counterparts. In this paper, the impact of the two WISPER-protocol fatigue-load spectra on service lifetime predictions are used to compare and contrast the impact of the two loading environments with one another. The service lifetime predictions are made using the LIFE2 Fatigue Analysis Code (Sutherland and Schluter), with the fatigue properties of typical fiber glass composite blade materials. Additional analyses, based on rainflow counted time histories from the San Gorgonio turbines, are also used in the comparisons. In general, these results indicate that the WISPER load spectrum from northern European sites significantly underestimates the WISPER protocol load spectrum from a US wind farm site; i.e., the WISPER load spectrum significantly underestimates the number and magnitude of the loads observed at a US wind farm site. The authors conclude that there are fundamental differences in the two service environments.

  7. Estimation of high temperature low cycle fatigue on the basis of inelastic strain and strainrate

    NASA Technical Reports Server (NTRS)

    Berkovits, A.

    1986-01-01

    Fatigue life at elevated temperature can be predicted by introducing parametric values obtained from monotonic constitutive behavior into the Universal-Slopes Equation. For directionally solidified MAR-M200+HF at 975 C, these parameters are the maximum stress achievable under entirely plastic (time-independent) and purely creep (time-dependent) conditions and the corresponding inelastic strains, as well as the elastic modulus. For materials which exhibit plasticity/creep interaction, two more pairs of monotonic parameters must be evaluated for fatigue life prediction. This life-prediction method based on the Universal-Slopes Equation, resulted from a constitutive model characterizing monotonic and cyclic data as inelastic strainrate as a function of inelastic strain. Characterizing monotonic data is this way, permitted distinction between different material responses such as strain-hardening, strain-softening, and dynamic recovery effects. Understanding and defining the region of influence of each of these effects facilitated formulation of the constitutive model in relation to the mechanical and microstructural processes occurring in the material under cyclic loading.

  8. Estimation of Sonic Fatigue by Reduced-Order Finite Element Based Analyses

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Przekop, Adam

    2006-01-01

    A computationally efficient, reduced-order method is presented for prediction of sonic fatigue of structures exhibiting geometrically nonlinear response. A procedure to determine the nonlinear modal stiffness using commercial finite element codes allows the coupled nonlinear equations of motion in physical degrees of freedom to be transformed to a smaller coupled system of equations in modal coordinates. The nonlinear modal system is first solved using a computationally light equivalent linearization solution to determine if the structure responds to the applied loading in a nonlinear fashion. If so, a higher fidelity numerical simulation in modal coordinates is undertaken to more accurately determine the nonlinear response. Comparisons of displacement and stress response obtained from the reduced-order analyses are made with results obtained from numerical simulation in physical degrees-of-freedom. Fatigue life predictions from nonlinear modal and physical simulations are made using the rainflow cycle counting method in a linear cumulative damage analysis. Results computed for a simple beam structure under a random acoustic loading demonstrate the effectiveness of the approach and compare favorably with results obtained from the solution in physical degrees-of-freedom.

  9. Damage depth estimation on a fatigue loaded composite structure using thermography and acoustic emission

    NASA Astrophysics Data System (ADS)

    Zalameda, Joseph N.; Winfree, William P.; Horne, Michael R.

    2017-02-01

    Passive thermography and acoustic emission data were obtained on a three stringer panel during periodic fatigue loading. The acoustic emission data were mapped onto thermal data, revealing the cluster of acoustic emission event locations around the thermal signatures of interest. By combining both techniques, progression of damage growth is confirmed and areas of failure are identified. Furthermore, sudden changes in thermally measured damage growth related to a previously measured higher energy acoustic emission event are studied to determine damage depth. A thermal model with a periodic flux heat source is presented to determine the relationship between the damage depth and thermal response. The model results are compared to the measured data. Lastly, the practical application and limitations of this technique are discussed.

  10. Improved fatigue resistance in Gsα-deficient and aging mouse skeletal muscles due to adaptive increases in slow fibers

    PubMed Central

    Feng, Han-Zhong; Chen, Min; Weinstein, Lee S.

    2011-01-01

    Genetically modified mice with deficiency of the G protein α-subunit (Gsα) in skeletal muscle showed metabolic abnormality with reduced glucose tolerance, low muscle mass, and low contractile force, along with a fast-to-slow-fiber-type switch (Chen M, Feng HZ, Gupta D, Kelleher J, Dickerson KE, Wang J, Hunt D, Jou W, Gavrilova O, Jin JP, Weinstein LS. Am J Physiol Cell Physiol 296: C930–C940, 2009). Here we investigated a hypothesis that the switching to more slow fibers is an adaptive response with specific benefit. The results showed that, corresponding to the switch of myosin isoforms, the thin-filament regulatory proteins troponin T and troponin I both switched to their slow isoforms in the atrophic soleus muscle of 3-mo-old Gsα-deficient mice. This fiber-type switch involving coordinated changes of both thick- and thin-myofilament proteins progressed in the Gsα-deficient soleus muscles of 18- to 24-mo-old mice, as reflected by the expression of solely slow isoforms of myosin and troponin. Compared with age-matched controls, Gsα-deficient soleus muscles with higher proportion of slow fibers exhibited slower contractile and relaxation kinetics and lower developed force, but significantly increased resistance to fatigue, followed by a better recovery. Gsα-deficient soleus muscles of neonatal and 3-wk-old mice did not show the increase in slow fibers. Therefore, the fast-to-slow-fiber-type switch in Gsα deficiency at older ages was likely an adaptive response. The benefit of higher fatigue resistance in adaption to metabolic deficiency and aging provides a mechanism to sustain skeletal muscle function in diabetic patients and elderly individuals. PMID:21680879

  11. Estimation of the maximal voltage induced on an overhead line due to the nearby lightning

    SciTech Connect

    Jankov, V.

    1997-01-01

    Determination of the maximal voltages induced on the overhead power lines by nearby lightning stroke is a complex problem. The scope of this paper is to recognize the parameters that affect the maximal voltages and to present an equation for their estimation. This equation gives an opportunity to calculate the maximal voltage with the reasonable accuracy avoiding complex electromagnetic field calculus. It may be very useful in the estimation of flashover and outage rates due to the nearby strokes.

  12. An estimate of particulates in the vicinity of a Shuttle orbiter due to meteoroid impact

    NASA Technical Reports Server (NTRS)

    Barengoltz, J.

    1978-01-01

    An estimate of the magnitude of released particles in the vicinity of a a Shuttle (STS) Orbiter due to meteoroid impact has been completed. A calculation of the number of particles existing as surface contamination and released by such impacts has been performed. In addition, two estimates of the creation of new particles due to meteoroid cratering (backsplash) have been obtained. In each case, the total number of particles per day as a function of size without regard to velocity, as a function of velocity without regard to size, and as a joint distribution in size and velocity has been calculated.

  13. An attempt to estimate the global burden of disease due to fluoride in drinking water.

    PubMed

    Fewtrell, Lorna; Smith, Stuart; Kay, Dave; Bartram, Jamie

    2006-12-01

    A study was conducted to examine the feasibility of estimating the global burden of disease due to fluoride in drinking water. Skeletal fluorosis is a serious and debilitating disease which, with the exception of one area in China, is overwhelmingly due to the presence of elevated fluoride levels in drinking water. The global burden of disease due to fluoride in drinking water was estimated by combining exposure-response curves for dental and skeletal fluorosis (derived from published data) with model-derived predicted drinking water fluoride concentrations and an estimate of the percentage population exposed. There are few data with which to validate the output but given the current uncertainties in the data used, both to form the exposure-response curves and those resulting from the prediction of fluoride concentrations, it is felt that the estimate is unlikely to be precise. However, the exercise has identified a number of data gaps and useful research avenues, especially in relation to determining exposure, which could contribute to future estimates of this problem.

  14. Probabilistic fatigue methodology and wind turbine reliability

    SciTech Connect

    Lange, C.H.

    1996-05-01

    Wind turbines subjected to highly irregular loadings due to wind, gravity, and gyroscopic effects are especially vulnerable to fatigue damage. The objective of this study is to develop and illustrate methods for the probabilistic analysis and design of fatigue-sensitive wind turbine components. A computer program (CYCLES) that estimates fatigue reliability of structural and mechanical components has been developed. A FORM/SORM analysis is used to compute failure probabilities and importance factors of the random variables. The limit state equation includes uncertainty in environmental loading, gross structural response, and local fatigue properties. Several techniques are shown to better study fatigue loads data. Common one-parameter models, such as the Rayleigh and exponential models are shown to produce dramatically different estimates of load distributions and fatigue damage. Improved fits may be achieved with the two-parameter Weibull model. High b values require better modeling of relatively large stress ranges; this is effectively done by matching at least two moments (Weibull) and better by matching still higher moments. For this purpose, a new, four-moment {open_quotes}generalized Weibull{close_quotes} model is introduced. Load and resistance factor design (LRFD) methodology for design against fatigue is proposed and demonstrated using data from two horizontal-axis wind turbines. To estimate fatigue damage, wind turbine blade loads have been represented by their first three statistical moments across a range of wind conditions. Based on the moments {mu}{sub 1}{hor_ellipsis}{mu}{sub 3}, new {open_quotes}quadratic Weibull{close_quotes} load distribution models are introduced. The fatigue reliability is found to be notably affected by the choice of load distribution model.

  15. Full-Scale 3-D Finite Element Modeling of a Two-Loop Pressurized Water Reactor for Heat Transfer, Thermal-Mechanical Cyclic Stress Analysis, and Environmental Fatigue Life Estimation

    SciTech Connect

    Mohanty, Subhasish; Soppet, William K.; Majumdar, Saurindranath; Natesan, Krishnamurti

    2015-12-15

    This paper discusses a system-level finite element model of a two-loop pressurized water reactor (PWR). Based on this model, system-level heat transfer analysis and subsequent sequentially coupled thermal-mechanical stress analysis were performed for typical thermal-mechanical fatigue cycles. The in-air fatigue lives of example components, such as the hot and cold legs, were estimated on the basis of stress analysis results, ASME in-air fatigue life estimation criteria, and fatigue design curves. Furthermore, environmental correction factors and associated PWR environment fatigue lives for the hot and cold legs were estimated by using estimated stress and strain histories and the approach described in US-NRC report: NUREG-6909.

  16. Quantifying lost information due to covariance matrix estimation in parameter inference

    NASA Astrophysics Data System (ADS)

    Sellentin, Elena; Heavens, Alan F.

    2017-02-01

    Parameter inference with an estimated covariance matrix systematically loses information due to the remaining uncertainty of the covariance matrix. Here, we quantify this loss of precision and develop a framework to hypothetically restore it, which allows to judge how far away a given analysis is from the ideal case of a known covariance matrix. We point out that it is insufficient to estimate this loss by debiasing the Fisher matrix as previously done, due to a fundamental inequality that describes how biases arise in non-linear functions. We therefore develop direct estimators for parameter credibility contours and the figure of merit, finding that significantly fewer simulations than previously thought are sufficient to reach satisfactory precisions. We apply our results to DES Science Verification weak lensing data, detecting a 10 per cent loss of information that increases their credibility contours. No significant loss of information is found for KiDS. For a Euclid-like survey, with about 10 nuisance parameters we find that 2900 simulations are sufficient to limit the systematically lost information to 1 per cent, with an additional uncertainty of about 2 per cent. Without any nuisance parameters, 1900 simulations are sufficient to only lose 1 per cent of information. We further derive estimators for all quantities needed for forecasting with estimated covariance matrices. Our formalism allows to determine the sweetspot between running sophisticated simulations to reduce the number of nuisance parameters, and running as many fast simulations as possible.

  17. Estimates of the direct and indirect radiative forcing due to tropospheric aerosols: A review

    NASA Astrophysics Data System (ADS)

    Haywood, James; Boucher, Olivier

    2000-11-01

    This paper reviews the many developments in estimates of the direct and indirect global annual mean radiative forcing due to present-day concentrations of anthropogenic tropospheric aerosols since Intergovernmental Panel on Climate Change [1996]. The range of estimates of the global mean direct radiative forcing due to six distinct aerosol types is presented. Additionally, the indirect effect is split into two components corresponding to the radiative forcing due to modification of the radiative properties of clouds (cloud albedo effect) and the effects of anthropogenic aerosols upon the lifetime of clouds (cloud lifetime effect). The radiative forcing for anthropogenic sulphate aerosol ranges from -0.26 to -0.82 W m-2. For fossil fuel black carbon the radiative forcing ranges from +0.16 W m-2 for an external mixture to +0.42 W m-2 for where the black carbon is modeled as internally mixed with sulphate aerosol. For fossil fuel organic carbon the two estimates of the likely weakest limit of the direct radiative forcing are -0.02 and -0.04 W m-2. For biomass-burning sources of black carbon and organic carbon the combined radiative forcing ranges from -0.14 to -0.74 W m-2. Estimates of the radiative forcing due to mineral dust vary widely from +0.09 to -0.46 W m-2; even the sign of the radiative forcing is not well established due to the competing effects of solar and terrestrial radiative forcings. A single study provides a very tentative estimate of the radiative forcing of nitrates to be -0.03 W m-2. Estimates of the cloud albedo indirect radiative forcing range from -0.3 to approximately -1.8 W m-2. Although the cloud lifetime effect is identified as a potentially important climate forcing mechanism, it is difficult to quantify in the context of the present definition of radiative forcing of climate change and current model simulations. This is because its estimation by general circulation models necessarily includes some level of cloud and water vapor feedbacks

  18. Estimation of the collective dose in the Portuguese population due to medical procedures in 2010.

    PubMed

    Teles, Pedro; Carmen de Sousa, M; Paulo, Graciano; Santos, Joana; Pascoal, Ana; Cardoso, Gabriela; Lança, Isabel; Matela, Nuno; Janeiro, Luís; Sousa, Patrick; Carvoeiras, Pedro; Parafita, Rui; Santos, Ana Isabel; Simãozinho, Paula; Vaz, Pedro

    2013-05-01

    In a wide range of medical fields, technological advancements have led to an increase in the average collective dose in national populations worldwide. Periodic estimations of the average collective population dose due to medical exposure is, therefore of utmost importance, and is now mandatory in countries within the European Union (article 12 of EURATOM directive 97/43). Presented in this work is a report on the estimation of the collective dose in the Portuguese population due to nuclear medicine diagnostic procedures and the Top 20 diagnostic radiology examinations, which represent the 20 exams that contribute the most to the total collective dose in diagnostic radiology and interventional procedures in Europe. This work involved the collaboration of a multidisciplinary taskforce comprising representatives of all major Portuguese stakeholders (universities, research institutions, public and private healthcare providers, administrative services of the National Healthcare System, scientific and professional associations and private service providers). This allowed us to gather a comprehensive amount of data necessary for a robust estimation of the collective effective dose to the Portuguese population. The methodology used for data collection and dose estimation was based on European Commission recommendations, as this work was performed in the framework of the European wide Dose Datamed II project. This is the first study estimating the collective dose for the population in Portugal, considering such a wide national coverage and range of procedures and consisting of important baseline reference data. The taskforce intends to continue developing periodic collective dose estimations in the future. The estimated annual average effective dose for the Portuguese population was of 0.080±0.017 mSv caput(-1) for nuclear medicine exams and of 0.96±0.68 mSv caput(-1) for the Top 20 diagnostic radiology exams.

  19. The Influence of Roughness on Gear Surface Fatigue

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy

    2005-01-01

    Gear working surfaces are subjected to repeated rolling and sliding contacts, and often designs require loads sufficient to cause eventual fatigue of the surface. This research provides experimental data and analytical tools to further the understanding of the causal relationship of gear surface roughness to surface fatigue. The research included evaluations and developments of statistical tools for gear fatigue data, experimental evaluation of the surface fatigue lives of superfinished gears with a near-mirror quality, and evaluations of the experiments by analytical methods and surface inspections. Alternative statistical methods were evaluated using Monte Carlo studies leading to a final recommendation to describe gear fatigue data using a Weibull distribution, maximum likelihood estimates of shape and scale parameters, and a presumed zero-valued location parameter. A new method was developed for comparing two datasets by extending the current methods of likelihood-ratio based statistics. The surface fatigue lives of superfinished gears were evaluated by carefully controlled experiments, and it is shown conclusively that superfinishing of gears can provide for significantly greater lives relative to ground gears. The measured life improvement was approximately a factor of five. To assist with application of this finding to products, the experimental condition was evaluated. The fatigue life results were expressed in terms of specific film thickness and shown to be consistent with bearing data. Elastohydrodynamic and stress analyses were completed to relate the stress condition to fatigue. Smooth-surface models do not adequately explain the improved fatigue lives. Based on analyses using a rough surface model, it is concluded that the improved fatigue lives of superfinished gears is due to a reduced rate of near-surface micropitting fatigue processes, not due to any reduced rate of spalling (sub-surface) fatigue processes. To complete the evaluations, surface

  20. The In-Flight Estimation and Indication of Cumulative Fatigue Damage to Helicopter Gears,

    DTIC Science & Technology

    1984-03-01

    AUTtHORITIES AND INDUSTRY Trans-Australia Airlines, Library Qantas Airways Limited - Gas & Fuel Corporation of Victoria, Manager Scientific Services SEC of Vic...aircraft in the fleet, were used to esti- mate the mean safe life. A statistical analysis 3 was developed whereby a tolerance limit on life, defined as...in the fleet and a subsequent ground station computer analysis along the lines indicated in Section 2.2.1 can be used to estimate the current alue of

  1. Measurement error in mobile source air pollution exposure estimates due to residential mobility during pregnancy.

    PubMed

    Pennington, Audrey Flak; Strickland, Matthew J; Klein, Mitchel; Zhai, Xinxin; Russell, Armistead G; Hansen, Craig; Darrow, Lyndsey A

    2016-12-14

    Prenatal air pollution exposure is frequently estimated using maternal residential location at the time of delivery as a proxy for residence during pregnancy. We describe residential mobility during pregnancy among 19,951 children from the Kaiser Air Pollution and Pediatric Asthma Study, quantify measurement error in spatially resolved estimates of prenatal exposure to mobile source fine particulate matter (PM2.5) due to ignoring this mobility, and simulate the impact of this error on estimates of epidemiologic associations. Two exposure estimates were compared, one calculated using complete residential histories during pregnancy (weighted average based on time spent at each address) and the second calculated using only residence at birth. Estimates were computed using annual averages of primary PM2.5 from traffic emissions modeled using a Research LINE-source dispersion model for near-surface releases (RLINE) at 250 m resolution. In this cohort, 18.6% of children were born to mothers who moved at least once during pregnancy. Mobile source PM2.5 exposure estimates calculated using complete residential histories during pregnancy and only residence at birth were highly correlated (rS>0.9). Simulations indicated that ignoring residential mobility resulted in modest bias of epidemiologic associations toward the null, but varied by maternal characteristics and prenatal exposure windows of interest (ranging from -2% to -10% bias).Journal of Exposure Science and Environmental Epidemiology advance online publication, 14 December 2016; doi:10.1038/jes.2016.66.

  2. Estimation of the resistance to the initiation of fatigue cracks in the welded joints of steel constructions

    NASA Astrophysics Data System (ADS)

    Odesskii, P. D.; Shuvalov, A. N.; Emel'yanov, O. V.

    2017-04-01

    The problem of choosing an effective approach to determining the fatigue strength of welded butt joints at the stage of crack nucleation is solved. The results of the calculations performed according to the existing building code from the specified strength characteristics and the calculations that take into account local elastoplastic deformation in stress concentration zones are compared. Full-scale specimens of the welded joints of pair angles are tested in the low-cycle fatigue region at a constant load. The kinetics of the state of stress in the zones of terminating flange welded joints is studied by a tensometric method. It is shown that the stage of fatigue crack nucleation is best described using the deformation criterion of fracture: a comparison of the results of calculating the number of cycles to the nucleation of a fatigue crack with experimental data demonstrates good agreement.

  3. Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling.

    PubMed

    Tunnell, James W; Torres, Jorge H; Anvari, Bahman

    2002-01-01

    Cryogen spray cooling (CSC) is an effective technique to protect the epidermis during cutaneous laser therapies. Spraying a cryogen onto the skin surface creates a time-varying heat flux, effectively cooling the skin during and following the cryogen spurt. In previous studies mathematical models were developed to predict the human skin temperature profiles during the cryogen spraying time. However, no studies have accounted for the additional cooling due to residual cryogen left on the skin surface following the spurt termination. We formulate and solve an inverse heat conduction (IHC) problem to predict the time-varying surface heat flux both during and following a cryogen spurt. The IHC formulation uses measured temperature profiles from within a medium to estimate the surface heat flux. We implement a one-dimensional sequential function specification method (SFSM) to estimate the surface heat flux from internal temperatures measured within an in vitro model in response to a cryogen spurt. Solution accuracy and experimental errors are examined using simulated temperature data. Heat flux following spurt termination appears substantial; however, it is less than that during the spraying time. The estimated time-varying heat flux can subsequently be used in forward heat conduction models to estimate temperature profiles in skin during and following a cryogen spurt and predict appropriate timing for onset of the laser pulse.

  4. Estimating deformation due to soil liquefaction in Urayasu city, Japan using permanent scatterers

    NASA Astrophysics Data System (ADS)

    ElGharbawi, Tamer; Tamura, Masayuki

    2015-11-01

    In Japan, several cities endured severe damage due to soil liquefaction phenomenon, which was developed in association with the massive shaking of the 2011 Tohoku earthquake. Measuring soil liquefaction deformations was not an easy task, mainly because of the total loss of signal coherence in the affected regions. In this paper, we present our approach to estimate the deformations associated with soil liquefaction using interferometric synthetic aperture radar techniques. We use a stack of coseismic interferograms to identify the reliable pixels in the damaged areas using permanent scatterers technique. Then, we estimate and remove the preseismic mean velocity and DEM error components. Finally, we identify the liquefaction deformation component using least squares inversion and spatial phase filtering. We test the performance of the proposed approach using synthetic data, simulating the effects of soil liquefaction. The simulation results show a RMSE of the liquefaction deformation of 5.23 mm. After that, we estimate the deformation associated with soil liquefaction in Urayasu city, Japan, using ALOS-PALSAR data. The proposed approach allows a prompt estimation of the liquefaction deformation by utilizing the SAR images archives with only one postseismic SAR image.

  5. Criteria to estimate the voltage unbalances due to high-speed railway demands

    SciTech Connect

    Chen, T.H. . Dept. of Electrical Engineering and Technology)

    1994-08-01

    This paper has presented simple criteria to estimate the voltage unbalances due to high-speed railway demands that are generally single-phase loads. Feeding traction loads from the public power system may lead to some voltage unbalance on the latter and consequently affect the operation of its energy-supply system and other equipment connected with it. Three transformer connection schemes that are commonly used in power-supply systems for the high-speed railway are discussed and compared. The estimating criteria have been derived and represented by simple formula that can be easily applied to evaluate this voltage unbalance. The results are of value to related engineers and consultants especially during periods of planning and design.

  6. Model-Based Estimates of HIV Acquisition Due to Prison Rape

    PubMed Central

    Pinkerton, Steven D.; Galletly, Carol L.; Seal, David W.

    2008-01-01

    Nearly 1.4 million men are incarcerated in federal and state prisons in the United States. These men are disproportionately affected by HIV in comparison with the at-large male population. The elevated prevalence of HIV infection in U.S. prisons has raised concerns over the potential for intraprison HIV transmission due to rape and other forms of sexual victimization. However, the number of men who acquire HIV after being raped in U.S. prisons is not known. We developed a mathematical model of HIV transmission to estimate the likelihood that an incarcerated man would become infected as a result of prison rape and to provide preliminary estimates of the number of prison rape victims who acquire HIV. Our results suggest that between 43 and 93 currently incarcerated men already have or will acquire HIV as a result of being raped in prison. PMID:18584061

  7. Fatigue loading on a 5MW offshore wind turbine due to the combined action of waves and current

    NASA Astrophysics Data System (ADS)

    Peeringa, Johan M.

    2014-06-01

    In the design of an offshore wind turbine the natural frequencies of the structure are of importance. In the design of fixed offshore wind turbine support structures it cannot be avoided that the first eigenmode of the structure lies in the frequency band of wave excitation. This study indicates that wave-current interaction should be taken into account for support structure design load calculations. Wave-current interaction changes the shape of the wave spectrum and the energy content in the wave frequency range of 0.2 - 0.35Hz. This is in the range of natural frequencies fixed offshore wind turbine structures are designed for. The waves are affected by the current in two ways. First there is a frequency shift, Doppler effect, for the fixed observer when the wave travels on a current. Second the shape of the wave is modified in case the wave travels from an area without current into an area with current. Due to wave-current interaction the wave height and wave length change. For waves on an opposing current the wave energy content increases, while for wave on a following current the wave energy content slightly reduces. Simulations of normal production cases between cut-in and cut-out wind speed are performed for a 5MW wind turbine in 20m water depth including waves with 1) a following current, 2) an opposing current and 3) no current present. In case of waves having an opposing current, the 1Hz equivalent fore-aft tower bending moment at the seabed is about 10% higher compared to load cases with waves only.

  8. Estimation of organ and effective dose due to Compton backscatter security scans

    SciTech Connect

    Hoppe, Michael E.; Schmidt, Taly Gilat

    2012-06-15

    Purpose: To estimate organ and effective radiation doses due to backscatter security scanners using Monte Carlo simulations and a voxelized phantom set. Methods: Voxelized phantoms of male and female adults and children were used with the GEANT4 toolkit to simulate a backscatter security scan. The backscatter system was modeled based on specifications available in the literature. The simulations modeled a 50 kVp spectrum with 1.0 mm-aluminum-equivalent filtration and a previously measured exposure of approximately 4.6 {mu}R at 30 cm from the source. Photons and secondary interactions were tracked from the source until they reached zero kinetic energy or exited from the simulation's boundaries. The energy deposited in the phantoms' respective organs was tallied and used to calculate total organ dose and total effective dose for frontal, rear, and full scans with subjects located 30 and 75 cm from the source. Results: For a full screen, all phantoms' total effective doses were below the established 0.25 {mu}Sv standard, with an estimated maximum total effective dose of 0.07 {mu}Sv for full screen of a male child. The estimated maximum organ dose due to a full screen was 1.03 {mu}Gy, deposited in the adipose tissue of the male child phantom when located 30 cm from the source. All organ dose estimates had a coefficient of variation of less than 3% for a frontal scan and less than 11% for a rear scan. Conclusions: Backscatter security scanners deposit dose in organs beyond the skin. The effective dose is below recommended standards set by the Health Physics Society (HPS) and the American National Standards Institute (ANSI) assuming the system provides a maximum exposure of approximately 4.6 {mu}R at 30 cm.

  9. Estimating Neural Control from Concentric vs. Eccentric Surface Electromyographic Representations during Fatiguing, Cyclic Submaximal Back Extension Exercises

    PubMed Central

    Ebenbichler, Gerold R.; Unterlerchner, Lena; Habenicht, Richard; Bonato, Paolo; Kollmitzer, Josef; Mair, Patrick; Riegler, Sara; Kienbacher, Thomas

    2017-01-01

    Purpose: To investigate the differences in neural control of back muscles activated during the eccentric vs. the concentric portions of a cyclic, submaximal, fatiguing trunk extension exercise via the analysis of amplitude and time-frequency parameters derived from surface electromyographic (SEMG) data. Methods: Using back dynamometers, 87 healthy volunteers performed three maximum voluntary isometric trunk extensions (MVC's), an isometric trunk extension at 80% MVC, and 25 cyclic, dynamic trunk extensions at 50% MVC. Dynamic testing was performed with the trunk angular displacement ranging from 0° to 40° and the trunk angular velocity set at 20°/s. SEMG data was recorded bilaterally from the iliocostalis lumborum at L1, the longissimus dorsi at L2, and the multifidus muscles at L5. The initial value and slope of the root mean square (RMS-SEMG) and the instantaneous median frequency (IMDF-SEMG) estimates derived from the SEMG recorded during each exercise cycle were used to investigate the differences in MU control marking the eccentric vs. the concentric portions of the exercise. Results: During the concentric portions of the exercise, the initial RMS-SEMG values were almost twice those observed during the eccentric portions of the exercise. The RMS-SEMG values generally increased during the concentric portions of the exercise while they mostly remained unchanged during the eccentric portions of the exercise with significant differences between contraction types. Neither the initial IMDF-SEMG values nor the time-course of the IMDF-SEMG values significantly differed between the eccentric and the concentric portions of the exercise. Conclusions: The comparison of the investigated SEMG parameters revealed distinct neural control strategies during the eccentric vs. the concentric portions of the cyclic exercise. We explain these differences by relying upon the principles of orderly recruitment and common drive governing motor unit behavior. PMID:28559851

  10. GLODEP2: a computer model for estimating gamma dose due to worldwide fallout of radioactive debris

    SciTech Connect

    Edwards, L.L.; Harvey, T.F.; Peterson, K.R.

    1984-03-01

    The GLODEP2 computer code provides estimates of the surface deposition of worldwide radioactivity and the gamma-ray dose to man from intermediate and long-term fallout. The code is based on empirical models derived primarily from injection-deposition experience gained from the US and USSR nuclear tests in 1958. Under the assumption that a nuclear power facility is destroyed and that its debris behaves in the same manner as the radioactive cloud produced by the nuclear weapon that attached the facility, predictions are made for the gamma does from this source of radioactivity. As a comparison study the gamma dose due to the atmospheric nuclear tests from the period of 1951 to 1962 has been computed. The computed and measured values from Grove, UK and Chiba, Japan agree to within a few percent. The global deposition of radioactivity and resultant gamma dose from a hypothetical strategic nuclear exchange between the US and the USSR is reported. Of the assumed 5300 Mton in the exchange, 2031 Mton of radioactive debris is injected in the atmosphere. The highest estimated average whole body total integrated dose over 50 years (assuming no reduction by sheltering or weathering) is 23 rem in the 30 to 50 degree latitude band. If the attack included a 100 GW(e) nuclear power industry as targets in the US, this dose is increased to 84.6 rem. Hotspots due to rainfall could increase these values by factors of 10 to 50.

  11. Estimation of debris dispersion due to a space vehicle breakup during reentry

    NASA Astrophysics Data System (ADS)

    Reyhanoglu, Mahmut; Alvarado, Juan

    2013-05-01

    This paper studies the problem of the estimation of the extent of the airspace containing falling debris due to a space vehicle breakup. A precise propagation of debris to the ground is not practical for many reasons. There is insufficient knowledge of the initial state vector, ambient wind conditions, and the key parameters including the ballistic coefficients. In addition, propagation of all debris pieces to the ground would require extensive computer time. In this paper, a covariance propagation method is introduced for the estimation of debris dispersion due to a space vehicle breakup. The falling debris is simulated, and the data are analyzed to derive the probability of debris evolution in different altitude layers over time. The concept of positional probability ellipsoids is employed for the visualization of the results. Through a case study, it is shown that while the results of the covariance propagation method are in close agreement with those of the Monte Carlo method, the covariance propagation method is much more computationally efficient than the Monte Carlo method.

  12. Direct estimation of entropy loss due to reduced translational and rotational motions upon molecular binding.

    PubMed

    Lu, Benzhuo; Wong, Chung F

    2005-12-05

    The entropic cost due to the loss of translational and rotational (T-R) degree of freedom upon binding has been well recognized for several decades. Tightly bound ligands have higher entropic costs than loosely bound ligands. Quantifying the ligand's residual T-R motions after binding, however, is not an easy task. We describe an approach that uses a reduced Hessian matrix to estimate the contributions due to translational and rotational degrees of freedom to entropy change upon molecular binding. The calculations use a harmonic model for the bound state but only include the T-R degrees of freedom. This approximation significantly speeds up entropy calculations because only 6 x 6 matrices need to be treated, which makes it easier to be used in computer-aided drug design for studying many ligands. The methodological connection with other methods is discussed as well. We tested this approximation by applying it to study the binding of ATP, peptide inhibitor (PKI), and several bound water molecules to protein kinase A (PKA). These ligands span a wide range in size. The model gave reasonable estimates of the residual T-R entropy of bound ligands or water molecules. The residual T-R entropy demonstrated a wide range of values, e.g., 4 to 16 cal/K.mol for the bound water molecules of PKA.

  13. Flexural fatigue life prediction of closed hat-section using materially nonlinear axial fatigue characteristics

    NASA Technical Reports Server (NTRS)

    Razzaq, Zia

    1989-01-01

    Straight or curved hat-section members are often used as structural stiffeners in aircraft. For instance, they are employed as stiffeners for the dorsal skin as well as in the aerial refueling adjacent area structure in F-106 aircraft. The flanges of the hat-section are connected to the aircraft skin. Thus, the portion of the skin closing the hat-section interacts with the section itself when resisting the stresses due to service loads. The flexural fatigue life of such a closed section is estimated using materially nonlinear axial fatigue characteristics. It should be recognized that when a structural shape is subjected to bending, the fatigue life at the neutral axis is infinity since the normal stresses are zero at that location. Conversely, the fatigue life at the extreme fibers where the normal bending stresses are maximum can be expected to be finite. Thus, different fatigue life estimates can be visualized at various distances from the neural axis. The problem becomes compounded further when significant portions away from the neutral axis are stressed into plastic range. A theoretical analysis of the closed hat-section subjected to flexural cyclic loading is first conducted. The axial fatigue characteristics together with the related axial fatigue life formula and its inverted form given by Manson and Muralidharan are adopted for an aluminum alloy used in aircraft construction. A closed-form expression for predicting the flexural fatigue life is then derived for the closed hat-section including materially nonlinear action. A computer program is written to conduct a study of the variables such as the thicknesses of the hat-section and the skin, and the type of alloy used. The study has provided a fundamental understanding of the flexural fatigue life characteristics of a practical structural component used in aircraft when materially nonlinear action is present.

  14. Estimating challenge load due to disease outbreaks and other challenges using reproduction records of sows.

    PubMed

    Mathur, P K; Herrero-Medrano, J M; Alexandri, P; Knol, E F; ten Napel, J; Rashidi, H; Mulder, H A

    2014-12-01

    A method was developed and tested to estimate challenge load due to disease outbreaks and other challenges in sows using reproduction records. The method was based on reproduction records from a farm with known disease outbreaks. It was assumed that the reduction in weekly reproductive output within a farm is proportional to the magnitude of the challenge. As the challenge increases beyond certain threshold, it is manifested as an outbreak. The reproduction records were divided into 3 datasets. The first dataset called the Training dataset consisted of 57,135 reproduction records from 10,901 sows from 1 farm in Canada with several outbreaks of porcine reproductive and respiratory syndrome (PRRS). The known disease status of sows was regressed on the traits number born alive, number of losses as a combination of still birth and mummified piglets, and number of weaned piglets. The regression coefficients from this analysis were then used as weighting factors for derivation of an index measure called challenge load indicator. These weighting factors were derived with i) a two-step approach using residuals or year-week solutions estimated from a previous step, and ii) a single-step approach using the trait values directly. Two types of models were used for each approach: a logistic regression model and a general additive model. The estimates of challenge load indicator were then compared based on their ability to detect PRRS outbreaks in a Test dataset consisting of records from 65,826 sows from 15 farms in the Netherlands. These farms differed from the Canadian farm with respect to PRRS virus strains, severity and frequency of outbreaks. The single-step approach using a general additive model was best and detected 14 out of the 15 outbreaks. This approach was then further validated using the third dataset consisting of reproduction records of 831,855 sows in 431 farms located in different countries in Europe and America. A total of 41 out of 48 outbreaks detected

  15. Error due to unresolved scales in estimation problems for atmospheric data assimilation

    NASA Astrophysics Data System (ADS)

    Janjic, Tijana

    The error arising due to unresolved scales in data assimilation procedures is examined. The problem of estimating the projection of the state of a passive scalar undergoing advection at a sequence of times is considered. The projection belongs to a finite- dimensional function space and is defined on the continuum. Using the continuum projection of the state of a passive scalar, a mathematical definition is obtained for the error arising due to the presence, in the continuum system, of scales unresolved by the discrete dynamical model. This error affects the estimation procedure through point observations that include the unresolved scales. In this work, two approximate methods for taking into account the error due to unresolved scales and the resulting correlations are developed and employed in the estimation procedure. The resulting formulas resemble the Schmidt-Kalman filter and the usual discrete Kalman filter, respectively. For this reason, the newly developed filters are called the Schmidt-Kalman filter and the traditional filter. In order to test the assimilation methods, a two- dimensional advection model with nonstationary spectrum was developed for passive scalar transport in the atmosphere. An analytical solution on the sphere was found depicting the model dynamics evolution. Using this analytical solution the model error is avoided, and the error due to unresolved scales is the only error left in the estimation problem. It is demonstrated that the traditional and the Schmidt- Kalman filter work well provided the exact covariance function of the unresolved scales is known. However, this requirement is not satisfied in practice, and the covariance function must be modeled. The Schmidt-Kalman filter cannot be computed in practice without further approximations. Therefore, the traditional filter is better suited for practical use. Also, the traditional filter does not require modeling of the full covariance function of the unresolved scales, but only

  16. Estimating the loss in expectation of life due to cancer using flexible parametric survival models.

    PubMed

    Andersson, Therese M-L; Dickman, Paul W; Eloranta, Sandra; Lambe, Mats; Lambert, Paul C

    2013-12-30

    A useful summary measure for survival data is the expectation of life, which is calculated by obtaining the area under a survival curve. The loss in expectation of life due to a certain type of cancer is the difference between the expectation of life in the general population and the expectation of life among the cancer patients. This measure is used little in practice as its estimation generally requires extrapolation of both the expected and observed survival. A parametric distribution can be used for extrapolation of the observed survival, but it is difficult to find a distribution that captures the underlying shape of the survival function after the end of follow-up. In this paper, we base our extrapolation on relative survival, because it is more stable and reliable. Relative survival is defined as the observed survival divided by the expected survival, and the mortality analogue is excess mortality. Approaches have been suggested for extrapolation of relative survival within life-table data, by assuming that the excess mortality has reached zero (statistical cure) or has stabilized to a constant. We propose the use of flexible parametric survival models for relative survival, which enables estimating the loss in expectation of life on individual level data by making these assumptions or by extrapolating the estimated linear trend at the end of follow-up. We have evaluated the extrapolation from this model using data on four types of cancer, and the results agree well with observed data.

  17. Estimating Random Errors Due to Shot Noise in Backscatter Lidar Observations

    NASA Technical Reports Server (NTRS)

    Liu, Zhaoyan; Hunt, William; Vaughan, Mark A.; Hostetler, Chris A.; McGill, Matthew J.; Powell, Kathy; Winker, David M.; Hu, Yongxiang

    2006-01-01

    In this paper, we discuss the estimation of random errors due to shot noise in backscatter lidar observations that use either photomultiplier tube (PMT) or avalanche photodiode (APD) detectors. The statistical characteristics of photodetection are reviewed, and photon count distributions of solar background signals and laser backscatter signals are examined using airborne lidar observations at 532 nm using a photon-counting mode APD. Both distributions appear to be Poisson, indicating that the arrival at the photodetector of photons for these signals is a Poisson stochastic process. For Poisson-distributed signals, a proportional, one-to-one relationship is known to exist between the mean of a distribution and its variance. Although the multiplied photocurrent no longer follows a strict Poisson distribution in analog-mode APD and PMT detectors, the proportionality still exists between the mean and the variance of the multiplied photocurrent. We make use of this relationship by introducing the noise scale factor (NSF), which quantifies the constant of proportionality that exists between the root-mean-square of the random noise in a measurement and the square root of the mean signal. Using the NSF to estimate random errors in lidar measurements due to shot noise provides a significant advantage over the conventional error estimation techniques, in that with the NSF uncertainties can be reliably calculated from/for a single data sample. Methods for evaluating the NSF are presented. Algorithms to compute the NSF are developed for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar and tested using data from the Lidar In-space Technology Experiment (LITE). OCIS Codes:

  18. Estimating random errors due to shot noise in backscatter lidar observations

    NASA Astrophysics Data System (ADS)

    Liu, Zhaoyan; Hunt, William; Vaughan, Mark; Hostetler, Chris; McGill, Matthew; Powell, Kathleen; Winker, David; Hu, Yongxiang

    2006-06-01

    We discuss the estimation of random errors due to shot noise in backscatter lidar observations that use either photomultiplier tube (PMT) or avalanche photodiode (APD) detectors. The statistical characteristics of photodetection are reviewed, and photon count distributions of solar background signals and laser backscatter signals are examined using airborne lidar observations at 532 nm using a photon-counting mode APD. Both distributions appear to be Poisson, indicating that the arrival at the photodetector of photons for these signals is a Poisson stochastic process. For Poisson- distributed signals, a proportional, one-to-one relationship is known to exist between the mean of a distribution and its variance. Although the multiplied photocurrent no longer follows a strict Poisson distribution in analog-mode APD and PMT detectors, the proportionality still exists between the mean and the variance of the multiplied photocurrent. We make use of this relationship by introducing the noise scale factor (NSF), which quantifies the constant of proportionality that exists between the root mean square of the random noise in a measurement and the square root of the mean signal. Using the NSF to estimate random errors in lidar measurements due to shot noise provides a significant advantage over the conventional error estimation techniques, in that with the NSF, uncertainties can be reliably calculated from or for a single data sample. Methods for evaluating the NSF are presented. Algorithms to compute the NSF are developed for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations lidar and tested using data from the Lidar In-space Technology Experiment.

  19. Estimating random errors due to shot noise in backscatter lidar observations.

    PubMed

    Liu, Zhaoyan; Hunt, William; Vaughan, Mark; Hostetler, Chris; McGill, Matthew; Powell, Kathleen; Winker, David; Hu, Yongxiang

    2006-06-20

    We discuss the estimation of random errors due to shot noise in backscatter lidar observations that use either photomultiplier tube (PMT) or avalanche photodiode (APD) detectors. The statistical characteristics of photodetection are reviewed, and photon count distributions of solar background signals and laser backscatter signals are examined using airborne lidar observations at 532 nm using a photon-counting mode APD. Both distributions appear to be Poisson, indicating that the arrival at the photodetector of photons for these signals is a Poisson stochastic process. For Poisson- distributed signals, a proportional, one-to-one relationship is known to exist between the mean of a distribution and its variance. Although the multiplied photocurrent no longer follows a strict Poisson distribution in analog-mode APD and PMT detectors, the proportionality still exists between the mean and the variance of the multiplied photocurrent. We make use of this relationship by introducing the noise scale factor (NSF), which quantifies the constant of proportionality that exists between the root mean square of the random noise in a measurement and the square root of the mean signal. Using the NSF to estimate random errors in lidar measurements due to shot noise provides a significant advantage over the conventional error estimation techniques, in that with the NSF, uncertainties can be reliably calculated from or for a single data sample. Methods for evaluating the NSF are presented. Algorithms to compute the NSF are developed for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations lidar and tested using data from the Lidar In-space Technology Experiment.

  20. Estimated crop yield losses due to surface ozone exposure and economic damage in India.

    PubMed

    Debaje, S B

    2014-06-01

    In this study, we estimate yield losses and economic damage of two major crops (winter wheat and rabi rice) due to surface ozone (O3) exposure using hourly O3 concentrations for the period 2002-2007 in India. This study estimates crop yield losses according to two indices of O3 exposure: 7-h seasonal daytime (0900-1600 hours) mean measured O3 concentration (M7) and AOT40 (accumulation exposure of O3 concentration over a threshold of 40 parts per billion by volume during daylight hours (0700-1800 hours), established by field studies. Our results indicate that relative yield loss from 5 to 11% (6-30%) for winter wheat and 3-6% (9-16%) for rabi rice using M7 (AOT40) index of the mean total winter wheat 81 million metric tons (Mt) and rabi rice 12 Mt production per year for the period 2002-2007. The estimated mean crop production loss (CPL) for winter wheat are from 9 to 29 Mt, account for economic cost loss was from 1,222 to 4,091 million US$ annually. Similarly, the mean CPL for rabi rice are from 0.64 to 2.1 Mt, worth 86-276 million US$. Our calculated winter wheat and rabi rice losses agree well with previous results, providing the further evidence that large crop yield losses occurring in India due to current O3 concentration and further elevated O3 concentration in future may pose threat to food security.

  1. Clinical neurophysiology of fatigue.

    PubMed

    Zwarts, M J; Bleijenberg, G; van Engelen, B G M

    2008-01-01

    Fatigue is a multidimensional concept covering both physiological and psychological aspects. Chronic fatigue is a typical symptom of diseases such as cancer, multiple sclerosis (MS), Parkinson's disease (PD) and cerebrovascular disorders but is also presented by people in whom no defined somatic disease has been established. If certain criteria are met, chronic fatigue syndrome can be diagnosed. The 4-item Abbreviated Fatigue Questionnaire allows the extent of the experienced fatigue to be assessed with a high degree of reliability and validity. Physiological fatigue has been well defined and originates in both the peripheral and central nervous system. The condition can be assessed by combining force and surface-EMG measurements (including frequency analyses and muscle-fibre conduction estimations), twitch interpolation, magnetic stimulation of the motor cortex and analysis of changes in the readiness potential. Fatigue is a well-known phenomenon in both central and peripheral neurological disorders. Examples of the former conditions are multiple sclerosis, Parkinson's disease and stroke. Although it seems to be a universal symptom of many brain disorders, the unique characteristics of the concomitant fatigue also point to a specific relationship with several of these syndromes. As regards neuromuscular disorders, fatigue has been reported in patients with post-polio syndrome, myasthenia gravis, Guillain-Barré syndrome, facioscapulohumeral dystrophy, myotonic dystrophy and hereditary motor and sensory neuropathy type-I. More than 60% of all neuromuscular patients suffer from severe fatigue, a prevalence resembling that of patients with MS. Except for several rare myopathies with specific metabolic derangements leading to exercise-induced muscle fatigue, most studies have not identified a prominent peripheral cause for the fatigue in this population. In contrast, the central activation of the diseased neuromuscular system is generally found to be suboptimal. The

  2. A new Tool for Estimating Losses due to Earthquakes: QUAKELOSS2

    NASA Astrophysics Data System (ADS)

    Kaestli, P.; Wyss, M.; Bonjour, C.; Wiemer, S.; Wyss, B. M.

    2007-12-01

    WAPMERR and the Swiss Seismological Service are developing new software for estimating mean damage to buildings, number of injured and number of fatalities due to earthquakes worldwide. The focus for applications is real-time estimates of losses after earthquakes in countries without dense seismograph networks, and results that are easy to digest by relief agencies. Therefore, the standard version of the software addresses losses by settlement, subdivisions of settlements and important pieces of infrastructure. However, a generic design, an open source policy and well defined interfaces will allow the software to work on any gridded or discrete building stock data, to do Monte-Carlo simulations for error assessment and to plug in more elaborate source models than simple point and line sources and thus to compute realistic loss scenarios as well as probabilistic risk maps. It will provide interfaces to SHAKEMAP and PAGER, such that innovations developed for the latter programs may be used in QUAKELOSS2, and vice versa. A client server design will provide a front-end web interface where the user may directly manage servers as well as run the software in one's&pown laboratory. The input-output features and mapping will be designed to allow the user to run QUAKELOSS2 remotely with basic functions, as well as in a laboratory setting including a full-featured GIS setup for additional analysis. In many cases, the input data (earthquake parameters as well as population and building stock data) are poorly known for developing countries. Calibration of loss estimates, using past earthquakes that have caused damage and WAPMERR's experience of four years" estimating losses, will help to produce approximately correct results in countries with strong earthquake activity. A worldwide standard dataset on population and building stock will be provided as open source together with the software. The dataset will be improved successively, based on input from satellite images

  3. Bias in acoustic biomass estimates of Euphausia superba due to diel vertical migration

    NASA Astrophysics Data System (ADS)

    Demer, David A.; Hewitt, Roger P.

    1995-04-01

    The diel vertical migration (DVM) of Antarctic krill ( Euphausia superba) can greatly bias the results of qualitative and quantitative hydroacoustic surveys which are conducted with a down-looking sonar and irrespective of the time of day. To demonstrate and quantify these negative biases on both the estimates of biomass distribution and abundance, a time-depth-density analysis was performed. Data were collected, as part of the United States Antarctic Marine Living Resources Program (AMLR), in the vicinities of Elephant Island, Antarctica, during the austral summers of 1992 and 1993. Five surveys were conducted in 1992; two covered a 105 by 105 n.mi. area centered on Elephant Island, two encompassed a 60 by 35 n.mi. area immediately to the north of the Island, and one covered a 1 n.mi. 2 area centered on a large krill swarm to the west of Seal Island. The 1993 data include repetitions of the two small-area and two large-area surveys. Average krill volume densities were calculated for each hour as well as for three daily periods: day, twilight and night. These data were normalized and presented as a probability of daily average density. With spectral analysis to identify the frequencies of migration, a four-term periodic function was fitted to the probability density function of average daily biomass versus local apparent time. This function was transformed to create a temporal compensation function (TCF) for upwardly adjusting acoustic biomass estimates. The TCF was then applied to the original 1992 survey data; the resulting biomass estimates are an average of 49.5% higher than those calculated disregarding biases due to diel vertical migration. The effect of DVM on the estimates of krill distribution are illustrated by a comparison of compensated and uncompensated density maps of two 1992 surveys. Through this technique, high density kril areas are revealed where uncompensated maps indicated low densities.

  4. Estimating Energy Dissipation Due to Wave Breaking in the Surf Zone Using Infrared Imagery

    NASA Astrophysics Data System (ADS)

    Carini, Roxanne J.

    Wave breaking is the largest forcing mechanism in the surf zone. Therefore, quantifying energy dissipation due to wave breaking is important for improving models that seek to predict nearshore circulation, wave-current interactions, air-sea gas exchange, erosion and accretion of sediment, and storm surge. Wave energy dissipation is difficult to measure with in situ instruments, and even the most reliable estimates are limited to point measurements. Using remote sensing technologies, specifically infrared (IR) imagery, the high spatial and temporal variability of wave breaking may be sampled. Duncan (1981) proposed a model (D81) for dissipation on a wave-by-wave basis, based on wave slope and roller length, the crest-perpendicular length of the aerated region of a breaking wave. The wave roller is composed of active foam, which, in thermal IR images, appears brighter than the surrounding water and the residual foam, the foam left behind in the wake of a breaking wave. Using IR imagery taken during the Surf Zone Optics 2010 experiment at Duck, NC, and exploiting the distinct signature of active foam, a retrieval algorithm was developed to identify and extract breaking wave roller length. Roller length was then used to estimate dissipation rate via the D81 formulation. The D81 dissipation rate estimates compare reasonably to in situ dissipation estimates at a point. When the D81 estimates are compared to the bulk energy flux into the surf zone, it is found that wave breaking dissipates approximately 25-36% of the incoming wave energy. The D81 dissipation rate estimates also agree closely with those from a dissipation parameterization proposed by Janssen and Battjes (2007) (JB07) and commonly applied within larger nearshore circulation models. The JB07 formulation, however, requires additional physical parameters (wave height and water depth) that are often sparsely sampled and are difficult to attain from remote sensing alone. The power of the D81 formulation lies in

  5. Incubating Isolated Mouse EDL Muscles with Creatine Improves Force Production and Twitch Kinetics in Fatigue Due to Reduction in Ionic Strength

    PubMed Central

    Head, Stewart I.; Greenaway, Bronwen; Chan, Stephen

    2011-01-01

    Background Creatine supplementation can improve performance during high intensity exercise in humans and improve muscle strength in certain myopathies. In this present study, we investigated the direct effects of acute creatine incubation on isolated mouse fast-twitch EDL muscles, and examined how these effects change with fatigue. Methods and Results The extensor digitorum longus muscle from mice aged 12–14 weeks was isolated and stimulated with field electrodes to measure force characteristics in 3 different states: (i) before fatigue; (ii) immediately after a fatigue protocol; and (iii) after recovery. These served as the control measurements for the muscle. The muscle was then incubated in a creatine solution and washed. The measurement of force characteristics in the 3 different states was then repeated. In un-fatigued muscle, creatine incubation increased the maximal tetanic force. In fatigued muscle, creatine treatment increased the force produced at all frequencies of stimulation. Incubation also increased the rate of twitch relaxation and twitch contraction in fatigued muscle. During repetitive fatiguing stimulation, creatine-treated muscles took 55.1±9.5% longer than control muscles to lose half of their original force. Measurement of weight changes showed that creatine incubation increased EDL muscle mass by 7%. Conclusion Acute creatine application improves force production in isolated fast-twitch EDL muscle, and these improvements are particularly apparent when the muscle is fatigued. One likely mechanism for this improvement is an increase in Ca2+ sensitivity of contractile proteins as a result of ionic strength decreases following creatine incubation. PMID:21850234

  6. Interconnect fatigue design for terrestrial photovoltaic modules

    SciTech Connect

    Mon, G. R.; Moore, D. M.; Ross, Jr., R. G.

    1982-03-01

    Fatigue of solar cell electrical interconnects due to thermal cycling has historically been a major failure mechanism in photovoltaic arrays; the results of a comprehensive investigation of interconnect fatigue that has led to the definition of useful reliability-design and life-prediction algorithms are presented. Experimental data gathered in this study indicate that the classical strain-cycle (fatigue) curve for the interconnect material is a good model of mean interconnect fatigue performance, but it fails to account for the broad statistical scatter, which is critical to reliability prediction. To fill this shortcoming the classical fatigue curve is combined with experimental cumulative interconnect failure rate data to yield statistical fatigue curves (having failure probability as a parameter) which enable: (1) the prediction of cumulative interconnect failures during the design life of an array field; and (2) the unambiguous - i.e., quantitative - interpretation of data from field-service qualification (accelerated thermal cycling) tests. Optimal interconnect cost-reliability design algorithms are derived based on minimizing the cost of energy over the design life of the array field. This procedure yields not only the minimum break-even cost of delivered energy, but also the required degree of interconnect redundancy and an estimate of array power degradation during the design life of the array field. The usefulness of the design algorithms is demonstrated with realistic examples of design optimization, prediction, and service qualification testing.

  7. Estimation of Surface Roughness due to Electrode Erosion in Field-Distortion Gas Switch

    NASA Astrophysics Data System (ADS)

    Liu, Xuandong; Wang, Hu; Li, Xiaoang; Zhang, Qiaogen; Wei, Jin; Qiu, Aici

    2013-08-01

    Field distortion gas switch is one of the crucial elements in a Marx generator, fast linear transformer driver and other pulsed power installations. The performance of the gas switch, which is dramatically affected by the surface roughness due to electrode erosion during the discharge process, directly influences the output parameters, stability and reliability of the pulsed power system. In this paper, an electrode surface roughness (ESR) calculation model has been established based on a great deal of experimental data under operating current. The discharge current waveform, the peak height of the burr, the radius and the depth of etch pits in the electrode erosion region were used to predict the ESR. Also, experimental results indicate that this calculation model can effectively estimate the ESR of the test gas switch.

  8. New perspectives on the damage estimation for buried pipeline systems due to seismic wave propagation

    SciTech Connect

    Pineda Porras, Omar Andrey

    2009-01-01

    Over the past three decades, seismic fragility fonnulations for buried pipeline systems have been developed following two tendencies: the use of earthquake damage scenarios from several pipeline systems to create general pipeline fragility functions; and, the use of damage scenarios from one pipeline system to create specific-system fragility functions. In this paper, the advantages and disadvantages of both tendencies are analyzed and discussed; in addition, a summary of what can be considered the new challenges for developing better pipeline seismic fragility formulations is discussed. The most important conclusion of this paper states that more efforts are needed to improve the estimation of transient ground strain -the main cause of pipeline damage due to seismic wave propagation; with relevant advances in that research field, new and better fragility formulations could be developed.

  9. Estimating Global Burden of Disease due to congenital anomaly: an analysis of European data.

    PubMed

    Boyle, Breidge; Addor, Marie-Claude; Arriola, Larraitz; Barisic, Ingeborg; Bianchi, Fabrizio; Csáky-Szunyogh, Melinda; de Walle, Hermien E K; Dias, Carlos Matias; Draper, Elizabeth; Gatt, Miriam; Garne, Ester; Haeusler, Martin; Källén, Karin; Latos-Bielenska, Anna; McDonnell, Bob; Mullaney, Carmel; Nelen, Vera; Neville, Amanda J; O'Mahony, Mary; Queisser-Wahrendorf, Annette; Randrianaivo, Hanitra; Rankin, Judith; Rissmann, Anke; Ritvanen, Annukka; Rounding, Catherine; Tucker, David; Verellen-Dumoulin, Christine; Wellesley, Diana; Wreyford, Ben; Zymak-Zakutnia, Natalia; Dolk, Helen

    2017-06-30

    To validate the estimates of Global Burden of Disease (GBD) due to congenital anomaly for Europe by comparing infant mortality data collected by EUROCAT registries with the WHO Mortality Database, and by assessing the significance of stillbirths and terminations of pregnancy for fetal anomaly (TOPFA) in the interpretation of infant mortality statistics. EUROCAT is a network of congenital anomaly registries collecting data on live births, fetal deaths from 20 weeks' gestation and TOPFA. Data from 29 registries in 19 countries were analysed for 2005-2009, and infant mortality (deaths of live births at age <1 year) compared with the WHO Mortality Database. Eight EUROCAT countries were excluded from further analysis on the basis that this comparison showed poor ascertainment of survival status. According to WHO, 17%-42% of infant mortality was attributed to congenital anomaly. In 11 EUROCAT countries, average infant mortality with congenital anomaly was 1.1 per 1000 births, with higher rates where TOPFA is illegal (Malta 3.0, Ireland 2.1). The rate of stillbirths with congenital anomaly was 0.6 per 1000. The average TOPFA prevalence was 4.6 per 1000, nearly three times more prevalent than stillbirths and infant deaths combined. TOPFA also impacted on the prevalence of postneonatal survivors with non-lethal congenital anomaly. By excluding TOPFA and stillbirths from GBD years of life lost (YLL) estimates, GBD underestimates the burden of disease due to congenital anomaly, and thus declining YLL over time may obscure lack of progress in primary, secondary and tertiary prevention. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  10. A statistical method to estimate outflow volume in case of levee breach due to overtopping

    NASA Astrophysics Data System (ADS)

    Brandimarte, Luigia; Martina, Mario; Dottori, Francesco; Mazzoleni, Maurizio

    2015-04-01

    The aim of this study is to propose a statistical method to assess the outflowing water volume through a levee breach, due to overtopping, in case of three different types of grass cover quality. The first step in the proposed methodology is the definition of the reliability function, a the relation between loading and resistance conditions on the levee system, in case of overtopping. Secondly, the fragility curve, which relates the probability of failure with loading condition over the levee system, is estimated having defined the stochastic variables in the reliability function. Thus, different fragility curves are assessed in case of different scenarios of grass cover quality. Then, a levee breach model is implemented and combined with a 1D hydrodynamic model in order to assess the outflow hydrograph given the water level in the main channel and stochastic values of the breach width. Finally, the water volume is estimated as a combination of the probability density function of the breach width and levee failure. The case study is located in the in 98km-braided reach of Po River, Italy, between the cross-sections of Cremona and Borgoforte. The analysis showed how different counter measures, different grass cover quality in this case, can reduce the probability of failure of the levee system. In particular, for a given values of breach width good levee cover qualities can significantly reduce the outflowing water volume, compared to bad cover qualities, inducing a consequent lower flood risk within the flood-prone area.

  11. Estimation of financial burden due to oversupply of medications for chronic diseases.

    PubMed

    Chaiyakunapruk, Nathorn; Thanarungroj, Aekdisak; Cheewasithirungrueng, Nonglak; Srisupha-olarn, Warunee; Nimpitakpong, Piyarat; Dilokthornsakul, Piyameth; Jeanpeerapong, Napawan

    2012-05-01

    Given the potential of financial burden due to oversupply of medications for chronic diseases, this study aims to determine the prevalence of oversupply and to estimate the magnitude of financial loss in Thailand. Electronic patient database in a university-affiliated hospital in Thailand was used. Based on the utilization of top 5 high drug expenditure in 2005, the prevalence and the financial loss of oversupply (medication possession ratio [MPR] >1.00) were estimated. In total, 1893 patients were included in this study. The average age was 65.2 years and the majority were female (56%). The prevalence of oversupply ranged from 23.2% to 62.8%, whereas the annual financial loss ranged from US $4108 to US $10 517. The total amount of loss was US $32 903 or 3.77% of total medication costs. In summary, because of the high prevalence and associated high financial loss, oversupply of medication is a significant financial burden on hospitals and society.

  12. On Assessment and Estimation of Potential Losses due to Land Subsidence in Urban Areas of Indonesia

    NASA Astrophysics Data System (ADS)

    Abidin, Hasanuddin Z.; Andreas, Heri; Gumilar, Irwan; Sidiq, Teguh P.

    2016-04-01

    subsidence have also relation among each other, the accurate quantification of the potential losses caused by land subsidence in urban areas is not an easy task to accomplish. The direct losses can be easier to estimate than the indirect losses. For example, the direct losses due to land subsidence in Bandung was estimated to be at least 180 Million USD; but the indirect losses is still unknown.

  13. Estimating hazard ratios in cohort data with missing disease information due to death.

    PubMed

    Binder, Nadine; Herrnböck, Anne-Sophie; Schumacher, Martin

    2017-03-01

    In clinical and epidemiological studies information on the primary outcome of interest, that is, the disease status, is usually collected at a limited number of follow-up visits. The disease status can often only be retrieved retrospectively in individuals who are alive at follow-up, but will be missing for those who died before. Right-censoring the death cases at the last visit (ad-hoc analysis) yields biased hazard ratio estimates of a potential risk factor, and the bias can be substantial and occur in either direction. In this work, we investigate three different approaches that use the same likelihood contributions derived from an illness-death multistate model in order to more adequately estimate the hazard ratio by including the death cases into the analysis: a parametric approach, a penalized likelihood approach, and an imputation-based approach. We investigate to which extent these approaches allow for an unbiased regression analysis by evaluating their performance in simulation studies and on a real data example. In doing so, we use the full cohort with complete illness-death data as reference and artificially induce missing information due to death by setting discrete follow-up visits. Compared to an ad-hoc analysis, all considered approaches provide less biased or even unbiased results, depending on the situation studied. In the real data example, the parametric approach is seen to be too restrictive, whereas the imputation-based approach could almost reconstruct the original event history information. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Selective Effect of Physical Fatigue on Motor Imagery Accuracy

    PubMed Central

    Di Rienzo, Franck; Collet, Christian; Hoyek, Nady; Guillot, Aymeric

    2012-01-01

    While the use of motor imagery (the mental representation of an action without overt execution) during actual training sessions is usually recommended, experimental studies examining the effect of physical fatigue on subsequent motor imagery performance are sparse and yielded divergent findings. Here, we investigated whether physical fatigue occurring during an intense sport training session affected motor imagery ability. Twelve swimmers (nine males, mean age 15.5 years) conducted a 45 min physically-fatiguing protocol where they swam from 70% to 100% of their maximal aerobic speed. We tested motor imagery ability immediately before and after fatigue state. Participants randomly imagined performing a swim turn using internal and external visual imagery. Self-reports ratings, imagery times and electrodermal responses, an index of alertness from the autonomic nervous system, were the dependent variables. Self-reports ratings indicated that participants did not encounter difficulty when performing motor imagery after fatigue. However, motor imagery times were significantly shortened during posttest compared to both pretest and actual turn times, thus indicating reduced timing accuracy. Looking at the selective effect of physical fatigue on external visual imagery did not reveal any difference before and after fatigue, whereas significantly shorter imagined times and electrodermal responses (respectively 15% and 48% decrease, p<0.001) were observed during the posttest for internal visual imagery. A significant correlation (r = 0.64; p<0.05) was observed between motor imagery vividness (estimated through imagery questionnaire) and autonomic responses during motor imagery after fatigue. These data support that unlike local muscle fatigue, physical fatigue occurring during intense sport training sessions is likely to affect motor imagery accuracy. These results might be explained by the updating of the internal representation of the motor sequence, due to temporary

  15. Uncertainty in techno-economic estimates of cellulosic ethanol production due to experimental measurement uncertainty.

    PubMed

    Vicari, Kristin J; Tallam, Sai Sandeep; Shatova, Tatyana; Joo, Koh Kang; Scarlata, Christopher J; Humbird, David; Wolfrum, Edward J; Beckham, Gregg T

    2012-04-17

    Cost-effective production of lignocellulosic biofuels remains a major financial and technical challenge at the industrial scale. A critical tool in biofuels process development is the techno-economic (TE) model, which calculates biofuel production costs using a process model and an economic model. The process model solves mass and energy balances for each unit, and the economic model estimates capital and operating costs from the process model based on economic assumptions. The process model inputs include experimental data on the feedstock composition and intermediate product yields for each unit. These experimental yield data are calculated from primary measurements. Uncertainty in these primary measurements is propagated to the calculated yields, to the process model, and ultimately to the economic model. Thus, outputs of the TE model have a minimum uncertainty associated with the uncertainty in the primary measurements. We calculate the uncertainty in the Minimum Ethanol Selling Price (MESP) estimate for lignocellulosic ethanol production via a biochemical conversion process: dilute sulfuric acid pretreatment of corn stover followed by enzymatic hydrolysis and co-fermentation of the resulting sugars to ethanol. We perform a sensitivity analysis on the TE model and identify the feedstock composition and conversion yields from three unit operations (xylose from pretreatment, glucose from enzymatic hydrolysis, and ethanol from fermentation) as the most important variables. The uncertainty in the pretreatment xylose yield arises from multiple measurements, whereas the glucose and ethanol yields from enzymatic hydrolysis and fermentation, respectively, are dominated by a single measurement: the fraction of insoluble solids (fIS) in the biomass slurries. We calculate a $0.15/gal uncertainty in MESP from the TE model due to uncertainties in primary measurements. This result sets a lower bound on the error bars of the TE model predictions. This analysis highlights the

  16. Uncertainty in techno-economic estimates of cellulosic ethanol production due to experimental measurement uncertainty

    PubMed Central

    2012-01-01

    Background Cost-effective production of lignocellulosic biofuels remains a major financial and technical challenge at the industrial scale. A critical tool in biofuels process development is the techno-economic (TE) model, which calculates biofuel production costs using a process model and an economic model. The process model solves mass and energy balances for each unit, and the economic model estimates capital and operating costs from the process model based on economic assumptions. The process model inputs include experimental data on the feedstock composition and intermediate product yields for each unit. These experimental yield data are calculated from primary measurements. Uncertainty in these primary measurements is propagated to the calculated yields, to the process model, and ultimately to the economic model. Thus, outputs of the TE model have a minimum uncertainty associated with the uncertainty in the primary measurements. Results We calculate the uncertainty in the Minimum Ethanol Selling Price (MESP) estimate for lignocellulosic ethanol production via a biochemical conversion process: dilute sulfuric acid pretreatment of corn stover followed by enzymatic hydrolysis and co-fermentation of the resulting sugars to ethanol. We perform a sensitivity analysis on the TE model and identify the feedstock composition and conversion yields from three unit operations (xylose from pretreatment, glucose from enzymatic hydrolysis, and ethanol from fermentation) as the most important variables. The uncertainty in the pretreatment xylose yield arises from multiple measurements, whereas the glucose and ethanol yields from enzymatic hydrolysis and fermentation, respectively, are dominated by a single measurement: the fraction of insoluble solids (fIS) in the biomass slurries. Conclusions We calculate a $0.15/gal uncertainty in MESP from the TE model due to uncertainties in primary measurements. This result sets a lower bound on the error bars of the TE model predictions

  17. Child mortality estimation: methods used to adjust for bias due to AIDS in estimating trends in under-five mortality.

    PubMed

    Walker, Neff; Hill, Kenneth; Zhao, Fengmin

    2012-01-01

    In most low- and middle-income countries, child mortality is estimated from data provided by mothers concerning the survival of their children using methods that assume no correlation between the mortality risks of the mothers and those of their children. This assumption is not valid for populations with generalized HIV epidemics, however, and in this review, we show how the United Nations Inter-agency Group for Child Mortality Estimation (UN IGME) uses a cohort component projection model to correct for AIDS-related biases in the data used to estimate trends in under-five mortality. In this model, births in a given year are identified as occurring to HIV-positive or HIV-negative mothers, the lives of the infants and mothers are projected forward using survivorship probabilities to estimate survivors at the time of a given survey, and the extent to which excess mortality of children goes unreported because of the deaths of HIV-infected mothers prior to the survey is calculated. Estimates from the survey for past periods can then be adjusted for the estimated bias. The extent of the AIDS-related bias depends crucially on the dynamics of the HIV epidemic, on the length of time before the survey that the estimates are made for, and on the underlying non-AIDS child mortality. This simple methodology (which does not take into account the use of effective antiretroviral interventions) gives results qualitatively similar to those of other studies.

  18. Time evolving bed shear stress due the passage of gravity currents estimated with ADVP velocity measurements

    NASA Astrophysics Data System (ADS)

    Zordan, Jessica; Schleiss, Anton J.; Franca, Mário J.

    2016-04-01

    Density or gravity currents are geophysical flows driven by density gradients between two contacting fluids. The physical trigger mechanism of these phenomena lays in the density differences which may be caused by differences in the temperature, dissolved substances or concentration of suspended sediments. Saline density currents are capable to entrain bed sediments inducing signatures in the bottom of sedimentary basins. Herein, saline density currents are reproduced in laboratory over a movable bed. The experimental channel is of the lock-exchange type, it is 7.5 m long and 0.3 m wide, divided into two sections of comparable volumes by a sliding gate. An upstream reach serves as a head tank for the dense mixture; the current propagates through a downstream reach where the main measurements are made. Downstream of the channel a tank exist to absorb the reflection of the current and thus artifacts due to the limited length of the channel. High performance thermoplastic polyurethane simulating fine sediments forms the movable bed. Measures of 3D instantaneous velocities will be made with the use of the non-intrusive technique of the ADV (Acoustic Doppler Current Profiler). With the velocity measurements, the evolution in time of the channel-bed shear stress due the passage of gravity currents is estimated. This is in turn related to the observed erosion and to such parameters determinant for the dynamics of the current as initial density difference, lock length and channel slope. This work was funded by the ITN-Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7-PEOPLE-2013-ITN under REA grant agreement n_607394-SEDITRANS.

  19. Potential bias of daily soil CO2 efflux estimates due to sampling time.

    PubMed

    Cueva, Alejandro; Bullock, Stephen H; López-Reyes, Eulogio; Vargas, Rodrigo

    2017-09-20

    Soil respiration (Rs) has been usually measured during daylight hours using manual chambers. This approach assumes that measurements made during a typical time interval (e.g., 9 to 11 am) represent the mean daily value; locally, this may not always be correct and could result in systematic bias of daily and annual Rs budgets. We propose a simple method, based on the temporal stability concept, to determine the most appropriate time of the day for manual measurements to capture a representative mean daily Rs value. We introduce a correction factor to adjust for biases due to non-optimally timed sampling. This approach was tested in a semiarid shrubland using 24 hr campaigns using two treatments: trenched plots and plots with shrubs. In general, we found optimum times were at night and potential biases ranged from -29 to + 40% in relation to the 24 hr mean of Rs, especially in trenched plots. The degree of bias varied between treatments and seasons, having a greater influence during the wet season when efflux was high than during the dry season when efflux was low. This study proposes a framework for improving local Rs estimates that informs how to decrease temporal uncertainties in upscaling to the annual total.

  20. Eliminating bias in rainfall estimates from microwave links due to antenna wetting

    NASA Astrophysics Data System (ADS)

    Fencl, Martin; Rieckermann, Jörg; Bareš, Vojtěch

    2014-05-01

    Commercial microwave links (MWLs) are point-to-point radio systems which are widely used in telecommunication systems. They operate at frequencies where the transmitted power is mainly disturbed by precipitation. Thus, signal attenuation from MWLs can be used to estimate path-averaged rain rates, which is conceptually very promising, since MWLs cover about 20 % of surface area. Unfortunately, MWL rainfall estimates are often positively biased due to additional attenuation caused by antenna wetting. To correct MWL observations a posteriori to reduce the wet antenna effect (WAE), both empirically and physically based models have been suggested. However, it is challenging to calibrate these models, because the wet antenna attenuation depends both on the MWL properties (frequency, type of antennas, shielding etc.) and different climatic factors (temperature, due point, wind velocity and direction, etc.). Instead, it seems straight forward to keep antennas dry by shielding them. In this investigation we compare the effectiveness of antenna shielding to model-based corrections to reduce the WAE. The experimental setup, located in Dübendorf-Switzerland, consisted of 1.85-km long commercial dual-polarization microwave link at 38 GHz and 5 optical disdrometers. The MWL was operated without shielding in the period from March to October 2011 and with shielding from October 2011 to July 2012. This unique experimental design made it possible to identify the attenuation due to antenna wetting, which can be computed as the difference between the measured and theoretical attenuation. The theoretical path-averaged attenuation was calculated from the path-averaged drop size distribution. During the unshielded periods, the total bias caused by WAE was 0.74 dB, which was reduced by shielding to 0.39 dB for the horizontal polarization (vertical: reduction from 0.96 dB to 0.44 dB). Interestingly, the model-based correction (Schleiss et al. 2013) was more effective because it reduced

  1. [Estimation of the Power Spectrum of Heart Rate Variability Using Improved Welch Method to Analyze the Degree of Fatigue].

    PubMed

    Xu, Wenhui; Liu, Kaihua; Wang, Liting

    2016-02-01

    Heart rate variability (HRV) is an important point to judge a person's state in modern medicine. This paper is aimed to research a person's fatigue level connected with vagal nerve based on the HRV using the improved Welch method. The process of this method is that it firstly uses a time window function on the signal to be processed, then sets the length of time according to the requirement, and finally makes frequency domain analysis. Compared with classical periodogram method, the variance and consistency of the present method have been improved. We can set time span freely using this method (at present, the time of international standard to measure HRV is 5 minutes). This paper analyses the HRV's characteristics of fatigue crowd based on the database provided by Physio-Net. We therefore draw the conclusion that the accuracy of Welch analyzing HRV combining with appropriate window function has been improved enormously, and when the person changes to fatigue, the vagal activity is diminished and sympathetic activity is raised.

  2. Estimating Indirect Emissions from Land Use Change Due to Biofuels (Invited)

    NASA Astrophysics Data System (ADS)

    Reilly, J. M.

    2010-12-01

    Interest in biofuels as an alternative fuel has led to the realization that they may not be a viable low greenhouse gas alternative, even if process emissions are low, because expansions of land area in biomass crops may lead to forest destruction and hence carbon emissions.(1,2)If the concern was only direct land use effects—changes in carbon stocks on land directly used for biomass—direct measurement would be an option. However, agricultural economists recognize that if biofuels are produced from crops grown on existing cropland the crops previously grown there will likely be replaced by production elsewhere. Given international markets in agricultural products a diversion of land or part of the corn crop in the US for biofuels would result in higher market prices for corn and other crops, and thus spur land conversion almost anywhere around the world. There have now been a number of estimates of the potential land use emissions, and those estimates vary widely and are sensitive to key parameters of both the economic models used in the analysis and the representation of biophysical processes.(3,4,5)Among the important parameters are those that describe the willingness to convert unmanaged land, the ability to intensify production on existing land, the productivity of new land coming to production compared to existing cropland, demand elasticities for agricultural products, and the representation of carbon and nitrogen cycles and storage.(6,7) 1. J. Fargione, J. et al., Science 319, 1235 (2008). 2. T. Searchinger, T et al., Science 319, 1238 (2008) 3. J.M. Melillo, Science, 326: 1397-1399 (2009) 4. M. Wise et al., Science 324, 1183 (2009). 5. W. E. Tyner, et al., Land Use Changes and Consequent CO2 Emissions due to US Corn Ethanol Production: A Comprehensive Analysis, Department of Agricultural Economics, Purdue University (July 2010). 6. T. W. Hertel, The Global Supply and Demand for Agricultural Land in 2050: A Perfect Storm in the Making? AAEA Presidential

  3. Recent wetland land loss due to hurricanes: improved estimates based upon multiple source images

    USGS Publications Warehouse

    Kranenburg, Christine J.; Palaseanu-Lovejoy, Monica; Barras, John A.; Brock, John C.; Wang, Ping; Rosati, Julie D.; Roberts, Tiffany M.

    2011-01-01

    The objective of this study was to provide a moderate resolution 30-m fractional water map of the Chenier Plain for 2003, 2006 and 2009 by using information contained in high-resolution satellite imagery of a subset of the study area. Indices and transforms pertaining to vegetation and water were created using the high-resolution imagery, and a threshold was applied to obtain a categorical land/water map. The high-resolution data was used to train a decision-tree classifier to estimate percent water in a lower resolution (Landsat) image. Two new water indices based on the tasseled cap transformation were proposed for IKONOS imagery in wetland environments and more than 700 input parameter combinations were considered for each Landsat image classified. Final selection and thresholding of the resulting percent water maps involved over 5,000 unambiguous classified random points using corresponding 1-m resolution aerial photographs, and a statistical optimization procedure to determine the threshold at which the maximum Kappa coefficient occurs. Each selected dataset has a Kappa coefficient, percent correctly classified (PCC) water, land and total greater than 90%. An accuracy assessment using 1,000 independent random points was performed. Using the validation points, the PCC values decreased to around 90%. The time series change analysis indicated that due to Hurricane Rita, the study area lost 6.5% of marsh area, and transient changes were less than 3% for either land or water. Hurricane Ike resulted in an additional 8% land loss, although not enough time has passed to discriminate between persistent and transient changes.

  4. Substantial under-estimation in cancer incidence estimates for developing countries due to under-ascertainment in elderly cancer cases.

    PubMed

    Fallah, Mahdi; Kharazmi, Elham

    2008-06-18

    Under-ascertainment of elderly cases in cancer registry data is a well-known problem. This article provides the cancer incidence in developing countries corrected for the under-ascertainment in elderly cancer cases (aged 65+). The original incidence rate by GLOBOCAN 2002 was 11% (men 15%; women 7%) under-estimated, so there were 6,462,000 new cancer cases (3,093,000 men; 2,737,000 women) in 2002 topping the original estimate by 632,000. This paper is the first attempt to quantify the under-ascertainment bias in the cancer burden of developing countries and opens the discussion on how cancer incidence could be corrected in this increasing part of the population.

  5. A Structural Weight Estimation Program (SWEEP) for Aircraft. Volume 4 - Material Properties, Structure Temperature, Flutter and Fatigue

    DTIC Science & Technology

    1974-06-01

    3 NUMBER OF PAGES -Agfr ^K IS. SECURITY CLASS, (ol Ihl...Section -y I’art 3 - l-’atiguc Module II III INTROlHICnON /VN1) SUMMiY Progr.’un objectives Approacli to l-’atlgue Evaluation Summary of...IHfiwifmMiwK’wwwm^^ r.vimf’r n.r-frtrrriniwwv’w* IVI* m’r>Tr’*’’<’>7’fV"li*W’!l.Jl^!»’-’«’m ■ lyure Title Page Part 3 - Fatigue Module 30

  6. Correcting the bias of spike field coherence estimators due to a finite number of spikes.

    PubMed

    Grasse, D W; Moxon, K A

    2010-07-01

    The coherence between oscillatory activity in local field potentials (LFPs) and single neuron action potentials, or spikes, has been suggested as a neural substrate for the representation of information. The power spectrum of a spike-triggered average (STA) is commonly used to estimate spike field coherence (SFC). However, when a finite number of spikes is used to construct the STA, the coherence estimator is biased. We introduce here a correction for the bias imposed by the limited number of spikes available in experimental conditions. In addition, we present an alternative method for estimating SFC from an STA by using a filter bank approach. This method is shown to be more appropriate in some analyses, such as comparing coherence across frequency bands. The proposed bias correction is a linear transformation derived from an idealized model of spike-field interaction but is shown to hold in more realistic settings. Uncorrected and corrected SFC estimates from both estimation methods are compared across multiple simulated spike-field models and experimentally collected data. The bias correction was shown to reduce the bias of the estimators, but add variance. However, the corrected estimates had a reduced or unchanged mean squared error in the majority of conditions evaluated. The bias correction provides an effective way to reduce bias in an SFC estimator without increasing the mean squared error.

  7. Visual fatigue versus eye-movements

    NASA Astrophysics Data System (ADS)

    Vienne, Cyril; Blondé, Laurent; Doyen, Didier

    2012-03-01

    Observing 3D content on a cinema or TV screen potentially generates fatigue. In psychovisual research, experience of visual symptoms following the observation of stereo-content is usually assessed thanks to questionnaires and subjective reports. We attempted to explore the occurrence of visual fatigue using more objective methods, namely by using binocular eye-tracking and psychophysics. A main objective was to study the emergence of visual fatigue in relation with eye-movement knowing the stimulation of the oculomotor system and its response. We designed an experiment in which participants were asked to perform a repeated vergence effort task, just followed by, and interlaced with, a 3D space perception task. Participants' eye movements were recorded during the whole session using an eye-tracking system. The analysis revealed that the perception of 3D shapes was gradually affected by the intensity of the vergence effort task. The effect on stereo-estimation was actually due to visual fatigue. 3D objects and scenes are perceived flatter. Results on the subjective reports of SSQ revealed that oculomotor factors were predominant in the visual symptoms. In addition, some effects and correlations on the micro-saccadic rate were obtained. This work offers a perspective to characterize objectively visual fatigue when watching stereoscopic 3D content.

  8. Postdialysis fatigue.

    PubMed

    Sklar, A H; Riesenberg, L A; Silber, A K; Ahmed, W; Ali, A

    1996-11-01

    To clarify the demographic and clinicolaboratory features of postdialysis fatigue (PDF), we enrolled 85 patients on maintenance hemodialysis in a cross-sectional study using validated questionnaires and chart review. Forty-three patients complained of fatigue after dialysis. On formal testing using the Kidney Disease Questionnaire, the PDF group had statistically greater severity of fatigue and somatic complaints than the group of patients without subjective fatigue (P = 0.03 and 0.04, respectively). On a scale measuring intensity of fatigue (1 = least to 5 = worst), the PDF group average was 3.4 +/- 1.2. PDF subjects reported that 80% +/- 25% of dialysis treatments were followed by fatigue symptoms. In 28 (65%) of patients, the symptoms started with the first dialysis treatment. They reported needing an average of 4.8 hours of rest or sleep to overcome the fatigue symptoms (range, 0 to 24 hours). There were no significant differences between patients with and without PDF in the following parameters: age; sex; type of renal disease; presence of diabetes mellitus, heart disease (congestive, ischemic), or chronic obstructive lung disease; blood pressure response to dialysis; type or adequacy of dialysis regimen; hematocrit; electrolytes; blood urea nitrogen; creatinine; cholesterol; albumin; parathyroid hormone; ejection fraction; and use of antihistamines, benzodiazepines, and narcotics. In the fatigue group, there was significantly greater use of antihypertensive medications known to have fatigue as a side effect (P = 0.007). Depression was more common in the fatigue group by Beck Depression score (11.6 +/- 8.0 v 7.8 +/- 6.3; P = 0.02). We conclude that (1) postdialysis fatigue is a common, often incapacitating symptom in patients on chronic extracorporeal dialysis; (2) no routinely measured parameter of clinical or dialytic function appears to predict postdialysis fatigue; and (3) depression is highly associated with postdialysis fatigue, but the cause

  9. Pedigree error due to extra-pair reproduction substantially biases estimates of inbreeding depression.

    PubMed

    Reid, Jane M; Keller, Lukas F; Marr, Amy B; Nietlisbach, Pirmin; Sardell, Rebecca J; Arcese, Peter

    2014-03-01

    Understanding the evolutionary dynamics of inbreeding and inbreeding depression requires unbiased estimation of inbreeding depression across diverse mating systems. However, studies estimating inbreeding depression often measure inbreeding with error, for example, based on pedigree data derived from observed parental behavior that ignore paternity error stemming from multiple mating. Such paternity error causes error in estimated coefficients of inbreeding (f) and reproductive success and could bias estimates of inbreeding depression. We used complete "apparent" pedigree data compiled from observed parental behavior and analogous "actual" pedigree data comprising genetic parentage to quantify effects of paternity error stemming from extra-pair reproduction on estimates of f, reproductive success, and inbreeding depression in free-living song sparrows (Melospiza melodia). Paternity error caused widespread error in estimates of f and male reproductive success, causing inbreeding depression in male and female annual and lifetime reproductive success and juvenile male survival to be substantially underestimated. Conversely, inbreeding depression in adult male survival tended to be overestimated when paternity error was ignored. Pedigree error stemming from extra-pair reproduction therefore caused substantial and divergent bias in estimates of inbreeding depression that could bias tests of evolutionary theories regarding inbreeding and inbreeding depression and their links to variation in mating system. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

  10. Fatigue life of laser cut metals

    NASA Technical Reports Server (NTRS)

    Martin, M. R.

    1986-01-01

    Fatigue tests were conducted to determine the actual reduction in fatigue life due to weight removal for balancing by: hand grinding, low power (20 watt) Nd:glass laser, and high power (400 watt) Nd:YAG laser.

  11. Estimation of blood alcohol concentration in deaths due to roadside accidents.

    PubMed

    Arora, Puneet; Chanana, Ashok; Tejpal, Hakumat R

    2013-05-01

    Like any other disease, accidents too are caused by interaction between agent, host, and environment. Human factors include age, (accidents most common between 10 and 24 years), sex, education, medical conditions (heart attack, impaired vision), fatigue, influence of alcohol and other drugs, lack of bodily protection (like helmets, seat belts) and psychosocial factors like lack of experience, impulsiveness, aggressiveness, defective judgment and delay in decisions. Drunken driving is an important risk factor in causing accidents. This study was focused on the status of alcohol consumption in relation with roadside accidents in northern India in the region of Amritsar. The present study was carried out in 100 cases alleged to have died of roadside accident and brought to the mortuary attached to the Department of Forensic Medicine and Toxicology, Government Medical College, Amritsar for autopsy examination. Blood samples were collected from the femoral vein and were tested for the presence of alcohol with steam distillation and titration method using potassium dichromate and sulfuric acid. In the present study, 23% of the fatal driver/pedestrian victims of roadside accidents were found to have consumed alcohol before accident. Most of the victims of road accident were from the age group 21-30 and 31-40 years. Most of the accidents occurred on straight roads instead of bends or intersections, more during daytime and weekends. 57% of the blood alcohol positives were between 100 mg% and 149 mg%. Majority of the victims of roadside accidents were motorcyclists and the striking vehicles were trucks and buses causing head & neck injuries in most of the victims. Death occurred within a few minutes in most of the cases.

  12. Limitation of Ground-based Estimates of Solar Irradiance Due to Atmospheric Variations

    NASA Technical Reports Server (NTRS)

    Wen, Guoyong; Cahalan, Robert F.; Holben, Brent N.

    2003-01-01

    The uncertainty in ground-based estimates of solar irradiance is quantitatively related to the temporal variability of the atmosphere's optical thickness. The upper and lower bounds of the accuracy of estimates using the Langley Plot technique are proportional to the standard deviation of aerosol optical thickness (approx. +/- 13 sigma(delta tau)). The estimates of spectral solar irradiance (SSI) in two Cimel sun photometer channels from the Mauna Loa site of AERONET are compared with satellite observations from SOLSTICE (Solar Stellar Irradiance Comparison Experiment) on UARS (Upper Atmospheric Research Satellite) for almost two years of data. The true solar variations related to the 27-day solar rotation cycle observed from SOLSTICE are about 0.15% at the two sun photometer channels. The variability in ground-based estimates is statistically one order of magnitude larger. Even though about 30% of these estimates from all Level 2.0 Cimel data fall within the 0.4 to approx. 0.5% variation level, ground-based estimates are not able to capture the 27-day solar variation observed from SOLSTICE.

  13. Chronic fatigue and chronic fatigue syndrome: shifting boundaries and attributions.

    PubMed

    Lloyd, A R

    1998-09-28

    The subjective symptom of "fatigue" is one of the most widespread in the general population and is a major source of healthcare utilization. Prolonged fatigue is often associated with neuropsychological and musculoskeletal symptoms that form the basis of several syndromal diagnoses including chronic fatigue syndrome, fibromyalgia, and neurasthenia, and is clearly not simply the result of a lack of force generation from the muscle. Current epidemiologic research in this area relies predominantly on self-report data to document the prevalence and associations of chronic fatigue. Of necessity, this subjective data source gives rise to uncertain diagnostic boundaries and consequent divergent epidemiologic, clinical, and pathophysiologic research findings. This review will highlight the impact of the case definition and ascertainment methods on the varying prevalence estimates of chronic fatigue syndrome and patterns of reported psychological comorbidty. It will also evaluate the evidence for a true postinfective fatigue syndrome.

  14. Risk assessment in diabetes management: how do general practitioners estimate risks due to diabetes?

    PubMed Central

    Häussler, Bertram; Fischer, Gisela C; Meyer, Sibylle; Sturm, Diethard

    2007-01-01

    Objectives To evaluate the ability of general practitioners (GPs) in Germany to estimate the risk of patients with diabetes developing complications. Methods An interview study using a structured questionnaire to estimate risks of four case vignettes having diabetes‐specific complications within the next 10 years, risk reduction and life expectancy potential. A representative random sample of 584 GPs has been drawn, of which 150 could be interviewed. We compared GPs' estimates among each other (intraclass correlation coefficient (ICC) and Cohen's (multirater‐) κ) and with risks for long‐term complications generated by the multifactor disease model “Mellibase”, which is a knowledge‐based support system for medical decision management. Results The risk estimates by GPs varied widely (ICC 0.21 95% CI (0.13 to 0.36)). The average level of potential risk reduction was between 47% and 70%. Compared with Mellibase values, on average, the GPs overestimated the risk threefold. Mean estimates of potential prolongation of life expectancy were close to 10 years for each patient, whereas the Mellibase calculations ranged from 3 to 10 years. Conclusions Overestimation could lead to unnecessary care and waste of resources. PMID:17545348

  15. Path-averaged rainfall estimation using microwave links: Uncertainty due to spatial rainfall variability

    NASA Astrophysics Data System (ADS)

    Berne, A.; Uijlenhoet, R.

    2007-04-01

    Microwave links can be used to estimate the path-averaged rain rate along the link when precipitation occurs. They take advantage of the near proportionality between the specific attenuation affecting the link signal and the rain rate. This paper deals with the influence of the spatial variability of rainfall along the link on the accuracy of the rainfall estimates. We focus on single-polarization single-frequency links operating at frequencies ranging from 5 to 50 GHz and with path lengths ranging from 500 m to 30 km. A stochastic simulation framework is used to investigate the frequency at which the linearity occurs (found to be about 30 GHz) for intense Mediterranean precipitation. In addition, the error associated with path-averaged rain rate estimates is being quantified. For instance, the bias is found to be in the order of -15% with an uncertainty of about 10% for microwave links described in the recent literature.

  16. Estimated trichloroethene transformation rates due to naturally occurring biodegradation in a fractured-rock aquifer

    USGS Publications Warehouse

    Chapelle, Francis H.; Lacombe, Pierre J.; Bradley, Paul M.

    2012-01-01

    Rates of trichloroethene (TCE) mass transformed by naturally occurring biodegradation processes in a fractured rock aquifer underlying a former Naval Air Warfare Center (NAWC) site in West Trenton, New Jersey, were estimated. The methodology included (1) dividing the site into eight elements of equal size and vertically integrating observed concentrations of two daughter products of TCE biodegradation–cis-dichloroethene (cis-DCE) and chloride–using water chemistry data from a network of 88 observation wells; (2) summing the molar mass of cis-DCE, the first biodegradation product of TCE, to provide a probable underestimate of reductive biodegradation of TCE, (3) summing the molar mass of chloride, the final product of chlorinated ethene degradation, to provide a probable overestimate of overall biodegradation. Finally, lower and higher estimates of aquifer porosities and groundwater residence times were used to estimate a range of overall transformation rates. The highest TCE transformation rates estimated using this procedure for the combined overburden and bedrock aquifers was 945 kg/yr, and the lowest was 37 kg/yr. However, hydrologic considerations suggest that approximately 100 to 500 kg/yr is the probable range for overall TCE transformation rates in this system. Estimated rates of TCE transformation were much higher in shallow overburden sediments (approximately 100 to 500 kg/yr) than in the deeper bedrock aquifer (approximately 20 to 0.15 kg/yr), which reflects the higher porosity and higher contaminant mass present in the overburden. By way of comparison, pump-and-treat operations at the NAWC site are estimated to have removed between 1,073 and 1,565 kg/yr of TCE between 1996 and 2009.

  17. A method for estimating the rolling moment due to spin rate for arbitrary planform wings

    NASA Technical Reports Server (NTRS)

    Poppen, W. A., Jr.

    1985-01-01

    The application of aerodynamic theory for estimating the force and moments acting upon spinning airplanes is of interest. For example, strip theory has been used to generate estimates of the aerodynamic characteristics as a function of spin rate for wing-dominated configurations for angles of attack up to 90 degrees. This work, which had been limited to constant chord wings, is extended here to wings comprised of tapered segments. Comparison of the analytical predictions with rotary balance wind tunnel results shows that large discrepancies remain, particularly for those angles-of-attack greater than 40 degrees.

  18. Analytical estimation show low depth-independent water loss due to vapor flux from deep aquifers

    NASA Astrophysics Data System (ADS)

    Selker, John S.

    2017-06-01

    Recent articles have provided estimates of evaporative flux from water tables in deserts that span 5 orders of magnitude. In this paper, we present an analytical calculation that indicates aquifer vapor flux to be limited to 0.01 mm/yr for sites where there is negligible recharge and the water table is well over 20 m below the surface. This value arises from the geothermal gradient, and therefore, is nearly independent of the actual depth of the aquifer. The value is in agreement with several numerical studies, but is 500 times lower than recently reported experimental values, and 100 times larger than an earlier analytical estimate.

  19. Estimating How Often Mass Extinctions Due to Impacts Occur on the Earth

    NASA Technical Reports Server (NTRS)

    Buratti, Bonnie J.

    2013-01-01

    This hands-on, inquiry based activity has been taught at JPL's summer workshop "Teachers Touch the Sky" for the past two decades. Students act as mini-investigators as they gather and analyze data to estimate how often an impact large enough to cause a mass extinction occurs on the Earth. Large craters are counted on the Moon, and this number is extrapolated to the size of the Earth. Given the age of the Solar System, the students can then estimate how often large impacts occur on the Earth. This activity is based on an idea by Dr. David Morrison, NASA Ames Research Center.

  20. Estimating How Often Mass Extinctions Due to Impacts Occur on the Earth

    NASA Technical Reports Server (NTRS)

    Buratti, Bonnie J.

    2013-01-01

    This hands-on, inquiry based activity has been taught at JPL's summer workshop "Teachers Touch the Sky" for the past two decades. Students act as mini-investigators as they gather and analyze data to estimate how often an impact large enough to cause a mass extinction occurs on the Earth. Large craters are counted on the Moon, and this number is extrapolated to the size of the Earth. Given the age of the Solar System, the students can then estimate how often large impacts occur on the Earth. This activity is based on an idea by Dr. David Morrison, NASA Ames Research Center.

  1. Fatigue in advanced cancer: a prospective study.

    PubMed

    Hauser, Katherine; Walsh, Declan; Rybicki, Lisa A; Davis, Mellar P; Seyidova-Khoshknabi, Dilara

    2008-01-01

    Fatigue is a common advanced cancer symptom. Clinical features are not well known. The authors surveyed consecutive patients admitted to a palliative medicine program to identify clinical correlates of fatigue. Data collected included age, sex, performance status, primary site, prior chemotherapy/radiation therapy, and blood transfusions. Visual analogue scales assessed fatigue, quality of life, and ability to perform daily activities. Weight change was estimated. Laboratory results including lactate dehydrogenase and hemoglobin were recorded. Fatigue severity was associated with brain metastases, poor performance status, poor quality of life, and reduced ability to perform activities. Prior radiation therapy was associated with less severe fatigue. Age, sex, and hemoglobin level were not associated with fatigue. Fatigue was universal on referral. Brain metastases and poor quality of life independently predicted severity. Hemoglobin level did not predict fatigue. Further studies are necessary to define the clinical features and relationships of fatigue.

  2. Inaccurate Estimation of Disparities Due to Mischievous Responders: Several Suggestions to Assess Conclusions

    ERIC Educational Resources Information Center

    Robinson-Cimpian, Joseph P.

    2014-01-01

    This article introduces novel sensitivity-analysis procedures for investigating and reducing the bias that mischievous responders (i.e., youths who provide extreme, and potentially untruthful, responses to multiple questions) often introduce in adolescent disparity estimates based on data from self-administered questionnaires (SAQs). Mischievous…

  3. Probabilistic Fatigue Damage Program (FATIG)

    NASA Technical Reports Server (NTRS)

    Michalopoulos, Constantine

    2012-01-01

    FATIG computes fatigue damage/fatigue life using the stress rms (root mean square) value, the total number of cycles, and S-N curve parameters. The damage is computed by the following methods: (a) traditional method using Miner s rule with stress cycles determined from a Rayleigh distribution up to 3*sigma; and (b) classical fatigue damage formula involving the Gamma function, which is derived from the integral version of Miner's rule. The integration is carried out over all stress amplitudes. This software solves the problem of probabilistic fatigue damage using the integral form of the Palmgren-Miner rule. The software computes fatigue life using an approach involving all stress amplitudes, up to N*sigma, as specified by the user. It can be used in the design of structural components subjected to random dynamic loading, or by any stress analyst with minimal training for fatigue life estimates of structural components.

  4. Fatigue in aviation.

    PubMed

    Caldwell, John A

    2005-05-01

    Pilot fatigue is a significant, but often under-reported problem in both civilian and military aviation operations. Although estimates vary, official statistics indicate that fatigue is involved in at least 4-8% of aviation mishaps, and surveys of pilots and aircrew members reveal that fatigue is an important concern throughout today's 24/7 flight operations. Regulatory efforts aimed at limiting flight hours and ensuring at least minimal periods of crew rest have to some extent mitigated fatigue-related difficulties in the cockpit, but it is clear that much remains to be done about this insidious threat to air safety. Scheduling factors, sleep deprivation, circadian disruptions, and extended duty periods continue to challenge the alertness and performance levels of both short-haul and long-haul pilots and crews. Solutions for these problems are not straightforward, but they can be developed through the cooperative efforts of scientists, regulators, managers, and the pilots themselves. Over the past 20 years, scientific understanding of human sleep, fatigue, and circadian rhythms has expanded considerably. The thorough integration of this new knowledge into modern crew-resource management practices will facilitate the establishment of optimal crew scheduling routines and the implementation of valid aviation fatigue countermeasures.

  5. Dynamic modelling and estimation of the error due to asynchronism in a redundant asynchronous multiprocessor system

    NASA Technical Reports Server (NTRS)

    Huynh, Loc C.; Duval, R. W.

    1986-01-01

    The use of Redundant Asynchronous Multiprocessor System to achieve ultrareliable Fault Tolerant Control Systems shows great promise. The development has been hampered by the inability to determine whether differences in the outputs of redundant CPU's are due to failures or to accrued error built up by slight differences in CPU clock intervals. This study derives an analytical dynamic model of the difference between redundant CPU's due to differences in their clock intervals and uses this model with on-line parameter identification to idenitify the differences in the clock intervals. The ability of this methodology to accurately track errors due to asynchronisity generate an error signal with the effect of asynchronisity removed and this signal may be used to detect and isolate actual system failures.

  6. Estimating mortality, morbidity and disability due to malaria among Africa's non-pregnant population.

    PubMed Central

    Snow, R. W.; Craig, M.; Deichmann, U.; Marsh, K.

    1999-01-01

    The contribution of malaria to morbidity and mortality among people in Africa has been a subject of academic interest, political advocacy, and speculation. National statistics for much of sub-Saharan Africa have proved to be an unreliable source of disease-specific morbidity and mortality data. Credible estimates of disease-specific burdens are required for setting global and national priorities for health in order to rationalize the use of limited resources and lobby for financial support. We have taken an empirical approach to defining the limits of Plasmodium falciparum transmission across the continent and interpolated the distributions of projected populations in 1995. By combining a review of the literature on malaria in Africa and models of acquired functional immunity, we have estimated the age-structured rates of the fatal, morbid and disabling sequelae following exposure to malaria infection under different epidemiological conditions. PMID:10516785

  7. Estimation of true incidence of polio: overcoming misclassification errors due to stool culture insensitivity.

    PubMed

    Srinivas, V; Puliyel, Jacob M

    2007-08-01

    The diagnosis of polio dependents on culturing the virus in stool samples of children with AFP. Using data obtained under the "Right to Information Act" of instances where only one of the two samples was positive for polio, it was possible to estimate the sensitivity of the system to detect cases of polio. The calculations suggest that there were 1625 (95% CI 1528 to 1725) cases of polio in India in 2006 rather than the 674 reported widely!

  8. One strategy for estimating the potential soil carbon storage due to CO{sub 2} fertilization

    SciTech Connect

    Harrison, K.G.; Bonani, G.

    1994-06-01

    Soil radiocarbon measurements can be used to estimate soil carbon turnover rates and inventories. A labile component of soil carbon has the potential to respond to perturbations such as CO{sub 2} fertilization, changing climate, and changing land use. Soil carbon has influenced past and present atmospheric CO{sub 2} levels and will influence future levels. A model is used to calculate the amount of additional carbon stored in soil because of CO{sub 2} fertilization.

  9. Multimodel estimates of premature human mortality due to intercontinental transport of air pollution

    NASA Astrophysics Data System (ADS)

    Liang, C.; Silva, R.; West, J. J.; Sudo, K.; Lund, M. T.; Emmons, L. K.; Takemura, T.; Bian, H.

    2015-12-01

    Numerous modeling studies indicate that emissions from one continent influence air quality over others. Reducing air pollutant emissions from one continent can therefore benefit air quality and health on multiple continents. Here, we estimate the impacts of the intercontinental transport of ozone (O3) and fine particulate matter (PM2.5) on premature human mortality by using an ensemble of global chemical transport models coordinated by the Task Force on Hemispheric Transport of Air Pollution (TF HTAP). We use simulations of 20% reductions of all anthropogenic emissions from 13 regions (North America, Central America, South America, Europe, Northern Africa, Sub-Saharan Africa, Former Soviet Union, Middle East, East Asia, South Asia, South East Asia, Central Asia, and Australia) to calculate their impact on premature mortality within each region and elsewhere in the world. To better understand the impact of potential control strategies, we also analyze premature mortality for global 20% perturbations from five sectors individually: power and industry, ground transport, forest and savannah fires, residential, and others (shipping, aviation, and agriculture). Following previous studies, premature human mortality resulting from each perturbation scenario is calculated using a health impact function based on a log-linear model for O3 and an integrated exposure response model for PM2.5 to estimate relative risk. The spatial distribution of the exposed population (adults aged 25 and over) is obtained from the LandScan 2011 Global Population Dataset. Baseline mortality rates for chronic respiratory disease, ischemic heart disease, cerebrovascular disease, chronic obstructive pulmonary disease, and lung cancer are estimated from the GBD 2010 country-level mortality dataset for the exposed population. Model results are regridded from each model's original grid to a common 0.5°x0.5° grid used to estimate mortality. We perform uncertainty analysis and evaluate the sensitivity

  10. Creep-Fatigue Interaction Testing

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.

    2001-01-01

    Fatigue fives in metals are nominally time independent below 0.5 T(sub Melt). At higher temperatures, fatigue lives are altered due to time-dependent, thermally activated creep. Conversely, creep rates are altered by super. imposed fatigue loading. Creep and fatigue generally interact synergistically to reduce material lifetime. Their interaction, therefore, is of importance to structural durability of high-temperature structures such as nuclear reactors, reusable rocket engines, gas turbine engines, terrestrial steam turbines, pressure vessel and piping components, casting dies, molds for plastics, and pollution control devices. Safety and lifecycle costs force designers to quantify these interactions. Analytical and experimental approaches to creep-fatigue began in the era following World War II. In this article experimental and life prediction approaches are reviewed for assessing creep-fatigue interactions of metallic materials. Mechanistic models are also discussed briefly.

  11. Estimation of Phase Delay due to Precipitable Water for Dinsarbased Land Deformation Monitoring

    NASA Astrophysics Data System (ADS)

    Susaki, J.; Maeda, N.; Akatsuka, S.

    2017-09-01

    In this paper, we present a method for using the estimated precipitable water (PW) to mitigate atmospheric phase delay in order to improve the accuracy of land-deformation assessment with differential interferometric synthetic aperture radar (DInSAR). The phase difference obtained from multi-temporal synthetic aperture radar images contains errors of several types, and the atmospheric phase delay can be an obstacle to estimating surface subsidence. In this study, we calculate PW from external meteorological data. Firstly, we interpolate the data with regard to their spatial and temporal resolutions. Then, assuming a range direction between a target pixel and the sensor, we derive the cumulative amount of differential PW at the height of the slant range vector at pixels along that direction. The atmospheric phase delay of each interferogram is acquired by taking a residual after a preliminary determination of the linear deformation velocity and digital elevation model (DEM) error, and by applying high-pass temporal and low-pass spatial filters. Next, we estimate a regression model that connects the cumulative amount of PW and the atmospheric phase delay. Finally, we subtract the contribution of the atmospheric phase delay from the phase difference of the interferogram, and determine the linear deformation velocity and DEM error. The experimental results show a consistent relationship between the cumulative amount of differential PW and the atmospheric phase delay. An improvement in land-deformation accuracy is observed at a point at which the deformation is relatively large. Although further investigation is necessary, we conclude at this stage that the proposed approach has the potential to improve the accuracy of the DInSAR technique.

  12. Estimating earnings losses due to mental illness: a quantile regression approach.

    PubMed

    Marcotte, Dave E; Wilcox-Gök, Virginia

    2003-09-01

    The ability of workers to remain productive and sustain earnings when afflicted with mental illness depends importantly on access to appropriate treatment and on flexibility and support from employers. In the United States there is substantial variation in access to health care and sick leave and other employment flexibilities across the earnings distribution. Consequently, a worker's ability to work and how much his/her earnings are impeded likely depend upon his/her position in the earnings distribution. Because of this, focusing on average earnings losses may provide insufficient information on the impact of mental illness in the labor market. In this paper, we examine the effects of mental illness on earnings by recognizing that effects could vary across the distribution of earnings. Using data from the National Comorbidity Survey, we employ a quantile regression estimator to identify the effects at key points in the earnings distribution. We find that earnings effects vary importantly across the distribution. While average effects are often not large, mental illness more commonly imposes earnings losses at the lower tail of the distribution, especially for women. In only one case do we find an illness to have negative effects across the distribution. Mental illness can have larger negative impacts on economic outcomes than previously estimated, even if those effects are not uniform. Consequently, researchers and policy makers alike should not be placated by findings that mean earnings effects are relatively small. Such estimates miss important features of how and where mental illness is associated with real economic losses for the ill.

  13. Estimates of Vertical Eddy Diffusion Due to Turbulent Layers in the Stratosphere

    DTIC Science & Technology

    1979-02-01

    turbulence depends upon estimates of the dissipation rate, e, based in turn upon the spectral analisis of in situ velocity fluctuations. Lilly2 has...of problem is well known in heat conduction, and the solution is obtained in the classic manner of separation of variables and Fourier series expan...sion (see for example, Ingersoll et al, p. 126). One thus arrives at C(Z AtM)NCo e KLEtM sin •b) (21) where bm is the Fourier coefficient given by

  14. Estimating the change in asymptotic direction due to secular changes in the geomagnetic field

    NASA Technical Reports Server (NTRS)

    Flueckiger, E. O.; Smart, D. F.; Shea, M. A.; Gentile, L. C.; Bathurat, A. A.

    1985-01-01

    The concept of geomagnetic optics, as described by the asymptotic directions of approach, is extremely useful in the analysis of cosmic radiation data. However, when changes in cutoff occur as a result of evolution in the geomagnetic field, there are corresponding changes in the asymptotic cones of acceptance. A method is introduced of estimating the change in the asymptotic direction of approach for vertically incident cosmic ray particles from a reference set of directions at a specific epoch by considering the change in the geomagnetic cutoff.

  15. Model estimates of sea-level change due to anthropogenic impacts on terrestrial water storage

    NASA Astrophysics Data System (ADS)

    Pokhrel, Yadu N.; Hanasaki, Naota; Yeh, Pat J.-F.; Yamada, Tomohito J.; Kanae, Shinjiro; Oki, Taikan

    2012-06-01

    Global sea level has been rising over the past half century, according to tide-gauge data. Thermal expansion of oceans, melting of glaciers and loss of the ice masses in Greenland and Antarctica are commonly considered as the largest contributors, but these contributions do not entirely explain the observed sea-level rise. Changes in terrestrial water storage are also likely to affect sea level, but comprehensive and reliable estimates of this contribution, particularly through human water use, are scarce. Here, we estimate sea-level change in response to human impacts on terrestrial water storage by using an integrated model that simulates global terrestrial water stocks and flows (exclusive to Greenland and Antarctica) and especially accounts for human activities such as reservoir operation and irrigation. We find that, together, unsustainable groundwater use, artificial reservoir water impoundment, climate-driven changes in terrestrial water storage and the loss of water from closed basins have contributed a sea-level rise of about 0.77mmyr-1 between 1961 and 2003, about 42% of the observed sea-level rise. We note that, of these components, the unsustainable use of groundwater represents the largest contribution.

  16. Estimated variability of real-ear insertion response (REIR) due to loudspeaker type and placement.

    PubMed

    Stone, Michael A; Moore, Brian C

    2004-05-01

    The real-ear insertion response (REIR) of a hearing aid is estimated as the difference between the aided response and the unaided response in the ear canal. Changes in the position of the loudspeaker relative to the head, between the two measurements, may reduce the accuracy of the estimate. The spatial variability of the sound field at distances close to the loudspeaker is less for a 'flat-panel' loudspeaker than for a conventional cone loudspeaker; the panel might thus lead to a reduced influence of loud-speaker position. To assess this, we measured the real-ear unaided response (REUR) as each of three loudspeakers (two cone type and one panel) was moved in a three-dimensional space centred at either 0 degrees or 45 degrees azimuth, at a distance of 50cm from a KEMAR manikin. Contrary to our expectation, the variability of the REUR was larger for the panel than for the cone loudspeakers The REUR varied less with position for the 0 degrees than for the 45 degrees azimuth. The variability of the REUR decreased with increasing distance of the loudspeaker from KEMAR. We tentatively suggest that loudspeaker-to-client distances of 40-50 cm should be used and that a 0 degrees azimuth is preferable.

  17. Errors in NAPL volume estimates due to systematic measurement errors during partitioning tracer tests.

    PubMed

    Brooks, Michael C; Wise, William R

    2005-09-15

    During moment-based analyses of partitioning tracer tests, systematic errors in volume and concentration measurements propagate to yield errors in the saturation and volume estimates for nonaqueous phase liquid (NAPL). Derived expressions could be applied to help practitioners bracket their estimates of NAPL saturation and volume obtained from such tests. In practice, many of these effects may be overshadowed by other complications experienced in the field. Errors are propagated for systematic constant (offset) volume, proportional volume, and constant (offset) concentration errors. Previous efforts to quantify the impact of these errors were predicated upon the specific assumption that nonpartitioning and partitioning masses were equal. The current work relaxes that assumption and is therefore more general in scope. Through the use of nondimensional concentration, systematic proportional concentration errors do not affect the accuracy of the method. Specific consideration needs to be given to accurate flow measurements and minimizing baseline concentration errors when performing partitioning tracer tests in order to prevent the propagation of systematic errors.

  18. Uncertainty in NAPL volume estimates due to random measurement errors during partitioning tracer tests.

    PubMed

    Brooks, Michael C; Wise, William R

    2005-09-15

    The uncertainty in NAPL volume estimates obtained through partitioning tracers can be quantified as a function of random errors in volume and concentration measurements when moments are calculated from experimentally measured breakthrough curves using the trapezoidal rule for numerical integration. The methodology is based upon standard stochastic methods for random error propagation. Monte Carlo simulations using a synthetic data set derived from the one-dimensional solution of the advective-dispersive equation serve to verify the process. It is shown that the uncertainty in NAPL volume predictions nonlinearly increases as the retardation factor decreases. An important result of this observation is that there is a large degree of uncertainty in using partitioning tracers to conclude NAPL is absent from the swept zone. Under the conditions investigated, random errors in concentration measurements are shown to have a greater impact on NAPL volume uncertainty than random errors in volume measurements, and it is also shown that uncertainty in NAPL volume decreases as the resolution of the breakthrough curves increases. The impact of uncertainty in background retardation (i.e., sorption of partitioning tracers in the absence of NAPL) was also investigated, and it likewise indicated that the relative uncertainty in NAPL volume estimates increases as the retardation factor decreases.

  19. Dynamic strain estimation for fatigue assessment of an offshore monopile wind turbine using filtering and modal expansion algorithms

    NASA Astrophysics Data System (ADS)

    Maes, K.; Iliopoulos, A.; Weijtjens, W.; Devriendt, C.; Lombaert, G.

    2016-08-01

    Offshore wind turbines are exposed to continuous wind and wave excitation. The monitoring of high periodic strains at critical locations is important to assess the remaining lifetime of the structure. At some critical locations below the water level, direct measurements of the strains are not feasible. Response estimation techniques can then be used to estimate the strains from a limited set of response measurements and a system model. This paper compares a Kalman filtering algorithm, a joint input-state estimation algorithm, and a modal expansion algorithm, for the estimation of dynamic strains in the tower of an offshore monopile wind turbine. The algorithms make use of a model of the structure and a limited number of response measurements for the prediction of the strain responses. The strain signals obtained from the response estimation algorithms are compared to the actual measured strains in the tower.

  20. Estimating Errors in Satellite Retrievals of Bio-Optical Properties due to Incorrect Aerosol Model Selection

    DTIC Science & Technology

    2011-01-01

    as Martha’s Vineyard or Venice. This is due to a large amount of cloud coverage during the year, as well as the AERONET-OC station being unavailable...can be used to produce a good result for nLw(412) for day 176. This is an instance where the MODIS image has sporadic cloud coverage, as well as haze...1989). [10] Gordon, H. R., Brown, J. W. and Evans, R. H., "Exact Rayleigh scattering calculations for use with the Nimbus -7 Coastal Zone Color

  1. Lateral velocity estimation bias due to beamforming delay errors (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Rodriguez-Molares, Alfonso; Fadnes, Solveig; Swillens, Abigail; Løvstakken, Lasse

    2017-03-01

    An artefact has recently been reported [1,2] in the estimation of the lateral blood velocity using speckle tracking. This artefact shows as a net velocity bias in presence of strong spatial velocity gradients such as those that occur at the edges of the filling jets in the heart. Even though this artifact has been found both in vitro and in simulated data, its causes are still undescribed. Here we demonstrate that a potential source of this artefact can be traced to smaller errors in the beamforming setup. By inserting a small offset in the beamforming delay, one can artificially create a net lateral movement in the speckle in areas of high velocity gradient. That offset does not have a strong impact in the image quality and can easily go undetected.

  2. Detection of incoherent joint state due to inaccurate bone motion estimation.

    PubMed

    Schwartz, Cédric; Leboeuf, Fabien; Rémy-Néris, Olivier; Brochard, Sylvain; Lempereur, Mathieu; Burdin, Valérie

    2013-01-01

    In biomechanical modelling and motion analysis, the use of personalised data such as bone geometry would provide more accurate and reliable results. However, there are still a limited number of tools used to measure the evolution of articular interactions. This paper proposes a coherence index to describe the articular status of contact surfaces during motion. The index relies on a robust estimation of the evolution of surfacic interactions between the joint surfaces. The index is first compared to distance maps on simulated motions. It is then used to compare two motion capture protocols (two different localisations of the markers for scapula tracking). The results show that the index detects progressive modifications in the joint and allows distinguishing the two protocols, in accordance with the literature. In the future, the index could, among other things, be used to compare/improve biomechanical models and motion analysis protocols.

  3. Completeness of the fossil record: Estimating losses due to small body size

    NASA Astrophysics Data System (ADS)

    Cooper, Roger A.; Maxwell, Phillip A.; Crampton, James S.; Beu, Alan G.; Jones, Craig M.; Marshall, Bruce A.

    2006-04-01

    Size bias in the fossil record limits its use for interpreting patterns of past biodiversity and ecological change. Using comparative size frequency distributions of exceptionally good regional records of New Zealand Holocene and Cenozoic Mollusca in museum archive collections, we derive first-order estimates of the magnitude of the bias against small body size and the effect of this bias on completeness of the fossil record. Our database of 3907 fossil species represents an original living pool of 9086 species, from which ˜36% have been removed by size culling, 27% from the smallest size class (<5 mm). In contrast, non-size-related losses compose only 21% of the total. In soft rocks, the loss of small taxa can be reduced by nearly 50% through the employment of exhaustive collection and preparation techniques.

  4. Quantification and Radiological Risk Estimation Due to the Presence of Natural Radionuclides in Maiganga Coal, Nigeria

    PubMed Central

    Kolo, Matthew Tikpangi; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd; Abdullah, Wan Hasiah Binti

    2016-01-01

    Following the increasing demand of coal for power generation, activity concentrations of primordial radionuclides were determined in Nigerian coal using the gamma spectrometric technique with the aim of evaluating the radiological implications of coal utilization and exploitation in the country. Mean activity concentrations of 226Ra, 232Th, and 40K were 8.18±0.3, 6.97±0.3, and 27.38±0.8 Bq kg-1, respectively. These values were compared with those of similar studies reported in literature. The mean estimated radium equivalent activity was 20.26 Bq kg-1 with corresponding average external hazard index of 0.05. Internal hazard index and representative gamma index recorded mean values of 0.08 and 0.14, respectively. These values were lower than their respective precautionary limits set by UNSCEAR. Average excess lifetime cancer risk was calculated to be 0.04×10−3, which was insignificant compared with 0.05 prescribed by ICRP for low level radiation. Pearson correlation matrix showed significant positive relationship between 226Ra and 232Th, and with other estimated hazard parameters. Cumulative mean occupational dose received by coal workers via the three exposure routes was 7.69 ×10−3 mSv y-1, with inhalation pathway accounting for about 98%. All radiological hazard indices evaluated showed values within limits of safety. There is, therefore, no likelihood of any immediate radiological health hazards to coal workers, final users, and the environment from the exploitation and utilization of Maiganga coal. PMID:27348624

  5. Quantification and Radiological Risk Estimation Due to the Presence of Natural Radionuclides in Maiganga Coal, Nigeria.

    PubMed

    Kolo, Matthew Tikpangi; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd; Abdullah, Wan Hasiah Binti

    2016-01-01

    Following the increasing demand of coal for power generation, activity concentrations of primordial radionuclides were determined in Nigerian coal using the gamma spectrometric technique with the aim of evaluating the radiological implications of coal utilization and exploitation in the country. Mean activity concentrations of 226Ra, 232Th, and 40K were 8.18±0.3, 6.97±0.3, and 27.38±0.8 Bq kg-1, respectively. These values were compared with those of similar studies reported in literature. The mean estimated radium equivalent activity was 20.26 Bq kg-1 with corresponding average external hazard index of 0.05. Internal hazard index and representative gamma index recorded mean values of 0.08 and 0.14, respectively. These values were lower than their respective precautionary limits set by UNSCEAR. Average excess lifetime cancer risk was calculated to be 0.04×10-3, which was insignificant compared with 0.05 prescribed by ICRP for low level radiation. Pearson correlation matrix showed significant positive relationship between 226Ra and 232Th, and with other estimated hazard parameters. Cumulative mean occupational dose received by coal workers via the three exposure routes was 7.69 ×10-3 mSv y-1, with inhalation pathway accounting for about 98%. All radiological hazard indices evaluated showed values within limits of safety. There is, therefore, no likelihood of any immediate radiological health hazards to coal workers, final users, and the environment from the exploitation and utilization of Maiganga coal.

  6. Mediation analysis to estimate direct and indirect milk losses due to clinical mastitis in dairy cattle.

    PubMed

    Detilleux, J; Kastelic, J P; Barkema, H W

    2015-03-01

    Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e., direct losses) or effects of the immune response triggered by intramammary infection (indirect losses). The distinction is important in terms of mastitis prevention and treatment. Regardless, the number of pathogens is often unknown (particularly in field studies), making it difficult to estimate direct losses, whereas indirect losses can be approximated by measuring the association between increased somatic cell count (SCC) and milk production. An alternative is to perform a mediation analysis in which changes in milk yield are allocated into their direct and indirect components. We applied this method on data for clinical mastitis, milk and SCC test-day recordings, results of bacteriological cultures (Escherichia coli, Staphylococcus aureus, Streptococcus uberis, coagulase-negative staphylococci, Streptococcus dysgalactiae, and streptococci other than Strep. dysgalactiae and Strep. uberis), and cow characteristics. Following a diagnosis of clinical mastitis, the cow was treated and changes (increase or decrease) in milk production before and after a diagnosis were interpreted counterfactually. On a daily basis, indirect changes, mediated by SCC increase, were significantly different from zero for all bacterial species, with a milk yield decrease (ranging among species from 4 to 33g and mediated by an increase of 1000 SCC/mL/day) before and a daily milk increase (ranging among species from 2 to 12g and mediated by a decrease of 1000 SCC/mL/day) after detection. Direct changes, not mediated by SCC, were only different from zero for coagulase-negative staphylococci before diagnosis (72g per day). We concluded that mixed structural equation models were useful to estimate direct and indirect effects of the presence of clinical mastitis on milk yield. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. An Approach for Nonlinear Fatigue Damage Evaluation in Asphalt Pavements

    NASA Astrophysics Data System (ADS)

    Rajbongshi, Pabitra; Thongram, Sonika

    2016-09-01

    Fatigue due to vehicular loads is one of the primary distress mechanisms in asphalt pavements. It happens primarily due to deterioration in asphalt material with load repetitions. Degradation of asphalt material may be evaluated using different parameters. In view of degradation, the incremental damage in a given pavement section would be different for different repetitions, even with same loadings. Therefore, the damage progression becomes nonlinear with repetitions. Accounting such nonlinearity in damage accumulation, and based on different damage evaluation parameters, this paper presents an equivalent approach for fatigue damage evaluation in asphalt pavements. Traditional fatigue equation adopted in mechanistic-empirical pavement design has been used in the present work. Four different criteria, namely number of load repetitions, asphalt stiffness reduction, strain enhancement and fatigue life reduction with repetitions are considered for damage estimation. The proposed approach could estimate same value of nonlinear damage, irrespective of the criteria used. The simplest form of criterion i.e. the number of load repetitions can be used for fatigue performance evaluation. Probabilistically, the damage propagation is also correlated and assessed with the failure probability.

  8. Estimating Orion Heat Shield Failure Due To Ablator Cracking During The EFT-1 Mission

    NASA Technical Reports Server (NTRS)

    Vander Kam, Jeremy C.; Gage, Peter

    2016-01-01

    The Orion EFT-1 heatshield suffered from two major certification challenges: First, the mechanical properties used in design were not evident in the flight hardware and second, the flight article itself cracked during fabrication. The combination of these events motivated the Orion Program to pursue an engineering-level Probabilistic Risk Assessment (PRA) as part of heatshield certification rationale. The PRA provided loss of Mission (LOM) likelihoods considering the probability of a crack occurring during the mission and the likelihood of subsequent structure over-temperature. The methods and input data for the PRA are presented along with a discussion of the test data used to anchor the results. The Orion program accepted an EFT-1 Loss of Vehicle (LOV) risk of 1-in-160,000 due to in-mission Avcoat cracking based on the results of this analysis. Conservatisms in the result, along with future considerations for Exploration Missions (EM) are also addressed.

  9. Application of fuzzy sets to estimate cost savings due to variance reduction

    NASA Astrophysics Data System (ADS)

    Munoz, Jairo; Ostwald, Phillip F.

    1993-12-01

    One common assumption of models to evaluate the cost of variation is that the quality characteristic can be approximated by a standard normal distribution. Such an assumption is invalid for three important cases: (a) when the random variable is always positive, (b) when manual intervention distorts random variation, and (c) when the variable of interest is evaluated by linguistic terms. This paper applies the Weibull distribution to address nonnormal situations and fuzzy logic theory to study the case of quality evaluated via lexical terms. The approach concentrates on the cost incurred by inspection to formulate a probabilistic-possibilistic model that determines cost savings due to variance reduction. The model is tested with actual data from a manual TIG welding process.

  10. Estimation of surface temperature variations due to changes in sky and solar flux with elevation

    NASA Technical Reports Server (NTRS)

    Hummer-Miller, S.

    1981-01-01

    The magnitude of elevation effects due to changes in solar and sky fluxes, on interpretation of single thermal images and composite products such as temperature difference and thermal inertia, are examined. Simple expressions are derived for the diurnal behavior of the two parameters, by fitting field observations in one tropic (Hawaii) and two semi-arid climates (Wyoming and Colorado) (Hummer-Miller, 1981). It is shown that flux variations with elevation can cause changes in the mean diurnal temperature gradient from -4 to -14 degrees C/km, evaluated at 2000 m. Changes in the temperature-difference gradient of 1 to 2 degrees C/km are also produced which is equivalent to an effective thermal-inertia gradient of 100 W s(exp 1/2)/sq m-K-km. An example is presented showing an elevation effect of 12 degrees C on the day and night thermal scenes of a test site in Arizona.

  11. Estimation of wildfire size and risk changes due to fuels treatments

    USGS Publications Warehouse

    Cochrane, M.A.; Moran, C.J.; Wimberly, M.C.; Baer, A.D.; Finney, M.A.; Beckendorf, K.L.; Eidenshink, J.; Zhu, Z.

    2012-01-01

    Human land use practices, altered climates, and shifting forest and fire management policies have increased the frequency of large wildfires several-fold. Mitigation of potential fire behaviour and fire severity have increasingly been attempted through pre-fire alteration of wildland fuels using mechanical treatments and prescribed fires. Despite annual treatment of more than a million hectares of land, quantitative assessments of the effectiveness of existing fuel treatments at reducing the size of actual wildfires or how they might alter the risk of burning across landscapes are currently lacking. Here, we present a method for estimating spatial probabilities of burning as a function of extant fuels treatments for any wildland fire-affected landscape. We examined the landscape effects of more than 72 000 ha of wildland fuel treatments involved in 14 large wildfires that burned 314 000 ha of forests in nine US states between 2002 and 2010. Fuels treatments altered the probability of fire occurrence both positively and negatively across landscapes, effectively redistributing fire risk by changing surface fire spread rates and reducing the likelihood of crowning behaviour. Trade offs are created between formation of large areas with low probabilities of increased burning and smaller, well-defined regions with reduced fire risk.

  12. Estimate of neutral atoms contribution to the Mercury exosphere due to a new flux of micrometeoroids

    NASA Astrophysics Data System (ADS)

    Borin, Patrizia; Bruno, Marco; Cremonese, Gabriele; Marzari, Francesco

    2010-05-01

    Meteoroid impacts are an important source of neutral atoms in the exosphere of Mercury. Recent papers attribute to impacting particles smaller than 1 cm most of the contribution to exospheric gases. In this work we calculate the vapour and neutral atoms production rates on Mercury, as due to the impacts of micrometeoroids in the size range between 5-100 μm according to the new dynamical model of Borin et al. (2009). The calculations have been performed taking into account two different calibration sources for the meteoroid flux provided by Love and Brownlee (1993) (as for Borin et al., 2009) and by Grun et al. (1985). Moreover, we give different values of the vapour production rates assuming both asteroidal and cometary sources of the dust particles (Wiegert, 2009; Dermott et al., 2002). Following the assumption that the surface of the planet is spatially homogeneous and made up of regolith with anorthositic composition (Cremonese et al., 2005) we provide the production rate for different neutral atoms.

  13. [Effects of Xiaopi Yishen herbal extract granules in treatment of fatigue-predominant subhealth due to liver-qi stagnation and spleen-qi deficiency: a prospective, randomized, placebo-controlled and double-blind clinical trial].

    PubMed

    Wang, Tian-fang; Xue, Xiao-lin; Zhang, Ya-jing; Han, Ping; Li, Zhen; Wang, Wen-ping; Xing, Jian-min; Wang, Qing-bo; Tang, Yu; Li, Li; Wang, Jia-jia; Li, Guan-ru; Ji, Shao-liang; Wu, Liu-xin; Zhao, Yan; Wu, Xiu-yan; Zhao, Run-shuan

    2011-05-01

    The demand for effective intervention for subhealth conditions is growing with increasing numbers of people being in a state of subhealth with a poor quality of life. Future research and evaluation of the treatment methods for subhealth conditions from the perspective of traditional Chinese medicine (TCM) may provide an important direction for developing effective management of these conditions. To evaluate the efficacy and safety of Xiaopi Yishen herbal extract granules (XPYS-HEG), a compound traditional Chinese herbal medicine for relieving fatigue and promoting a cheerful spirit for the treatment of people with fatigue-predominant subhealth due to liver-qi stagnation and spleen-qi deficiency. DESIGN, SETTING PARTICIPANTS AND INTERVENTIONS: A multi-center, randomized, double-blinded, placebo-controlled clinical study was undertaken. The study period was 18 weeks, including 6 weeks for intervention and 12 weeks for follow-up. Participants were recruited from medical center and outpatient clinics of three hospitals in China, i.e. Xiaotangshan Hospital of Beijing, the First Affiliated Hospital of Henan University of TCM and the Affiliated Hospital of Liaoning University of TCM. Two hundred participants who met the criteria of fatigue-predominant subhealth and liver-qi stagnation and spleen-qi deficiency in TCM were allocated randomly to the treatment group (XPYS, n=100) and control group (placebo, n=100). The total score of Fatigue Scale-14 (FS-14) was used to evaluate the fatigue status of subjects and the extent of liver-qi stagnation and spleen-qi deficiency syndrome was also recorded. Three cases in the XPYS group withdrew from the trial. There were 200 subjects who entered to full analysis set (FAS) analysis and 197 subjects fitted in the per-protocol set (PPS) analysis. (1) According to the score changes of FS-14, the effectiveness rates in the XPYS and placebo group were as follows: 14.0% vs 9.0% (FAS) and 14.4% vs 9.0% (PPS) for complete remission, 19.0% vs

  14. Impacts of individual fish movement patterns on estimates of mortality due to dissolved gas supersaturation in the Columbia River Basin.

    SciTech Connect

    Scheibe, Timothy D.; Richmond, Marshall C.; Fidler, Larry E.

    2002-12-31

    Spatial and temporal distributions of dissolved gases in the Columbia and Snake rivers vary due to many factors including river channel and dam geometries, operational decisions, and natural variations in flow rates. As a result, the dissolved gas exposure histories experienced by migrating juvenile salmonids can vary significantly among individual fish. A discrete, particle-based model of individual fish movements and dissolved gas exposure history has been developed and applied to examine the effects of such variability on estimates of fish mortality. The model, called the Fish Individual-based Numerical Simulator or FINS, is linked to a two-dimensional (vertically-averaged) hydrodynamic simulator that quantifies local water velocity, temperature, and dissolved gas levels as a function of river flow rates and dam operations. Simulated gas exposure histories are then input to biological mortality models to predict the effects of various river configurations on fish injury and mortality due to dissolved gas supersaturation. This model framework provides a critical linkage between hydrodynamic models of the river system and models of biological effects. FINS model parameters were estimated and validated based on observations of individual fish movements collected using radiotelemetry methods during 1997 and 1998. The model was then used to simulate exposure histories under selected operational scenarios. We compare mortality rates estimated using the FINS model approach (incorporating individual behavior and spatial and temporal variability) to those estimated using average exposure times and levels as is done in traditional lumped-parameter model approaches.

  15. Exposure estimation errors to nitrogen oxides on a population scale due to daytime activity away from home.

    PubMed

    Shafran-Nathan, Rakefet; Yuval; Levy, Ilan; Broday, David M

    2017-02-15

    Accurate estimation of exposure to air pollution is necessary for assessing the impact of air pollution on the public health. Most environmental epidemiology studies assign the home address exposure to the study subjects. Here, we quantify the exposure estimation error at the population scale due to assigning it solely at the residence place. A cohort of most schoolchildren in Israel (~950,000), age 6-18, and a representative cohort of Israeli adults (~380,000), age 24-65, were used. For each subject the home and the work or school addresses were geocoded. Together, these two microenvironments account for the locations at which people are present during most of the weekdays. For each subject, we estimated ambient nitrogen oxide concentrations at the home and work or school addresses using two air quality models: a stationary land use regression model and a dynamic dispersion-like model. On average, accounting for the subjects' work or school address as well as for the daily pollutant variation reduced the estimation error of exposure to ambient NOx/NO2 by 5-10ppb, since daytime concentrations at work/school and at home can differ significantly. These results were consistent regardless which air quality model as used and even for subjects that work or study close to their home. Yet, due to their usually short commute, assigning schoolchildren exposure solely at their residential place seems to be a reasonable estimation. In contrast, since adults commute for longer distances, assigning exposure of adults only at the residential place has a lower correlation with the daily weighted exposure, resulting in larger exposure estimation errors. We show that exposure misclassification can result from not accounting for the subjects' time-location trajectories through the spatiotemporally varying pollutant concentrations field. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Estimated Reduction in Cancer Risk due to PAH Exposures If Source Control Measures during the 2008 Beijing Olympics Were Sustained

    PubMed Central

    Jia, Yuling; Stone, Dave; Wang, Wentao; Schrlau, Jill; Tao, Shu; Massey Simonich, Staci L.

    2011-01-01

    Background The 2008 Beijing Olympic Games provided a unique case study to investigate the effect of source control measures on the reduction in air pollution, and associated inhalation cancer risk, in a Chinese megacity. Objectives We measured 17 carcinogenic polycyclic aromatic hydrocarbons (PAHs) and estimated the lifetime excess inhalation cancer risk during different periods of the Beijing Olympic Games, to assess the effectiveness of source control measures in reducing PAH-induced inhalation cancer risks. Methods PAH concentrations were measured in samples of particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5) collected during the Beijing Olympic Games, and the associated inhalation cancer risks were estimated using a point-estimate approach based on relative potency factors. Results We estimated the number of lifetime excess cancer cases due to exposure to the 17 carcinogenic PAHs [12 priority pollutant PAHs and five high-molecular-weight (302 Da) PAHs (MW 302 PAHs)] to range from 6.5 to 518 per million people for the source control period concentrations and from 12.2 to 964 per million people for the nonsource control period concentrations. This would correspond to a 46% reduction in estimated inhalation cancer risk due to source control measures, if these measures were sustained over time. Benzo[b]fluoranthene, dibenz[a,h]anthracene, benzo[a]pyrene, and dibenzo[a,l]pyrene were the most carcinogenic PAH species evaluated. Total excess inhalation cancer risk would be underestimated by 23% if we did not include the five MW 302 PAHs in the risk calculation. Conclusions Source control measures, such as those imposed during the 2008 Beijing Olympics, can significantly reduce the inhalation cancer risk associated with PAH exposure in Chinese megacities similar to Beijing. MW 302 PAHs are a significant contributor to the estimated overall inhalation cancer risk. PMID:21632310

  17. A revised estimate of the processes contributing to global warming due to climate-carbon feedback

    NASA Astrophysics Data System (ADS)

    Cadule, P.; Bopp, L.; Friedlingstein, P.

    2009-07-01

    Coupled climate-carbon cycle models have shown that anthropogenic climate change has a negative effect on natural carbon sinks i.e., climate change induces a reduction in both land and ocean carbon uptake leading to an additional amount of CO2 in the atmosphere. Friedlingstein et al. (2006) concluded that such supplementary CO2 in the atmosphere would lead to an additional climate warming in 2100. However, as given by Friedlingstein et al. (2006), the role of non-CO2 greenhouse gases (GHGs) and aerosols was neglected both for their direct impact on climate and their indirect impact on the carbon cycle. Besides, the climate models used for IPCC AR4 accounted for the radiative forcing of all GHGs and anthropogenic aerosols but neglected the climate-carbon cycle feedback. In IPCC AR4, Meehl et al. (2007) attempted to reconcile these two methods in order to derive the global warming that would arise from both all anthropogenic forcings and climate-carbon cycle feedback. Here we show that the approach they used is wrong for several reasons. First, as previously done by Friedlingstein et al. (2006), they considered that the warming is proportional to the change in atmospheric CO2 concentration. This assumption leads to consider that the gain in temperature is equal to the gain in CO2. However, because of the non-linearity of the climate response to increased CO2 concentrations, the gain in temperature is lower than the gain in CO2. Second, they assumed that the temperature gains of the climate-carbon cycle feedback generated by CO2, non-CO2 GHGs and aerosols are all equal. We show here that, because of the specific spatial and temporal distribution of the radiative forcing exerted by those external perturbations, the temperature gains are all different. Based on our revised method, we found that, for the SRES A2 scenario, the projected global warming in 2100, due to increases in atmospheric CO2, non-CO2 GHGs and anthropogenic sulphate aerosols, is 2.3-5.6°C. This is

  18. Estimating salinity intrusion effects due to climate change on the Lower Savannah River Estuary

    USGS Publications Warehouse

    Conrads, Paul A.; Roehl, Edwin A.; Daamen, Ruby C.; Cook, John B.; Sexton, Charles T.; Tufford, Daniel L.; Carbone, Gregory J.; Dow, Kristin

    2010-01-01

    alternative scenarios of interest. Important freshwater resources are located proximal to the freshwater-saltwater interface of the estuary. The Savannah National Wildlife Refuge is located in the upper portion of the Savannah River Estuary. The tidal freshwater marsh is an essential part of the 28,000-acre refuge and is home to a diverse variety of wildlife and plant communities. Two municipal freshwater intakes are located upstream from the refuge. To evaluate the impact of climate change on salinity intrusion on these resources, inputs of streamflows and mean tidal water levels were modified to incorporate estimated changes in precipitation patterns and sea-level rise appropriate for the Southeastern United States. Changes in mean tidal water levels were changed parametrically for various sea-level rise conditions. Preliminary model results at the U.S. Geological Survey (USGS) Interstate-95 streamgage (station 02198840) for a 7½-year simulation show that historical daily salinity concentrations never exceeded 0.5 practical salinity units (psu). A 1-foot sea-level rise (ft, 30.5 centimeters [cm]) would increase the number of days of salinity concentrations greater than 0.5 psu to 47 days. A 2-ft (61 cm) sea-level rise would increase the number of days to 248.

  19. Probabilistic Fatigue: Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.

    2002-01-01

    Fatigue is a primary consideration in the design of aerospace structures for long term durability and reliability. There are several types of fatigue that must be considered in the design. These include low cycle, high cycle, combined for different cyclic loading conditions - for example, mechanical, thermal, erosion, etc. The traditional approach to evaluate fatigue has been to conduct many tests in the various service-environment conditions that the component will be subjected to in a specific design. This approach is reasonable and robust for that specific design. However, it is time consuming, costly and needs to be repeated for designs in different operating conditions in general. Recent research has demonstrated that fatigue of structural components/structures can be evaluated by computational simulation based on a novel paradigm. Main features in this novel paradigm are progressive telescoping scale mechanics, progressive scale substructuring and progressive structural fracture, encompassed with probabilistic simulation. These generic features of this approach are to probabilistically telescope scale local material point damage all the way up to the structural component and to probabilistically scale decompose structural loads and boundary conditions all the way down to material point. Additional features include a multifactor interaction model that probabilistically describes material properties evolution, any changes due to various cyclic load and other mutually interacting effects. The objective of the proposed paper is to describe this novel paradigm of computational simulation and present typical fatigue results for structural components. Additionally, advantages, versatility and inclusiveness of computational simulation versus testing are discussed. Guidelines for complementing simulated results with strategic testing are outlined. Typical results are shown for computational simulation of fatigue in metallic composite structures to demonstrate the

  20. Mortality due to noncommunicable diseases in Brazil, 1990 to 2015, according to estimates from the Global Burden of Disease study.

    PubMed

    Malta, Deborah Carvalho; França, Elisabeth; Abreu, Daisy Maria Xavier; Perillo, Rosângela Durso; Salmen, Maíra Coube; Teixeira, Renato Azeredo; Passos, Valeria; Souza, Maria de Fátima Marinho; Mooney, Meghan; Naghavi, Mohsen

    2017-01-01

    Noncommunicable diseases (NCDs) are the leading health problem globally and generate high numbers of premature deaths and loss of quality of life. The aim here was to describe the major groups of causes of death due to NCDs and the ranking of the leading causes of premature death between 1990 and 2015, according to the Global Burden of Disease (GBD) 2015 study estimates for Brazil. Cross-sectional study covering Brazil and its 27 federal states. This was a descriptive study on rates of mortality due to NCDs, with corrections for garbage codes and underreporting of deaths. This study shows the epidemiological transition in Brazil between 1990 and 2015, with increasing proportional mortality due to NCDs, followed by violence, and decreasing mortality due to communicable, maternal and neonatal causes within the global burden of diseases. NCDs had the highest mortality rates over the whole period, but with reductions in cardiovascular diseases, chronic respiratory diseases and cancer. Diabetes increased over this period. NCDs were the leading causes of premature death (30 to 69 years): ischemic heart diseases and cerebrovascular diseases, followed by interpersonal violence, traffic injuries and HIV/AIDS. The decline in mortality due to NCDs confirms that improvements in disease control have been achieved in Brazil. Nonetheless, the high mortality due to violence is a warning sign. Through maintaining the current decline in NCDs, Brazil should meet the target of 25% reduction proposed by the World Health Organization by 2025.

  1. High Speed Research Program Sonic Fatigue

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A. (Technical Monitor); Beier, Theodor H.; Heaton, Paul

    2005-01-01

    The objective of this sonic fatigue summary is to provide major findings and technical results of studies, initiated in 1994, to assess sonic fatigue behavior of structure that is being considered for the High Speed Civil Transport (HSCT). High Speed Research (HSR) program objectives in the area of sonic fatigue were to predict inlet, exhaust and boundary layer acoustic loads; measure high cycle fatigue data for materials developed during the HSR program; develop advanced sonic fatigue calculation methods to reduce required conservatism in airframe designs; develop damping techniques for sonic fatigue reduction where weight effective; develop wing and fuselage sonic fatigue design requirements; and perform sonic fatigue analyses on HSCT structural concepts to provide guidance to design teams. All goals were partially achieved, but none were completed due to the premature conclusion of the HSR program. A summary of major program findings and recommendations for continued effort are included in the report.

  2. Exploring the uncertainty associated with satellite-based estimates of premature mortality due to exposure to fine particulate matter

    NASA Astrophysics Data System (ADS)

    Ford, Bonne; Heald, Colette L.

    2016-03-01

    The negative impacts of fine particulate matter (PM2.5) exposure on human health are a primary motivator for air quality research. However, estimates of the air pollution health burden vary considerably and strongly depend on the data sets and methodology. Satellite observations of aerosol optical depth (AOD) have been widely used to overcome limited coverage from surface monitoring and to assess the global population exposure to PM2.5 and the associated premature mortality. Here we quantify the uncertainty in determining the burden of disease using this approach, discuss different methods and data sets, and explain sources of discrepancies among values in the literature. For this purpose we primarily use the MODIS satellite observations in concert with the GEOS-Chem chemical transport model. We contrast results in the United States and China for the years 2004-2011. Using the Burnett et al. (2014) integrated exposure response function, we estimate that in the United States, exposure to PM2.5 accounts for approximately 2 % of total deaths compared to 14 % in China (using satellite-based exposure), which falls within the range of previous estimates. The difference in estimated mortality burden based solely on a global model vs. that derived from satellite is approximately 14 % for the US and 2 % for China on a nationwide basis, although regionally the differences can be much greater. This difference is overshadowed by the uncertainty in the methodology for deriving PM2.5 burden from satellite observations, which we quantify to be on the order of 20 % due to uncertainties in the AOD-to-surface-PM2.5 relationship, 10 % due to the satellite observational uncertainty, and 30 % or greater uncertainty associated with the application of concentration response functions to estimated exposure.

  3. Exploring the uncertainty associated with satellite-based estimates of premature mortality due to exposure to fine particulate matter

    NASA Astrophysics Data System (ADS)

    Ford, B.; Heald, C. L.

    2015-09-01

    The negative impacts of fine particulate matter (PM2.5) exposure on human health are a primary motivator for air quality research. However, estimates of the air pollution health burden vary considerably and strongly depend on the datasets and methodology. Satellite observations of aerosol optical depth (AOD) have been widely used to overcome limited coverage from surface monitoring and to assess the global population exposure to PM2.5 and the associated premature mortality. Here we quantify the uncertainty in determining the burden of disease using this approach, discuss different methods and datasets, and explain sources of discrepancies among values in the literature. For this purpose we primarily use the MODIS satellite observations in concert with the GEOS-Chem chemical transport model. We contrast results in the United States and China for the years 2004-2011. We estimate that in the United States, exposure to PM2.5 accounts for approximately 4 % of total deaths compared to 22 % in China (using satellite-based exposure), which falls within the range of previous estimates. The difference in estimated mortality burden based solely on a global model vs. that derived from satellite is approximately 9 % for the US and 4 % for China on a nationwide basis, although regionally the differences can be much greater. This difference is overshadowed by the uncertainty in the methodology for deriving PM2.5 burden from satellite observations, which we quantify to be on order of 20 % due to uncertainties in the AOD-to-surface-PM2.5 relationship, 10 % due to the satellite observational uncertainty, and 30 % or greater uncertainty associated with the application of concentration response functions to estimated exposure.

  4. Exploring the Uncertainty Associated with Satellite-Based Estimates of Premature Mortality due to Exposure to Fine Particulate Matter

    PubMed Central

    Ford, Bonne; Heald, Colette L.

    2017-01-01

    The negative impacts of fine particulate matter (PM2.5) exposure on human health are a primary motivator for air quality research. However, estimates of the air pollution health burden vary considerably and strongly depend on the datasets and methodology. Satellite observations of aerosol optical depth (AOD) have been widely used to overcome limited coverage from surface monitoring and to assess the global population exposure to PM2.5 and the associated premature mortality. Here we quantify the uncertainty in determining the burden of disease using this approach, discuss different methods and datasets, and explain sources of discrepancies among values in the literature. For this purpose we primarily use the MODIS satellite observations in concert with the GEOS-Chem chemical transport model. We contrast results in the United States and China for the years 2004–2011. Using the Burnett et al. (2014) integrated exposure response function, we estimate that in the United States, exposure to PM2.5 accounts for approximately 2% of total deaths compared to 14% in China (using satellite-based exposure), which falls within the range of previous estimates. The difference in estimated mortality burden based solely on a global model vs. that derived from satellite is approximately 14% for the U.S. and 2% for China on a nationwide basis, although regionally the differences can be much greater. This difference is overshadowed by the uncertainty in the methodology for deriving PM2.5 burden from satellite observations, which we quantify to be on the order of 20% due to uncertainties in the AOD-to-surface-PM2.5 relationship, 10% due to the satellite observational uncertainty, and 30% or greater uncertainty associated with the application of concentration response functions to estimated exposure. PMID:28649266

  5. Estimating PM2.5-associated mortality increase in California due to the Volkswagen emission control defeat device

    NASA Astrophysics Data System (ADS)

    Wang, Tianyang; Jerrett, Michael; Sinsheimer, Peter; Zhu, Yifang

    2016-11-01

    The Volkswagen Group of America (VW) was found by the US Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) to have installed "defeat devices" and emit more oxides of nitrogen (NOx) than permitted under current EPA standards. In this paper, we quantify the hidden NOx emissions from this so-called VW scandal and the resulting public health impacts in California. The NOx emissions are calculated based on VW road test data and the CARB Emission Factors (EMFAC) model. Cumulative hidden NOx emissions from 2009 to 2015 were estimated to be over 3500 tons. Adult mortality changes were estimated based on ambient fine particulate matter (PM2.5) change due to secondary nitrate formation and the related concentration-response functions. We estimated that hidden NOx emissions from 2009 to 2015 have resulted in a total of 12 PM2.5-associated adult mortality increases in California. Most of the mortality increase happened in metropolitan areas, due to their high population and vehicle density.

  6. Chronic Fatigue Syndrome

    MedlinePlus

    Chronic fatigue syndrome (CFS) is a disorder that causes extreme fatigue. This fatigue is not the kind of tired feeling that ... activities. The main symptom of CFS is severe fatigue that lasts for 6 months or more. You ...

  7. Residual stress evaluation and fatigue life prediction in the welded joint by x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Yoo, Keun Bong; Hwang, Kwon Tae; Chang, Jung Chel; Kim, Jae Hoon

    2009-07-01

    In the fossil power plant, the reliability of the components which consist of the many welded parts depends on the quality of welding. The residual stress is occurred by the heat flux of high temperature during weld process. This decreases the mechanical properties as the strength of fatigue and fracture. The residual stress of the welded part in the recently constructed power plants has been the cause of a variety of accidents. The objective of this study is measurement of the residual stress and the full width at half maximum intensity (FWHM) by X-ray diffraction method and to estimate the feasibility of this application for fatigue life assessment of the high-temperature pipeline. The materials used for the study is P92 steel for the use of high temperature pipe on super critical condition. The test results were analyzed by the distributed characteristics of residual stresses and FWHM in x-ray diffraction intensity curve. Also, X-ray diffraction tests using specimens simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages. As a result of X-ray diffraction tests for specimens simulated fatigue damages, we conformed that the ratio of the FWHM due to fatigue damage has linear relationship with fatigue life ratio algebraically. From this relationship, it was suggested that direct expectation of the life consumption rate was feasible.

  8. Fatigue in type 1 diabetes: A systematic review of Observational studies.

    PubMed

    Jensen, Øystein; Bernklev, Tomm; Jelsness-Jørgensen, Lars-Petter

    2017-01-01

    To systematically review the literature on fatigue in people with type 1 diabetes. In the period from April to June 2015 and with an updated search in May 2016, eight electronic databases as well as the grey literature were searched. Studies of all types of design were included if they reported data on fatigue in adult people with type 1 diabetes. All studies were assessed for quality. Out of 4259 references (including grey literature), 10 papers were reviewed in full. Three of these papers investigated fatigue as the primary endpoint, and one was assessed to be high quality. Two papers provided a definition of fatigue. Prevalence estimates ranged from 23 to 40%, dependent on the cut-off used. Six different questionnaires were used to measure fatigue/vitality and these were only validated to a limited extent in a diabetes population. Several demographic, personal and clinical factors were associated with fatigue, but the results were conflicting. Few studies have been published that investigate fatigue in type 1 diabetes and there is a large variability in findings due to different measurement methods and factors investigated. There is still an unmet need to understand what contributes to fatigue in these patients through rigorous research. Copyright © 2016. Published by Elsevier B.V.

  9. Study on fatigue crack propagation characteristics around welded joint interface in complexed conditions

    NASA Astrophysics Data System (ADS)

    Ota, Akihiko; Suzuki, Naoyuki; Maeda, Yoshio; Mawari, Toshio; Matsuoka, Saburo; Nishijima, Satoshi

    1993-01-01

    Marine structures are often constructed by welding, and they are subject to repeated loading such as waves and mechanical vibrations which can create fatigue cracks and consequently break the structures. Fatigue crack propagation properties of welded joints are studied under random loading in the air, synthetic sea water, and compressive cycling. It was found that the most crucial factor that controls fatigue crack propagation was high tensile residual stress fields of welded joints. This stress constantly kept the cracks open, simplifying fatigue crack propagation, and therefore, the rate of crack propagation could be assessed with high accuracy. In the transverse matching welded joints with cracks in the center, crack closure did not occur due to the tensile residual stress constantly induced at the crack ends in the center of the test samples. Fatigue crack propagation was accelerated both in artificial sea water and in compressive cycling compared to that in the air, and the fatigue lowest values were about half. Serious crack closures occurred in compressive cycling in which dry hours exceeded 45 minutes, and the fatigue crack propagation rate deteriorated remarkably. Mean fatigue crack propagation rate under the random loading is estimated precisely using equivalent stress intensity factor limit.

  10. Estimation of 210Po and its risk to human beings due to consumption of marine species at Mumbai, India.

    PubMed

    Mishra, S; Bhalke, S; Pandit, G G; Puranik, V D

    2009-07-01

    (210)Po was estimated in the edible muscle and soft tissue of 15 different marine species (fish, crab, prawn and bivalve) collected from Trans-Thane Creek area (Trombay) and Thane. Potential risks associated with consumption of marine organisms due to (210)Po collected from this particular area to human beings were assessed. Estimation of (210)Po was carried out using radiochemical separation and alpha spectrometric technique. The concentration of (210)Po was found to vary from 0.18 to 10.9 Bqkg(-1) wet wt in different biota species and maximum concentrations were observed in bivalves. The variations in (210)Po concentration in different species are mainly due to difference in metabolism and feeding habits. The daily intake and individual dose of (210)Po to human beings through biota consumption was calculated and found to be 31.89 mBqd(-1) and 19.44 microSvyr(-1), respectively. An assessment of the risk on human beings due to consumption of marine organism was undertaken using carcinogenic slope factor for (210)Po. 5th, 50th and 95th percentile of life time risk was calculated to be 9.74E-06, 4.39E-05 and 2.12E-04, respectively.

  11. Roughness Effects on Fretting Fatigue

    NASA Astrophysics Data System (ADS)

    Yue, Tongyan; Abdel Wahab, Magd

    2017-05-01

    Fretting is a small oscillatory relative motion between two normal loaded contact surfaces. It may cause fretting fatigue, fretting wear and/or fretting corrosion damage depending on various fretting couples and working conditions. Fretting fatigue usually occurs at partial slip condition, and results in catastrophic failure at the stress levels below the fatigue limit of the material. Many parameters may affect fretting behaviour, including the applied normal load and displacement, material properties, roughness of the contact surfaces, frequency, etc. Since fretting damage is undesirable due to contacting, the effect of rough contact surfaces on fretting damage has been studied by many researchers. Experimental method on this topic is usually focusing on rough surface effects by finishing treatment and random rough surface effects in order to increase fretting fatigue life. However, most of numerical models on roughness are based on random surface. This paper reviewed both experimental and numerical methodology on the rough surface effects on fretting fatigue.

  12. Analysis of Muscle Fatigue Progression using Cyclostationary Property of Surface Electromyography Signals.

    PubMed

    Karthick, P A; Venugopal, G; Ramakrishnan, S

    2016-01-01

    Analysis of neuromuscular fatigue finds various applications ranging from clinical studies to biomechanics. Surface electromyography (sEMG) signals are widely used for these studies due to its non-invasiveness. During cyclic dynamic contractions, these signals are nonstationary and cyclostationary. In recent years, several nonstationary methods have been employed for the muscle fatigue analysis. However, cyclostationary based approach is not well established for the assessment of muscle fatigue. In this work, cyclostationarity associated with the biceps brachii muscle fatigue progression is analyzed using sEMG signals and Spectral Correlation Density (SCD) functions. Signals are recorded from fifty healthy adult volunteers during dynamic contractions under a prescribed protocol. These signals are preprocessed and are divided into three segments, namely, non-fatigue, first muscle discomfort and fatigue zones. Then SCD is estimated using fast Fourier transform accumulation method. Further, Cyclic Frequency Spectral Density (CFSD) is calculated from the SCD spectrum. Two features, namely, cyclic frequency spectral area (CFSA) and cyclic frequency spectral entropy (CFSE) are proposed to study the progression of muscle fatigue. Additionally, degree of cyclostationarity (DCS) is computed to quantify the amount of cyclostationarity present in the signals. Results show that there is a progressive increase in cyclostationary during the progression of muscle fatigue. CFSA shows an increasing trend in muscle fatiguing contraction. However, CFSE shows a decreasing trend. It is observed that when the muscle progresses from non-fatigue to fatigue condition, the mean DCS of fifty subjects increases from 0.016 to 0.99. All the extracted features found to be distinct and statistically significant in the three zones of muscle contraction (p < 0.05). It appears that these SCD features could be useful in the automated analysis of sEMG signals for different neuromuscular conditions.

  13. On Measurement of Avoidable and Unavoidable Cost of Alcohol: An Application of Method for Estimating Costs Due To Prior Consumption

    PubMed Central

    Jarl, Johan; Gerdtham, Ulf-G; Ludbrook, Anne; Petrie, Dennis

    2010-01-01

    This study estimates the avoidable and unavoidable costs of alcohol-related, liver cirrhosis inpatient care, controlling for the lag structure and period of decline in disease risk. Lag structures with different lengths are applied to the exposure to risk from alcohol consumption, which allows for differentiation between avoidable and unavoidable cases due to prior consumption. A lag length of 20 (men) and 23 (women) years (expected remaining life years) gives a total cost of 592 million SEK. Given alcohol consumption is reduced to zero, 72% of cost could potentially be avoided. It is important to account for the length and structure of the risk decline following a consumption change as this substantially affects the estimates. PMID:20717547

  14. [Compassion fatigue: a concept analysis].

    PubMed

    Fu, Chia-Yun; Chen, Hsing-Mei

    2011-04-01

    Compassion fatigue is a relatively new term in nursing. This term describes mood swings experienced by healthcare providers that are both complex in origin and intensify over time due to cumulative stress. Quality of care can be affected if compassion fatigue goes untreated. This paper presents a concept analysis of compassion fatigue using Walker & Avant's method. Results show the defining attributes of compassion fatigue to include: 1. accumulated patient and family suffering; 2. sufferer unable to release built-up stresses effectively; and 3. negative effects on physical, psychological, and spiritual health. Identified antecedents of compassion fatigue included: (1) working as a healthcare provider; (2) investing sympathy in others over a long period of time; and (3) ignoring stress symptoms and personal emotional needs over time. Identified consequences of compassion fatigue included: (1) decreased coping ability; (2) damage / destruction of patient relationship; and (3) increased medical care costs. This study conducted a concept analysis to offer a better understanding of the concept of compassion fatigue and provide a reference for nursing practice and compassion fatigue-related nursing research.

  15. Damage Evolution and Life Prediction of Cross-Ply C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading at Room Temperature and 800 °C in Air

    PubMed Central

    Li, Longbiao

    2015-01-01

    The damage evolution and life prediction of cross-ply C/SiC ceramic-matrix composite (CMC) under cyclic-fatigue loading at room temperature and 800 °C in air have been investigated using damage parameters derived from fatigue hysteresis loops, i.e., fatigue hysteresis modulus and fatigue hysteresis loss energy. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy degrade with increasing applied cycles attributed to transverse cracks in the 90° plies, matrix cracks and fiber/matrix interface debonding in the 0° plies, interface wear at room temperature, and interface and carbon fibers oxidation at 800 °C in air. The relationships between fatigue hysteresis loops, fatigue hysteresis modulus and fatigue hysteresis loss energy have been established. Comparing experimental fatigue hysteresis loss energy with theoretical computational values, the fiber/matrix interface shear stress corresponding to different cycle numbers has been estimated. It was found that the degradation rate at 800 °C in air is much faster than that at room temperature due to serious oxidation in the pyrolytic carbon (PyC) interphase and carbon fibers. Combining the fiber fracture model with the interface shear stress degradation model and the fibers strength degradation model, the fraction of broken fibers versus the cycle number can be determined for different fatigue peak stresses. The fatigue life S-N curves of cross-ply C/SiC composite at room temperature and 800 °C in air have been predicted. PMID:28793728

  16. Damage Evolution and Life Prediction of Cross-Ply C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading at Room Temperature and 800 °C in Air.

    PubMed

    Li, Longbiao

    2015-12-09

    The damage evolution and life prediction of cross-ply C/SiC ceramic-matrix composite (CMC) under cyclic-fatigue loading at room temperature and 800 °C in air have been investigated using damage parameters derived from fatigue hysteresis loops, i.e., fatigue hysteresis modulus and fatigue hysteresis loss energy. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy degrade with increasing applied cycles attributed to transverse cracks in the 90° plies, matrix cracks and fiber/matrix interface debonding in the 0° plies, interface wear at room temperature, and interface and carbon fibers oxidation at 800 °C in air. The relationships between fatigue hysteresis loops, fatigue hysteresis modulus and fatigue hysteresis loss energy have been established. Comparing experimental fatigue hysteresis loss energy with theoretical computational values, the fiber/matrix interface shear stress corresponding to different cycle numbers has been estimated. It was found that the degradation rate at 800 °C in air is much faster than that at room temperature due to serious oxidation in the pyrolytic carbon (PyC) interphase and carbon fibers. Combining the fiber fracture model with the interface shear stress degradation model and the fibers strength degradation model, the fraction of broken fibers versus the cycle number can be determined for different fatigue peak stresses. The fatigue life S-N curves of cross-ply C/SiC composite at room temperature and 800 °C in air have been predicted.

  17. An estimate by two methods of thyroid absorbed doses due to BRAVO fallout in several Northern Marshall Islands.

    PubMed

    Musolino, S V; Greenhouse, N A; Hull, A P

    1997-10-01

    Estimates of the thyroid absorbed doses due to fallout originating from the 1 March 1954 BRAVO thermonuclear test on Bikini Atoll have been made for several inhabited locations in the Northern Marshall Islands. Rongelap, Utirik, Rongerik and Ailinginae Atolls were also inhabited on 1 March 1954, where retrospective thyroid absorbed doses have previously been reconstructed. The current estimates are based primarily on external exposure data, which were recorded shortly after each nuclear test in the Castle Series, and secondarily on soil concentrations of 137Cs in samples collected in 1978 and 1988, along with aerial monitoring done in 1978. The external exposures and 137Cs soil concentrations were representative of the atmospheric transport and deposition patterns of the entire Castle Series tests and show that the BRAVO test was the major contributor to fallout exposure during the Castle series and other test series which were carried out in the Marshall Islands. These data have been used as surrogates for fission product radioiodines and telluriums in order to estimate the range of thyroid absorbed doses that may have occurred throughout the Marshall Islands. Dosimetry based on these two sets of estimates agreed within a factor of 4 at the locations where BRAVO was the dominant contributor to the total exposure and deposition. Both methods indicate that thyroid absorbed doses in the range of 1 Gy (100 rad) may have been incurred in some of the northern locations, whereas the doses at southern locations did not significantly exceed levels comparable to those from worldwide fallout. The results of these estimates indicate that a systematic medical survey for thyroid disease should be conducted, and that a more definitive dose reconstruction should be made for all the populated atolls and islands in the Northern Marshall Islands beyond Rongelap, Utirik, Rongerik and Ailinginae, which were significantly contaminated by BRAVO fallout.

  18. An estimate by two methods of thyroid absorbed doses due to BRAVO fallout in several northern Marshall Islands

    SciTech Connect

    Musolino, S.V.; Hull, A.P.; Greenhouse, N.A.

    1997-10-01

    Estimates of the thyroid absorbed doses due to fallout originating from the 1 March 1954 BRAVO thermonuclear test on Bikini Atoll have been made for several inhabited locations in the Northern Marshall Islands. Rongelap, Utirik, Rongerik and Ailinginae Atolls were also inhabited on 1 March 1954, where retrospective thyroid absorbed doses have previously been reconstructed. Current estimates are based primarily on external exposure data, which were recorded shortly after each nuclear test in the Castle Series, and secondarily on soil concentrations of {sup 137}Cs in samples collected in 1978 and 1988, along with aerial monitoring done in 1978. External exposures and {sup 137}Cs Soil concentrations were representative of the atmospheric transport and deposition patterns of the entire Castle Series tests and show that the BRAVO test was the major contributor to fallout exposure during the Castle series and other test series which were carried out in the Marshall Islands. These data have been used as surrogates for fission product radioiodines and telluriums in order to estimate the range of thyroid absorbed doses that may have occurred throughout the Marshall Islands. Dosimetry based on these two sets of estimates agreed within a factor of 4 at the locations where BRAVO was the dominant contributor to the total exposure and deposition. Both methods indicate that thyroid absorbed doses in the range of 1 Gy (100 rad) may have been incurred in some of the northern locations, whereas the doses at southern locations did not significantly exceed levels comparable to those from worldwide fallout. The results of these estimates indicate that a systematic medical survey for thyroid disease should be conducted, and that a more definitive dose reconstruction should be made for all the populated atolls and islands in the Northern Marshall Islands beyond Rongelap, Utirik, Rongerik and Ailinginae, which were significantly contaminated by BRAVO fallout. 30 refs., 2 figs., 10 tabs.

  19. Variation in the estimations of ETo and crop water use due to the sensor accuracy of the meteorological variables

    NASA Astrophysics Data System (ADS)

    Moratiel, R.; Martínez-Cob, A.; Latorre, B.

    2013-06-01

    In agricultural ecosystems the use of evapotranspiration (ET) to improve irrigation water management is generally widespread. Commonly, the crop ET (ETc) is estimated by multiplying the reference crop evapotranspiration (ETo) by a crop coefficient (Kc). Accurate estimation of ETo is critical because it is the main factor affecting the calculation of crop water use and water management. The ETo is generally estimated from recorded meteorological variables at reference weather stations. The main objective of this paper was assessing the effect of the uncertainty due to random noise in the sensors used for measurement of meteorological variables on the estimation of ETo, crop ET and net irrigation requirements of grain corn and alfalfa in three irrigation districts of the middle Ebro River basin. Five scenarios were simulated, four of them individually considering each recorded meteorological variable (temperature, relative humidity, solar radiation and wind speed) and a fifth scenario combining together the uncertainty of all sensors. The uncertainty in relative humidity for irrigation districts Riegos del Alto Aragón (RAA) and Bardenas (BAR), and temperature for irrigation district Canal de Aragón y Cataluña (CAC), were the two most important factors affecting the estimation of ETo, corn ET (ETc_corn), alfalfa ET (ETc_alf), net corn irrigation water requirements (IRncorn) and net alfalfa irrigation water requirements (IRnalf). Nevertheless, this effect was never greater than ±0.5% over annual scale time. The wind speed variable (Scenario 3) was the third variable more influential in the fluctuations (±) of evapotranspiration, followed by solar radiation. Considering the accuracy for all sensors over annual scale time, the variation was about ±1% of ETo, ETc_corn, ETc_alf, IRncorn, and IRnalf. The fluctuations of evapotranspiration were higher at shorter time scale. ETo daily fluctuation remained lower than 5 % during the growing season of corn and alfalfa

  20. Estimating Potential Increased Bladder Cancer Risk Due to Increased Bromide Concentrations in Sources of Disinfected Drinking Waters.

    PubMed

    Regli, Stig; Chen, Jimmy; Messner, Michael; Elovitz, Michael S; Letkiewicz, Frank J; Pegram, Rex A; Pepping, T J; Richardson, Susan D; Wright, J Michael

    2015-11-17

    Public water systems are increasingly facing higher bromide levels in their source waters from anthropogenic contamination through coal-fired power plants, conventional oil and gas extraction, textile mills, and hydraulic fracturing. Climate change is likely to exacerbate this in coming years. We estimate bladder cancer risk from potential increased bromide levels in source waters of disinfecting public drinking water systems in the United States. Bladder cancer is the health end point used by the United States Environmental Protection Agency (EPA) in its benefits analysis for regulating disinfection byproducts in drinking water. We use estimated increases in the mass of the four regulated trihalomethanes (THM4) concentrations (due to increased bromide incorporation) as the surrogate disinfection byproduct (DBP) occurrence metric for informing potential bladder cancer risk. We estimate potential increased excess lifetime bladder cancer risk as a function of increased source water bromide levels. Results based on data from 201 drinking water treatment plants indicate that a bromide increase of 50 μg/L could result in a potential increase of between 10(-3) and 10(-4) excess lifetime bladder cancer risk in populations served by roughly 90% of these plants.

  1. Estimating statistical isotropy violation in CMB due to non-circular beam and complex scan in minutes

    SciTech Connect

    Pant, Nidhi; Das, Santanu; Mitra, Sanjit; Souradeep, Tarun; Rotti, Aditya E-mail: santanud@iucaa.ernet.in E-mail: sanjit@iucaa.in

    2016-03-01

    Mild, unavoidable deviations from circular-symmetry of instrumental beams along with scan strategy can give rise to measurable Statistical Isotropy (SI) violation in Cosmic Microwave Background (CMB) experiments. If not accounted properly, this spurious signal can complicate the extraction of other SI violation signals (if any) in the data. However, estimation of this effect through exact numerical simulation is computationally intensive and time consuming. A generalized analytical formalism not only provides a quick way of estimating this signal, but also gives a detailed understanding connecting the leading beam anisotropy components to a measurable BipoSH characterisation of SI violation. In this paper, we provide an approximate generic analytical method for estimating the SI violation generated due to a non-circular (NC) beam and arbitrary scan strategy, in terms of the Bipolar Spherical Harmonic (BipoSH) spectra. Our analytical method can predict almost all the features introduced by a NC beam in a complex scan and thus reduces the need for extensive numerical simulation worth tens of thousands of CPU hours into minutes long calculations. As an illustrative example, we use WMAP beams and scanning strategy to demonstrate the easability, usability and efficiency of our method. We test all our analytical results against that from exact numerical simulations.

  2. Schooling and wage income losses due to early-childhood growth faltering in developing countries: national, regional, and global estimates.

    PubMed

    Fink, Günther; Peet, Evan; Danaei, Goodarz; Andrews, Kathryn; McCoy, Dana Charles; Sudfeld, Christopher R; Smith Fawzi, Mary C; Ezzati, Majid; Fawzi, Wafaie W

    2016-07-01

    The growth of >300 million children <5 y old was mildly, moderately, or severely stunted worldwide in 2010. However, national estimates of the human capital and financial losses due to growth faltering in early childhood are not available. We quantified the economic cost of growth faltering in developing countries. We combined the most recent country-level estimates of linear growth delays from the Nutrition Impact Model Study with estimates of returns to education in developing countries to estimate the impact of early-life growth faltering on educational attainment and future incomes. Primary outcomes were total years of educational attainment lost as well as the net present value of future wage earnings lost per child and birth cohort due to growth faltering in 137 developing countries. Bootstrapped standard errors were computed to account for uncertainty in modeling inputs. Our estimates suggest that early-life growth faltering in developing countries caused a total loss of 69.4 million y of educational attainment (95% CI: 41.7 million, 92.6 million y) per birth cohort. Educational attainment losses were largest in South Asia (27.6 million y; 95% CI: 20.0 million, 35.8 million y) as well as in Eastern (10.3 million y; 95% CI: 7.2 million, 12.9 million y) and Western sub-Saharan Africa (8.8 million y; 95% CI: 6.4 million, 11.5 million y). Globally, growth faltering in developing countries caused a total economic cost of $176.8 billion (95% CI: $100.9 billion, $262.6 billion)/birth cohort at nominal exchange rates, and $616.5 billion (95% CI: $365.3 billion, $898.9 billion) at purchasing power parity-adjusted exchange rates. At the regional level, economic costs were largest in South Asia ($46.6 billion; 95% CI: $33.3 billion, $61.1 billion), followed by Latin America ($44.7 billion; 95% CI: $19.2 billion, $74.6 billion) and sub-Saharan Africa ($34.2 billion; 95% CI: $24.4 billion, $45.3 billion). Our results indicate that the annual cost of early

  3. Hysteresis and Fatigue

    NASA Astrophysics Data System (ADS)

    Erber, T.; Guralnick, S. A.; Michels, S. C.

    1993-06-01

    Fatigue in materials is the result of cumulative damage processes that are usually induced be repeated loading cycles. Since the energy dissipation associated with damage is irreversible, and the loading cycles are accompanied by the evolution of heat, the corresponding relation between stress and strain is not single-valued; but rather exhibits a memory dependence, or hysteresis. Conversely, sustained hysteresis is a necessary condition for fatigue and is related to the rate of damage accumulation. Engineering design and safety standards for estimating fatigue life are based in part on the Manson-Coffin relations between the width of stress-strain hysteresis loops and the number of loading cycles required to produce failure in test pieces. Experimental and theoretical results show that this relation can be extended into a simple phenomenological description of fatigue that directly links total hysteresis energy dissipation, the cumulation of material damage, and the average number of loading cycles leading to failure. Detailed features of the hysteresis can be understood with the help of analogies between the incremental collapse of structures and the inception and organization of damage in materials. In particular, scanning tunneling microscope measurements of the threshold of mechanical irreversibility and acoustic emission patterns may be used to check on the evolution of hysteresis at the microscopic level.

  4. Model parameter estimations from residual gravity anomalies due to simple-shaped sources using Differential Evolution Algorithm

    NASA Astrophysics Data System (ADS)

    Ekinci, Yunus Levent; Balkaya, Çağlayan; Göktürkler, Gökhan; Turan, Seçil

    2016-06-01

    An efficient approach to estimate model parameters from residual gravity data based on differential evolution (DE), a stochastic vector-based metaheuristic algorithm, has been presented. We have showed the applicability and effectiveness of this algorithm on both synthetic and field anomalies. According to our knowledge, this is a first attempt of applying DE for the parameter estimations of residual gravity anomalies due to isolated causative sources embedded in the subsurface. The model parameters dealt with here are the amplitude coefficient (A), the depth and exact origin of causative source (zo and xo, respectively) and the shape factors (q and ƞ). The error energy maps generated for some parameter pairs have successfully revealed the nature of the parameter estimation problem under consideration. Noise-free and noisy synthetic single gravity anomalies have been evaluated with success via DE/best/1/bin, which is a widely used strategy in DE. Additionally some complicated gravity anomalies caused by multiple source bodies have been considered, and the results obtained have showed the efficiency of the algorithm. Then using the strategy applied in synthetic examples some field anomalies observed for various mineral explorations such as a chromite deposit (Camaguey district, Cuba), a manganese deposit (Nagpur, India) and a base metal sulphide deposit (Quebec, Canada) have been considered to estimate the model parameters of the ore bodies. Applications have exhibited that the obtained results such as the depths and shapes of the ore bodies are quite consistent with those published in the literature. Uncertainty in the solutions obtained from DE algorithm has been also investigated by Metropolis-Hastings (M-H) sampling algorithm based on simulated annealing without cooling schedule. Based on the resulting histogram reconstructions of both synthetic and field data examples the algorithm has provided reliable parameter estimations being within the sampling limits of

  5. Pilot Fatigue and Circadian Desynchronosis

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Pilot fatigue and circadian desynchronosis, its significance to air transport safety, and research approaches, were examined. There is a need for better data on sleep, activity, and other pertinent factors from pilots flying a variety of demanding schedules. Simulation studies of flight crew performance should be utilized to determine the degree of fatigue induced by demanding schedules and to delineate more precisely the factors responsible for performance decrements in flight and to test solutions proposed to resolve problems induced by fatigue and desynchronosis. It was concluded that there is a safety problem of uncertain magnitude due to transmeridian flying and a potential problem due to fatigue associated with various factors found in air transport operations.

  6. Reliability based fatigue design and maintenance procedures

    NASA Technical Reports Server (NTRS)

    Hanagud, S.

    1977-01-01

    A stochastic model has been developed to describe a probability for fatigue process by assuming a varying hazard rate. This stochastic model can be used to obtain the desired probability of a crack of certain length at a given location after a certain number of cycles or time. Quantitative estimation of the developed model was also discussed. Application of the model to develop a procedure for reliability-based cost-effective fail-safe structural design is presented. This design procedure includes the reliability improvement due to inspection and repair. Methods of obtaining optimum inspection and maintenance schemes are treated.

  7. Supravital energy production in early post-mortem phase - estimate based on heat loss due to radiation and natural convection.

    PubMed

    Mall, Gita; Hubig, Michael; Beier, Gundolf; Büttner, Andreas; Eisenmenger, Wolfgang

    2002-06-01

    The temperature-based determination of the time since death in the early post-mortem (pm) period plays an important role in medico-legal practice. In contrast to the common opinion according to which convection and conduction are mainly responsible for post-mortem heat loss, a considerable part of energy is emitted by thermal radiation. The present paper concentrates on the heat loss due to radiation and natural convection. Since both heat transfer mechanisms depend on the temperature gradient between skin and environment, the skin temperature was measured in corpses of different constitution (lean, medium and obese) and its decrease fitted by a single-exponential model. Heat loss due to radiation was calculated according to the non-linearized form of the law of Stefan and Boltzmann, heat loss due to natural convection according to the semi-empirical thermodynamic laws; the shape of the body in supine position was approximated to a semi-cylinder of finite length. The power due to radiation ranged between 386kJ/h (lean) and 550kJ/h (obese), that due to natural convection between 307kJ/h (lean) and 429kJ/h (obese) initially. Cumulative energy loss amounted to 2167kJ (lean) and 4239kJ (obese) by radiation and 1485kJ (lean) and 2922kJ (obese) by natural convection up to 20h pm. The energy loss due to radiation plus natural convection initially exceeded the energy loss due the decrease of the energy content of the body (mass x heat capacity x temperature decrease). This surplus can be explained only by exothermal processes in the phase of intermediary life and directly provides lower bounds for supravital energy production. Cumulative supravital energy ranges between 1139kJ up to 5h pm in the lean and 2516kJ up to 10h pm in the obese corpses. The courses of supravital energies and powers are presented as functions of time. Under standard conditions like still air (no forced convection) and insulating ground (little conductive heat transfer), the lower bounds represent

  8. Estimation of ancient organic matter transformation due to thermokarst process at the Bykovsky peninsula on Laptev Sea coast

    NASA Astrophysics Data System (ADS)

    Kholodov, A. L.; Meyer, H.; Schirrmeister, L.; Zolotareva, B.; Nicolsky, D.

    2013-12-01

    Organic carbon stored in frozen Quaternary deposits can potentially be released into the modern biogeochemical cycle due to permafrost degradation. This task takes more and more attention recently including one of the important research questions related to the quality of organic matter (OM) in permafrost. The main method of OM liability estimation is the incubation. But it is impossible to reconstruct in the lab all varieties of natural conditions and real time frames of the organics decay process. Our approach is based on the comparison of quality of OM in (1) initial edoma and (2) taberal deposits (i.e. thawed under the lakes, packed and refrozen after lake drainage). Two pairs of boreholes located at the top of edoma and within adjoining thermokarst depressions had been drilled on Bykovsky Peninsula; northern Siberia near the Lena River delta. Samples taken from permafrost cores were analyzed for TOC, C/N ratio, δ13C and composition of humus. Results show an overall decrease of the carbon pool due to partial decomposition of OM in talik under the lake. Insignificant differences of C/N ratio in original edoma (10.83 in average) and taberal deposits (11.82) point to relatively low stage of decomposition. The average δ13C in edoma is about -24‰, while in taberal deposits δ13C decreases from close to edoma (-24‰) to the bottom of taberal layer to -26‰ in the upper part with exponential trend. This trend can be explained by the increasing duration of organic decomposition within the talik under the lake at the top of the taberal layer in comparison with the bottom due to the process of talik formation. The humic acid content and the humic/fulvic acids ratio have similar patterns. Average content of humus content in edoma is 20% of TOC and ratio of humic and fulvic acids is 1. In taberal deposits content of humus increasing downward from 10 to 20% of TOC and the ratio of humic and fulvic acids is 0.8. The one-dimensional mathematical model of edoma thaw and

  9. Gross margin losses due to Salmonella Dublin infection in Danish dairy cattle herds estimated by simulation modelling.

    PubMed

    Nielsen, T D; Kudahl, A B; Østergaard, S; Nielsen, L R

    2013-08-01

    assumptions about milk yield losses for cows in the resistant or carrier stages had the greatest influence on the estimated GM losses. This was more influential in the poorer management scenarios due to increased number of infected cows. The results can be used to inform dairy farmers of the benefits of preventing introduction and controlling spread of S. Dublin. Furthermore, they can be used in cost-benefit analyses of control actions for S. Dublin both at herd and sector level.

  10. Engineering Aspects of Fatigue Crack Propagation

    DTIC Science & Technology

    1962-01-01

    Estimating Notch-Size Effect in Fatigue Tests on Steel. NACA TN 2805, 1952. - 37 - 19. Landers, Charles B., and Hardrath, Herbert F.: Results of Axial- Load... Charles B., and Howell, F. M.: Axial-Load Fatigue Properties of 24S-T and 75S-T Aluminum Alloy as Determined in Several Laboratories. NACA TR 1190, 1954...Hardrath, Herbert F., Leybold, Herbert A., Landers, Charles B., and Hauschild, Louis W.: Fatigue-Crack Propagation in Aluminum- Alloy Box Beams. NACA

  11. Ischemia reperfusion dysfunction changes model-estimated kinetics of myofilament interaction due to inotropic drugs in isolated hearts

    PubMed Central

    Rhodes, Samhita S; Camara, Amadou KS; Ropella, Kristina M; Audi, Said H; Riess, Matthias L; Pagel, Paul S; Stowe, David F

    2006-01-01

    Background The phase-space relationship between simultaneously measured myoplasmic [Ca2+] and isovolumetric left ventricular pressure (LVP) in guinea pig intact hearts is altered by ischemic and inotropic interventions. Our objective was to mathematically model this phase-space relationship between [Ca2+] and LVP with a focus on the changes in cross-bridge kinetics and myofilament Ca2+ sensitivity responsible for alterations in Ca2+-contraction coupling due to inotropic drugs in the presence and absence of ischemia reperfusion (IR) injury. Methods We used a four state computational model to predict LVP using experimentally measured, averaged myoplasmic [Ca2+] transients from unpaced, isolated guinea pig hearts as the model input. Values of model parameters were estimated by minimizing the error between experimentally measured LVP and model-predicted LVP. Results We found that IR injury resulted in reduced myofilament Ca2+ sensitivity, and decreased cross-bridge association and dissociation rates. Dopamine (8 μM) reduced myofilament Ca2+ sensitivity before, but enhanced it after ischemia while improving cross-bridge kinetics before and after IR injury. Dobutamine (4 μM) reduced myofilament Ca2+ sensitivity while improving cross-bridge kinetics before and after ischemia. Digoxin (1 μM) increased myofilament Ca2+ sensitivity and cross-bridge kinetics after but not before ischemia. Levosimendan (1 μM) enhanced myofilament Ca2+ affinity and cross-bridge kinetics only after ischemia. Conclusion Estimated model parameters reveal mechanistic changes in Ca2+-contraction coupling due to IR injury, specifically the inefficient utilization of Ca2+ for contractile function with diastolic contracture (increase in resting diastolic LVP). The model parameters also reveal drug-induced improvements in Ca2+-contraction coupling before and after IR injury. PMID:16512898

  12. An estimation of the global burden of disease due to skin lesions caused by arsenic in drinking water.

    PubMed

    Fewtrell, Lorna; Fuge, Ron; Kay, David

    2005-06-01

    The global burden of disease due to skin lesions caused by arsenic in drinking water was estimated by combining country-based exposure data with selected exposure-response relationships derived from the literature. Populations were considered to be exposed to elevated arsenic levels if their drinking water contained arsenic concentrations of 50 microg I(-1) or greater. Elevated arsenic concentrations in drinking water result in a significant global burden of disease, even when confining the health outcome to skin lesions. The burden of disease was particularly marked in the World Health Organization (WHO) comparative risk assessment (CRA) 'Sear D' region, which includes Bangladesh, India and Nepal. Unsurprisingly, Bangladesh was the worst affected country with 143 disability adjusted life years (DALYs) per 1,000 population. Although this initial estimate is subject to a large degree of uncertainty, it does represent an important first step in allowing the comparison of the problem relating to elevated arsenic in drinking water to other environmental health outcomes.

  13. Helicopter Fatigue Design Guide

    DTIC Science & Technology

    1983-11-01

    de nouveaux materiaux ou technologies accentue I’importance que presente pour les forces de I’O.T.A.N. ce probleme de la maitrise des phenomenes de...fatigue interessant les helicopteres. La commission Structures et Materiaux de I’AGARD a ete conduite a proposer et developper une serie de reflexions...service life for the suspension components due to their vulnerabihty to darnage at high speeds. Spectrum No. 2 led to limitations being applied to

  14. A semi-empirical model for the estimation of maximum horizontal displacement due to liquefaction-induced lateral spreading

    USGS Publications Warehouse

    Faris, Allison T.; Seed, Raymond B.; Kayen, Robert E.; Wu, Jiaer

    2006-01-01

    During the 1906 San Francisco Earthquake, liquefaction-induced lateral spreading and resultant ground displacements damaged bridges, buried utilities, and lifelines, conventional structures, and other developed works. This paper presents an improved engineering tool for the prediction of maximum displacement due to liquefaction-induced lateral spreading. A semi-empirical approach is employed, combining mechanistic understanding and data from laboratory testing with data and lessons from full-scale earthquake field case histories. The principle of strain potential index, based primary on correlation of cyclic simple shear laboratory testing results with in-situ Standard Penetration Test (SPT) results, is used as an index to characterized the deformation potential of soils after they liquefy. A Bayesian probabilistic approach is adopted for development of the final predictive model, in order to take fullest advantage of the data available and to deal with the inherent uncertainties intrinstiic to the back-analyses of field case histories. A case history from the 1906 San Francisco Earthquake is utilized to demonstrate the ability of the resultant semi-empirical model to estimate maximum horizontal displacement due to liquefaction-induced lateral spreading.

  15. Comprehensive chemical characterisation of size-segregated PM10 in Dresden and estimation of changes due to global warming

    NASA Astrophysics Data System (ADS)

    Scheinhardt, Sebastian; Spindler, Gerald; Leise, Silvia; Müller, Konrad; Iinuma, Yoshiteru; Zimmermann, Frank; Matschullat, Jörg; Herrmann, Hartmut

    2013-08-01

    To identify current and future human health risks from urban air pollution, size-segregated particle samples were collected under various seasonal and meteorological conditions in Dresden, Germany. Sampling days were grouped into twelve categories depending on season, air mass origin and temperature. A comprehensive chemical characterisation and mass closure were performed. The particulate matter (PM) mass concentration and composition were shown to be highly dependent on these categories. The highest PM mass concentrations were found on cold winter days, mainly due to compounds of anthropogenic origin. The current annual mean PM mass concentration and composition were calculated using the occurrence frequencies of the categories (weighted mean). Information about future changes of the occurrence frequencies of the categories was deduced from climate models. Assuming that PM concentration and composition within a given category do not change, the annual mean PM mass concentration and composition were calculated for two scenarios (weighted mean, 2071-2100). As a result, it was found that the annual mean PM mass concentration is likely to decrease slightly by 2100, mainly due to a decrease of sulphate and soot mass concentrations. Generally, chemicals originating from anthropogenic emissions (PAHs, trace metals) are estimated to decrease. However, it is concluded that emission reduction measures are still necessary to control urban air quality including PM even if climate change will lead to a certain reduction in PM.

  16. Fatigue Characterization of Fire Resistant Syntactic Foam Core Material

    NASA Astrophysics Data System (ADS)

    Hossain, Mohammad Mynul

    established for the three stress states and three types of the failure modes. This equation was used to estimate endurance limit (106 cycles) of the material. Like metallic materials, the compression fatigue life of Eco-Core was found to be dependent on the stress range instead of maximum or mean cyclic stress. Furthermore shear and flexural ultimate failure of the core material was found to be due to a combination of shear and tensile stress.

  17. Corrosion Fatigue

    DTIC Science & Technology

    1981-10-01

    their scientific and technical potential; - Recommending effective ways for the member nations to use their research and development capabilities for the...be major considerations In aircraft design. Environmental effects are known to infloij- ence both the initiation and the propagation of fatigue cracks...for the assessment of the effectiveness of sharing between different laboratories an investigation of a size prohibit- Ive for its execution at a

  18. Assessing fatigue.

    PubMed

    Foushee, H C

    1986-05-01

    Despite impressive advances in aircraft technology over the past several decades and an overall decline in the airline accident rate since the introduction of turbine-powered aircraft, flight crew performance problems continue to dominate air transport accident statistics. Researchers have offered many hypotheses to explain this finding, and interest in pilot fatigue has stimulated a large volume of laboratory research. Much of this work, however, is difficult to generalize and to apply to the real world of flight operations, and researchers disagree about the extent and operational significance of fatigue-related reductions in pilot performance. As a result, in 1980 Congress asked the National Aeronautics and Space Administration to undertake a comprehensive research program to assess whether fatigue-related problems are prevalent in long- and short-haul flying. The two major goals of this project are: (1) to assess the psychophysiological effects on pilot performance of flying various types of flight and duty cycles, and (2) to determine the operational significance to flight safety and efficiency of flying these flight and duty cycles.

  19. Effects of residual stress and texture on the high-cycle fatigue properties of light metals

    NASA Astrophysics Data System (ADS)

    Jiang, Xiuping

    2007-12-01

    High cycle fatigue tests were conducted on a commercially pure Ti, a forged Ti-6Al-4V alloy, and newly developed high strength AA2026 and AA2099 Al alloys in four-point bend. The effects of surface compressive residual stress and texture on the fatigue properties of these alloys were systematically investigated. The resistance to fatigue crack growth in an alloy was estimated using a simple model that took into account texture and grain structure. The resistance calculations were able to explain the observed behaviors of fatigue crack growth in planar slip materials. Due to strengthening in the surface by enhancement treatment, fatigue cracks were found to be initiated in the subsurface region in the short peened Ti-6Al-4V alloy and sandblasted CP Ti, in contrast to crack initiation on the surface of the untreated samples. When the shot peened Ti-6A1-4V alloy was tested between 25°C and 200°C, the surface compressive residual stress could only be slightly relaxed due to thermal exposure, which did not deteriorate the fatigue strength of the alloy. Similarly, no obvious redistribution of the residual stress was observed when the sandblasted Ti was annealed below 200°C. With increase in the annealing temperature (300°C˜700°C), the compressive residual stresses were significantly relaxed, leading to relatively a lower fatigue strength. In AA2026 & AA2099 Al alloys, crack growth was found to be in a predominantly crystallographic mode in unrecrystallized regions, and a non-crystallographic mode in recrystallized regions. Fatigue cracks were deflected at grain boundaries usually with small twist angles in the unrecrystallized regions, but with large twist angles in the recrystallized regions. The theoretical analysis verified that a large percentage of recrystallized grains could provide strong resistance to fatigue crack growth by producing larger twist angles of crack deflection at their grain boundaries than those of most of the gains in unrecrystallized

  20. Fatigue, Creep-Fatigue, and Thermomechanical Fatigue Life Testing of Alloys

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.; Lerch, Bradley A.; McGaw, Michael A.

    2000-01-01

    low-cycle fatigue testing, wherein some prescribed indication of impending failure due to cracking is adopted. Specific criteria will be described later. As a rule, cracks that develop during testing are not measured nor are the test parameters intentionally altered owing to the presence of cracking.

  1. Low-Cycle Fatigue Life and Fatigue Crack Propagation of Sintered Ag Nanoparticles

    NASA Astrophysics Data System (ADS)

    Shioda, Ryutaro; Kariya, Yoshiharu; Mizumura, Noritsuka; Sasaki, Koji

    2017-02-01

    The low-cycle fatigue life and fatigue crack propagation behavior of sintered silver nanoparticles were investigated using miniature specimens sintered at two different temperatures. The fatigue crack initiation life and fatigue crack propagation rate of sintered Ag nanoparticles were extremely sensitive to changes in the range of inelastic energy density and the cyclic J integral, exhibiting brittle characteristics, in contrast to tin-based lead-free solder alloys. With increasing sintering temperature, the fatigue crack propagation rate decreased. On the other hand, the effect of sintering temperature on the fatigue crack initiation life differed depending on the use of either a smooth specimen (low-cycle fatigue test) or notched specimen (fatigue crack propagation test). For the notched specimens, the probability of grain boundaries around the notch decreased due to increased sintering temperature. Therefore, the fatigue crack initiation life was increased with an increase in sintering temperature in the fatigue crack propagation test. In the smooth specimen, however, the fatigue life decreased with an increase in sintering temperature, as the elastic modulus of the specimen increased with increasing sintering temperature. In the low-cycle fatigue test, the specimen sintered with high internal stress started to develop crack initiation early, causing a decrease in the crack initiation life.

  2. Side Effects: Fatigue

    Cancer.gov

    Fatigue is a common side effect of many cancer treatments such as chemotherapy, radiation therapy, immunotherapy, and surgery. Anemia and pain can also cause fatigue. Learn about symptoms and way to manage fatigue.

  3. Chronic Fatigue Syndrome (CFS) and Cancer Related Fatigue (CRF): two "fatigue" syndromes with overlapping symptoms and possibly related aetiologies.

    PubMed

    Rovigatti, Ugo

    2012-12-01

    In July 2010, at the Muscle Fatigue Meeting, I presented an overview of Chronic Fatigue Syndrome and Cancer Related Fatigue, emphasizing a critical interpretation of the potential association between Chronic Fatigue Syndrome and Cancer Related Fatigue and a newly discovered retrovirus: Xenotropic Murine Related Virus. Since this association was hotly debated at that time, I suggested at the Meeting that it was wrong and most likely due to the identification of the wrong virus culprit. Today, 20 months after the Meeting, the first part of our prediction has turned out to be correct, as Xenotropic Murine Related Virus was shown to be a laboratory-created artefact. Still, the potential association of fatigue-syndromes with an infection (most likely viral) is sustained by a plethora of evidence and this overview will initially summarize data suggesting prior viral infection(s). The principal hypothesized mechanisms for both peripheral and central Chronic Fatigue Syndrome/Cancer Related Fatigue will be then summarized, also indicating plausible associations and triggering factors. All evidence accrued so far suggests that further research work should be performed in this interesting area and in order to identify an infectious agent for Chronic Fatigue Syndrome/Cancer Related Fatigue. One candidate RNA virus, Micro-Foci inducing Virus, will be described in this overview.

  4. A multi-feature integration method for fatigue crack detection and crack length estimation in riveted lap joints using Lamb waves

    NASA Astrophysics Data System (ADS)

    He, Jingjing; Guan, Xuefei; Peng, Tishun; Liu, Yongming; Saxena, Abhinav; Celaya, Jose; Goebel, Kai

    2013-10-01

    This paper presents an experimental study of damage detection and quantification in riveted lap joints. Embedded lead zirconate titanate piezoelectric (PZT) ceramic wafer-type sensors are employed to perform in situ non-destructive evaluation (NDE) during fatigue cyclical loading. PZT wafers are used to monitor the wave reflection from the boundaries of the fatigue crack at the edge of bolt joints. The group velocity of the guided wave is calculated to select a proper time window in which the received signal contains the damage information. It is found that the fatigue crack lengths are correlated with three main features of the signal, i.e., correlation coefficient, amplitude change, and phase change. It was also observed that a single feature cannot be used to quantify the damage among different specimens since a considerable variability was observed in the response from different specimens. A multi-feature integration method based on a second-order multivariate regression analysis is proposed for the prediction of fatigue crack lengths using sensor measurements. The model parameters are obtained using training datasets from five specimens. The effectiveness of the proposed methodology is demonstrated using several lap joint specimens from different manufactures and under different loading conditions.

  5. Estimated crop loss due to coconut mite and financial analysis of controlling the pest using the acaricide abamectin.

    PubMed

    Rezende, Daniela; Melo, José W S; Oliveira, José E M; Gondim, Manoel G C

    2016-07-01

    Reducing the losses caused by Aceria guerreronis Keifer has been an arduous task for farmers. However, there are no detailed studies on losses that simultaneously analyse correlated parameters, and very few studies that address the economic viability of chemical control, the main strategy for managing this pest. In this study the objectives were (1) to estimate the crop loss due to coconut mite and (2) to perform a financial analysis of acaricide application to control the pest. For this, the following parameters were evaluated: number and weight of fruits, liquid albumen volume, and market destination of plants with and without monthly abamectin spraying (three harvests). The costs involved in the chemical control of A. guerreronis were also quantified. Higher A. guerreronis incidence on plants resulted in a 60 % decrease in the mean number of fruits harvested per bunch and a 28 % decrease in liquid albumen volume. Mean fruit weight remained unaffected. The market destination of the harvested fruit was also affected by higher A. guerreronis incidence. Untreated plants, with higher A. guerreronis infestation intensity, produced a lower proportion of fruit intended for fresh market and higher proportions of non-marketable fruit and fruit intended for industrial processing. Despite the costs involved in controlling A. guerreronis, the difference between the profit from the treated site and the untreated site was 18,123.50 Brazilian Real; this value represents 69.1 % higher profit at the treated site.

  6. Approach for Estimating Exposures and Incremental Health Effects from Lead Due to Renovation Repair and Painting Activities in Public and Commercial Buildings

    EPA Pesticide Factsheets

    Approach for Estimating Exposures and Incremental Health Effects from Lead Due to Renovation Repair and Painting Activities in Public and Commercial Buildings: links to documents at www.regulations.gov, links to PDFs related to Approach document

  7. Structural health monitoring and condition based fatigue damage prognosis of complex metallic structures

    NASA Astrophysics Data System (ADS)

    Mohanty, Subhasish

    Current practice in fatigue life prediction is based on assumed initial structural flaws regardless of whether these assumed flaws actually occur in service. Furthermore, the model parameters are often estimated empirically based on previous coupon test results. Small deviations of the initial conditions and model parameters may generate large errors in the expected dynamical behavior of fatigue damage growth. Consequently, a large degree of conservatism is incorporated into structural designs due to these expected uncertainties. The current research in the area of Structural Health Monitoring (SHM) and probabilistic fatigue modeling can help in improved fatigue damage modeling and remaining useful life estimation (RULE) techniques. This thesis discusses an integrated approach of SHM and adaptive prognosis model that not only estimates the current health, but can also forecast the future health and calculate RULE of an aerospace structural component with high level of confidence. The approach does not assume any fixed initial condition and model parameters. This dissertation include the following novel contributions. 1) A Bayesian based off-line Gaussian Process (GP) model is developed, which is the core of the present condition based prognosis approach. 2) Different passive and active SHM approaches are used for on-line damage state estimation. Applications of passive sensing are shown to estimate the time-series fatigue damage states both under constant and random fatigue loading. It is found that there is a good correlation between estimated damage states and optically measured damage states. In addition, applications for both narrow and broadband active sensing approaches are presented to estimate smaller incipient damage. It is demonstrated that the active sensing techniques not only can identify smaller incipient damage but also can quantify fatigue damage during all the three stages (stages I, II, and III) of fatigue life. 3) An integrated on-line SHM and

  8. [Chronic fatigue syndrome: more than fatigue].

    PubMed

    Royes, Badía; Alvarez, Carballo; Lalinde, Sevillano; Vidal, Llinas; Martín, Alegre

    2010-12-01

    Chronic fatigue syndrome (CFS) is a disease recognized by all international medical organizations and WHO, and is classified under the code G93.3 of the International Classification of Diseases. Its prevalence is estimated around 2.54% being more common in women than in men (8/2) aged between 20 and 40 Is defined as a chronic new description characterized by the presence of subjective feeling of fatigue and exhaustion long disabling of more than 6 months duration that is not relieved by rest. It is a multisystem disorder that often presents a significant number of comorbid phenomena. Not known until specific tests to confirm the diagnosis, nor is there a cure to solve this health problem definitively The strongest evidence is based on the multidisciplinary approach for the symptomatic treatment of pain, sleep disorders, neurocognitive dysfunction, autonomic and control of depression and anxiety. The specific contribution of nursing to care for the person who lives and live with the SFC should be developed primarily in the field of health education and supportive care, support and assistance to help the patient and their relatives are an adaptive response to changes in health.

  9. Multiaxial Fatigue and Fracture: A Literature Review

    DTIC Science & Technology

    1984-07-01

    correlation. Brown and Miller 571 determined the biaxial eycli" stress-strai cures f’r a I% Cr-Mo-V steel and an AISI 316 stainless steel at various...Multiaxial Low-Cycle Fatigue BLASS, J. J. and ZAMRIK. S. Y. Multiaxial low-cycle fatigue of type 304 stainless steel . Proc. Symposium on Creep-Fatigue...the tensile strength of the metal. T + Saim-cOF Direct tr~ess due. bo bendrx" tos/m FIG. 2. FATIGUE LIMITS OF THREE STEELS UNDER COMBINED BENDING AND

  10. Hysteresis and fatigue

    SciTech Connect

    Erber, T. ); Guralnick, S.A.; Michels, S.C. )

    1993-06-01

    Energy dissipation associated with damage of materials is irreversible and loading cycles are accompanied by the evolution of heat. The relation between energy dissipation and loading therefore exhibits a memory dependence or hysteresis. Conversely, sustained hysteresis is a necessary condition for fatigue and is related to the rate of damage accumulation. Standards for estimating fatigue life are partially based on the Manson-Coffin relations between the width of stress strain hysteresis loops and the number of loading cycles required to produce failure in test pieces. In the present study, experimental and theoretical results demonstrate that this relation can be extended into a simple phenomenological description of fatigue that directly links total hysteresis energy dissipation, the cumulation of material damage, and the average number of loading cycles leading to failure. Analogies between the incremental collapse of structures and the inception and organization of damage in materials are used to aid understanding of the detailed features of hysteresis. Scanning tunneling microscope measurements of the threshold of mechanical irreversibility and acoustic emission patterns are used to detect the evolution of hysteresis at the microscopic level. 61 refs., 14 figs., 1 tab.

  11. Thermo-acoustic fatigue characterization.

    PubMed

    Meyendorf, Norbert G H; Rösner, Henrik; Kramb, Victoria; Sathish, Shamachary

    2002-05-01

    The nondestructive detection of early fatigue damage states is of high importance for safety in aircraft, automobiles, railways, nuclear energy industries and chemical industries. Titanium alloys commonly used in aerospace for structures and engine components are subject to fatigue damage during service. In the current study fatigue damage progression in a titanium alloy (Ti-6Al-4V) was investigated using thermographic detection of the heat dissipated during short-term mechanical loading. The initial rate of temperature increase induced by the short-term mechanical loading was used to indicate the current microstructural state and presence of prior fatigue damage. Two methods for thermal excitation were investigated (a) high amplitude mechanical loading and (b) small amplitude ultrasonic loading. A formula that describes the temperature enhancement due to heat generation during one loading cycle is derived from high amplitude loading data. A correlation between the temperature increase during short-term ultrasonic loading and accumulated fatigue cycles is used to suggest a methodology for in-field assessment of fatigue condition.

  12. An energy-based approach to estimate seismic attenuation due to wave-induced fluid flow in heterogeneous poroelastic media

    NASA Astrophysics Data System (ADS)

    Solazzi, Santiago G.; Rubino, J. Germán; Müller, Tobias M.; Milani, Marco; Guarracino, Luis; Holliger, Klaus

    2016-11-01

    Wave-induced fluid flow (WIFF) due to the presence of mesoscopic heterogeneities is considered as one of the main seismic attenuation mechanisms in the shallower parts of the Earth's crust. For this reason, several models have been developed to quantify seismic attenuation in the presence of heterogeneities of varying complexity, ranging from periodically layered media to rocks containing fractures and highly irregular distributions of fluid patches. Most of these models are based on Biot's theory of poroelasticity and make use of the assumption that the upscaled counterpart of a heterogeneous poroelastic medium can be represented by a homogeneous viscoelastic solid. Under this dynamic-equivalent viscoelastic medium (DEVM) assumption, attenuation is quantified in terms of the ratio of the imaginary and real parts of a frequency-dependent, complex-valued viscoelastic modulus. Laboratory measurements on fluid-saturated rock samples also rely on this DEVM assumption when inferring attenuation from the phase shift between the applied stress and the resulting strain. However, whether it is correct to use an effective viscoelastic medium to represent the attenuation arising from WIFF at mesoscopic scales in heterogeneous poroelastic media remains largely unexplored. In this work, we present an alternative approach to estimate seismic attenuation due to WIFF. It is fully rooted in the framework of poroelasticity and is based on the quantification of the dissipated power and stored strain energy resulting from numerical oscillatory relaxation tests. We employ this methodology to compare different definitions of the inverse quality factor for a set of pertinent scenarios, including patchy saturation and fractured rocks. This numerical analysis allows us to verify the correctness of the DEVM assumption in the presence of different kinds of heterogeneities. The proposed methodology has the key advantage of providing the local contributions of energy dissipation to the overall

  13. Estimation of the risks of thermal stress due to the microclimate for manual fruit and vegetable harvesters in central Italy.

    PubMed

    Cecchini, M; Colantoni, A; Massantini, R; Monarca, D

    2010-07-01

    Agricultural workers are exposed to various risks, including chemical agents, noise, and many other factors. One of the most characteristic and least known risk factors is constituted by the microclimatic conditions in the different phases of work (in field, in greenhouse, etc). A typical condition is thermal stress due to high temperatures during harvesting operations in open fields or in greenhouses. In Italy, harvesting is carried out for many hours during the day, mainly in the summer, with temperatures often higher than 30 degrees C. According to ISO 7243, these conditions can be considered dangerous for workers' health. The aim of this study is to assess the risks of exposure to microclimatic conditions (heat) for fruit and vegetable harvesters in central Italy by applying methods established by international standards. In order to estimate the risk for workers, the air temperature, radiative temperature, and air speed were measured using instruments in conformity with ISO 7726. Thermodynamic parameters and two more subjective parameters, clothing and the metabolic heat production rate related to the worker's physical activity, were used to calculate the predicted heat strain (PHS) for the exposed workers in conformity with ISO 7933. Environmental and subjective parameters were also measured for greenhouse workers, according to ISO 7243, in order to calculate the wet-bulb globe temperature (WBGT). The results show a slight risk for workers during manual harvesting in the field. On the other hand, the data collected in the greenhouses show that the risk for workers must not be underestimated. The results of the study show that, for manual harvesting work in climates similar to central Italy, it is essential to provide plenty of drinking water and acclimatization for the workers in order to reduce health risks. Moreover, the study emphasizes that the possible health risks for greenhouse workers increase from the month of April through July.

  14. Nursing on empty: compassion fatigue signs, symptoms, and system interventions.

    PubMed

    Harris, Chelsia; Griffin, Mary T Quinn

    2015-01-01

    Few healthcare organizations acknowledge, discuss, or provide interventions for assisting with compassion fatigue. Yet, it is an important concept due to its individual, professional, and financial costs. This article defines compassion fatigue, differentiates it from burnout, and offers system interventions for supporting nurses and reducing compassion fatigue.

  15. Fatigue life extension

    NASA Technical Reports Server (NTRS)

    Matejczyk, D. E.; Lin, J.

    1985-01-01

    Potential fatigue rejuvenation processes were carried out on fatigue-damaged material both with and without observable surface-connected fatigue cracks. The fatigue life of fatigue-damaged MAR-M246(Hf)(DS), a directionally solidified nickel-base superalloy used in turbine airfoils, was extended by reheat treatment. The fatigue life of fatigue-cracked Inconel 718, a wrought nickel-base superalloy used in a wide variety of advanced rocket engine components, was extended by electron-beam welding to close off the surface-connected crack, followed by hot isostatic pressing and reheat treatment.

  16. Fatigue of Advanced In-Situ Composite Solders

    DTIC Science & Technology

    2007-11-02

    ABSTRACT (Maximum 200 words) " ~~" Solder joints used in surface mount technology experience thermomechanical fatigue due to the mismatches in...solder joint to undergo shear strains. The purpose of this study was to examine and explain the thermomechanical fatigue damage mechanisms of various...types of solder compositions. Shear, creep, low cycle fatigue , and thermomechanical fatigue tests were conducted in this research. The development

  17. Quantification of the uncertainty in estimates of climate system properties due to differences in available reconstructions of historical data

    NASA Astrophysics Data System (ADS)

    Forest, C. E.; Libardoni, A.; Sokolov, A. P.

    2013-12-01

    Climate models of intermediate complexity have been used extensively to help determine climate system properties because of their efficiency and ability to easily adjust key climate system components. By comparing model output over a wide range of possible states of the climate with observations, probability distributions for climate system properties can be derived. Observational data for a number of climate variables are available, and in many cases multiple reconstructions are available for the same variable. This study first evaluates how differences in the estimated historical trends of upper-air temperatures translate into uncertainty in estimates of three climate system properties: climate sensitivity, the rate of ocean heat uptake, and net aerosol forcing. These results build upon previous work that explored similar estimates associated with trends in surface temperatures and ocean heat content. Also addressed in this study is quantifying uncertainties in the estimates of the three properties associated with how surface temperature observations are used in the estimation process. Other studies have estimated climate parameters using only global mean surface temperature trends. It is shown here that estimates of all parameters are dependent upon the spatial variation of surface temperature trends. In particular, lower estimates of climate sensitivity are shown to be inconsistent with most observational data sources when using latitude-dependent surface trends. Low climate sensitivity is also shown to lead to inconsistent patterns in ocean heat uptake. These results will be presented in the context of recent investigations using data from previous work by the authors.

  18. Dipole estimation errors due to differences in modeling anisotropic conductivities in realistic head models for EEG source analysis.

    PubMed

    Hallez, Hans; Vanrumste, Bart; Van Hese, Peter; Delputte, Steven; Lemahieu, Ignace

    2008-04-07

    To improve the EEG source localization in the brain, the conductivities used in the head model play a very important role. In this study, we focus on the modeling of the anisotropic conductivity of the white matter. The anisotropic conductivity profile can be derived from diffusion weighted magnetic resonance images (DW-MRI). However, deriving these anisotropic conductivities from diffusion weighted MR images of the white matter is not straightforward. In the literature, two methods can be found for calculating the conductivity from the diffusion weighted images. One method uses a fixed value for the ratio of the conductivity in different directions, while the other method uses a conductivity profile obtained from a linear scaling of the diffusion ellipsoid. We propose a model which can be used to derive the conductivity profile from the diffusion tensor images. This model is based on the variable anisotropic ratio throughout the white matter and is a combination of the linear relationship as stated in the literature, with a constraint on the magnitude of the conductivity tensor (also known as the volume constraint). This approach is stated in the paper as approach A. In our study we want to investigate dipole estimation differences due to using a more simplified model for white matter anisotropy (approach B), while the electrode potentials are derived using a head model with a more realistic approach for the white matter anisotropy (approach A). We used a realistic head model, in which the forward problem was solved using a finite difference method that can incorporate anisotropic conductivities. As error measures we considered the dipole location error and the dipole orientation error. The results show that the dipole location errors are all below 10 mm and have an average of 4 mm in gray matter regions. The dipole orientation errors ranged up to 66.4 degrees, and had a mean of, on average, 11.6 degrees in gray matter regions. In a qualitative manner, the results

  19. Reduction of CO2 Emissions Due to Wind Energy - Methods and Issues in Estimating Operational Emission Reductions

    SciTech Connect

    Holttinen, Hannele; Kiviluoma, Juha; McCann, John; Clancy, Matthew; Millgan, Michael; Pineda, Ivan; Eriksen, Peter Borre; Orths, Antje; Wolfgang, Ove

    2015-10-05

    This paper presents ways of estimating CO2 reductions of wind power using different methodologies. Estimates based on historical data have more pitfalls in methodology than estimates based on dispatch simulations. Taking into account exchange of electricity with neighboring regions is challenging for all methods. Results for CO2 emission reductions are shown from several countries. Wind power will reduce emissions for about 0.3-0.4 MtCO2/MWh when replacing mainly gas and up to 0.7 MtCO2/MWh when replacing mainly coal powered generation. The paper focuses on CO2 emissions from power system operation phase, but long term impacts are shortly discussed.

  20. Effect of residual stress and surface roughness on the fatigue behaviour of aluminium matrix composites

    NASA Astrophysics Data System (ADS)

    Smaga, M.; Eifler, D.

    2010-07-01

    In this investigation the fatigue properties of specimens manufactured with different turning parameters were investigated in stress-controlled constant amplitude tests at ambient temperature. The change of feed rate and depth of cut lead to a change in the near surface microstructure. Hence the fatigue properties were influenced significantly due to different surface roughness and surface residual stress resulting from the unequal turning processes. The cyclic deformation behaviour of AMC225xe is characterised by pronounced initial cyclic hardening. Continuous load increase tests allow a reliable estimation of the endurance limit of AMC225xe with one single specimen on the basis of cyclic deformation, temperature and electrical resistance data.

  1. Creep-Fatigue Damage Investigation and Modeling of Alloy 617 at High Temperatures

    NASA Astrophysics Data System (ADS)

    Tahir, Fraaz

    The Very High Temperature Reactor (VHTR) is one of six conceptual designs proposed for Generation IV nuclear reactors. Alloy 617, a solid solution strengthened Ni-base superalloy, is currently the primary candidate material for the tubing of the Intermediate Heat Exchanger (IHX) in the VHTR design. Steady-state operation of the nuclear power plant at elevated temperatures leads to creep deformation, whereas loading transients including startup and shutdown generate fatigue. A detailed understanding of the creep-fatigue interaction in Alloy 617 is necessary before it can be considered as a material for nuclear construction in ASME Boiler and Pressure Vessel Code. Current design codes for components undergoing creep-fatigue interaction at elevated temperatures require creep-fatigue testing data covering the entire range from fatigue-dominant to creep-dominant loading. Classical strain-controlled tests, which produce stress relaxation during the hold period, show a saturation in cycle life with increasing hold periods due to the rapid stress-relaxation of Alloy 617 at high temperatures. Therefore, applying longer hold time in these tests cannot generate creep-dominated failure. In this study, uniaxial isothermal creep-fatigue tests with non-traditional loading waveforms were designed and performed at 850 and 950°C, with an objective of generating test data in the creep-dominant regime. The new loading waveforms are hybrid strain-controlled and force-controlled testing which avoid stress relaxation during the creep hold. The experimental data showed varying proportions of creep and fatigue damage, and provided evidence for the inadequacy of the widely-used time fraction rule for estimating creep damage under creep-fatigue conditions. Micro-scale damage features in failed test specimens, such as fatigue cracks and creep voids, were quantified using a Scanning Electron Microscope (SEM) to find a correlation between creep and fatigue damage. Quantitative statistical

  2. A Strategy to Estimate the Systematic Uncertainty of Eddy Covariance Fluxes due to the Post-field Raw Data Processing

    NASA Astrophysics Data System (ADS)

    Sabbatini, Simone; Fratini, Gerardo; Fidaleo, Marcello; Papale, Dario

    2017-04-01

    Among several sources of uncertainty characterising the fluxes of atmospheric constituents to and from a given ecosystem calculated using the eddy covariance (EC) methodology, the systematic error due to the corrections applied in the post-field raw data processing is still relatively unknown. We performed an extensive analysis aiming at quantifying this portion of the uncertainty for the CO2 exchange, and at defining a strategy of processing to be generically applied as to understand this uncertainty. We selected 11 years of raw EC data from 9 stations all over the Europe, corresponding to 4 different setups. Then we chose 2 or 3 possible valid options for each of the 8 most relevant corrections to be applied to the raw data, and produced as many outputs (1-year-long calculated hourly and half-hourly fluxes) as the combinations of all the different options (full-factorial design). Statistical analysis was used to quantify and characterise the uncertainty (n-way ANOVA) both on the (half-)hourly and the yearly cumulative fluxes. Factorial design of Experiment (DOE) was used to select a relatively small sub-group of combinations of processing options (fractional factorial design) to be applied to a given dataset in order to quantify the processing uncertainty, with a limited loss of information as compared to the full factorial. Our results show that: (i) the variability as expressed by the inter-quartile range (IQR) of the cumulate CO2 flux is between 50 and 400 gC m-2 year-1. (ii) The importance of the single corrections (factors) in terms of variance explained is not constant among datasets, but a general trend is found such that the coordinate rotation (CR) and the trend removal (TR) have often a high weight on the overall uncertainty (i.e. between 10% and 50%), while the importance of the time-lag compensation (TL) is highly variable. (iii) 2x2 interactions between factors have some importance, mostly between the most relevant ones. (iv) The percentage error of

  3. Fatigue in epilepsy: A systematic review and meta-analysis.

    PubMed

    Kwon, Oh-Young; Ahn, Hyeong Sik; Kim, Hyun Jung

    2017-02-01

    To estimate the frequency and strength of fatigue in epilepsy patients. The MEDLINE, EMBASE, COCHRANE, Web of Science, and SCOPUS databases were searched, and hand-searched data were added. For inclusion, the studies had to be original research articles that included fatigue data from adult epilepsy patients. The strength was estimated using studies reporting fatigue scores of standardized inventories for the patients and healthy controls. The fatigue frequency was estimated based on studies reporting the number of fatigue events in patients. We also investigated risk factors for fatigue and the correlation of depression with fatigue in epilepsy patients. Of 25,613 abstracts screened, we included 12 articles or proceedings with distinctive data. The Fatigue Severity Scale (FSS) was the most commonly used inventory for fatigue in epilepsy patients. Four studies compared FSS scores between 499 epilepsy patients and 295 healthy controls. The overall mean difference in the FSS scores was significant. Seven of the 12 studies reported the frequency of fatigue determined by the FSS for 700 epilepsy patients. As stated by the studies, the overall frequency of fatigue was 47.1%. The risk factors for fatigue in epilepsy patients were depression, sleep-related impairment, and sleep quality. Of the 12 studies, 7 revealed a significant correlation between depression and fatigue. Fatigue is common in epilepsy patients and is closely correlated with depression. The identification and management of fatigue and its risk factors, especially depression, is mandatory for the management of epilepsy. Copyright © 2016 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

  4. Crystallographic Analysis of Fatigue Crack Initiation Behavior in Coarse-Grained Magnesium Alloy Under Tension-Tension Loading Cycles

    NASA Astrophysics Data System (ADS)

    Tamada, Kazuhiro; Kakiuchi, Toshifumi; Uematsu, Yoshihiko

    2017-07-01

    Plane bending fatigue tests are conducted to investigate fatigue crack initiation mechanisms in coarse-grained magnesium alloy, AZ31, under the stress ratios R = -1 and 0.1. The initial crystallographic structures are analyzed by an electron backscatter diffraction method. The slip or twin operation during fatigue tests is identified from the line angle analyses based on Euler angles of the grains. Under the stress ratio R = -1, relatively thick tension twin bands are formed in coarse grains. Subsequently, compression twin or secondary pyramidal slip operates within the tension twin band, resulting in the fatigue crack initiation. On the other hand, under R = 0.1 with tension-tension loading cycles, twin bands are formed on the specimen surface, but the angles of those bands do not correspond to tension twins. Misorientation analyses of c-axes in the matrix grain and twin band reveal that double twins are activated. Under R = 0.1, fatigue crack initiates along the double twin boundaries. The different manners of fatigue crack initiation at R = -1 and 0.1 are related to the asymmetricity of twining under tension and compression loadings. The fatigue strengths under different stress ratios cannot be estimated by the modified Goodman diagram due to the effect of stress ratio on crack initiation mechanisms.

  5. Fatigue in Rheumatoid Arthritis.

    PubMed

    Katz, Patricia

    2017-05-01

    The purpose of this study was to review the current information on fatigue in rheumatoid arthritis (RA). Severe fatigue is common among individuals with RA and has a significant impact on quality of life (QOL). RA-related factors (e.g., inflammation, pain) are associated with greater fatigue, but other factors, such as obesity, physical inactivity, sleep disturbance, and depression, explain the majority of variation in fatigue. Medications targeting RA have little effect on fatigue. Instead, the most effective interventions seem to address non-RA-specific factors such as physical inactivity or use cognitive behavioral approaches. No recommendations have been made for tools to measure fatigue in RA, leading to potential difficulty comparing studies. Although fatigue has great impact on patients' QOL, effective interventions that are feasible for broad dissemination remain elusive. Additional multi-faceted research is needed to identify modifiable sources of fatigue. Such research would be enhanced by harmonization of fatigue measurement across studies.

  6. Low cycle fatigue

    NASA Technical Reports Server (NTRS)

    Solomon, H. D. (Editor); Kaisand, L. R. (Editor); Halford, G. R. (Editor); Leis, B. N. (Editor)

    1988-01-01

    The papers contained in this volume focus on various aspects of low cycle fatigue, including cyclic deformation, crack propagation, high-temperature low cycle fatigue, microstructural defects, multiaxial and variable amplitude loading, and life prediction. Papers are presented on the low cycle fatigue of some aluminum alloys, prediction of crack growth under creep-fatigue loading conditions, high-temperature low cycle fatigue behavior and lifetime prediction of a nickel-base ODS alloy, and an integrated approach to creep-fatigue life prediction. Other topics discussed include thermal fatigue testing of coated monocrystalline superalloys, low cycle fatigue of Al-Mg-Si alloys, and the effect of superimposed stresses at high frequency on low cycle fatigue.

  7. Low cycle fatigue

    NASA Technical Reports Server (NTRS)

    Solomon, H. D. (Editor); Kaisand, L. R. (Editor); Halford, G. R. (Editor); Leis, B. N. (Editor)

    1988-01-01

    The papers contained in this volume focus on various aspects of low cycle fatigue, including cyclic deformation, crack propagation, high-temperature low cycle fatigue, microstructural defects, multiaxial and variable amplitude loading, and life prediction. Papers are presented on the low cycle fatigue of some aluminum alloys, prediction of crack growth under creep-fatigue loading conditions, high-temperature low cycle fatigue behavior and lifetime prediction of a nickel-base ODS alloy, and an integrated approach to creep-fatigue life prediction. Other topics discussed include thermal fatigue testing of coated monocrystalline superalloys, low cycle fatigue of Al-Mg-Si alloys, and the effect of superimposed stresses at high frequency on low cycle fatigue.

  8. 75 FR 793 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-06

    ... amendment would require evaluation of fatigue and residual static strength of composite rotorcraft... static or fatigue loads. The proposal would require consideration of the effects of fatigue damage on... applicant must show that catastrophic failure due to static and fatigue loads, considering the intrinsic...

  9. Anomalous Fatigue Behavior and Fatigue-Induced Grain Growth in Nanocrystalline Nickel Alloys

    NASA Astrophysics Data System (ADS)

    Boyce, Brad L.; Padilla, Henry A.

    2011-07-01

    Fatigue failure due to repetitive loading of metallic devices is a pervasive engineering concern. The present work reveals extraordinary fatigue resistance in nanocrystalline (NC) alloys, which appears to be associated with the small (<100 nm) grain size inhibiting traditional cyclic damage processes. In this study, we examine the fatigue performance of three electrodeposited NC Ni-based metals: Ni, Ni-0.5Mn, and Ni-22Fe (PERMALLOY). When subjected to fatigue stresses at and above the tensile yield strength where conventional coarse-grained (CG) counterparts undergo low-cycle fatigue failure (<104 cycles to failure), these alloys exhibit exceptional fatigue lives (in some cases, >107 cycles to failure). Postmortem examinations show that failed samples contain an aggregate of coarsened grains at the crack initiation site. The experimental data and accompanying microscopy suggest that the NC matrix undergoes abnormal grain growth during cyclic loading, allowing dislocation activity to persist over length scales necessary to initiate a fatigue crack by traditional fatigue mechanisms. Thus, the present observations demonstrate anomalous fatigue behavior in two regards: (1) quantitatively anomalous when considering the extremely high stress levels needed to drive fatigue failure and (2) mechanistically anomalous in light of the grain growth process that appears to be a necessary precursor to crack initiation.

  10. Evaluation of models for estimating changes in fracture permeability due to thermo-mechanical stresses in host rock surrounding a potential repository

    SciTech Connect

    Berge, P A; Blair, S C; Shaffer, R J; Wang, H F

    1997-02-18

    We provide in this report a methodology to estimate bounds on the changes in fracture permeability due to thermal-mechanical processes associated with excavation of drifts and emplacement of waste. This report is the first milestone associated with Task A of the LLNL initiative to evaluate available methods for estimating chamges in fracture permeability surrounding drifts in the Exploratory Studies Facility (ESF) and the potential repository at Yucca Mountain in response to (1) construction-induced stress changes and (2) subsequent thermal pulse effects due to waste emplacement. These results are needed for modeling changes in repository-level moisture movement and seepage.

  11. Cancer risk estimation in Belarussian children due to thyroid irradiation as a consequence of the Chernobyl nuclear accident

    SciTech Connect

    Buglova, E.; Kenigsberg, J.E.; Sergeeva, N.V.

    1996-07-01

    The thyroid doses received by the juvenile population of Belarus following the Chernobyl accident ranged up to about 10 Gy. The thyroid cancer risk estimate recommended in NCRP Report No. 80 was used to predict the number of thyroid cancer cases among children during 1990-1992 in selected Belarussian regions and cities. The results obtained using this risk estimate show an excess of thyroid cancer cases being registered vs. the predicted cases. Thyroid cancer incidence rate among boys under investigation is higher than among girls in the postaccident period. The excess of the observed over the expected incidence in the general juvenile population is caused by the high thyroid cancer incidence rate among boys. These results, which can be considered part of the first stage of a thorough thyroid cancer risk estimation after the Chernobyl accident, demonstrate the critical need to complete these studies in depth. 6 refs., 5 figs., 3 tabs.

  12. Peridynamic model for fatigue cracking.

    SciTech Connect

    Silling, Stewart Andrew; Abe Askari

    2014-10-01

    The peridynamic theory is an extension of traditional solid mechanics in which the field equations can be applied on discontinuities, such as growing cracks. This paper proposes a bond damage model within peridynamics to treat the nucleation and growth of cracks due to cyclic loading. Bond damage occurs according to the evolution of a variable called the "remaining life" of each bond that changes over time according to the cyclic strain in the bond. It is shown that the model reproduces the main features of S-N data for typical materials and also reproduces the Paris law for fatigue crack growth. Extensions of the model account for the effects of loading spectrum, fatigue limit, and variable load ratio. A three-dimensional example illustrates the nucleation and growth of a helical fatigue crack in the torsion of an aluminum alloy rod.

  13. Estimation of the radiation dose in man due to 6-(/sup 18/F) fluoro-L-dopa

    SciTech Connect

    Harvey, J.; Firnau, G.; Garnett, E.S.

    1985-08-01

    The radiation dose to the organs of the human body after an intravenous administration of 6-(/sup 18/F) fluoro-L-dopa was estimated using the recommendations of the International Committee on Radiological Protection (ICRP). The bladder wall received the highest dose, and as a consequence the dose to the genitalia was high. The major organs received a dose of 5.66E- 12 to 1.87E- 11 Sv/Bq (20 to 60 mrem/mCi). The effective dose equivalent was estimated at 5.39E- 11 Sv/Bq (200 mrem/mCi).

  14. The potential for regional-scale bias in top-down CO2 flux estimates due to atmospheric transport errors

    NASA Astrophysics Data System (ADS)

    Miller, S. M.; Fung, I.; Liu, J.; Hayek, M. N.; Andrews, A. E.

    2014-09-01

    Estimates of CO2 fluxes that are based on atmospheric data rely upon a meteorological model to simulate atmospheric CO2 transport. These models provide a quantitative link between surface fluxes of CO2 and atmospheric measurements taken downwind. Therefore, any errors in the meteorological model can propagate into atmospheric CO2 transport and ultimately bias the estimated CO2 fluxes. These errors, however, have traditionally been difficult to characterize. To examine the effects of CO2 transport errors on estimated CO2 fluxes, we use a global meteorological model-data assimilation system known as "CAM-LETKF" to quantify two aspects of the transport errors: error variances (standard deviations) and temporal error correlations. Furthermore, we develop two case studies. In the first case study, we examine the extent to which CO2 transport uncertainties can bias CO2 flux estimates. In particular, we use a common flux estimate known as CarbonTracker to discover the minimum hypothetical bias that can be detected above the CO2 transport uncertainties. In the second case study, we then investigate which meteorological conditions may contribute to month-long biases in modeled atmospheric transport. We estimate 6 hourly CO2 transport uncertainties in the model surface layer that range from 0.15 to 9.6 ppm (standard deviation), depending on location, and we estimate an average error decorrelation time of ∼2.3 days at existing CO2 observation sites. As a consequence of these uncertainties, we find that CarbonTracker CO2 fluxes would need to be biased by at least 29%, on average, before that bias were detectable at existing non-marine atmospheric CO2 observation sites. Furthermore, we find that persistent, bias-type errors in atmospheric transport are associated with consistent low net radiation, low energy boundary layer conditions. The meteorological model is not necessarily more uncertain in these conditions. Rather, the extent to which meteorological uncertainties

  15. Estimates of over-diagnosis of breast cancer due to population-based mammography screening in South Australia after adjustment for lead time effects.

    PubMed

    Beckmann, Kerri; Duffy, Stephen W; Lynch, John; Hiller, Janet; Farshid, Gelareh; Roder, David

    2015-09-01

    To estimate over-diagnosis due to population-based mammography screening using a lead time adjustment approach, with lead time measures based on symptomatic cancers only. Women aged 40-84 in 1989-2009 in South Australia eligible for mammography screening. Numbers of observed and expected breast cancer cases were compared, after adjustment for lead time. Lead time effects were modelled using age-specific estimates of lead time (derived from interval cancer rates and predicted background incidence, using maximum likelihood methods) and screening sensitivity, projected background breast cancer incidence rates (in the absence of screening), and proportions screened, by age and calendar year. Lead time estimates were 12, 26, 43 and 53 months, for women aged 40-49, 50-59, 60-69 and 70-79 respectively. Background incidence rates were estimated to have increased by 0.9% and 1.2% per year for invasive and all breast cancer. Over-diagnosis among women aged 40-84 was estimated at 7.9% (0.1-12.0%) for invasive cases and 12.0% (5.7-15.4%) when including ductal carcinoma in-situ (DCIS). We estimated 8% over-diagnosis for invasive breast cancer and 12% inclusive of DCIS cancers due to mammography screening among women aged 40-84. These estimates may overstate the extent of over-diagnosis if the increasing prevalence of breast cancer risk factors has led to higher background incidence than projected. © The Author(s) 2015.

  16. Variation in Estimated Ozone-Related Health Impacts of Climate Change due to Modeling Choices and Assumptions

    SciTech Connect

    Post, Ellen S.; Grambsch, A.; Weaver, C. P.; Morefield, Philip; Huang, Jin; Leung, Lai-Yung R.; Nolte, Christopher G.; Adams, P. J.; Liang, Xin-Zhong; Zhu, J.; Mahoney, Hardee

    2012-11-01

    Future climate change may cause air quality degradation via climate-induced changes in meteorology, atmospheric chemistry, and emissions into the air. Few studies have explicitly modeled the potential relationships between climate change, air quality, and human health, and fewer still have investigated the sensitivity of estimates to the underlying modeling choices.

  17. Biases in Estimating Treatment Effects Due to Attrition in Randomized Controlled Trials and Cluster Randomized Controlled Trials: A Simulation Study

    ERIC Educational Resources Information Center

    Dong, Nianbo; Lipsey, Mark W.

    2011-01-01

    Attrition occurs when study participants who were assigned to the treatment and control conditions do not provide outcome data and thus do not contribute to the estimation of the treatment effects. It is very common in experimental studies in education as illustrated, for instance, in a meta-analysis studying "the effects of attrition on baseline…

  18. Investigation of bias in meta-analyses due to selective inclusion of trial effect estimates: empirical study

    PubMed Central

    Page, Matthew J; Forbes, Andrew; Chau, Marisa; Green, Sally E; McKenzie, Joanne E

    2016-01-01

    Objective To explore whether systematic reviewers selectively include trial effect estimates in meta-analyses when multiple are available, and what impact this may have on meta-analytic effects. Design Cross-sectional study. Data sources We randomly selected systematic reviews of interventions from 2 clinical specialties published between January 2010 and 2012. The first presented meta-analysis of a continuous outcome in each review was selected (index meta-analysis), and all trial effect estimates that were eligible for inclusion in the meta-analysis (eg, from multiple scales or time points) were extracted from trial reports. Analysis We calculated a statistic (the Potential Bias Index (PBI)) to quantify and test for evidence of selective inclusion. The PBI ranges from 0 to 1; values above or below 0.5 are suggestive of selective inclusion of effect estimates more or less favourable to the intervention, respectively. The impact of any potential selective inclusion was investigated by comparing the index meta-analytic standardised mean difference (SMD) to the median of a randomly constructed distribution of meta-analytic SMDs (representing the meta-analytic SMD expected when there is no selective inclusion). Results 31 reviews (250 trials) were included. The estimated PBI was 0.57 (95% CI 0.50 to 0.63), suggesting that trial effect estimates that were more favourable to the intervention were included in meta-analyses slightly more often than expected under a process consistent with random selection; however, the 95% CI included the null hypothesis of no selective inclusion. Any potential selective inclusion did not have an important impact on the meta-analytic effects. Conclusion There was no clear evidence that selective inclusion of trial effect estimates occurred in this sample of meta-analyses. Further research on selective inclusion in other clinical specialties is needed. To enable readers to assess the risk of selective inclusion bias, we recommend that

  19. Multiscale Fatigue Life Prediction for Composite Panels

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Yarrington, Phillip W.; Arnold, Steven M.

    2012-01-01

    Fatigue life prediction capabilities have been incorporated into the HyperSizer Composite Analysis and Structural Sizing Software. The fatigue damage model is introduced at the fiber/matrix constituent scale through HyperSizer s coupling with NASA s MAC/GMC micromechanics software. This enables prediction of the micro scale damage progression throughout stiffened and sandwich panels as a function of cycles leading ultimately to simulated panel failure. The fatigue model implementation uses a cycle jumping technique such that, rather than applying a specified number of additional cycles, a specified local damage increment is specified and the number of additional cycles to reach this damage increment is calculated. In this way, the effect of stress redistribution due to damage-induced stiffness change is captured, but the fatigue simulations remain computationally efficient. The model is compared to experimental fatigue life data for two composite facesheet/foam core sandwich panels, demonstrating very good agreement.

  20. Environmental fatigue in aluminum-lithium alloys

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.

    1992-01-01

    Aluminum-lithium alloys exhibit similar environmental fatigue crack growth characteristics compared to conventional 2000 series alloys and are more resistant to environmental fatigue compared to 7000 series alloys. The superior fatigue crack growth behavior of Al-Li alloys 2090, 2091, 8090, and 8091 is due to crack closure caused by tortuous crack path morphology and crack surface corrosion products. At high R and reduced closure, chemical environment effects are pronounced resulting in accelerated near threshold da/dN. The beneficial effects of crack closure are minimized for small cracks resulting in rapid growth rates. Limited data suggest that the 'chemically small crack' effect, observed in other alloy system, is not pronounced in Al-Li alloys. Modeling of environmental fatigue in Al-Li-Cu alloys related accelerated fatigue crack growth in moist air and salt water to hydrogen embrittlement.

  1. Measurement of soil contamination by radionuclides due to the Fukushima Dai-ichi Nuclear Power Plant accident and associated estimated cumulative external dose estimation.

    PubMed

    Endo, S; Kimura, S; Takatsuji, T; Nanasawa, K; Imanaka, T; Shizuma, K

    2012-09-01

    Soil sampling was carried out at an early stage of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Samples were taken from areas around FDNPP, at four locations northwest of FDNPP, at four schools and in four cities, including Fukushima City. Radioactive contaminants in soil samples were identified and measured by using a Ge detector and included (129 m)Te, (129)Te, (131)I, (132)Te, (132)I, (134)Cs, (136)Cs, (137)Cs, (140)Ba and (140)La. The highest soil depositions were measured to the northwest of FDNPP. From this soil deposition data, variations in dose rates over time and the cumulative external doses at the locations for 3 months and 1y after deposition were estimated. At locations northwest of FDNPP, the external dose rate at 3 months after deposition was 4.8-98 μSv/h and the cumulative dose for 1 y was 51 to 1.0 × 10(3)mSv; the highest values were at Futaba Yamada. At the four schools, which were used as evacuation shelters, and in the four urban cities, the external dose rate at 3 months after deposition ranged from 0.03 to 3.8μSv/h and the cumulative doses for 1 y ranged from 3 to 40 mSv. The cumulative dose at Fukushima Niihama Park was estimated as the highest in the four cities. The estimated external dose rates and cumulative doses show that careful countermeasures and remediation will be needed as a result of the accident, and detailed measurements of radionuclide deposition densities in soil will be important input data to conduct these activities. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Variation in Estimated Ozone-Related Health Impacts of Climate Change due to Modeling Choices and Assumptions

    PubMed Central

    Post, Ellen S.; Grambsch, Anne; Weaver, Chris; Morefield, Philip; Leung, Lai-Yung; Nolte, Christopher G.; Adams, Peter; Liang, Xin-Zhong; Zhu, Jin-Hong; Mahoney, Hardee

    2012-01-01

    Background: Future climate change may cause air quality degradation via climate-induced changes in meteorology, atmospheric chemistry, and emissions into the air. Few studies have explicitly modeled the potential relationships between climate change, air quality, and human health, and fewer still have investigated the sensitivity of estimates to the underlying modeling choices. Objectives: Our goal was to assess the sensitivity of estimated ozone-related human health impacts of climate change to key modeling choices. Methods: Our analysis included seven modeling systems in which a climate change model is linked to an air quality model, five population projections, and multiple concentration–response functions. Using the U.S. Environmental Protection Agency’s (EPA’s) Environmental Benefits Mapping and Analysis Program (BenMAP), we estimated future ozone (O3)-related health effects in the United States attributable to simulated climate change between the years 2000 and approximately 2050, given each combination of modeling choices. Health effects and concentration–response functions were chosen to match those used in the U.S. EPA’s 2008 Regulatory Impact Analysis of the National Ambient Air Quality Standards for O3. Results: Different combinations of methodological choices produced a range of estimates of national O3-related mortality from roughly 600 deaths avoided as a result of climate change to 2,500 deaths attributable to climate change (although the large majority produced increases in mortality). The choice of the climate change and the air quality model reflected the greatest source of uncertainty, with the other modeling choices having lesser but still substantial effects. Conclusions: Our results highlight the need to use an ensemble approach, instead of relying on any one set of modeling choices, to assess the potential risks associated with O3-related human health effects resulting from climate change. PMID:22796531

  3. Variation in estimated ozone-related health impacts of climate change due to modeling choices and assumptions.

    PubMed

    Post, Ellen S; Grambsch, Anne; Weaver, Chris; Morefield, Philip; Huang, Jin; Leung, Lai-Yung; Nolte, Christopher G; Adams, Peter; Liang, Xin-Zhong; Zhu, Jin-Hong; Mahoney, Hardee

    2012-11-01

    Future climate change may cause air quality degradation via climate-induced changes in meteorology, atmospheric chemistry, and emissions into the air. Few studies have explicitly modeled the potential relationships between climate change, air quality, and human health, and fewer still have investigated the sensitivity of estimates to the underlying modeling choices. Our goal was to assess the sensitivity of estimated ozone-related human health impacts of climate change to key modeling choices. Our analysis included seven modeling systems in which a climate change model is linked to an air quality model, five population projections, and multiple concentration-response functions. Using the U.S. Environmental Protection Agency's (EPA's) Environmental Benefits Mapping and Analysis Program (BenMAP), we estimated future ozone (O(3))-related health effects in the United States attributable to simulated climate change between the years 2000 and approximately 2050, given each combination of modeling choices. Health effects and concentration-response functions were chosen to match those used in the U.S. EPA's 2008 Regulatory Impact Analysis of the National Ambient Air Quality Standards for O(3). Different combinations of methodological choices produced a range of estimates of national O(3)-related mortality from roughly 600 deaths avoided as a result of climate change to 2,500 deaths attributable to climate change (although the large majority produced increases in mortality). The choice of the climate change and the air quality model reflected the greatest source of uncertainty, with the other modeling choices having lesser but still substantial effects. Our results highlight the need to use an ensemble approach, instead of relying on any one set of modeling choices, to assess the potential risks associated with O(3)-related human health effects resulting from climate change.

  4. Toward a Real-Time Measurement-Based System for Estimation of Helicopter Engine Degradation Due to Compressor Erosion

    NASA Technical Reports Server (NTRS)

    Litt, Jonathan S.; Simo, Donald L.

    2007-01-01

    This paper presents a preliminary demonstration of an automated health assessment tool, capable of real-time on-board operation using existing engine control hardware. The tool allows operators to discern how rapidly individual turboshaft engines are degrading. As the compressor erodes, performance is lost, and with it the ability to generate power. Thus, such a tool would provide an instant assessment of the engine s fitness to perform a mission, and would help to pinpoint any abnormal wear or performance anomalies before they became serious, thereby decreasing uncertainty and enabling improved maintenance scheduling. The research described in the paper utilized test stand data from a T700-GE-401 turboshaft engine that underwent sand-ingestion testing to scale a model-based compressor efficiency degradation estimation algorithm. This algorithm was then applied to real-time Health Usage and Monitoring System (HUMS) data from a T700-GE-701C to track compressor efficiency on-line. The approach uses an optimal estimator called a Kalman filter. The filter is designed to estimate the compressor efficiency using only data from the engine s sensors as input.

  5. Dose estimation by ESR on tooth enamel from two workers exposed to radiation due to the JCO accident.

    PubMed

    Shiraishi, Kunio; Iwasaki, Midori; Miyazawa, Chyuzo; Yonehara, Hidenori; Matsumoto, Masaki

    2002-09-01

    ESR dosimetry is useful to estimate the external dose for the general population as well as for occupational workers in a nuclear emergency. Three teeth were extracted from two exposed workers (A and B) related to the JCO criticality accident. Tooth enamel was carefully separated from other tooth parts and subjected to ESR dosimetry. Doses equivalent to the gamma-ray dose of 60Co were estimated as follows: for worker A, the buccal and lingual sides of the eighth tooth in the upper right side, 11.8 +/- 3.6 and 12.0 +/- 3.6 Gy, respectively; for worker B, the buccal and lingual sides of the fourth tooth in the upper right side and the fifth tooth in the upper left side, 11.3 +/- 3.4 and 10.8 +/- 3.3 Gy, 11.7 +/- 3.5 and 11.4 +/- 3.4 Gy, respectively. The estimated doses were found to be similar and not dependent on the tooth positions, whether the buccal or lingual sides in each tooth.

  6. Differential effects of fatigue on movement variability.

    PubMed

    Cortes, N; Onate, J; Morrison, S

    2014-03-01

    When individuals perform purposeful actions to fatigue, there is typically a general decline in their movement performance. This study was designed to investigate the effects exercise-induced fatigue has on lower limb kinetics and kinematics during a side-step cutting task. In particular, it was of interest to determine what changes could be seen in mean amplitude and all metrics of signal variability with fatigue. The results of the study revealed that post-fatigue there was an overall decrease in absolute force production as reflected by a decline in mean amplitude and variability (SD) of the ground reaction forces (GRFV and GRFML). A decrease in mean and SD of the knee moments were also observed post-exercise. Interestingly, this trend was not mirrored by similar changes in time-dependent properties of these signals. Instead, there was an increase in the SampEn values (reflecting a more variable, irregular signal) for GRF force profiles, knee kinematics and moments following the exercise-induced fatigue. These results illustrate that fatigue can have differential effects on movement variability, resulting in a both an increase and decrease in movement variability, depending on the variable selected. Thus, the impact of fatigue is not simply restricted to a decline in force producing capacity of the system but more importantly it demonstrates that the ability of the person to perform a smooth and controlled action is limited due to fatigue.

  7. Differential Effects of Fatigue on Movement Variability

    PubMed Central

    Cortes, N.; Onate, J.; Morrison, S.

    2014-01-01

    When individuals perform purposeful actions to fatigue, there is typically a general decline in their movement performance. This study was designed to investigate the effects exercise-induced fatigue has on lower limb kinetics and kinematics during a side-step cutting task. In particular, it was of interest to determine what changes could be seen in mean amplitude and all metrics of signal variability with fatigue. The results of the study revealed that post-fatigue there was an overall decrease in absolute force production as reflected by a decline in mean amplitude and variability (SD) of the ground reaction forces (GRFV and GRFML). A decrease in mean and SD of the knee moments were also observed post-exercise. Interestingly, this trend was not mirrored by similar changes in time-dependent properties of these signals. Instead, there was an increase in the SampEn values (reflecting a more variable, irregular signal) for GRF force profiles, knee kinematics and moments following the exercise-induced fatigue. These results illustrate that fatigue can have differential effects on movement variability, resulting in a both an increase and decrease in movement variability, depending on the variable selected. Thus, the impact of fatigue is not simply restricted to a decline in force producing capacity of the system but more importantly it demonstrates that the ability of the person to perform a smooth and controlled action is limited due to fatigue. PMID:24370441

  8. Compassion fatigue and the adult protective services social worker.

    PubMed

    Bourassa, Dara Bergel

    2009-04-01

    Compassion fatigue is a relatively new term that describes the symptoms that are experienced by social workers and other helping professionals who work with clients experiencing trauma. This article defines the concept of compassion fatigue and relates compassion fatigue to Adult Protective Services (APS) social workers. It is proposed that APS social workers may be susceptible to the deleterious effects of compassion fatigue due to the nature of their work and environment. Suggestions for avoidance of compassion fatigue are also discussed, including self-care strategies and the need for continuing education regarding this phenomenon.

  9. Radiation dose from MDCT using Monte Carlo simulations: estimating fetal dose due to pulmonary embolism scans accounting for overscan

    NASA Astrophysics Data System (ADS)

    Angel, E.; Wellnitz, C.; Goodsitt, M.; DeMarco, J.; Cagnon, C.; Ghatali, M.; Cody, D.; Stevens, D.; McCollough, C.; Primak, A.; McNitt-Gray, M.

    2007-03-01

    Pregnant women with shortness of breath are increasingly referred for CT Angiography to rule out Pulmonary Embolism (PE). While this exam is typically focused on the lungs, extending scan boundaries and overscan can add to the irradiated volume and have implications on fetal dose. The purpose of this work was to estimate radiation dose to the fetus when various levels of overscan were encountered. Two voxelized models of pregnant patients derived from actual patient anatomy were created based on image data. The models represent an early (< 7 weeks) and late term pregnancy (36 weeks). A previously validated Monte Carlo model of an MDCT scanner was used that takes into account physical details of the scanner. Simulated helical scans used 120 kVp, 4x5 mm beam collimation, pitch 1, and varying beam-off locations (edge of the irradiated volume) were used to represent different protocols plus overscan. Normalized dose (mGy/100mAs) was calculated for each fetus. For the early term and the late term pregnancy models, fetal dose estimates for a standard thoracic PE exam were estimated to be 0.05 and 0.3 mGy/100mAs, respectively, increasing to 9 mGy/100mAs when the beam-off location was extended to encompass the fetus. When performing PE exams to rule out PE in pregnant patients, the beam-off location may have a large effect on fetal dose, especially for late term pregnancies. Careful consideration of ending location of the x-ray beam - and not the end of image data - could result in significant reduction in radiation dose to the fetus.

  10. Estimation of Cyclic Error Due to Scattering in the Internal OPD Metrology of the Space Interferometry Mission

    NASA Technical Reports Server (NTRS)

    Tang, Hong; Zhao, Feng

    2005-01-01

    A common-path laser heterodyne interferometer capable of measuring the internal optical path difference (OPD) with accuracy of the order of 10 pm was demonstrated at JPL. To achieve this accuracy, the relative power received by the detector that is contributed by the scattering of light at the optical surfaces should be less than -97 dB. A method has been developed to estimate the cyclic error caused by the scattering of the optical surfaces. The result of the analysis is presented.

  11. Estimation of years lived with disability due to noncommunicable diseases and injuries using a population-representative survey.

    PubMed

    Park, Ji In; Jung, Hae Hyuk

    2017-01-01

    The Global Burden of Disease 2010 and the WHO Global Health Estimates of years lived with disability (YLDs) uses disability-weights obtained from lay health-state descriptions, which cannot fully reflect different disease manifestations, according to severity, treatment, and environment. The aim of this study was to provide population-representative YLDs of noncommunicable diseases and injuries using a prevalence-based approach, with the disability weight measured in subjects with specific diseases or injuries. We included a total of 44969 adults, who completed the EQ-5D questionnaire as participation in the Korea National Health and Nutrition Examination Survey 2007-2014. We estimated the prevalence of each of 40 conditions identified from the noncommunicable diseases and injuries in the WHO list. Modified condition-specific disability-weight was determined from the adjusted mean difference of the EQ-5D index between the condition and reference groups. Condition-specific YLDs were calculated as the condition's prevalence multiplied by the condition's disability-weight. All-cause YLDs, estimated as "number of population × (1 - mean score of EQ-5D)" were 2165 thousands in 39044 thousand adults aged ≥20. The combined YLDs for all 40 conditions accounted for 67.6% of all-cause YLDs, and were 1604, 2126, 8749, and 12847 per 100000 young (age 20-59) males, young females, old (age ≥60) males, and old females, respectively. Back pain/osteoarthritis YLDs were exceptionally large (442/40, 864/146, 2037/836, and 4644/3039 per 100000 young males, young females, old males, and old females, respectively). Back pain, osteoarthritis, depression, diabetes, periodontitis, and stroke accounted for 22.3%, 9.1%, 4.6%, 3.3%, 3.2%, and 2.9% of all-cause YLDs, respectively. In conclusion, this estimation of YLDs using prevalence rates and disability-weights measured in a population-representative survey may form the basis for population-level strategies to prevent age

  12. Estimation of years lived with disability due to noncommunicable diseases and injuries using a population-representative survey

    PubMed Central

    Park, Ji In

    2017-01-01

    The Global Burden of Disease 2010 and the WHO Global Health Estimates of years lived with disability (YLDs) uses disability-weights obtained from lay health-state descriptions, which cannot fully reflect different disease manifestations, according to severity, treatment, and environment. The aim of this study was to provide population-representative YLDs of noncommunicable diseases and injuries using a prevalence-based approach, with the disability weight measured in subjects with specific diseases or injuries. We included a total of 44969 adults, who completed the EQ-5D questionnaire as participation in the Korea National Health and Nutrition Examination Survey 2007–2014. We estimated the prevalence of each of 40 conditions identified from the noncommunicable diseases and injuries in the WHO list. Modified condition-specific disability-weight was determined from the adjusted mean difference of the EQ-5D index between the condition and reference groups. Condition-specific YLDs were calculated as the condition’s prevalence multiplied by the condition’s disability-weight. All-cause YLDs, estimated as “number of population × (1 − mean score of EQ-5D)” were 2165 thousands in 39044 thousand adults aged ≥20. The combined YLDs for all 40 conditions accounted for 67.6% of all-cause YLDs, and were 1604, 2126, 8749, and 12847 per 100000 young (age 20−59) males, young females, old (age ≥60) males, and old females, respectively. Back pain/osteoarthritis YLDs were exceptionally large (442/40, 864/146, 2037/836, and 4644/3039 per 100000 young males, young females, old males, and old females, respectively). Back pain, osteoarthritis, depression, diabetes, periodontitis, and stroke accounted for 22.3%, 9.1%, 4.6%, 3.3%, 3.2%, and 2.9% of all-cause YLDs, respectively. In conclusion, this estimation of YLDs using prevalence rates and disability-weights measured in a population-representative survey may form the basis for population-level strategies to prevent age

  13. Informing disinvestment with limited evidence: cobalamin deficiency in the fatigued.

    PubMed

    Mnatzaganian, George; Karnon, Jonathan; Moss, John R; Elshaug, Adam G; Metz, Michael; Frank, Oliver R; Hiller, Janet E

    2015-01-01

    Health technology reassessment and disinvestment can be difficult due to uncertainties regarding available evidence. Pathology testing to investigate cobalamin (vitamin B12) deficiency is a strong case in point. We conducted a 3-month economic evaluation of five strategies for diagnosing and treating cobalamin deficiency in adult patients hypothetically presenting with new unexplained fatigue in the primary care setting. The first consultation per patient was considered. Screening tests other than serum cobalamin were not included. A cost-effectiveness analysis was undertaken using a decision tree to represent the diagnostic / treatment pathways, with relevant cost and utility scores assigned to different stages in the evaluation process. Input parameter values were estimated from published evidence, supplemented by expert opinion, with sensitivity analysis undertaken to represent parameter uncertainty. Ordering serum vitamin B12 to assess cobalamin deficiency among patients with unexplained fatigue was not cost-effective in any patient population, irrespective of pretest prevalence of this deficiency. For patients with a pretest prevalence above 1 percent, treating all with oral vitamin B12 supplements without testing was most cost-effective, whereas watchful waiting with symptoms monitoring was most cost-effective for patients with lower pretest prevalence probabilities. Substantial evidence gaps exist for parameter estimation: questionable cobalamin deficiency levels in the fatigued; debatable treatment methods; unknown natural history of the condition. Despite this, we reveal a robust path for disinvestment decision making in the face of a paradox between the evidence required to inform disinvestment compared with its paucity in informing initial funding decisions.

  14. Fatigue of composites

    NASA Technical Reports Server (NTRS)

    Salkind, M. J.

    1972-01-01

    The failure mechanisms in the fatigue of composite materials are analyzed in terms of the requirements for designing fatigue-critical composite structures. Fiber reinforced polymers, fiber reinforced metals, fatigue of composite structures, and composite design considerations are discussed. It is concluded that composite materials offer the engineer the opportunity for tailoring stiffness in different directions for designing dynamic components.

  15. [Fatigue and depression].

    PubMed

    Hell, Daniel

    2015-04-22

    Fatigue is characterised in an overview of the literature as a specific phenomenon of depression. Its differential diagnosis is discussed. Distinctions and correspondences to burnout are elaborated. Fatigue is not an obligatory symptom of depressive episodes, although it can contribute to depressive developments. The importance of fatigue in depressive episodes and its therapy is shown with the help of a circular model of depression.

  16. Estimation of the population attributable fraction of road-related injuries due to speeding and passing in Iran

    PubMed Central

    2016-01-01

    OBJECTIVES Speeding and passing are considered to be the main human factors resulting in road traffic injuries (RTIs). This study aimed to estimate the population attributeable fraction (PAF) of speeding and passing in RTIs in rural Iran during 2012. METHODS The contribution of speeding and passing to RTI-related morbidity and mortality was estimated using the PAF method. The prevalence of speeding and passing was obtained from the national traffic police data registry. A logistic regression model was used to measure the association between the above risk factors and RTIs. RESULTS Speeding accounted for 20.96% and 16.61% of rural road-related deaths and injuries, respectively. The corresponding values for passing were 13.50% and 13.44%, respectively. Jointly, the PAF of these factors was 31.63% for road-related deaths and 27.81% for injuries. CONCLUSIONS This study illustrates the importance of controlling speeding and passing as a high-priority aspect of public-health approaches to RTIs in Iran. It is recommended that laws restricting speeding and passing be enforced more strictly. PMID:27608807

  17. A survey of fatigue monitoring in the nuclear power industry

    SciTech Connect

    Ware, A.G.

    1991-12-31

    The original design of nuclear power plants addressed fatigue concerns by including calculations of projected fatigue usage for specific components; the calculations were based on estimates of the number and severity of expected transients over the 40-year design life of the plants. In some cases, the transients occurring in the plants are not as severe as was anticipated in the original design analyses, while in other cases events have occurred that were not anticipated in the design basis documents. Field failures caused by fatigue have identified some of those cases. In response, several organizations in the United States and overseas have developed fatigue monitoring programs to more accurately estimate the fatigue usage. One basic approach consists of reconstructing the fatigue usage to date based on the transients recorded in the operating history instead of those projected in the design documents. Another approach includes monitoring the plant instrumentation to determine actual values for parameters such as temperature and pressure and using the measured values in the fatigue usage calculations instead of the values projected in the design documents. The use of existing plant instrumentation to measure temperature, pressure, flow rate, etc., along with the incorporation of conservative assumptions, had generally proven adequate for estimating fatigue usage; however, in some cases additional instrumentation installed for local monitoring can provide a more accurate estimate, especially where thermal stratification is known to occur. Fatigue monitoring can aid in identifying fatigue concerns not anticipated in the original design and for reducing the excessive conservatism in some of the original design calculations so that the fatigue lives of these components can be justified as they age. Fatigue monitoring can also assist efforts to reduce ongoing fatigue usage through design modifications and operating procedure changes.

  18. A survey of fatigue monitoring in the nuclear power industry

    SciTech Connect

    Ware, A.G.

    1991-01-01

    The original design of nuclear power plants addressed fatigue concerns by including calculations of projected fatigue usage for specific components; the calculations were based on estimates of the number and severity of expected transients over the 40-year design life of the plants. In some cases, the transients occurring in the plants are not as severe as was anticipated in the original design analyses, while in other cases events have occurred that were not anticipated in the design basis documents. Field failures caused by fatigue have identified some of those cases. In response, several organizations in the United States and overseas have developed fatigue monitoring programs to more accurately estimate the fatigue usage. One basic approach consists of reconstructing the fatigue usage to date based on the transients recorded in the operating history instead of those projected in the design documents. Another approach includes monitoring the plant instrumentation to determine actual values for parameters such as temperature and pressure and using the measured values in the fatigue usage calculations instead of the values projected in the design documents. The use of existing plant instrumentation to measure temperature, pressure, flow rate, etc., along with the incorporation of conservative assumptions, had generally proven adequate for estimating fatigue usage; however, in some cases additional instrumentation installed for local monitoring can provide a more accurate estimate, especially where thermal stratification is known to occur. Fatigue monitoring can aid in identifying fatigue concerns not anticipated in the original design and for reducing the excessive conservatism in some of the original design calculations so that the fatigue lives of these components can be justified as they age. Fatigue monitoring can also assist efforts to reduce ongoing fatigue usage through design modifications and operating procedure changes.

  19. Bottom attenuation estimation using sound intensity fluctuations due to mode coupling by nonlinear internal waves in shallow water.

    PubMed

    Grigorev, Valery A; Katsnelson, Boris G; Lynch, James F

    2016-11-01

    Analyses of fluctuations of low frequency signals (300 ± 30 Hz) propagating in shallow water in the presence of nonlinear internal waves (NIWs) in the Shallow Water 2006 experiment are carried out. Signals were received by a vertical line array at a distance of ∼20 km from the source. A NIW train was moving totally inside of the acoustic track, and the angle between the wave front of the NIW and the acoustic track in the horizontal plane was ∼10°. It is shown that the spectrum of the sound intensity fluctuations contains peaks corresponding to the coupling of pairs of propagating modes. Analysis of spectra at different hydrophone depths, and also summed over depth allows the authors to estimate attenuation in the bottom sediments.

  20. Estimating In Vivo Death Rates of Targets due to CD8 T-Cell-Mediated Killing▿ †

    PubMed Central

    Ganusov, Vitaly V.; De Boer, Rob J.

    2008-01-01

    Despite recent advances in immunology, several key parameters determining virus dynamics in infected hosts remain largely unknown. For example, the rate at which specific effector and memory CD8 T cells clear virus-infected cells in vivo is hardly known for any viral infection. We propose a framework to quantify T-cell-mediated killing of infected or peptide-pulsed target cells using the widely used in vivo cytotoxicity assay. We have reanalyzed recently published data on killing of peptide-pulsed splenocytes by cytotoxic T lymphocytes and memory CD8 T cells specific to NP396 and GP276 epitopes of lymphocytic choriomeningitis virus (LCMV) in the mouse spleen. Because there are so many effector CD8 T cells in spleens of mice at the peak of the immune response, NP396- and GP276-pulsed targets are estimated to have very short half-lives of 2 and 14 min, respectively. After the effector numbers have diminished, i.e., in LCMV-immune mice, the half-lives become 48 min and 2.8 h for NP396- and GP276-expressing targets, respectively. Analysis of several alternative models demonstrates that the estimates of half-life times of peptide-pulsed targets are not affected when changes are made in the model assumptions. Our report provides a unifying framework to compare killing efficacies of CD8 T-cell responses specific to different viral and bacterial infections in vivo, which may be used to compare efficacies of various cytotoxic-T-lymphocyte-based vaccines. PMID:18815293

  1. Estimate of the trigger inefficiency due to extra hits in H1 and H2, using clean Chi(2) events

    SciTech Connect

    Mussa, R.; /INFN, Turin /Turin U.

    1992-07-01

    An accurate study of the inefficiency of the trigger selection criterium based on the multiplicity of hits in the two hodoscopes has been done using {chi}{sub 2} events take during the 1991 run, selected requiring that both electron tracks were associated to a Cherenkov hit (so that no multiplicity requirement at trigger level was asked), and a {chi}{sup 2} probability for the kinematic fit bigger than 0.01. In a table it is shown the number of events found for different multiplicities in the two hodoscopes. They have 554/1819 = 30.5 {+-} 1.3% of the events with extra-hits in the two hodoscopes, and they can think of 3 possible sources for this effect: (1) accidental {delta} rays due to the interactions of the beam halo inside or against the walls of the beam pipe give an extra activity on H1 that should be uncorrelated to the hits due to real tracks; (2) {delta} rays at large angles emitted by the electrons interacting with the inner layers of the detector, so that they expect extra-hits close to the real tracks; and (3) the conversion of the {delta} inside the beam pipe and in the inner detectors can give an extra-hit in H2 or H1 and H2: this also doubles the number of sources of {delta} rays, so that a big number of these events have 4 H2 firing.

  2. Post-traumatic hypopituitarism and fatigue.

    PubMed

    Masel, Brent E; Zgaljardic, Dennis J; Forman, Jack

    2017-10-01

    Post-traumatic hypopituitarism (PTH) associated with chronic cognitive, psychiatric, and/or behavioural sequelae is common following moderate to severe traumatic brain injury (TBI). More specifically, due to a cascade of hormonal deficiencies secondary to PTH, individuals with TBI may experience debilitating fatigue that can negatively impact functional recovery, as it can limit participation in brain injury rehabilitation services and lead to an increase in maladaptive lifestyle practices. While the mechanisms underlying fatigue and TBI are not entirely understood, the current review will address the specific anatomy and physiology of the pituitary gland, as well as the association between pituitary dysfunction and fatigue in individuals with TBI.

  3. Estimation of torque on mechanical heart valves due to magnetic resonance imaging including an estimation of the significance of the Lenz effect using a computational model

    NASA Astrophysics Data System (ADS)

    Robertson, Neil M.; Diaz-Gomez, Manuel; Condon, Barrie

    2000-12-01

    Mitral and aortic valve replacement is a procedure which is common in cardiac surgery. Some of these replacement valves are mechanical and contain moving metal parts. Should the patient in whom such a valve has been implanted be involved in magnetic resonance imaging, there is a possible dangerous interaction between the moving metal parts and the static magnetic field due to the Lenz effect. Mathematical models of two relatively common forms of single-leaflet valves have been derived and the magnitude of the torque which opposes the motion of the valve leaflet has been calculated for a valve disc of solid metal. In addition, a differential model of a ring-strengthener valve type has been considered to determine the likely significance of the Lenz effect in the context of the human heart. For common magnetic field strengths at present, i.e. 1 to 2 T, the effect is not particularly significant. However, there is a marked increase in back pressure as static magnetic field strength increases. There are concerns that, since field strengths in the range 3 to 4 T are increasingly being used, the Lenz effect could become significant. At 5 to 10 T the malfunction of the mechanical heart valve could cause the heart to behave as though it is diseased. For unhealthy or old patients this could possibly prove fatal.

  4. Estimating changes in carbon burial on the western US coastal shelf due to anthropogenic influences on river exports

    NASA Astrophysics Data System (ADS)

    Sauer, M.; Bergamaschi, B. A.; Smith, R. A.; Zhu, Z.; Shih, J.

    2012-12-01

    Flux of nutrients and sediments to the coastal zone varies in response to land-use modification, reservoir construction, management action and population change. It is anticipated that future changes in the flux of these components in response to climate and terrestrial processes will affect carbon (C) burial in the coastal ocean. Coastal oceans store appreciable amounts of C as a result of river inflows: coastal primary production is enhanced by inputs of terrestrially derived nutrients, and C burial is controlled by terrestrial sediment supply. Assessing the capacity and changes to coastal C preservation, therefore, requires estimation of (1) riverine nutrient and sediment delivery to the coastal ocean, and (2) the enhanced C production and sediment deposition in the coastal ocean. The United States Geological Survey (USGS) has embarked on a congressionally-mandated nationwide effort to assess the future effects of climate and land use and land cover change (LULC) on C storage. The USGS has developed alternative scenarios for changes in US LULC from 2006 to 2100 based on the Intergovernmental Panel on Climate Change (IPCC) climate, economic, and demographic scenarios (Sohl et al 2012). These spatially-detailed scenarios provide inputs to national-scale SPARROW watershed models of total nitrogen, total phosphorus, total organic C (TOC), and suspended sediment (Smith et al 1997; Schwarz et al, 2006). The watershed models, in turn, provide inputs of nutrients, TOC, and sediment to a coupled model of coastal transport, production, and sedimentation. This coastal modelling component includes particulate C sedimentation and burial estimated as functions of bathymetry and pycnocline depth (Armstrong, et al 2002; Dunne et al 2007). River borne fluxes of TOC to US Pacific coastal waters under baseline conditions (1992) were 1.59 TgC/yr. Projected future (2050) fluxes under a regionally-downscaled LULC scenario aligned with the IPCC A2 scenario were similar (1.61TgC/yr). C

  5. Ultrasonic absortion in fatigued materials

    NASA Astrophysics Data System (ADS)

    Dugan, S.; Arnold, W.

    2013-01-01

    Non-destructive detection of fatigue damage, allowing an estimate of the residual life-time of components, could contribute to a safe and reliable operation of components and installations. Ultrasonic absorption, i.e. the internal friction, of a material increases with increasing fatigue or creep damage and there are many theories trying to explain the physics behind this phenomenon. Measurement of ultrasonic absorption directly on components could provide information on the degree of damage. A laser ultrasonic method, using laser-generated pulses and optical detection, was applied to study ultrasonic absorption in fatigue specimens of different metals. A characteristic behavior of the ultrasonic absorption coefficient with increasing levels of fatigue damage was found for the titanium alloy Ti-6Al-4V. Another aim of this study was to relate the absorption mechanisms to the behavior of ultrasonic absorption observed in metals with complex microstructure. To achieve this, different ultrasonic absorption mechanisms were analyzed with respect to experimental data. A thermoelastic effect related to the size and elasticity of the microstructure is discussed as the origin of the increased ultrasonic absorption.

  6. Cognitive and Physical Fatigue Tasks Enhance Pain, Cognitive Fatigue and Physical Fatigue in People with Fibromyalgia

    PubMed Central

    Dailey, Dana L; Keffala, Valerie J; Sluka, Kathleen A

    2014-01-01

    Objective Fibromyalgia is a condition characterized by chronic widespread muscle pain and fatigue. The primary objective of this study was to determine if pain, perceived cognitive fatigue, and perceived physical fatigue were enhanced in participants with fibromyalgia compared to healthy controls during a cognitive fatigue task, a physical fatigue task and a dual fatigue task. Methods Twenty four people with fibromyalgia and 33 healthy controls completed pain, fatigue and function measures. A cognitive fatigue task (Controlled Oral Word Association Test) and physical fatigue task (Valpar peg test) were done individually and combined for a dual fatigue task. Resting pain, perceived cognitive fatigue and perceived physical fatigue were assessed during each task using visual analogue scales. Function was assessed with shoulder range of motion and grip. Results People with fibromyalgia had significantly higher increases in pain, cognitive fatigue and physical fatigue when compared to healthy controls after completion of a cognitive fatigue task, a physical fatigue task, or a dual fatigue task (p<0.01). People with fibromyalgia performed equivalently on measures of physical performance and cognitive performance on the physical and cognitive fatigue tasks, respectively. Conclusions These data show that people with fibromyalgia show larger increases in pain, perceived cognitive fatigue and perceived physical fatigue to both cognitive and physical fatigue tasks compared to healthy controls. The increases in pain and fatigue during cognitive and physical fatigue tasks could influence subject participation in daily activities and rehabilitation. PMID:25074583

  7. Uncertainties in sediment erodibility estimates due to a lack of standards for experimental protocols and data interpretation.

    PubMed

    Sanford, Lawrence P

    2006-01-01

    Quantitative prediction of the erodibility of muds and mud-sand mixtures is, at present, seldom possible without resorting to direct measurements, preferably in situ. A variety of devices and protocols have been developed for erosion testing, but a considerable degree of uncertainty remains with regard to the accuracy and comparability of the resulting data. This paper argues that differences in experimental protocols and data analysis procedures are a major contributing factor to uncertainty in estimates of sediment erodibility. In particular, the likelihood of a time-dependent erosion rate response under typical erosion testing conditions means that the time history of applied forcing and the chosen protocols for analyzing and interpreting data directly affect derived erosion parameters. Several straightforward ways to address this problem are suggested, including standardization of experimental design and data analysis protocols, explicit recognition and adoption of appropriate erosion model(s), and allowing for potential time/depth changes in erodibility. Experimentalists should also archive and share erosion-test time series, not just derived parameters, so that data sets may be reanalyzed within a different framework if necessary. An example is presented from an intercomparison experiment between the Virginia Institute of Marine Sciences Sea Carousel and the University of Maryland Center for Environmental Science Microcosm System, carried out in the upper Chesapeake Bay (Maryland, USA) in May 2002. Derived parameters appear to be incompatible when the data are analyzed using different procedures, but real similarities and differences are readily apparent when the data are analyzed using the same procedures.

  8. 210Po and 210Pb Activity Concentrations in Cigarettes Produced in Vietnam and Their Estimated Dose Contribution Due to Smoking

    NASA Astrophysics Data System (ADS)

    Tran, Thuy-Ngan N.; Le, Cong-Hao; Chau, Van-Tao

    Smoking cigarettes contributes significantly to the increase of radiation in human body because 210Po and 210Pb exist relatively high in tobacco leaves. Therefore, these two radioisotopes in eighteen of the most frequently sold cigarette brands produced in Vietnam were examined in this study. 210Po was determined by alpha spectroscopy using a passivated implanted planar silicon (PIPS) detector after a procedure including radiochemical separation and spontaneous deposition of polonium on a copper disc (the deposition efficiency of 210Po on a copper disc was approximately 94%). Sequentially, 210Pb was determined through the ingrowth of 210Po after storing the sample solutions for approximately six months. The activity concentrations of 210Po in cigarettes ranged from 13.8 to 82.6 mBq/cigarette (the mean value was 26.4 mBq/cigarette) and the activity concentrations of 210Pb in cigarettes ranged from 13.9 to 78.8 mBq/cigarette (the mean value was 25.8 mBq/cigarette). The annual committed effective dose for smokers who smoke one pack per day was also estimated to be 295.4 µSv/year (223.0 µSv/year and 72.4 µSv/year from 210Po and 210Pb, respectively). These indicated that smoking increased the risk of developing lung cancer was approximately 60 times greater for smokers than for non-smokers.

  9. Natural radioactivity in groundwater and estimates of committed effective dose due to water ingestion in the state of Chihuahua (Mexico).

    PubMed

    Villalba, L; Montero-Cabrera, M E; Manjón-Collado, G; Colmenero-Sujo, L; Rentería-Villalobos, M; Cano-Jiménez, A; Rodríguez-Pineda, A; Dávila-Rangel, I; Quirino-Torres, L; Herrera-Peraza, E F

    2006-01-01

    The activity concentration of 222Rn, 226Ra and total uranium in groundwater samples collected from wells distributed throughout the state of Chihuahua has been measured. The values obtained of total uranium activity concentration in groundwater throughout the state run from <0.03 up to 1.34 Bq l-1. Generally, radium activity concentration was <0.16 Bq l-1, with some exceptions; in spring water of San Diego de Alcalá, in contrast, the value reached approximately 5.3 Bq l-1. Radon activity concentration obtained throughout the state was from 1.0 to 39.8 Bq l-1. A linear correlation between uranium and radon dissolved in groundwater of individual wells was observed near Chihuahua City. Committed effective dose estimates for reference individuals were performed, with results as high as 134 microSv for infants in Aldama city. In Aldama and Chihuahua cities the average and many individual wells showed activity concentration values of uranium exceeding the Mexican norm of drinking water quality.

  10. Estimation of the carbon monoxide emissions due to Sandia National Laboratories commuter and on-base traffic for conformity determination

    SciTech Connect

    McClellan, Y.; Royer, R.

    1996-09-01

    This report describes the analysis and conclusion of an investigation of the carbon monoxide emissions resulting from Sandia National Laboratories and Department of Energy (DOE) commuter and on-base traffic for the Clean Air Act (CAA) Conformity Determination. Albuquerque/Bernalillo County was classified as a nonattainment area by the Environmental Protection Agency. Nonattainment area is an area which is shown by monitored data or which is calculated by air quality modeling to exceed any National Ambient Air Quality Standard (NAAQS) for the pollutant. Albuquerque/Bernalillo County exceeds the NAAQS for carbon monoxide and ozone. The Conformity Determination was needed to complete the CAA Title V Permitting process for SNL and the DOE. The analysis used the EPA approved MOBILE5a Carbon Monoxide (CO) emissions modeling program. This analysis will provide a baseline for mobile sources to allow Sandia to estimate any future activity and how that activity will impact CO emissions. The General Conformity Rule (AQCR 43) requires that operations which will increase CO emissions in nonattaimnent or maintenance areas such as Bernalillo County undergo conformity analyses to determine whether or not they will impact ambient air quality in the area.

  11. Development of a reliable estimation procedure of radioactivity inventory in a BWR plant due to neutron irradiation for decommissioning

    NASA Astrophysics Data System (ADS)

    Tanaka, Ken-ichi; Ueno, Jun

    2017-09-01

    Reliable information of radioactivity inventory resulted from the radiological characterization is important in order to plan decommissioning planning and is also crucial in order to promote decommissioning in effectiveness and in safe. The information is referred to by planning of decommissioning strategy and by an application to regulator. Reliable information of radioactivity inventory can be used to optimize the decommissioning processes. In order to perform the radiological characterization reliably, we improved a procedure of an evaluation of neutron-activated materials for a Boiling Water Reactor (BWR). Neutron-activated materials are calculated with calculation codes and their validity should be verified with measurements. The evaluation of neutron-activated materials can be divided into two processes. One is a distribution calculation of neutron-flux. Another is an activation calculation of materials. The distribution calculation of neutron-flux is performed with neutron transport calculation codes with appropriate cross section library to simulate neutron transport phenomena well. Using the distribution of neutron-flux, we perform distribution calculations of radioactivity concentration. We also estimate a time dependent distribution of radioactivity classification and a radioactive-waste classification. The information obtained from the evaluation is utilized by other tasks in the preparatory tasks to make the decommissioning plan and the activity safe and rational.

  12. SIMPLE estimate of the free energy change due to aliphatic mutations: superior predictions based on first principles.

    PubMed

    Bueno, Marta; Camacho, Carlos J; Sancho, Javier

    2007-09-01

    The bioinformatics revolution of the last decade has been instrumental in the development of empirical potentials to quantitatively estimate protein interactions for modeling and design. Although computationally efficient, these potentials hide most of the relevant thermodynamics in 5-to-40 parameters that are fitted against a large experimental database. Here, we revisit this longstanding problem and show that a careful consideration of the change in hydrophobicity, electrostatics, and configurational entropy between the folded and unfolded state of aliphatic point mutations predicts 20-30% less false positives and yields more accurate predictions than any published empirical energy function. This significant improvement is achieved with essentially no free parameters, validating past theoretical and experimental efforts to understand the thermodynamics of protein folding. Our first principle analysis strongly suggests that both the solute-solute van der Waals interactions in the folded state and the electrostatics free energy change of exposed aliphatic mutations are almost completely compensated by similar interactions operating in the unfolded ensemble. Not surprisingly, the problem of properly accounting for the solvent contribution to the free energy of polar and charged group mutations, as well as of mutations that disrupt the protein backbone remains open.

  13. A Simple Method for Estimating the Economic Cost of Productivity Loss Due to Blindness and Moderate to Severe Visual Impairment.

    PubMed

    Eckert, Kristen A; Carter, Marissa J; Lansingh, Van C; Wilson, David A; Furtado, João M; Frick, Kevin D; Resnikoff, Serge

    2015-01-01

    To estimate the annual loss of productivity from blindness and moderate to severe visual impairment (MSVI) using simple models (analogous to how a rapid assessment model relates to a comprehensive model) based on minimum wage (MW) and gross national income (GNI) per capita (US$, 2011). Cost of blindness (COB) was calculated for the age group ≥50 years in nine sample countries by assuming the loss of current MW and loss of GNI per capita. It was assumed that all individuals work until 65 years old and that half of visual impairment prevalent in the ≥50 years age group is prevalent in the 50-64 years age group. For cost of MSVI (COMSVI), individual wage and GNI loss of 30% was assumed. Results were compared with the values of the uncorrected refractive error (URE) model of productivity loss. COB (MW method) ranged from $0.1 billion in Honduras to $2.5 billion in the United States, and COMSVI ranged from $0.1 billion in Honduras to $5.3 billion in the US. COB (GNI method) ranged from $0.1 million in Honduras to $7.8 billion in the US, and COMSVI ranged from $0.1 billion in Honduras to $16.5 billion in the US. Most GNI method values were near equivalent to those of the URE model. Although most people with blindness and MSVI live in developing countries, the highest productivity losses are in high income countries. The global economy could improve if eye care were made more accessible and more affordable to all.

  14. Use of 2H2O for estimating rates of gluconeogenesis: determination and correction of error due to transaldolase exchange

    PubMed Central

    Burgess, Shawn C.

    2012-01-01

    The use of deuterated water as a method to measure gluconeogenesis has previously been well validated and is reflective of normal human physiology. However, there has been concern since the method was first introduced that transaldolase exchange may lead to the overestimation of gluconeogenesis. We examined the impact of transaldolase exchange on the estimation of gluconenogenesis using the deuterated water method under a variety of physiological conditions in humans by using the gluconeogenic tracer [U-13C]propionate, 2H2O, and 2H/13C nuclear magnetic resonance (NMR) spectroscopy. When [U-13C]propionate was used, 13C labeling inequality occurred between the top and bottom halves of glucose in individuals fasted for 12–24 h who were weight stable (n = 18) or had lost weight via calorie restriction (n = 7), consistent with transaldolase exchange. Similar analysis of glucose standards revealed no significant difference in the total 13C enrichment between the top and bottom halves of glucose, indicating that the differences detected were biological, not analytical, in origin. This labeling inequality was attenuated by extending the fasting period to 48 h (n = 12) as well as by dietary carbohydrate restriction (n = 7), both conditions associated with decreased glycogenolysis. These findings were consistent with a transaldolase effect; however, the resultant overestimation of gluconeogenesis in the overnight-fasted state was modest (7–12%), leading to an error of 14–24% that was easily correctable by using either a simultaneous 13C gluconeogenic tracer or a correction nomogram generated from data in the present study. PMID:23032685

  15. Indoor inhalation dose estimates due to radon and thoron in some areas of South-Western Punjab, India.

    PubMed

    Kumar, Sanjeev; Singh, Surinder; Bajwa, Bikramjit Singh; Singh, Bhupinder; Sabharwal, Arvind D; Eappen, K P

    2012-08-01

    LR-115 (type II)-based radon-thoron discriminating twin-chamber dosemeters have been used for estimating radon ((222)Rn) and thoron ((220)Rn) concentrations in dwellings of south-western Punjab, India. The present study region has shown pronounced cases of cancer incidents in the public [Thakur, Rao, Rajwanshi, Parwana and Kumar (Epidemiological study of high cancer among rural agricultural community of Punjab in Northern India. Int J Environ Res Public Health 2008; 5(5):399-407) and Kumar et al. (Risk assessment for natural uranium in subsurface water of Punjab state, India. Hum Ecol Risk Assess 2011;17:381-93)]. Radon being a carcinogen has been monitored in some dwellings selected randomly in the study area. Results show that the values of radon ((222)Rn)  varied from 21 to 79 Bq m(-3), with a geometric mean of 45 Bq m(-3) [geometric standard deviation (GSD 1.39)], and those of thoron ((220)Rn)  from minimum detection level to 58 Bq m(-3) with a geometric mean of 19 Bq m(-3) (GSD 1.88). Bare card data are used for computing the progeny concentration by deriving the equilibrium factor (F) using a root finding method [Mayya, Eappen and Nambi (Methodology for mixed field inhalation dosimetry in monazite areas using a twin-cup dosemeter with three track detectors. Radiat Prot Dosim 1998;77(3):177-84)]. Inhalation doses have been calculated and compared using UNSCEAR equilibrium factors and by using the calculated F-values. The results show satisfactory comparison between the values.

  16. Fatigue handbook: Offshore steel structures

    SciTech Connect

    Almarnaess, A.

    1985-01-01

    The contents of this book are: Overview of Offshore Steel Structures; Loads on Ocean Structures; Fracture Mechanics As a Tool in Fatigue Analysis; Basic Fatigue Properties of Welded Joints; Significance of Defects; Improving the Fatigue Strength of Welded Joints; Effects of Marine Environment and Cathodic Protection on Fatigue of Structural Steels Fatigue of Tubular Joints; Unstable Fracture; Fatigue Life Calculations; and Fatigue in Building Codes Background and Applications.

  17. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

    SciTech Connect

    Keisler, J.; Chopra, O.K.; Shack, W.J.

    1995-08-01

    The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. Statistical models have been developed for estimating the effects of the various service conditions on the fatigue life of these materials. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by adjusting the probability distribution curves for smooth test specimens for the effect of mean stress and applying design margins to account for the uncertainties due to component size/geometry and surface finish. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves published in NUREG/CR-5999 is discussed. Estimations of the probability of fatigue cracking in sample components from BWRs and PWRs are presented.

  18. Probabilistic Flexural Fatigue in Plain and Fiber-Reinforced Concrete.

    PubMed

    Ríos, José D; Cifuentes, Héctor; Yu, Rena C; Ruiz, Gonzalo

    2017-07-07

    The objective of this work is two-fold. First, we attempt to fit the experimental data on the flexural fatigue of plain and fiber-reinforced concrete with a probabilistic model (Saucedo, Yu, Medeiros, Zhang and Ruiz, Int. J. Fatigue, 2013, 48, 308-318). This model was validated for compressive fatigue at various loading frequencies, but not for flexural fatigue. Since the model is probabilistic, it is not necessarily related to the specific mechanism of fatigue damage, but rather generically explains the fatigue distribution in concrete (plain or reinforced with fibers) for damage under compression, tension or flexion. In this work, more than 100 series of flexural fatigue tests in the literature are fit with excellent results. Since the distribution of monotonic tests was not available in the majority of cases, a two-step procedure is established to estimate the model parameters based solely on fatigue tests. The coefficient of regression was more than 0.90 except for particular cases where not all tests were strictly performed under the same loading conditions, which confirms the applicability of the model to flexural fatigue data analysis. Moreover, the model parameters are closely related to fatigue performance, which demonstrates the predictive capacity of the model. For instance, the scale parameter is related to flexural strength, which improves with the addition of fibers. Similarly, fiber increases the scattering of fatigue life, which is reflected by the decreasing shape parameter.

  19. Probabilistic Flexural Fatigue in Plain and Fiber-Reinforced Concrete

    PubMed Central

    Ríos, José D.

    2017-01-01

    The objective of this work is two-fold. First, we attempt to fit the experimental data on the flexural fatigue of plain and fiber-reinforced concrete with a probabilistic model (Saucedo, Yu, Medeiros, Zhang and Ruiz, Int. J. Fatigue, 2013, 48, 308–318). This model was validated for compressive fatigue at various loading frequencies, but not for flexural fatigue. Since the model is probabilistic, it is not necessarily related to the specific mechanism of fatigue damage, but rather generically explains the fatigue distribution in concrete (plain or reinforced with fibers) for damage under compression, tension or flexion. In this work, more than 100 series of flexural fatigue tests in the literature are fit with excellent results. Since the distribution of monotonic tests was not available in the majority of cases, a two-step procedure is established to estimate the model parameters based solely on fatigue tests. The coefficient of regression was more than 0.90 except for particular cases where not all tests were strictly performed under the same loading conditions, which confirms the applicability of the model to flexural fatigue data analysis. Moreover, the model parameters are closely related to fatigue performance, which demonstrates the predictive capacity of the model. For instance, the scale parameter is related to flexural strength, which improves with the addition of fibers. Similarly, fiber increases the scattering of fatigue life, which is reflected by the decreasing shape parameter. PMID:28773123

  20. German experiences in local fatigue monitoring

    SciTech Connect

    Abib, E.; Bergholz, S.; Rudolph, J.

    2012-07-01

    The ageing management of nuclear power plants (NPP) has gained an increasing importance in the last years. The reasons are mainly due to the international context of extending period of plants operation. Moreover, new scientific discoveries, such as the corrosive influence of the medium on the fatigue process (environmentally assisted fatigue - EAF) play an important role and influence the code development (ASME, EAF code cases). The fatigue damage process takes a central position in ageing mechanisms of components. It must be ensured through appropriate evidence that facilities are being operated under allowable boundary conditions. In the design phase of NPP, fatigue analyses are still based on theoretical considerations and empirical values, which are summarized in the design transient catalogue, necessary for licensing. These analyses aim at proving the admissibility of the loads in terms of stress and fatigue usage. These analyses will also provide the fatigue-relevant positions in the NPP and give a basis for future design improvements and optimization of operating modes. The design transients are in practice conservatively correlated with the real transients occurring during operation. Uncertainties reveal very conservative assumptions regarding forecast temperatures, temperature gradients and frequencies of events. During operation of the plant, it has to be recurrently proved, that the plant is being operated under designed boundary conditions. Moreover, operating signals are constantly acquired to enable a fatigue evaluation. For example, in Germany fatigue evaluation is based on decades of experience and regulatory requirements. The rule KTA 3201.4 [1] establishes the rules for qualified fatigue monitoring. The rule DIN 25475-3 [2] on fatigue monitoring systems is available in draft version. Experience shows that some significant differences occur between the design transients and the real occurred transients during plant operation. The reasons for it

  1. Organ-specific radiation-induced cancer risk estimates due to radiotherapy for benign pigmented villonodular synovitis

    NASA Astrophysics Data System (ADS)

    Mazonakis, Michalis; Tzedakis, Antonis; Lyraraki, Efrossyni; Damilakis, John

    2016-09-01

    Pigmented villonodular synovitis (PVNS) is a benign disease affecting synovial membranes of young and middle-aged adults. The aggressive treatment of this disorder often involves external-beam irradiation. This study was motivated by the lack of data relating to the radiation exposure of healthy tissues and radiotherapy-induced cancer risk. Monte Carlo methodology was employed to simulate a patient’s irradiation for PVNS in the knee and hip joints with a 6 MV photon beam. The average radiation dose received by twenty-two out-of-field critical organs of the human body was calculated. These calculations were combined with the appropriate organ-, age- and gender-specific risk coefficients of the BEIR-VII model to estimate the lifetime probability of cancer development. The risk for carcinogenesis to colon, which was partly included in the treatment fields used for hip irradiation, was determined with a non-linear mechanistic model and differential dose-volume histograms obtained by CT-based 3D radiotherapy planning. Risk assessments were compared with the nominal lifetime intrinsic risk (LIR) values. Knee irradiation to 36 Gy resulted in out-of-field organ doses of 0.2-24.6 mGy. The corresponding range from hip radiotherapy was 1.2-455.1 mGy whereas the organ equivalent dose for the colon was up to 654.9 mGy. The organ-specific cancer risks from knee irradiation for PVNS were found to be inconsequential since they were at least 161.5 times lower than the LIRs irrespective of the patient’s age and gender. The bladder and colon cancer risk from radiotherapy in the hip joint was up to 3.2 and 6.6 times smaller than the LIR, respectively. These cancer risks may slightly elevate the nominal incidence rates and they should not be ignored during the patient’s treatment planning and follow-up. The probabilities for developing any other solid tumor were more than 20 times lower than the LIRs and, therefore, they may be considered as small.

  2. Estimating Damage Cost of Net Primary Production due to Climate Change and Ozone(O3) Effect

    NASA Astrophysics Data System (ADS)

    Park, J. H.; Lee, D. K.; Park, C.; Sung, S.; Kim, H. G.; Mo, Y.; Kim, S.; Kil, S.

    2016-12-01

    Forests are absorbing and storing carbon dioxide (CO2) through photosynthesis. The forests are not only preventing global warming but also influencing temperature, precipitation and humidity (Costanza et al., 1997; de Groot et al., 2002). Also the forests are recognized as a carbon sink internationally (van Kooten, 2009). The Korean Government supports the economic activity such as carbon offset projects in accordance with 'ACT ON THE MANAGEMENT AND IMPROVEMENT OF CARBON SINK' Article27 (Korea Forest Service, 2013) and aims to make a policy which improves the CO2 capacity of forest for Paris Agreement discussed in UNFCCC COP21, December 2015 (Korea Forest Service, 2015). However, the social-economic activities make to increase aerosols as well as greenhouse gases significantly since the industrial revolution, as a result, the chemical composition of the atmosphere has changed significantly. According to the resent studies, not only CO2 but atmospheric chemistries such as ozone (O3), aerosol and black carbon can be an important factor causing climate change (Hansen et al., 2007; IPCC, 2007). In the past, acid rain affected on forest, but in these days, O3, nitrogen oxide (NOX) and sulfur oxide (SOX) are the most threatening factors on forest ecosystem (Lee et al, 2011). In particular, O3accounts for most of the photochemical products and causes a direct significant impact or damage on the plant because of high toxicity (Han et al., 2006). The research questions of this study are "How does O3 effects on forest productivity in the present and future? " What is the damage cost by the O3 effect in the future? In this study, we developed a statistical model using the parameters which effect on the forest productivity. We estimated the forest productivity using on the derived model in the present and future on a SSP scenarios. Lastly, we evaluated the economic effect or damage cost of O3effect by introducing the concept of climate insurance. The average forest

  3. Estimation of landslides activities evolution due to land-use and climate change in a Pyrenean valley

    NASA Astrophysics Data System (ADS)

    Vandromme, Rosalie; Bernardie, Séverine; Houet, Thomas; Grémont, Marine; Grandjean, Gilles; Thiery, Yannick

    2016-04-01

    Global changes would have impacts worldwide, but their effects should be even more exacerbated in areas particularly vulnerable. Mountainous areas are among these vulnerable territories. Ecological systems are often at a fragile equilibrium, socio-economical activities are often climate-dependent and climate-driven natural hazards can be a major threat for human activities. In order to estimate the capacity of such mountainous valleys to face global changes (climate, but also climate- and human- induced land-use changes), it is necessary to be able to evaluate the evolution of the different threats. The present work shows a method to evaluate the influences of the evolution of both vegetation cover and climate on landslides activities over a whole valley until 2100, to propose adequate solutions for current and future forestry management. Firstly, the assessment of future land use is addressed through the construction of four prospective socio-economic scenarios up to 2050 and 2100, which are then spatially validated and modeled with LUCC models. Secondly, the climate change inputs of the project correspond to 2 scenarios of emission of greenhouse gases. The used simulations available on the portal DRIAS (http://www.drias-climat.fr) were performed with the GHG emissions scenarios (RCP: Representative concentration pathways, according to the standards defined by the GIEC) RCP 4.5 and RCP 8.5. The impact of land use and climate change is then addressed through the use of these scenarios into hazards computations. For that we use a large-scale slope stability assessment tool ALICE which combines a mechanical stability model (using finite slope analysis), a vegetation module which interfere with the first model, to take into account the effects of vegetation on the mechanical soil properties (cohesion and over-load), and an hydrogeological model. All these elements are interfaced within a GIS-based solution. In that way, future changes in temperature, precipitation and

  4. Estimation of loss and analysis of nicotine, reducing sugar and chloride in bidi tobacco due to reniform nematode under pot conditions.

    PubMed

    Bairwa, Aarti; Patel, H R

    2016-06-01

    Estimation of avoidable loss in yield of bidi tobacco due to reniform nematode under pot conditions revealed that variety A 119 suffered heavily than ABT 10 due to reniform nematode. Inoculation of reniform nematode @ 2000 J4 per plant significantly reduced the plant growth characters and increased nematode multiplication preferring A 119 variety. Estimation of avoidable loss in cured shoot yield of bidi tobacco due to infection of reniform nematode in individual variety ABT 10 and A 119 has been estimated to the tune of 30.5 and 34.2 per cent with overall loss 31.9 per cent in both the variety 60 DAI. Simply growing of ABT 10 variety irrespective of infection of reniform nematode avoided 29.5 per cent loss in cured shoot yield. ABT 10 recorded significantly high nicotine, reducing sugar and chloride than A 119; inoculation of reniform nematode significantly increased nicotine, reducing sugar and chloride compared to no inoculation. Interaction indicated that inoculation of 2000 J4 of reniform nematode significantly increased nicotine, reducing sugar and chloride in A 119 compared to no inoculation; while significantly reduced reducing sugar and increased chloride in ABT 10. There was no significant impact of infection of reniform nematode on nicotine in ABT 10.

  5. Future Estimation of Convenience Living Facilities Withdrawal due to Population Decline all Over Japan from 2010 TO 2040 - Focus on Supermarkets, Convenience Stores and Drugstores

    NASA Astrophysics Data System (ADS)

    Nishimoto, Yuka; Akiyama, Yuki; Shibasaki, Ryosuke

    2016-06-01

    Population explosion is considered to be one of the most crucial problems in the world. However, in Japan, the opposite problem: population decline has become serious now. Japanese population is estimated to decrease by twenty millions in 2040. This negative situation will cause to increase areas where many residents cannot make a daily living all over Japan because many convenience living facilities such as supermarkets, convenience stores and drugstores will be difficult to maintain their market area population due to future population decline. In our research, we used point data of convenience living facilities developed by address geocoding of digital telephone directory and point data of future population projection developed by distribution of Japanese official population projection data proportionally among the building volume of digital residential map, which can monitor building volumes all over Japan. In conclusion, we estimated that various convenience living facilities in Japan will shrink and close by population decline in near future. In particular, it is cleared that approximately 14.7% of supermarkets will be possible to withdraw all over Japan by 2040. In addition, it is cleared that over 40% of supermarkets in some countryside prefectures will be possible to withdraw by 2040. Thus, we estimated future distributions of convenience living facilities that cannot maintain their market area population due to future population decline. Moreover, we estimated the number of people that they will become inconvenience in buying fresh foods.

  6. Offshore wind turbine foundation monitoring, extrapolating fatigue measurements from fleet leaders to the entire wind farm

    NASA Astrophysics Data System (ADS)

    Weijtens, Wout; Noppe, Nymfa; Verbelen, Tim; Iliopoulos, Alexandros; Devriendt, Christof

    2016-09-01

    The present contribution is part of the ongoing development of a fatigue assessment strategy driven purely on in-situ measurements on operational wind turbines. The primary objective is to estimate the remaining life time of existing wind farms and individual turbines by instrumenting part of the farm with a load monitoring setup. This load monitoring setup allows to measure interface loads and local stress histories. This contribution will briefly discuss how these load measurements can be translated into fatigue assessment of the instrumented turbine. However, due to different conditions at the wind farm, such as turbulence, differences in water depth and foundation design this turbine will not be fully representable for all turbines in the farm. In this paper we will use the load measurements on two offshore wind turbines in the Northwind offshore wind farm to discuss fatigue progression in an operational wind farm. By calculating the damage equivalent loads on the two turbines the fatigue progression is quantified for every 10 minute interval and can be analyzed against turbulence and site conditions. In future work these results will be used to predict the fatigue life progression in the entire farm.

  7. Contribution of Hamstring Fatigue to Quadriceps Inhibition Following Lumbar Extension Exercise

    PubMed Central

    Hart, Joseph M.; Kerrigan, D. Casey; Fritz, Julie M.; Saliba, Ethan N.; Gansneder, Bruce; Ingersoll, Christopher D.

    2006-01-01

    The purpose of this study was to determine the contribution of hamstrings and quadriceps fatigue to quadriceps inhibition following lumbar extension exercise. Regression models were calculated consisting of the outcome variable: quadriceps inhibition and predictor variables: change in EMG median frequency in the quadriceps and hamstrings during lumbar fatiguing exercise. Twenty-five subjects with a history of low back pain were matched by gender, height and mass to 25 healthy controls. Subjects performed two sets of fatiguing isometric lumbar extension exercise until mild (set 1) and moderate (set 2) fatigue of the lumbar paraspinals. Quadriceps and hamstring EMG median frequency were measured while subjects performed fatiguing exercise. A burst of electrical stimuli was superimposed while subjects performed an isometric maximal quadriceps contraction to estimate quadriceps inhibition after each exercise set. Results indicate the change in hamstring median frequency explained variance in quadriceps inhibition following the exercise sets in the history of low back pain group only. Change in quadriceps median frequency explained variance in quadriceps inhibition following the first exercise set in the control group only. In conclusion, persons with a history of low back pain whose quadriceps become inhibited following lumbar paraspinal exercise may be adapting to the fatigue by using their hamstring muscles more than controls. Key Points A neuromuscular relationship between the lumbar paraspinals and quadriceps while performing lumbar extension exercise may be influenced by hamstring muscle fatigue. QI following lumbar extension exercise in persons with a history of LBP group may involve significant contribution from the hamstring muscle group. More hamstring muscle contribution may be a necessary adaptation in the history of LBP group due to weaker and more fatigable lumbar extensors. PMID:24198683

  8. Multiaxial fatigue low cycle fatigue testing

    NASA Technical Reports Server (NTRS)

    Zamrik, S. Y.

    1985-01-01

    Multiaxial testing methods are reviewed. Advantages and disadvantages of each type test is discussed. Significant multiaxial data available in the literature is analyzed. The yield theories are compared for multiaxial fatigue analysis.

  9. The scale-of-choice effect and how estimates of assortative mating in the wild can be biased due to heterogeneous samples.

    PubMed

    Rolán-Alvarez, Emilio; Carvajal-Rodríguez, Antonio; de Coo, Alicia; Cortés, Beatriz; Estévez, Daniel; Ferreira, Mar; González, Rubén; Briscoe, Adriana D

    2015-07-01

    The mode in which sexual organisms choose mates is a key evolutionary process, as it can have a profound impact on fitness and speciation. One way to study mate choice in the wild is by measuring trait correlation between mates. Positive assortative mating is inferred when individuals of a mating pair display traits that are more similar than those expected under random mating while negative assortative mating is the opposite. A recent review of 1134 trait correlations found that positive estimates of assortative mating were more frequent and larger in magnitude than negative estimates. Here, we describe the scale-of-choice effect (SCE), which occurs when mate choice exists at a smaller scale than that of the investigator's sampling, while simultaneously the trait is heterogeneously distributed at the true scale-of-choice. We demonstrate the SCE by Monte Carlo simulations and estimate it in two organisms showing positive (Littorina saxatilis) and negative (L. fabalis) assortative mating. Our results show that both positive and negative estimates are biased by the SCE by different magnitudes, typically toward positive values. Therefore, the low frequency of negative assortative mating observed in the literature may be due to the SCE's impact on correlation estimates, which demands new experimental evaluation.

  10. Continuous fatigue crack monitoring of bridges: Long-Term Electrochemical Fatigue Sensor (LTEFS)

    NASA Astrophysics Data System (ADS)

    Moshier, Monty A.; Nelson, Levi; Brinkerhoff, Ryan; Miceli, Marybeth

    2016-04-01

    Fatigue cracks in steel bridges degrade the load-carrying capacity of these structures. Fatigue damage accumulation caused by the repetitive loading of everyday truck traffic can cause small fatigue cracks initiate. Understanding the growth of these fatigue cracks is critical to the safety and reliability of our transportation infrastructure. However, modeling fatigue in bridges is difficult due to the nature of the loading and variations in connection integrity. When fatigue cracks reach critical lengths failures occur causing partial or full closures, emergency repairs, and even full structural failure. Given the aging US highway and the trend towards asset management and life extension, the need for reliable, cost effective sensors and monitoring technologies to alert bridge owners when fatigue cracks are growing is higher than ever. In this study, an innovative Long-Term Electrochemical Fatigue Sensor (LTEFS) has been developed and introduced to meet the growing NDT marketplace demand for sensors that have the ability to continuously monitor fatigue cracks. The performance of the LTEFS has been studied in the laboratory and in the field. Data was collected using machined specimens with different lengths of naturally initiated fatigue cracks, applied stress levels, applied stress ratios, and for both sinusoidal and real-life bridge spectrum type loading. The laboratory data was evaluated and used to develop an empirically based algorithm used for crack detection. Additionally, beta-tests on a real bridge structure has been completed. These studies have conclusively demonstrated that LTEFS holds great potential for long-term monitoring of fatigue cracks in steel structures

  11. Managing fatigue: It really is about sleep.

    PubMed

    Darwent, David; Dawson, Drew; Paterson, Jessica L; Roach, Gregory D; Ferguson, Sally A

    2015-09-01

    Biomathematical models of fatigue can assist organisations to estimate the fatigue consequences of a roster before operations commence. These estimates do not account for the diversity of sleep behaviours exhibited by employees. The purpose of this study was to develop sleep transfer functions describing the likely distributions of sleep around fatigue level estimates produced by a commercial biomathematical model of fatigue. Participants included 347 (18 females, 329 males) train drivers working commercial railway operations in Australia. They provided detailed information about their sleep behaviours using sleep diaries and wrist activity monitors. On average, drivers slept for 7.7 (±1.7)h in the 24h before work and 15.1 (±2.5)h in the 48h before work. The amount of sleep obtained by drivers before shifts differed only marginally across morning, afternoon and night shifts. Shifts were also classified into one of seven ranked categories using estimated fatigue level scores. Higher fatigue score categories were associated with significant reductions in the amount of sleep obtained before shifts, but there was substantial within-category variation. The study findings demonstrate that biomathematical models of fatigue have utility for designing round-the-clock rosters that provide sufficient sleep opportunities for the average employee. Robust variability in the amount of sleep obtained by drivers indicate that models are relatively poor tools for ensuring that all employees obtain sufficient sleep. These findings demonstrate the importance of developing approaches for managing the sleep behaviour of individual employees. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Driving fatigue in professional drivers: a survey of truck and taxi drivers.

    PubMed

    Meng, Fanxing; Li, Shuling; Cao, Lingzhi; Li, Musen; Peng, Qijia; Wang, Chunhui; Zhang, Wei

    2015-01-01

    Fatigue among truck drivers has been studied extensively; however, less is known regarding the fatigue experience of taxi drivers in heavily populated metropolitan areas. This study aimed to compare the differences and similarities between truck and taxi driver fatigue to provide implications for the fatigue management and education of professional drivers. A sample of 274 truck drivers and 286 taxi drivers in Beijing was surveyed via a questionnaire, which included items regarding work characteristics, fatigue experience, accident information, attitude toward fatigue, and methods of counteracting fatigue. Driver fatigue was prevalent among professional drivers, and it was even more serious for taxi drivers. Taxi drivers reported more frequent fatigue experiences and were involved in more accidents. Among the contributing factors to fatigue, prolonged driving time was the most important factor identified by both driver groups. Importantly, the reason for the engagement in prolonged driving was neither due to the lack of awareness concerning the serious outcome of fatigue driving nor because of their poor detection of fatigue. The most probable reason was the optimism bias, as a result of which these professional drivers thought that fatigue was more serious for other drivers than for themselves, and they thought that they were effective in counteracting the effect of fatigue on their driving performance. Moreover, truck drivers tended to employ methods that require stopping to counteract fatigue, whereas taxi drivers preferred methods that were simultaneous with driving. Although both driver groups considered taking a nap as one of the most effective means to address fatigue, this method was not commonly used. Interestingly, these drivers were aware that the methods they frequently used were not the most effective means to counteract fatigue. This study provides knowledge on truck and taxi drivers' characteristics in fatigue experience, fatigue attitude, and

  13. Fatigue of cellular materials

    SciTech Connect

    Huang, J.S.; Lin, J.Y.

    1996-01-01

    The fatigue of cellular materials is analyzed using dimensional arguments. When the first unbroken cell wall ahead of the macrocrack tip fails after some cycles of loading, the macrocrack advances one cell diameter, giving the macrocrack growth rate of cellular materials. Paris law for microcrack propagation, Basquin law for high cycle fatigue and Coffin-Manson law for low cycle fatigue are employed in calculating the number of cycles to failure of the first unbroken cell wall ahead of the macrocrack tip. It is found that fatigue of cellular materials depends on cyclic stress intensity range, cell size, relative density and the fatigue parameters of the solid from which they are made. Theoretical modelling of fatigue of foams is compared to data in polymer foams; agreement is good.

  14. Fatigue resistance of denture teeth.

    PubMed

    Heintze, Siegward D; Monreal, Dominik; Rousson, Valentin

    2016-01-01

    There is no standard test to determine the fatigue resistance of denture teeth. With the increasing number of patients with implant-retained dentures the mechanical strength of the denture teeth requires more attention and valid laboratory test set-ups. The purpose of the present study was to determine the fatigue resistance of various denture teeth using a dynamic load testing machine. Four denture teeth were used: Bonartic II (Candulor), Physiodens (Vita), SR Phonares II (Ivoclar Vivadent) and Trubyte (Dentsply). For dynamic load testing, first upper molars with a similar shape and cusp inclination were selected. The molar teeth were embedded in cylindrical steel molds with denture base material (ProBase, Ivoclar Vivadent). Dynamic fatigue loading was carried out on the mesio-buccal cusp at a 45° angle using dynamic testing machines and 2,000,000 cycles at 2Hz in water (37 °C). Three specimens per group and load were submitted to decreasing load levels (at least 4) until all the three specimens no longer showed any failures. All the specimens were evaluated under a stereo microscope (20× magnification). The number of cycles reached before observing a failure, and its dependence on the load and on the material, has been modeled using a parametric survival regression model with a lognormal distribution. This allowed to estimate the fatigue resistance for a given material as the maximal load for which one would observe less than 1% failure after 2,000,000 cycles. The failure pattern was similar for all denture teeth, showing a large chipping of the loaded mesio-buccal cusp. In our regression model, there were statistically significant differences among the different materials, with SR Phonares II and Bonartic II showing a higher resistance than Physiodens and Trubyte, the fatigue resistance being estimated at around 110 N for the former two, and at about 60 N for the latter two materials. The fatigue resistance may be a useful parameter to assess and to compare

  15. Chronic fatigue syndrome: aetiology, diagnosis and treatment

    PubMed Central

    Avellaneda Fernández, Alfredo; Pérez Martín, Álvaro; Izquierdo Martínez, Maravillas; Arruti Bustillo, Mar; Barbado Hernández, Francisco Javier; de la Cruz Labrado, Javier; Díaz-Delgado Peñas, Rafael; Gutiérrez Rivas, Eduardo; Palacín Delgado, Cecilia; Rivera Redondo, Javier; Ramón Giménez, José Ramón

    2009-01-01

    Chronic fatigue syndrome is characterised by intense fatigue, with duration of over six months and associated to other related symptoms. The latter include asthenia and easily induced tiredness that is not recovered after a night's sleep. The fatigue becomes so severe that it forces a 50% reduction in daily activities. Given its unknown aetiology, different hypotheses have been considered to explain the origin of the condition (from immunological disorders to the presence of post-traumatic oxidative stress), although there are no conclusive diagnostic tests. Diagnosis is established through the exclusion of other diseases causing fatigue. This syndrome is rare in childhood and adolescence, although the fatigue symptom per se is quite common in paediatric patients. Currently, no curative treatment exists for patients with chronic fatigue syndrome. The therapeutic approach to this syndrome requires a combination of different therapeutic modalities. The specific characteristics of the symptomatology of patients with chronic fatigue require a rapid adaptation of the educational, healthcare and social systems to prevent the problems derived from current systems. Such patients require multidisciplinary management due to the multiple and different issues affecting them. This document was realized by one of the Interdisciplinary Work Groups from the Institute for Rare Diseases, and its aim is to point out the main social and care needs for people affected with Chronic Fatigue Syndrome. For this, it includes not only the view of representatives for different scientific societies, but also the patient associations view, because they know the true history of their social and sanitary needs. In an interdisciplinary approach, this work also reviews the principal scientific, medical, socio-sanitary and psychological aspects of Chronic Fatigue Syndrome. PMID:19857242

  16. Fatigue and hysteresis modeling of ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Yoo, In. K.; Desu, Seshu B.

    1993-10-01

    Due to their nonlinear properties, ferroelectric materials are ideal candidates for smart materials. Degradation properties such as low voltage breakdown, fatigue, and aging have been major problems in commercial applications of these materials. Such degradations affect the lifetime of ferroelectric materials. Therefore, it is important to understand degradation for reliability improvement. In this article, recent studies on fatigue and hysteresis of ferroelectric ceramics such as Lead Zirconate Titanate (PZT) thin films is reviewed. A new fatigue model is discussed in detail which is based on effective one-directional movement of defects by internal field difference, defect entrapment at the ferroelectrics-electrode interface, and resultant polarization loss at the interface. A fatigue equation derived from this model is presented. Fatigue parameters such as initial polarization, piling constant, and decay constant are defined from the fatigue equation and voltage and temperature dependence of fatigue parameters are discussed. The jump distance of defect calculated from voltage dependence of the decay constant is close to the lattice constant of ferroelectric materials, which implies that oxygen or lead vacancies migrate either parallel or antiparallel to the polarization direction. From the temperature dependence of the decay constant, it is shown that the activation energy for domain wall movement plays an important role in fatigue. The hysteresis model of ferroelectrics is shown using polarization reversal. The hysteresis loop is made by four polarization stages: nucleation, growth, merging, and shrinkage of domains. The hysteresis equation confirms that dielectric viscosity controls hysteresis properties, and temperature dependence of the coefficient of dielectric viscosity is also discussed in conjunction with fatigue mechanism.

  17. Compassion fatigue in nurses.

    PubMed

    Yoder, Elizabeth A

    2010-11-01

    Compassion fatigue, trigger situations, and coping strategies were investigated in hospital and home care nurses. The Professional Quality of Life Scale measured compassion fatigue, compassion satisfaction, and burnout. Narrative questions elicited trigger situations and coping strategies. Compassion fatigue scores were significantly different between nurses who worked 8- or 12-hour shifts. Fifteen percent of the participants had scores indicating risk of the compassion fatigue. There were significant differences in compassion satisfaction, depending on the unit worked and time as a nurse. The most common category of trigger situations was caring for the patient. Work-related and personal coping strategies were identified. Copyright © 2010 Elsevier Inc. All rights reserved.

  18. Fatigue behaviour of composites

    NASA Astrophysics Data System (ADS)

    Hartwig, G.; Hübner, R.; Knaak, S.; Pannkoke, C.

    An important design parameter for cyclically loaded structures (e.g. transport vessels) is the fatigue endurance limit. The cryogenic fatigue behaviour with different types of fibres and matrices has been investigated. The main emphasis it put on the behaviour of fibre dominated properties. It is surprising that the fatigue strength even of unidirectional fibre composites is strongly influenced by the matrix type. This will be discussed for carbon fibre composites with thermoplastic and duroplastic matrices under tensile and shear loading. For crossplies (with non-woven fabrics) the interaction between laminates controls the fatigue behaviour. The interaction depends on the matrix type and is different for tensile and shear loading.

  19. Neurobiological studies of fatigue

    PubMed Central

    Harrington, Mary E.

    2012-01-01

    Fatigue is a symptom associated with many disorders, is especially common in women and in older adults, and can have a huge negative influence on quality of life. Although most past research on fatigue uses human subjects instead of animal models, the use of appropriate animal models has recently begun to advance our understanding of the neurobiology of fatigue. In this review, results from animal models using immunological, developmental, or physical approaches to study fatigue are described and compared. Common across these animal models is that fatigue arises when a stimulus induces activation of microglia and/or increased cytokines and chemokines in the brain. Neurobiological studies implicate structures in the ascending arousal system, sleep executive control areas, and areas important in reward. In addition, the suprachiasmatic nucleus clearly plays an important role in homeostatic regulation of the neural network mediating fatigue. This nucleus responds to cytokines, shows decreased amplitude firing rate output in models of fatigue, and responds to exercise, one of our few treatments for fatigue. This is a young field but very important as the symptom of fatigue is common across many disorders and we do not have effective treatments. PMID:22841649

  20. The fatigue strength of riveted joints and lugs

    NASA Technical Reports Server (NTRS)

    Schijve, J

    1956-01-01

    This report deals with a number of tests on riveted joints and lugs for the primary purpose of comparing the several types of riveted joints and to study the effect of various factors on the fatigue strength of lugs. A check was made to ascertain whether or not an estimate of the fatigue life at a certain loading could be made from the dimensions of the joint and the fatigue data of the unnotched materials. Recommendations are made on the proportioning of joints to obtain better fatigue behavior.

  1. Errors in the estimation of approximate entropy and other recurrence-plot-derived indices due to the finite resolution of RR time series.

    PubMed

    García-González, Miguel A; Fernández-Chimeno, Mireya; Ramos-Castro, Juan

    2009-02-01

    An analysis of the errors due to the finite resolution of RR time series in the estimation of the approximate entropy (ApEn) is described. The quantification errors in the discrete RR time series produce considerable errors in the ApEn estimation (bias and variance) when the signal variability or the sampling frequency is low. Similar errors can be found in indices related to the quantification of recurrence plots. An easy way to calculate a figure of merit [the signal to resolution of the neighborhood ratio (SRN)] is proposed in order to predict when the bias in the indices could be high. When SRN is close to an integer value n, the bias is higher than when near n - 1/2 or n + 1/2. Moreover, if SRN is close to an integer value, the lower this value, the greater the bias is.

  2. Fatigue crack growth in an aluminum alloy-fractographic study

    NASA Astrophysics Data System (ADS)

    Salam, I.; Muhammad, W.; Ejaz, N.

    2016-08-01

    A two-fold approach was adopted to understand the fatigue crack growth process in an Aluminum alloy; fatigue crack growth test of samples and analysis of fractured surfaces. Fatigue crack growth tests were conducted on middle tension M(T) samples prepared from an Aluminum alloy cylinder. The tests were conducted under constant amplitude loading at R ratio 0.1. The stress applied was from 20,30 and 40 per cent of the yield stress of the material. The fatigue crack growth data was recorded. After fatigue testing, the samples were subjected to detailed scanning electron microscopic (SEM) analysis. The resulting fracture surfaces were subjected to qualitative and quantitative fractographic examinations. Quantitative fracture analysis included an estimation of crack growth rate (CGR) in different regions. The effect of the microstructural features on fatigue crack growth was examined. It was observed that in stage II (crack growth region), the failure mode changes from intergranular to transgranular as the stress level increases. In the region of intergranular failure the localized brittle failure was observed and fatigue striations are difficult to reveal. However, in the region of transgranular failure the crack path is independent of the microstructural features. In this region, localized ductile failure mode was observed and well defined fatigue striations were present in the wake of fatigue crack. The effect of interaction of growing fatigue crack with microstructural features was not substantial. The final fracture (stage III) was ductile in all the cases.

  3. Modeling and Simulation for Estimating the Influence of Renal Dysfunction on the Hypouricemic Effect of Febuxostat in Hyperuricemic Patients Due to Overproduction or Underexcretion of Uric Acid.

    PubMed

    Hirai, Toshinori; Kimura, Toshimi; Echizen, Hirotoshi

    2016-01-01

    Whether renal dysfunction influences the hypouricemic effect of febuxostat, a xanthine oxidase (XO) inhibitor, in patients with hyperuricemia due to overproduction or underexcretion of uric acid (UA) remains unclear. We aimed to address this question with a modeling and simulation approach. The pharmacokinetics (PK) of febuxostat were analyzed using data from the literature. A kinetic model of UA was retrieved from a previous human study. Renal UA clearance was estimated as a function of creatinine clearance (CLcr) but non-renal UA clearance was assumed constant. A reversible inhibition model for bovine XO was adopted. Integrating these kinetic formulas, we developed a PK-pharmacodynamic (PK-PD) model for estimating the time course of the hypouricemic effect of febuxostat as a function of baseline UA level, febuxostat dose, treatment duration, body weight, and CLcr. Using the Monte Carlo simulation method, we examined the performance of the model by comparing predicted UA levels with those reported in the literature. We also modified the models for application to hyperuricemia due to UA overproduction or underexcretion. Thirty-nine data sets comprising 735 volunteers or patients were retrieved from the literature. A good correlation was observed between the hypouricemic effects of febuxostat estimated by our PK-PD model and those reported in the articles (observed) (r=0.89, p<0.001). The hypouricemic effect was estimated to be augmented in patients with renal dysfunction irrespective of the etiology of hyperuricemia. While validation in clinical studies is needed, the modeling and simulation approach may be useful for individualizing febuxostat doses in patients with various clinical characteristics.

  4. A Nonlinear Reduced Order Method for Prediction of Acoustic Fatigue

    NASA Technical Reports Server (NTRS)

    Przekop, Adam; Rizzi, Stephen A.

    2006-01-01

    The goal of this investigation is to assess the quality of high-cycle-fatigue life estimation via a reduced order method, for structures undergoing geometrically nonlinear random vibrations. Modal reduction is performed with several different suites of basis functions. After numerically solving the reduced order system equations of motion, the physical displacement time history is obtained by an inverse transformation and stresses are recovered. Stress ranges obtained through the rainflow counting procedure are used in a linear damage accumulation method to yield fatigue estimates. Fatigue life estimates obtained using various basis functions in the reduced order method are compared with those obtained from numerical simulation in physical degrees-of-freedom.

  5. Creep does not contribute to fatigue in bovine trabecular bone.

    PubMed

    Moore, T L A; O'Brien, F J; Gibson, L J

    2004-06-01

    In both cortical and trabecular bone loaded in fatigue, the stress-strain loops translate along the strain axis. Previous studies have suggested that this translation is the result of creep associated with the mean stress applied in the fatigue test. In this study, we measured the residual strrain (corresponding to the translation of the stress-strain loops) in fatigue tests on bovine trabecular bone and compared it to an upper bound estimate of the creep strain in each test. Our results indicate that the contribution of creep to the translation of the stress-strain loops is negligible in bovine trabecular bone. These results, combined with models for fatigue in lower density bone, suggest that that creep does not contribute to the fatigue of normal human bone. Creep may make a significant contribution to fatigue in low-density osteoporotic bone in which trabeculae have resorbed, reducing the connectivity of the trabecular structure.

  6. Creep-Fatigue Failure Diagnosis

    PubMed Central

    Holdsworth, Stuart

    2015-01-01

    Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of loading conditions ranging from pure cyclic to mainly steady loading with infrequent off-load transients. These require a range of mechanical analysis approaches, a number of which are reviewed. The microstructural information revealing material condition can vary with alloy class. In practice, the detail of the consequent cracking mechanism(s) can be camouflaged by oxidation at high temperatures, although the presence of oxide on fracture surfaces can be used to date events leading to failure. Routine laboratory specimen post-test examination is strongly recommended to characterise the detail of deformation and damage accumulation under known and well-controlled loading conditions to improve the effectiveness and efficiency of failure diagnosis. PMID:28793676

  7. Creep-Fatigue Failure Diagnosis.

    PubMed

    Holdsworth, Stuart

    2015-11-16

    Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of loading conditions ranging from pure cyclic to mainly steady loading with infrequent off-load transients. These require a range of mechanical analysis approaches, a number of which are reviewed. The microstructural information revealing material condition can vary with alloy class. In practice, the detail of the consequent cracking mechanism(s) can be camouflaged by oxidation at high temperatures, although the presence of oxide on fracture surfaces can be used to date events leading to failure. Routine laboratory specimen post-test examination is strongly recommended to characterise the detail of deformation and damage accumulation under known and well-controlled loading conditions to improve the effectiveness and efficiency of failure diagnosis.

  8. Estimation of dose due to ingestion of (210)pb in milk from dairy cattle in the semi-arid region of Pernambuco, Brazil.

    PubMed

    Silva, C M; Amaral, R S; Tabosa, J N; Júnior, J A S; Menezes, R S C; Ribeiro, F C A

    2010-08-01

    (210)Pb is widely distributed in the environment. In this context, the aim of this research has been: (1) to determine (210)Pb concentrations in milk and dairy products from farms located in the cities of Pedra and Venturosa in Pernambuco, Brazil; and (2) to calculate the dose due to the ingestion of (210)Pb in these products. The ion exchange resin method was used and the concentration of (210)Pb varied from 62 to 650 mBq l(-1) in fresh milk, from 202 to 1,494 mBq kg(-1) in curdled cheese and from 11 to 253 mBq l(-1) in milk whey. The estimated dose due to ingestion of milk and dairy products in this region was 0.2 Sv, which is at least two orders of magnitude above the maximum recommended levels.

  9. A Taxonomy of Fatigue Concepts and Their Relation to Hearing Loss.

    PubMed

    Hornsby, Benjamin W Y; Naylor, Graham; Bess, Fred H

    2016-01-01

    Fatigue is common in individuals with a variety of chronic health conditions and can have significant negative effects on quality of life. Although limited in scope, recent work suggests persons with hearing loss may be at increased risk for fatigue, in part due to effortful listening that is exacerbated by their hearing impairment. However, the mechanisms responsible for hearing loss-related fatigue, and the efficacy of audiologic interventions for reducing fatigue, remain unclear. To improve our understanding of hearing loss-related fatigue, as a field it is important to develop a common conceptual understanding of this construct. In this article, the broader fatigue literature is reviewed to identify and describe core constructs, consequences, and methods for assessing fatigue and related constructs. Finally, the current knowledge linking hearing loss and fatigue is described and may be summarized as follows: Hearing impairment may increase the risk of subjective fatigue and vigor deficits; adults with hearing loss require more time to recover from fatigue after work and have more work absences; sustained, effortful, listening can be fatiguing; optimal methods for eliciting and measuring fatigue in persons with hearing loss remain unclear and may vary with listening condition; and amplification may minimize decrements in cognitive processing speed during sustained effortful listening. Future research is needed to develop reliable measurement methods to quantify hearing loss-related fatigue, explore factors responsible for modulating fatigue in people with hearing loss, and identify and evaluate potential interventions for reducing hearing loss-related fatigue.

  10. A Taxonomy of Fatigue Concepts and Their Relation to Hearing Loss

    PubMed Central

    Hornsby, Benjamin W.Y.; Naylor, Graham; Bess, Fred H.

    2016-01-01

    Fatigue is common in individuals with a variety of chronic health conditions and can have significant negative effects on quality of life. Although limited in scope, recent work suggests persons with hearing loss may be at increased risk for fatigue, in part due to effortful listening that is exacerbated by their hearing impairment. However, the mechanisms responsible for hearing loss-related fatigue, and the efficacy of audiologic interventions for reducing fatigue, remain unclear. To improve our understanding of hearing loss-related fatigue, as a field it is important to develop a common conceptual understanding of this construct. In this paper the broader fatigue literature is reviewed to identify and describe core constructs, consequences and methods for assessing fatigue and related constructs. Finally, our current knowledge linking hearing loss and fatigue is described and may be summarised as follows: Hearing impairment increases the risk of subjective fatigue and vigor deficits.Adults with hearing loss require more time to recover from fatigue after work, and have more work absences.Sustained, effortful, listening can be fatiguing.Optimal methods for eliciting and measuring fatigue in persons with hearing loss remain unclear and may vary with listening condition.Amplification may minimize decrements in cognitive processing speed during sustained effortful listening. Future research is needed to develop reliable measurement methods to quantify hearing loss-related fatigue; explore factors responsible for modulating fatigue in people with hearing loss; and identify and evaluate potential interventions for reducing hearing loss-related fatigue. PMID:27355763

  11. Global, regional, and national disease burden estimates of acute lower respiratory infections due to respiratory syncytial virus in young children in 2015: a systematic review and modelling study.

    PubMed

    Shi, Ting; McAllister, David A; O'Brien, Katherine L; Simoes, Eric A F; Madhi, Shabir A; Gessner, Bradford D; Polack, Fernando P; Balsells, Evelyn; Acacio, Sozinho; Aguayo, Claudia; Alassani, Issifou; Ali, Asad; Antonio, Martin; Awasthi, Shally; Awori, Juliet O; Azziz-Baumgartner, Eduardo; Baggett, Henry C; Baillie, Vicky L; Balmaseda, Angel; Barahona, Alfredo; Basnet, Sudha; Bassat, Quique; Basualdo, Wilma; Bigogo, Godfrey; Bont, Louis; Breiman, Robert F; Brooks, W Abdullah; Broor, Shobha; Bruce, Nigel; Bruden, Dana; Buchy, Philippe; Campbell, Stuart; Carosone-Link, Phyllis; Chadha, Mandeep; Chipeta, James; Chou, Monidarin; Clara, Wilfrido; Cohen, Cheryl; de Cuellar, Elizabeth; Dang, Duc-Anh; Dash-Yandag, Budragchaagiin; Deloria-Knoll, Maria; Dherani, Mukesh; Eap, Tekchheng; Ebruke, Bernard E; Echavarria, Marcela; de Freitas Lázaro Emediato, Carla Cecília; Fasce, Rodrigo A; Feikin, Daniel R; Feng, Luzhao; Gentile, Angela; Gordon, Aubree; Goswami, Doli; Goyet, Sophie; Groome, Michelle; Halasa, Natasha; Hirve, Siddhivinayak; Homaira, Nusrat; Howie, Stephen R C; Jara, Jorge; Jroundi, Imane; Kartasasmita, Cissy B; Khuri-Bulos, Najwa; Kotloff, Karen L; Krishnan, Anand; Libster, Romina; Lopez, Olga; Lucero, Marilla G; Lucion, Florencia; Lupisan, Socorro P; Marcone, Debora N; McCracken, John P; Mejia, Mario; Moisi, Jennifer C; Montgomery, Joel M; Moore, David P; Moraleda, Cinta; Moyes, Jocelyn; Munywoki, Patrick; Mutyara, Kuswandewi; Nicol, Mark P; Nokes, D James; Nymadawa, Pagbajabyn; da Costa Oliveira, Maria Tereza; Oshitani, Histoshi; Pandey, Nitin; Paranhos-Baccalà, Gláucia; Phillips, Lia N; Picot, Valentina Sanchez; Rahman, Mustafizur; Rakoto-Andrianarivelo, Mala; Rasmussen, Zeba A; Rath, Barbara A; Robinson, Annick; Romero, Candice; Russomando, Graciela; Salimi, Vahid; Sawatwong, Pongpun; Scheltema, Nienke; Schweiger, Brunhilde; Scott, J Anthony G; Seidenberg, Phil; Shen, Kunling; Singleton, Rosalyn; Sotomayor, Viviana; Strand, Tor A; Sutanto, Agustinus; Sylla, Mariam; Tapia, Milagritos D; Thamthitiwat, Somsak; Thomas, Elizabeth D; Tokarz, Rafal; Turner, Claudia; Venter, Marietjie; Waicharoen, Sunthareeya; Wang, Jianwei; Watthanaworawit, Wanitda; Yoshida, Lay-Myint; Yu, Hongjie; Zar, Heather J; Campbell, Harry; Nair, Harish

    2017-09-02

    We have previously estimated that respiratory syncytial virus (RSV) was associated with 22% of all episodes of (severe) acute lower respiratory infection (ALRI) resulting in 55 000 to 199 000 deaths in children younger than 5 years in 2005. In the past 5 years, major research activity on RSV has yielded substantial new data from developing countries. With a considerably expanded dataset from a large international collaboration, we aimed to estimate the global incidence, hospital admission rate, and mortality from RSV-ALRI episodes in young children in 2015. We estimated the incidence and hospital admission rate of RSV-associated ALRI (RSV-ALRI) in children younger than 5 years stratified by age and World Bank income regions from a systematic review of studies published between Jan 1, 1995, and Dec 31, 2016, and unpublished data from 76 high quality population-based studies. We estimated the RSV-ALRI incidence for 132 developing countries using a risk factor-based model and 2015 population estimates. We estimated the in-hospital RSV-ALRI mortality by combining in-hospital case fatality ratios with hospital admission estimates from hospital-based (published and unpublished) studies. We also estimated overall RSV-ALRI mortality by identifying studies reporting monthly data for ALRI mortality in the community and RSV activity. We estimated that globally in 2015, 33·1 million (uncertainty range [UR] 21·6-50·3) episodes of RSV-ALRI, resulted in about 3·2 million (2·7-3·8) hospital admissions, and 59 600 (48 000-74 500) in-hospital deaths in children younger than 5 years. In children younger than 6 months, 1·4 million (UR 1·2-1·7) hospital admissions, and 27 300 (UR 20 700-36 200) in-hospital deaths were due to RSV-ALRI. We also estimated that the overall RSV-ALRI mortality could be as high as 118 200 (UR 94 600-149 400). Incidence and mortality varied substantially from year to year in any given population. Globally, RSV is a common cause

  12. The Effects of Hot Corrosion Pits on the Fatigue Resistance of a Disk Superalloy

    NASA Astrophysics Data System (ADS)

    Gabb, Timothy P.; Telesman, Jack; Hazel, Brian; Mourer, David P.

    2010-02-01

    The effects of hot corrosion pits on low-cycle fatigue life and failure modes of the disk superalloy ME3 were investigated. Low-cycle fatigue specimens were subjected to hot corrosion exposures producing pits, then tested at low and high temperatures. Fatigue lives and failure initiation points were compared to those of specimens without corrosion pits. Several tests were interrupted to estimate the fraction of fatigue life that fatigue cracks initiated at pits. Corrosion pits significantly reduced fatigue life by 60 to 98%. Fatigue cracks initiated at a very small fraction of life for high-temperature tests, but initiated at higher fractions in tests at low temperature. Critical pit sizes required to promote fatigue cracking were estimated based on measurements of pits initiating cracks on fracture surfaces.

  13. The Effects of Hot Corrosion Pits on the Fatigue Resistance of a Disk Superalloy

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Telesman, Jack; Hazel, Brian; Mourer, David P.

    2009-01-01

    The effects of hot corrosion pits on low cycle fatigue life and failure modes of the disk superalloy ME3 were investigated. Low cycle fatigue specimens were subjected to hot corrosion exposures producing pits, then tested at low and high temperatures. Fatigue lives and failure initiation points were compared to those of specimens without corrosion pits. Several tests were interrupted to estimate the fraction of fatigue life that fatigue cracks initiated at pits. Corrosion pits significantly reduced fatigue life by 60 to 98 percent. Fatigue cracks initiated at a very small fraction of life for high temperature tests, but initiated at higher fractions in tests at low temperature. Critical pit sizes required to promote fatigue cracking were estimated, based on measurements of pits initiating cracks on fracture surfaces.

  14. Dynamic Fatigue of ULE Glass

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Nettles, Alan T.; Brantley, Lott W. (Technical Monitor)

    2001-01-01

    Ultra Low Expansion (ULE) glass is used in a number of applications which require a low thermal expansion coefficient. One such application is telescope mirror elements. An allowable stress can be calculated for this material based upon modulus of rupture data; however, this does not take into account the problem of delayed failure. Delayed failure, due to stress corrosion can significantly shorten the lifetime of a glass article. Knowledge of the factors governing the rate of subcritical flaw growth in a given environment enables the development of relations between lifetime, applied stress and failure probability for the material under study. Dynamic fatigue is one method of obtaining the necessary information to develop these relationships. In this study, the dynamic fatigue method was used to construct time-to-failure diagrams for both 230/270 ground and optically polished samples. The grinding and polishing process reduces the surface flaw size and subsurface damage, and relieves residual stress by removing materials with successively smaller grinding media. This resulted in an increase in the strength of the optic during the grinding and polishing sequence. There was also an increase in the lifetime due to grinding and polishing. It was found that using the fatigue parameters determined from the 230/270 grit surface are not significantly different from the optically polished values. Although the lower bound of the polished samples is more conservative, neither time-to-failure curves lie beyond the upper or lower bound of the confidence limits. Therefore, designers preferring conservative limits could use samples without residual stress present (polished samples) to determine the fatigue parameters and inert Weibull parameters from samples with the service condition surface, to determine time-to-failure of the optical element.

  15. Velocity-specific fatigue: quantifying fatigue during variable velocity cycling.

    PubMed

    Gardner, A Scott; Martin, David T; Jenkins, David G; Dyer, Iain; Van Eiden, Jan; Barras, Martin; Martin, James C

    2009-04-01

    Previous investigators have quantified fatigue during short maximal cycling trials ( approximately 30 s) by calculating a fatigue index. Other investigators have reported a curvilinear power-pedaling rate relationship during short fatigue-free maximal cycling trials (<6 s). During maximal trials, pedaling rates may change with fatigue. Quantification of fatigue using fatigue index is therefore complicated by the power-pedaling rate relationship. The purpose of this study was to quantify fatigue while accounting for the effects of pedaling rate on power. Power and pedaling rate were recorded during Union Cycliste Internationale sanctioned 200-m time trials by eight male (height = 181.5 +/- 4.3 cm, mass = 87.0 +/- 8.0 kg) world-class sprint cyclists with SRM power meters and fixed-gear track bicycles. Data from the initial portion of maximal acceleration were used to establish maximal power-pedaling rate relationships. Fatigue was quantified three ways: 1) traditional fatigue index, 2) fatigue index modified to account for the power-pedaling rate relationship (net fatigue index), and 3) work deficit, the difference between actual work done and work that might have been accomplished without fatigue. Fatigue index (55.4% +/- 6.4%) was significantly greater than net fatigue index (41.0% +/- 7.9%, P < 0.001), indicating that the power-pedaling rate relationship accounted for 14.3% +/- 7% of the traditional fatigue index value. Work deficit (23.3% +/- 6%) was significantly less than either measure of fatigue (P < 0.001). Net fatigue index and work deficit account for the power-pedaling rate relation and therefore more precisely quantify fatigue during variable velocity cycling. These measures can be used to compare fatigue during different fatigue protocols, including world-class sprint cycling competition. Precise quantification of fatigue during elite cycling competition may improve evaluation of training status, gear ratio selection, and fatigue resistance.

  16. Aerodynamic Heating and Fatigue

    NASA Technical Reports Server (NTRS)

    Kroll, Wilhelmina D.

    1959-01-01

    A review of the physical condition's under which future airplanes will operate has been made and the necessity for considering fatigue in the design has been established. A survey of the literature shows what phases of elevated-temperature fatigue have been investigated. Other studies that would yield data of particular interest to the designer of aircraft structures are indicated.

  17. Estimating the burden of acute gastrointestinal illness due to Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus associated with private wells and small water systems in Canada.

    PubMed

    Murphy, H M; Thomas, M K; Schmidt, P J; Medeiros, D T; McFADYEN, S; Pintar, K D M

    2016-05-01

    Waterborne illness related to the consumption of contaminated or inadequately treated water is a global public health concern. Although the magnitude of drinking water-related illnesses in developed countries is lower than that observed in developing regions of the world, drinking water is still responsible for a proportion of all cases of acute gastrointestinal illness (AGI) in Canada. The estimated burden of endemic AGI in Canada is 20·5 million cases annually - this estimate accounts for under-reporting and under-diagnosis. About 4 million of these cases are domestically acquired and foodborne, yet the proportion of waterborne cases is unknown. There is evidence that individuals served by private systems and small community systems may be more at risk of waterborne illness than those served by municipal drinking water systems in Canada. However, little is known regarding the contribution of these systems to the overall drinking water-related AGI burden in Canada. Private water supplies serve an estimated 12% of the Canadian population, or ~4·1 million people. An estimated 1·4 million (4·1%) people in Canada are served by small groundwater (2·6%) and surface water (1·5%) supplies. The objective of this research is to estimate the number of AGI cases attributable to water consumption from these supplies in Canada using a quantitative microbial risk assessment (QMRA) approach. This provides a framework for others to develop burden of waterborne illness estimates for small water supplies. A multi-pathogen QMRA of Giardia, Cryptosporidium, Campylobacter, E. coli O157 and norovirus, chosen as index waterborne pathogens, for various source water and treatment combinations was performed. It is estimated that 103 230 AGI cases per year are due to the presence of these five pathogens in drinking water from private and small community water systems in Canada. In addition to providing a mechanism to assess the potential burden of AGI attributed to small systems and

  18. Experimental estimation of tungsten impurity sputtering due to Type I ELMs in JET-ITER-like wall using pedestal electron cyclotron emission and target Langmuir probe measurements

    NASA Astrophysics Data System (ADS)

    Guillemaut, C.; Jardin, A.; Horacek, J.; Borodkina, I.; Autricque, A.; Arnoux, G.; Boom, J.; Brezinsek, S.; Coenen, J. W.; De La Luna, E.; Devaux, S.; Eich, T.; Harting, D.; Kirschner, A.; Lipschultz, B.; Matthews, G. F.; Meigs, A.; Moulton, D.; O'Mullane, M.; Stamp, M.; contributors, JET

    2016-02-01

    The ITER baseline scenario, with 500 MW of DT fusion power and Q = 10, will rely on a Type I ELMy H-mode and will be achieved with a tungsten (W) divertor. W atoms sputtered from divertor targets during mitigated ELMs are expected to be the dominant source in ITER. W impurity concentration in the plasma core can dramatically degrade its performance and lead to potentially damaging disruptions. Understanding the physics of the target W source due to sputtering during ELMs and inter-ELMs is important and can be helped by experimental measurements with improved precision. It has been established that the ELMy target ion impact energy has a simple linear dependence with the pedestal electron temperature measured by Electron Cyclotron Emission (ECE). It has also been shown that Langmuir Probes (LP) ion flux measurements are reliable during ELMs due to the surprisingly low electron temperature. Therefore, in this paper, LP and ECE measurements in JET-ITER-Like-Wall (ILW) unseeded Type I ELMy H-mode experiments have been used to estimate the W sputtering flux from divertor targets in ELM and inter-ELM conditions. Comparison with similar estimates using W I spectroscopy measurements shows a reasonable agreement for the ELM and inter-ELM W source. The main advantage of the method involving LP measurements is the very high time resolution of the diagnostic (˜10 μs) allowing very precise description of the W sputtering source during ELMs.

  19. High temperature tension-compression fatigue behavior of a tungsten copper composite

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.; Gabb, Timothy P.

    1990-01-01

    The high temperature fatigue of a (O)12 tungsten fiber reinforced copper matrix composite was investigated. Specimens having fiber volume percentages of 10 and 36 were fatigued under fully-reversed, strain-controlled conditions at both 260 and 560 C. The fatigue life was found to be independent of fiber volume fraction because fatigue damage preferentially occurred in the matrix. Also, the composite fatigue lives were shorter at 560 C as compared to 260 C due to changes in mode of matrix failure. On a total strain basis, the fatigue life of the composite at 560 C was the same as the life of unreinforced copper, indicating that the presence of the fibers did not degrade the fatigue resistance of the copper matrix in this composite system. Comparison of strain-controlled fatigue data to previously-generated load-controlled data revealed that the strain-controlled fatigue lives were longer because of mean strain and mean stress effects.

  20. Fracture and fatigue in osteocytes.

    PubMed

    Mulargia, Simone; Dooley, Clodagh; Cristofolini, Luca; Taylor, David

    2014-11-01

    Fatigue is a common mode of mechanical failure which occurs when a material is subjected to repeated cycles at a strain level less than that needed for monotonic fracture. Fatigue has been observed and measured in many different materials but, until recently, not in cells. We devised a novel experiment which allowed us to create both monotonic failure and fatigue in the cellular processes of osteocytes within samples of bone (Dooley et al., European Cells and Materials 2014). In the present paper, we describe the results of further experiments and a computer simulation, which has allowed us to estimate the strain history of each sample tested and thus present, for the first time, strain/life data for cells. Failure occurred during the first cycle at strains of 0.1-0.2; at lower strains failure occurred after a number of cycles which depended inversely on the applied strain range. Scatter in the strain/life data was reduced when we allowed for the effects of mean stress using the Smith-Watson-Topper parameter. We confirmed that aspects of our experimental method (the types of microcrack used and the testing of fresh versus frozen samples) did not affect the results. Such information is useful because many cell types, including the cellular processes of osteocytes, experience cyclic strain in vivo.

  1. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1984-01-01

    A three year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for non-proportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved undertanding were through several critical non-proportional loading experiments. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C.

  2. Atlas of fatigue curves

    SciTech Connect

    Boyer, H.E.

    1986-01-01

    This book contains more than 500 fatigue curves for industrial ferrous and nonferrous alloys. It also includes a thorough explanation of fatigue testing and interpretation of test results. Each curve is presented independently and includes an explanation of its particular importance. The curves are titled by standard industrial designations (AISI, CDA, AA, etc.) of the metals, and a complete reference is given to the original source to facilitate further research. The collection includes standard S-N curves, curves showing effect of surface hardening on fatigue strength, crack growth-rate curves, curves comparing the fatigue strengths of various alloys, effect of variables (i,e, temperature, humidity, frequency, aging, environment, etc.) and much, much more. This one volume consolidates the fatigue data in a single source.

  3. Estimates of Nitrogen, Phosphorus, Biochemical Oxygen Demand, and Fecal Coliforms Entering the Environment Due to Inadequate Sanitation Treatment Technologies in 108 Low and Middle Income Countries.

    PubMed

    Fuhrmeister, Erica R; Schwab, Kellogg J; Julian, Timothy R

    2015-10-06

    Understanding the excretion and treatment of human waste (feces and urine) in low and middle income countries (LMICs) is necessary to design appropriate waste management strategies. However, excretion and treatment are often difficult to quantify due to decentralization of excreta management. We address this gap by developing a mechanistic, stochastic model to characterize phosphorus, nitrogen, biochemical oxygen demand (BOD), and fecal coliform pollution from human excreta for 108 LMICs. The model estimates excretion and treatment given three scenarios: (1) use of existing sanitation systems, (2) use of World Health Organization-defined "improved sanitation", and (3) use of best available technologies. Our model estimates that more than 10(9) kg/yr each of phosphorus, nitrogen and BOD are produced. Of this, 22(19-27)%, 11(7-15)%, 17(10-23)%, and 35 (23-47)% (mean and 95% range) BOD, nitrogen, phosphorus, and fecal coliforms, respectively, are removed by existing sanitation systems. Our model estimates that upgrading to "improved sanitation" increases mean removal slightly to between 17 and 53%. Under the best available technology scenario, only approximately 60-80% of pollutants are treated. To reduce impact of nutrient and microbial pollution on human and environmental health, improvements in both access to adequate sanitation and sanitation treatment efficiency are needed.

  4. [Estimation of the population attributable fraction due to obesity in hospital admissions for flu valued according to Body Mass Index (BMI) and CUN-BAE].

    PubMed

    Dávila-Batista, V; Carriedo, D; Díez, F; Pueyo Bastida, A; Martínez Durán, B; Martin, V

    2017-05-11

    The obesity pandemic together with the influenza pandemic could lead to a significant burden of disease. The body mass index (BMI) does not discriminate obesity appropriately. The CUN-BAE has recently been used as an estimate of body fatness for Caucasians, including BMI, gender, and age. The aim of this study is to assess the population attributable fraction of hospital admissions due to influenza, due to the body fatness measured with the BMI, and the CUN-BAE. A multicentre study was conducted using matched case-controls. Cases were hospital admissions with the influenza confirmed by the RT-PCR method between 2009 and 2011. The risk of hospital admission and the population attribuible fraction were calculated using the BMI or the CUN-BAE for each adiposity category in a conditional logical regression analysis adjusted for confounding variables. The analyzes were estimated in the total sample, in unvaccinated people, and those less than 65 years-old. A total of 472 hospitalised cases and 493 controls were included in the study. Compared to normal weight, the aOR of influenza hospital admissions increases with each level of BMI (aOR=1.26; 2.06 and 11.64) and CUN-BAE (aOR=2.78; 4.29; 5.43 and 15.18). The population attributable fraction of influenza admissions using CUN-BAE is 3 times higher than that estimated with BMI (0,72 vs. 0,27), with the differences found being similar the non-vaccinated and under 65 year-olds. The BMI could be underestimating the burden of disease attributable to obesity in individuals hospitalised with influenza. There needs to be an appropriate assessment of the impact of obesity and vaccine recommendation criteria. Copyright © 2017 Sociedad Española de Médicos de Atención Primaria (SEMERGEN). Publicado por Elsevier España, S.L.U. All rights reserved.

  5. Fatigue in soccer: a brief review.

    PubMed

    Mohr, Magni; Krustrup, Peter; Bangsbo, Jens

    2005-06-01

    This review describes when fatigue may develop during soccer games and the potential physiological mechanisms that cause fatigue in soccer. According to time-motion analyses and performance measures during match-play, fatigue or reduced performance seems to occur at three different stages in the game: (1) after short-term intense periods in both halves; (2) in the initial phase of the second half; and (3) towards the end of the game. Temporary fatigue after periods of intense exercise in the game does not appear to be linked directly to muscle glycogen concentration, lactate accumulation, acidity or the breakdown of creatine phosphate. Instead, it may be related to disturbances in muscle ion homeostasis and an impaired excitation of the sarcolemma. Soccer players' ability to perform maximally is inhibited in the initial phase of the second half, which may be due to lower muscle temperatures compared with the end of the first half. Thus, when players perform low-intensity activities in the interval between the two halves, both muscle temperature and performance are preserved. Several studies have shown that fatigue sets in towards the end of a game, which may be caused by low glycogen concentrations in a considerable number of individual muscle fibres. In a hot and humid environment, dehydration and a reduced cerebral function may also contribute to the deterioration in performance. In conclusion, fatigue or impaired performance in soccer occurs during various phases in a game, and different physiological mechanisms appear to operate in different periods of a game.

  6. Fatigue countermeasures in aviation.

    PubMed

    Caldwell, John A; Mallis, Melissa M; Caldwell, J Lynn; Paul, Michel A; Miller, James C; Neri, David F

    2009-01-01

    Pilot fatigue is a significant problem in modern aviation operations, largely because of the unpredictable work hours, long duty periods, circadian disruptions, and insufficient sleep that are commonplace in both civilian and military flight operations. The full impact of fatigue is often underappreciated, but many of its deleterious effects have long been known. Compared to people who are well-rested, people who are sleep deprived think and move more slowly, make more mistakes, and have memory difficulties. These negative effects may and do lead to aviation errors and accidents. In the 1930s, flight time limitations, suggested layover durations, and aircrew sleep recommendations were developed in an attempt to mitigate aircrew fatigue. Unfortunately, there have been few changes to aircrew scheduling provisions and flight time limitations since the time they were first introduced, despite evidence that updates are needed. Although the scientific understanding of fatigue, sleep, shift work, and circadian physiology has advanced significantly over the past several decades, current regulations and industry practices have in large part failed to adequately incorporate the new knowledge. Thus, the problem of pilot fatigue has steadily increased along with fatigue-related concerns over air safety. Accident statistics, reports from pilots themselves, and operational flight studies all show that fatigue is a growing concern within aviation operations. This position paper reviews the relevant scientific literature, summarizes applicable U.S. civilian and military flight regulations, evaluates various in-flight and pre-/postflight fatigue countermeasures, and describes emerging technologies for detecting and countering fatigue. Following the discussion of each major issue, position statements address ways to deal with fatigue in specific contexts with the goal of using current scientific knowledge to update policy and provide tools and techniques for improving air safety.

  7. Fatigue associated with prolonged graded running.

    PubMed

    Giandolini, Marlene; Vernillo, Gianluca; Samozino, Pierre; Horvais, Nicolas; Edwards, W Brent; Morin, Jean-Benoît; Millet, Guillaume Y

    2016-10-01

    Scientific experiments on running mainly consider level running. However, the magnitude and etiology of fatigue depend on the exercise under consideration, particularly the predominant type of contraction, which differs between level, uphill, and downhill running. The purpose of this review is to comprehensively summarize the neurophysiological and biomechanical changes due to fatigue in graded running. When comparing prolonged hilly running (i.e., a combination of uphill and downhill running) to level running, it is found that (1) the general shape of the neuromuscular fatigue-exercise duration curve as well as the etiology of fatigue in knee extensor and plantar flexor muscles are similar and (2) the biomechanical consequences are also relatively comparable, suggesting that duration rather than elevation changes affects neuromuscular function and running patterns. However, 'pure' uphill or downhill running has several fatigue-related intrinsic features compared with the level running. Downhill running induces severe lower limb tissue damage, indirectly evidenced by massive increases in plasma creatine kinase/myoglobin concentration or inflammatory markers. In addition, low-frequency fatigue (i.e., excitation-contraction coupling failure) is systematically observed after downhill running, although it has also been found in high-intensity uphill running for different reasons. Indeed, low-frequency fatigue in downhill running is attributed to mechanical stress at the interface sarcoplasmic reticulum/T-tubule, while the inorganic phosphate accumulation probably plays a central role in intense uphill running. Other fatigue-related specificities of graded running such as strategies to minimize the deleterious effects of downhill running on muscle function, the difference of energy cost versus heat storage or muscle activity changes in downhill, level, and uphill running are also discussed.

  8. Maintenance of genetic variation in human personality: testing evolutionary models by estimating heritability due to common causal variants and investigating the effect of distant inbreeding.

    PubMed

    Verweij, Karin J H; Yang, Jian; Lahti, Jari; Veijola, Juha; Hintsanen, Mirka; Pulkki-Råback, Laura; Heinonen, Kati; Pouta, Anneli; Pesonen, Anu-Katriina; Widen, Elisabeth; Taanila, Anja; Isohanni, Matti; Miettunen, Jouko; Palotie, Aarno; Penke, Lars; Service, Susan K; Heath, Andrew C; Montgomery, Grant W; Raitakari, Olli; Kähönen, Mika; Viikari, Jorma; Räikkönen, Katri; Eriksson, Johan G; Keltikangas-Järvinen, Liisa; Lehtimäki, Terho; Martin, Nicholas G; Järvelin, Marjo-Riitta; Visscher, Peter M; Keller, Matthew C; Zietsch, Brendan P

    2012-10-01

    Personality traits are basic dimensions of behavioral variation, and twin, family, and adoption studies show that around 30% of the between-individual variation is due to genetic variation. There is rapidly growing interest in understanding the evolutionary basis of this genetic variation. Several evolutionary mechanisms could explain how genetic variation is maintained in traits, and each of these makes predictions in terms of the relative contribution of rare and common genetic variants to personality variation, the magnitude of nonadditive genetic influences, and whether personality is affected by inbreeding. Using genome-wide single nucleotide polymorphism (SNP) data from > 8000 individuals, we estimated that little variation in the Cloninger personality dimensions (7.2% on average) is due to the combined effect of common, additive genetic variants across the genome, suggesting that most heritable variation in personality is due to rare variant effects and/or a combination of dominance and epistasis. Furthermore, higher levels of inbreeding were associated with less socially desirable personality trait levels in three of the four personality dimensions. These findings are consistent with genetic variation in personality traits having been maintained by mutation-selection balance.

  9. Maintenance of genetic variation in human personality: Testing evolutionary models by estimating heritability due to common causal variants and investigating the effect of distant inbreeding

    PubMed Central

    Verweij, Karin J.H.; Yang, Jian; Lahti, Jari; Veijola, Juha; Hintsanen, Mirka; Pulkki-Råback, Laura; Heinonen, Kati; Pouta, Anneli; Pesonen, Anu-Katriina; Widen, Elisabeth; Taanila, Anja; Isohanni, Matti; Miettunen, Jouko; Palotie, Aarno; Penke, Lars; Service, Susan K.; Heath, Andrew C.; Montgomery, Grant W.; Raitakari, Olli; Kähönen, Mika; Viikari, Jorma; Räikkönen, Katri; Eriksson, Johan G; Keltikangas-Järvinen, Liisa; Lehtimäki, Terho; Martin, Nicholas G.; Järvelin, Marjo-Riitta; Visscher, Peter M.; Keller, Matthew C.; Zietsch, Brendan P.

    2012-01-01

    Personality traits are basic dimensions of behavioural variation, and twin, family, and adoption studies show that around 30% of the between-individual variation is due to genetic variation. There is rapidly-growing interest in understanding the evolutionary basis of this genetic variation. Several evolutionary mechanisms could explain how genetic variation is maintained in traits, and each of these makes predictions in terms of the relative contribution of rare and common genetic variants to personality variation, the magnitude of nonadditive genetic influences, and whether personality is affected by inbreeding. Using genome-wide SNP data from >8,000 individuals, we estimated that little variation in the Cloninger personality dimensions (7.2% on average) is due to the combined effect of common, additive genetic variants across the genome, suggesting that most heritable variation in personality is due to rare variant effects and/or a combination of dominance and epistasis. Furthermore, higher levels of inbreeding were associated with less socially-desirable personality trait levels in three of the four personality dimensions. These findings are consistent with genetic variation in personality traits having been maintained by mutation-selection balance. PMID:23025612

  10. Multimodal tissue imaging: using coregistered optical tomography data to estimate tissue autofluorescence intensity change due to scattering and absorption by neoplastic epithelial cells.

    PubMed

    Pahlevaninezhad, Hamid; Cecic, Ivana; Lee, Anthony M D; Kyle, Alastair H; Lam, Stephen; MacAulay, Calum; Lane, Pierre M

    2013-10-01

    Autofluorescence (AF) imaging provides valuable information about the structural and chemical states of tissue that can be used for early cancer detection. Optical scattering and absorption of excitation and emission light by the epithelium can significantly affect observed tissue AF intensity. Determining the effect of epithelial attenuation on the AF intensity could lead to a more accurate interpretation of AF intensity. We propose to use optical coherence tomography coregistered with AF imaging to characterize the AF attenuation due to the epithelium. We present imaging results from three vital tissue models, each consisting of a three-dimensional tissue culture grown from one of three epithelial cell lines (HCT116, OVCAR8, and MCF7) and immobilized on a fluorescence substrate. The AF loss profiles in the tissue layer show two different regimes, each approximately linearly decreasing with thickness. For thin cell cultures (<300 μm), the AF signal changes as AF(t)/AF(0)=1-1.3t (t is the thickness in millimeter). For thick cell cultures (>400 μm), the AF loss profiles have different intercepts but similar slopes. The data presented here can be used to estimate AF loss due to a change in the epithelial layer thickness and potentially to reduce AF bronchoscopy false positives due to inflammation and non-neoplastic epithelial thickening.

  11. Interpolated twitches in fatiguing single mouse muscle fibres: implications for the assessment of central fatigue.

    PubMed

    Place, Nicolas; Yamada, Takashi; Bruton, Joseph D; Westerblad, Håkan

    2008-06-01

    An electrically evoked twitch during a maximal voluntary contraction (twitch interpolation) is frequently used to assess central fatigue. In this study we used intact single muscle fibres to determine if intramuscular mechanisms could affect the force increase with the twitch interpolation technique. Intact single fibres from flexor digitorum brevis of NMRI mice were dissected and mounted in a chamber equipped with a force transducer. Free myoplasmic [Ca2+] ([Ca2+](i)) was measured with the fluorescent Ca2+ indicator indo-1. Seven fibres were fatigued with repeated 70 Hz tetani until 40% initial force with an interpolated pulse evoked every fifth tetanus. Results showed that the force generated by the interpolated twitch increased throughout fatigue, being 9 +/- 1% of tetanic force at the start and 19 +/- 1% at the end (P < 0.001). This was not due to a larger increase in [Ca2+](i) induced by the interpolated twitch during fatigue but rather to the fact that the force-[Ca2+](i) relationship is sigmoidal and fibres entered a steeper part of the relationship during fatigue. In another set of experiments, we observed that repeated tetani evoked at 150 Hz resulted in more rapid fatigue development than at 70 Hz and there was a decrease in force ('sag') during contractions, which was not observed at 70 Hz. In conclusion, the extent of central fatigue is difficult to assess and it may be overestimated when using the twitch interpolation technique.

  12. Memory for Fatigue in Chronic Fatigue Syndrome: Relationships to Fatigue Variability, Catastrophizing, and Negative Affect

    PubMed Central

    Sohl, Stephanie J.; Friedberg, Fred

    2008-01-01

    Fatigue in chronic fatigue syndrome (CFS) is usually assessed with retrospective measures rather than real-time momentary symptom assessments. In this study, the authors hypothesized that in participants with CFS, discrepancies between recalled and momentary fatigue would be related to catastrophizing, anxiety, and depression and to variability of momentary fatigue. They also expected that catastrophizing, anxiety, and depression would be associated with momentary fatigue. The authors asked 53 adults with CFS to carry electronic diaries for 3 weeks and record their experiences of momentary fatigue. The authors assessed participants' fatigue recall with weekly ratings and administered questionnaires for catastrophizing, depression, and anxiety. Recall discrepancy was significantly related to the variability of momentary fatigue. In addition, catastrophizing, depression, and momentary fatigue were all significantly related to recall discrepancy. Catastrophizing, depression, anxiety, and momentary negative affect were all significantly associated with momentary fatigue. The findings suggest that momentary fatigue in patients with CFS is related to modifiable psychological factors. PMID:18400687

  13. Fatigue, fracture, and life prediction criteria for composite materials in magnets

    SciTech Connect

    Wong, F.M.G.

    1990-06-01

    An explosively-bonded copper/Inconel 718/copper laminate conductor was proposed to withstand the severe face compression stresses in the central core of the Alcator C-MOD tokamak toroidal field (TF) magnet. Due to the severe duty of the TF magnet, it is critical that an accurate estimate of useful life be determined. As part of the effort to formulate an appropriate life prediction, fatigue crack growth experiments were performed on the laminate as well as its components. Metallographic evaluation of the laminate interface revealed many shear bands in the Inconel 718. Shear bands and shear band cracks were produced in the Inconel 718 as a result of the explosion bonding process. These shear bands were shown to have a detrimental effect on the crack growth behavior of the laminate, by significantly reducing the load carrying capability of the reinforcement layer and providing for easy crack propagation paths. Fatigue crack growth rate was found not only to be dependent on temperature but also on orientation. Fatigue cracks grew faster in directions which contained shear bands in the plane of the propagating crack. Fractography showed crack advancement by fatigue cracking in the Inconel 718 and ductile tearing of the copper at the interface. However, further away from the interfaces, the copper exhibited fatigue striations indicating that cracks were now propagating by fatigue. Laminate life prediction results showed a strong dependence on shear band orientation, and exhibited little variation between room temperature and 77{degree}K. Predicted life of this laminate was lower when the crack propagation was along a shear band than when crack propagation was across the shear bands. Shear bands appear to have a dominating effect on crack growth behavior.

  14. Jumplike fatigue crack growth in compressor blades

    NASA Astrophysics Data System (ADS)

    Limar', L. V.; Demina, Yu. A.; Botvina, L. R.

    2014-04-01

    It is shown that power relations between the two main fractographic characteristics of fracture surfaces forming during jumplike fatigue crack growth, namely, the crack depth and the corresponding crack front length, can be used to estimate the fracture stress during vibration tests of the compressor blades of an aviation gas turbine engine, which are made of VT3-1 titanium alloy.

  15. 14 CFR 23.573 - Damage tolerance and fatigue evaluation of structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    .... (2) The growth rate or no-growth of damage that may occur from fatigue, corrosion, manufacturing... component, subcomponent, element, or coupon tests must be done to establish the fatigue scatter factor and... determination of the probable locations and modes of damage due to fatigue, corrosion, or accidental...

  16. 14 CFR 23.573 - Damage tolerance and fatigue evaluation of structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    .... (2) The growth rate or no-growth of damage that may occur from fatigue, corrosion, manufacturing... component, subcomponent, element, or coupon tests must be done to establish the fatigue scatter factor and... determination of the probable locations and modes of damage due to fatigue, corrosion, or accidental...

  17. 14 CFR 23.573 - Damage tolerance and fatigue evaluation of structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    .... (2) The growth rate or no-growth of damage that may occur from fatigue, corrosion, manufacturing... component, subcomponent, element, or coupon tests must be done to establish the fatigue scatter factor and... determination of the probable locations and modes of damage due to fatigue, corrosion, or accidental...

  18. 14 CFR 23.573 - Damage tolerance and fatigue evaluation of structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    .... (2) The growth rate or no-growth of damage that may occur from fatigue, corrosion, manufacturing... component, subcomponent, element, or coupon tests must be done to establish the fatigue scatter factor and... determination of the probable locations and modes of damage due to fatigue, corrosion, or accidental...

  19. 14 CFR 23.573 - Damage tolerance and fatigue evaluation of structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    .... (2) The growth rate or no-growth of damage that may occur from fatigue, corrosion, manufacturing... component, subcomponent, element, or coupon tests must be done to establish the fatigue scatter factor and... determination of the probable locations and modes of damage due to fatigue, corrosion, or accidental...

  20. Effect of heat treatment on fatigue resistance of spring steel 60Si2CrVAT

    NASA Astrophysics Data System (ADS)

    Shiyong, Liu; Deyi, Liu; Shicheng, Liu

    2010-07-01

    Fatigue resistance of heat-treated spring steel 60Si2CrVAT due to three-point bending with step growth in the load is studied. The microstructure of the steel and fatigue fracture surfaces are analyzed by the method of scanning electron microscopy. The possibilities of raising the fatigue resistance of springs used in high-speed freight bogies are considered.

  1. Altered resting brain connectivity in persistent cancer related fatigue

    PubMed Central

    Hampson, Johnson P.; Zick, Suzanna M.; Khabir, Tohfa; Wright, Benjamin D.; Harris, Richard E.

    2015-01-01

    There is an estimated 3 million women in the US living as breast cancer survivors and persistent cancer related fatigue (PCRF) disrupts the lives of an estimated 30% of these women. PCRF is associated with decreased quality of life, decreased sleep quality, impaired cognition and depression. The mechanisms of cancer related fatigue are not well understood; however, preliminary findings indicate dysfunctional activity in the brain as a potential factor. Here we investigate the relationship between PCRF on intrinsic resting state connectivity in this population. Twenty-three age matched breast cancer survivors (15 fatigued and 8 non-fatigued) who completed all cancer-related treatments at least 12 weeks prior to the study, were recruited to undergo functional connectivity magnetic resonance imaging (fcMRI). Intrinsic resting state networks were examined with both seed based and independent component analysis methods. Comparisons of brain connectivity patterns between groups as well as correlations with self-reported fatigue symptoms were performed. Fatigued patients displayed greater left inferior parietal lobule to superior frontal gyrus connectivity as compared to non-fatigued patients (P < 0.05 FDR corrected). This enhanced connectivity was associated with increased physical fatigue (P = 0.04, r = 0.52) and poor sleep quality (P = 0.04, r = 0.52) in the fatigued group. In contrast greater connectivity in the non-fatigued group was found between the right precuneus to the periaqueductal gray as well as the left IPL to subgenual cortex (P < 0.05 FDR corrected). Mental fatigue scores were associated with greater default mode network (DMN) connectivity to the superior frontal gyrus (P = 0.05 FDR corrected) among fatigued subjects (r = 0.82) and less connectivity in the non-fatigued group (r = −0.88). These findings indicate that there is enhanced intrinsic DMN connectivity to the frontal gyrus in breast cancer survivors with persistent fatigue. As

  2. Altered resting brain connectivity in persistent cancer related fatigue.

    PubMed

    Hampson, Johnson P; Zick, Suzanna M; Khabir, Tohfa; Wright, Benjamin D; Harris, Richard E

    2015-01-01

    There is an estimated 3 million women in the US living as breast cancer survivors and persistent cancer related fatigue (PCRF) disrupts the lives of an estimated 30% of these women. PCRF is associated with decreased quality of life, decreased sleep quality, impaired cognition and depression. The mechanisms of cancer related fatigue are not well understood; however, preliminary findings indicate dysfunctional activity in the brain as a potential factor. Here we investigate the relationship between PCRF on intrinsic resting state connectivity in this population. Twenty-three age matched breast cancer survivors (15 fatigued and 8 non-fatigued) who completed all cancer-related treatments at least 12 weeks prior to the study, were recruited to undergo functional connectivity magnetic resonance imaging (fcMRI). Intrinsic resting state networks were examined with both seed based and independent component analysis methods. Comparisons of brain connectivity patterns between groups as well as correlations with self-reported fatigue symptoms were performed. Fatigued patients displayed greater left inferior parietal lobule to superior frontal gyrus connectivity as compared to non-fatigued patients (P < 0.05 FDR corrected). This enhanced connectivity was associated with increased physical fatigue (P = 0.04, r = 0.52) and poor sleep quality (P = 0.04, r = 0.52) in the fatigued group. In contrast greater connectivity in the non-fatigued group was found between the right precuneus to the periaqueductal gray as well as the left IPL to subgenual cortex (P < 0.05 FDR corrected). Mental fatigue scores were associated with greater default mode network (DMN) connectivity to the superior frontal gyrus (P = 0.05 FDR corrected) among fatigued subjects (r = 0.82) and less connectivity in the non-fatigued group (r = -0.88). These findings indicate that there is enhanced intrinsic DMN connectivity to the frontal gyrus in breast cancer survivors with persistent fatigue. As

  3. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1985-01-01

    A 3 year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for nonproportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved understanding were through several critical nonproportional loading experiments. The direction of cracking observed on failed specimens was also recorded and used to guide the development of the theory. Cyclic deformation responses were permanently recorded digitally during each test. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C. In contrast to some other metals, loading path in nonproportional loading had little effect on fatigue lives. Strain rate had a small effect on fatigue lives at 649 C. Of the various correlating parameters the modified plastic work and octahedral shear stress were the most successful.

  4. Rethinking compassion fatigue.

    PubMed

    Gerard, Nathan

    2017-05-15

    Purpose The purpose of this paper is to argue for a revision of the concept of compassion fatigue in light of both its history and psychodynamics. Design/methodology/approach This paper calls into question conventional interpretations of compassion fatigue and the assumptions underlying them. As an alternative, a psychoanalytic interpretation is offered that sheds light on the phenomenon's unconscious and organizational dynamics. This interpretation also aligns with the concept's historical use in media and politics. Findings In contrast to the assumption that compassion fatigue arises from too much compassion, historical use of the term suggests just the opposite: compassion fatigue is the result of too little compassion. Healthcare literature on compassion fatigue has not only failed to account for this opposing view, but also the underlying psychodynamics at play. By attending to these neglected dimensions, healthcare scholars and practitioners can gain new insights into compassion fatigue and devise more sustainable interventions. Originality/value This paper reveals hidden dimensions to compassion fatigue that call into question conventional interpretations and offer novel perspectives on a core concern of healthcare work.

  5. Mechanisms of peripheral fatigue.

    PubMed

    Kirkendall, D T

    1990-08-01

    Fatigue can be defined as the failure to maintain an expected power output. This is often an antecedent to some sports-related injury. It is important for those involved in physical performance to be familiar with the variety of mechanisms which can lead to fatigue. All too often, a single factor is described as the cause of fatigue when actually fatigue may be a combination of factors that contribute to the sequence of events that results in decreased performance. It may be suggested that every step in the chain of events that leads to voluntary contraction of skeletal muscle could be a culprit in fatigue. Peripheral sites and processes include the motor neuron, neuromuscular junction, sarcolemmal membrane, excitation-contraction coupling, accumulation of metabolites, or depletion of fuels. Physical training is frequently designed to delay the onset of fatigue. The actual mechanism(s) add to the specificity concept, that is, a "specificity of fatigue". To the performer, the end result is the same, the inability to maintain his or her expected level of performance or power output.

  6. SU-E-J-164: Estimation of DVH Variation for PTV Due to Interfraction Organ Motion in Prostate VMAT Using Gaussian Error Function

    SciTech Connect

    Lewis, C; Jiang, R; Chow, J

    2015-06-15

    Purpose: We developed a method to predict the change of DVH for PTV due to interfraction organ motion in prostate VMAT without repeating the CT scan and treatment planning. The method is based on a pre-calculated patient database with DVH curves of PTV modelled by the Gaussian error function (GEF). Methods: For a group of 30 patients with different prostate sizes, their VMAT plans were recalculated by shifting their PTVs 1 cm with 10 increments in the anterior-posterior, left-right and superior-inferior directions. The DVH curve of PTV in each replan was then fitted by the GEF to determine parameters describing the shape of curve. Information of parameters, varying with the DVH change due to prostate motion for different prostate sizes, was analyzed and stored in a database of a program written by MATLAB. Results: To predict a new DVH for PTV due to prostate interfraction motion, prostate size and shift distance with direction were input to the program. Parameters modelling the DVH for PTV were determined based on the pre-calculated patient dataset. From the new parameters, DVH curves of PTVs with and without considering the prostate motion were plotted for comparison. The program was verified with different prostate cases involving interfraction prostate shifts and replans. Conclusion: Variation of DVH for PTV in prostate VMAT can be predicted using a pre-calculated patient database with DVH curve fitting. The computing time is fast because CT rescan and replan are not required. This quick DVH estimation can help radiation staff to determine if the changed PTV coverage due to prostate shift is tolerable in the treatment. However, it should be noted that the program can only consider prostate interfraction motions along three axes, and is restricted to prostate VMAT plan using the same plan script in the treatment planning system.

  7. A new method for estimation of TEC from GNSS receivers during multiple cycle slips and data loss due to ionospheric irregularities

    NASA Astrophysics Data System (ADS)

    Dashora, Nirvikar

    2012-07-01

    Estimation of total electron content (TEC) is a must to utilize the GNSS signal for ionospheric research. The estimation of absolute ionospheric TEC from raw GNSS data itself is a lengthy and complex task and requires knowledge of sophisticated computer programming skills, satellite orbital geometry and many other aspects like GNSS signal structure, satellite and receiver specific information etc. Not many software are available that automatize the complex task of cycle slip detection and correction. The estimation of satellite and receiver biases is one more step left before getting true TEC. In equatorial and low latitudes, where the nighttime ionospheric irregularities are oft-occurring phenomena, estimation of TEC becomes a challenge. This is because, during TEC depletions and scintillations, the loss of lock in the receiver results either in data loss or sharp gradients in the recorded delays; more often for phase than code. Raw data in form of accumulated phase in radians and total code-range in meters show random occurrences of multiple cycle slips and data loss of several minutes in the data file. Thus, such phase and code data has to be corrected first before processing it to obtain TEC. Almost all available software/algorithms suggest flagging such data for no further use. Hence, TEC cannot be estimated during multiple cycle slip events within few minutes from raw GPS data. But, for ionospheric research the time of occurrence, evolution and drift of depletions are very useful. This paper details a complete new software for pre-processing the raw RINEX (receiver independent exchange format) data and retrieval of TEC using code and carrier-phase measurements from an stand alone dual frequency GPS receiver. We use modified and new sets of algorithms a GNSS receiver. It is significant to note that we are able to retrieves almost all the the corrupted TEC data points due to random multiple cycle slip events which are oft-occurring phenomena during ESF in

  8. Too generous to a fault? Is reliable earthquake safety a lost art? Errors in expected human losses due to incorrect seismic hazard estimates

    NASA Astrophysics Data System (ADS)

    Bela, James

    2014-11-01

    "One is well advised, when traveling to a new territory, to take a good map and then to check the map with the actual territory during the journey." In just such a reality check, Global Seismic Hazard Assessment Program (GSHAP) maps (prepared using PSHA) portrayed a "low seismic hazard," which was then also assumed to be the "risk to which the populations were exposed." But time-after-time-after-time the actual earthquakes that occurred were not only "surprises" (many times larger than those implied on the maps), but they were often near the maximum potential size (Maximum Credible Earthquake or MCE) that geologically could occur. Given these "errors in expected human losses due to incorrect seismic hazard estimates" revealed globally in these past performances of the GSHAP maps (> 700,000 deaths 2001-2011), we need to ask not only: "Is reliable earthquake safety a lost art?" but also: "Who and what were the `Raiders of the Lost Art?' "

  9. Development of fatigue loading spectra

    SciTech Connect

    Potter, J.M.; Watanabe, R.T.

    1989-01-01

    The present work on fatigue-loading spectra encompasses the current status of standardized stress-time histories, European approaches to standard loading spectrum development, transport aircraft airframe fatigue test spectra, the TURBISTAN fatigue-loading standard for fighter-aircraft engine disks, an automated procedure for the creation of flight-by-flight spectra, and the development of a wave-action standard history for fatigue testing relevant to tubular structures in the North Sea. Also treated is the use of the TURBISTAN mission spectra to evaluate fatigue crack growth in a rotating disk, fatigue-spectra development for airborne stores, a simplified analysis of fatigue-loading spectra, variable-amplitude load models for fatigue-damage crack growth, the tracking time service histories for multiaxis fatigue problems, and the compilation of procedures for fatigue crack propagation testing under complex load sequences.

  10. Nondestructive characterization of fatigue damage with thermography

    NASA Astrophysics Data System (ADS)

    Roesner, Henrik; Sathish, Shamachary; Meyendorf, Norbert

    2001-08-01

    A thermal imaging NDE method has been developed for nondestructive characterization of early stages of fatigue damage. The method is based on evaluation of the thermal effects induced in a material by a short-term mechanical loading. The mechanical loading causes in addition to thermoelastic temperature change, an increase due to heat dissipation that depends upon the microstructure of the material in a characteristic manner. The origin of this heat dissipation is the mechanical damping process. Utilizing the initial temperature rise due to a short-term mechanical loading, the dissipated energy per cycle was evaluated as a thermal parameter. This new thermal NDE parameter allows a quantitative characterization of the mechanical hysteresis, without the need for calibration to eliminate influences of thermal boundary conditions. The measurement of the thermal NDE parameters has been performed on Ti-6Al-4V dog-bone specimens, fatigued in low cycle fatigue (LCF) as well as in high cycle fatigue (HCF) experiments. Characteristic dependence of the NDE parameters on the already accumulated fatigue damage has been observed. The advantage of the thermal method is the applicability to components under service conditions because of simplicity, rapid measurements (a few seconds) and the ability of locally resolved evaluations.

  11. Estimation of extreme sea levels along the Bangladesh coast due to storm surge and sea level rise using EEMD and EVA

    NASA Astrophysics Data System (ADS)

    Lee, Han Soo

    2013-09-01

    Extreme sea levels due to storm surge and future sea level rise (SLR) in the year 2050 are estimated using ensemble empirical mode decomposition (EEMD) and extreme value analysis (EVA) based on long-term sea level records from Hiron Point (HP) on the coast of western Bangladesh. EEMD is an adaptive method that can detrend the nonlinear trend and separate the tidal motions from the original sea level records to reconstruct storm surge levels at HP. The reconstructed storm surge levels are then applied to EVA to obtain the extreme storm surges in the target return periods at a 95% confidence interval (CI). The 30, 50, and 100 year return levels at HP obtained by EVA are 1.59, 1.66, and 1.75 m. The SLR trend obtained from EEMD is 4.46 mm/yr over April 1990 to March 2009, which is larger than the recent altimetry-based global rate of 3.3 ± 0.4 mm/yr over the period from 1993 to 2007. The resulting SLR in 2050 is estimated as 0.34 m. Therefore, the extreme sea level in 2050 due to SLR and the storm surge at a 100 year return level would be 2.09 m (95% CI from 1.91 to 2.48 m). The SLR depends not only on changes in the mass and volume of sea water but also on other factors, such as local subsidence, river discharge, sediment and the effects of vegetation. The residual nonlinear trend of SLR obtained from EEMD can be regarded as an adaptive sea level after considering those factors and their nonlinearity.

  12. Thermomechanical Multiaxial Fatigue Testing Capability Developed

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Structural components in aeronautical gas turbine engines typically experience multiaxial states of stress under nonisothermal conditions. To estimate the durability of the various components in the engine, one must characterize the cyclic deformation and fatigue behavior of the materials used under thermal and complex mechanical loading conditions. To this end, a testing protocol and associated test control software were developed at the NASA Lewis Research Center for thermomechanical axial-torsional fatigue tests. These tests are to be performed on thin-walled, tubular specimens fabricated from the cobalt-based superalloy Haynes 188. The software is written in C and runs on an MS-DOS based microcomputer.

  13. Utility of birefringence changes due to collagen thermal denaturation rate process analysis: vessel wall temperature estimation for new short term heating balloon angioplasty

    NASA Astrophysics Data System (ADS)

    Kaneko, Kenji; Shimazaki, Natsumi; Gotoh, Maya; Nakatani, Eriko; Arai, Tsunenori

    2007-02-01

    Our photo thermal reaction heating architecture balloon realizes less than 10 s short term heating that can soften vessel wall collagen without damaging surrounding tissue thermally. New thermal balloon angioplasty, photo-thermo dynamic balloon angioplasty (PTDBA) has experimentally shown sufficient opening with 2 atm low pressure dilation and prevention of chronic phase restenosis and acute phase thrombus in vivo. Even though PTDBA has high therapeutic potential, the most efficient heating condition is still under study, because relationship of treatment and thermal dose to vessel wall is not clarified yet. To study and set the most efficient heating condition, we have been working on establishment of temperature history estimation method from our previous experimental results. Heating target of PTDBA, collagen, thermally denatures following rate process. Denaturation is able to be quantified with measured collagen birefringence value. To express the denaturation with equation of rate process, the following ex vivo experiments were performed. Porcine extracted carotid artery was soaked in two different temperature saline baths to enforce constant temperature heating. Higher temperature bath was set to 40 to 80 degree Celsius and soaking duration was 5 to 40 s. Samples were observed by a polarizing microscope and a scanning electron microscope. The birefringence was measured by polarizing microscopic system using Brace-Koehler compensator 1/30 wavelength. The measured birefringence showed temperature dependency and quite fit with the rate process equation. We think vessel wall temperature is able to be estimated using the birefringence changes due to thermal denaturation.

  14. Effect of Extended CT Perfusion Acquisition Time on Ischemic Core and Penumbra Volume Estimation in Patients with Acute Ischemic Stroke due to a Large Vessel Occlusion

    PubMed Central

    Borst, Jordi; Marquering, Henk A.; Beenen, Ludo F. M.; Berkhemer, Olvert A.; Dankbaar, Jan Willem; Riordan, Alan J.; Majoie, Charles B. L. M.

    2015-01-01

    Background and Purpose It has been suggested that CT Perfusion acquisition times <60 seconds are too short to capture the complete in and out-wash of contrast in the tissue, resulting in incomplete time attenuation curves. Yet, these short acquisitions times are not uncommon in clinical practice. The purpose of this study was to investigate the occurrence of time attenuation curve truncation in 48 seconds CT Perfusion acquisition and to quantify its effect on ischemic core and penumbra estimation in patients with acute ischemic stroke due to a proximal intracranial arterial occlusion of the anterior circulation. Materials and Methods We analyzed CT Perfusion data with 48 seconds and extended acquisition times, assuring full time attenuation curves, of 36 patients. Time attenuation curves were classified as complete or truncated. Ischemic core and penumbra volumes resulting from both data sets were compared by median paired differences and interquartile ranges. Controlled experiments were performed using a digital CT Perfusion phantom to investigate the effect of time attenuation curve truncation on ischemic core and penumbra estimation. Results In 48 seconds acquisition data, truncation was observed in 24 (67%) cases for the time attenuation curves in the ischemic core, in 2 cases for the arterial input function and in 5 cases for the venous output function. Analysis of extended data resulted in smaller ischemic cores and larger penumbras with a median difference of 13.2 (IQR: 4.3–26.0)ml (P<0.001) and; 12.4 (IQR: 4.1–25.7)ml (P<0.001), respectively. The phantom data showed increasing ischemic core overestimation with increasing tissue time attenuation curve truncation. Conclusions Truncation is common in patients with large vessel occlusion and results in repartitioning of the area of hypoperfusion into larger ischemic core and smaller penumbra estimations. Phantom experiments confirmed that truncation results in overestimation of the ischemic core. PMID

  15. Nondestructive Evaluation of Metal Fatigue.

    DTIC Science & Technology

    1977-02-01

    Magnetic perturbation signatures and Barkhausen noise results have been obtained from an AISI 4340 steel fatigue specimen stress-cycled at 180ksi...vicinity of the fatigue crack. Barkhausen noise signals were obtained on a grid pattern in the vicinity of several fatigue cracks with a Barkhausen ...fatigue specimens are being fabricated for magnetic perturbation and Barkhausen noise analysis measurements. Fatigue cracks in Ti-6Al-4V specimens were investigated with the electric current injection technique.

  16. The power induced effects module: A FORTRAN code which estimates lift increments due to power induced effects for V/STOL flight

    NASA Technical Reports Server (NTRS)

    Sandlin, Doral R.; Howard, Kipp E.

    1991-01-01

    A user friendly FORTRAN code that can be used for preliminary design of V/STOL aircraft is described. The program estimates lift increments, due to power induced effects, encountered by aircraft in V/STOL flight. These lift increments are calculated using empirical relations developed from wind tunnel tests and are due to suckdown, fountain, ground vortex, jet wake, and the reaction control system. The code can be used as a preliminary design tool along with NASA Ames' Aircraft Synthesis design code or as a stand-alone program for V/STOL aircraft designers. The Power Induced Effects (PIE) module was validated using experimental data and data computed from lift increment routines. Results are presented for many flat plate models along with the McDonnell Aircraft Company's MFVT (mixed flow vectored thrust) V/STOL preliminary design and a 15 percent scale model of the YAV-8B Harrier V/STOL aircraft. Trends and magnitudes of lift increments versus aircraft height above the ground were predicted well by the PIE module. The code also provided good predictions of the magnitudes of lift increments versus aircraft forward velocity. More experimental results are needed to determine how well the code predicts lift increments as they vary with jet deflection angle and angle of attack. The FORTRAN code is provided in the appendix.

  17. Statistical optimisation techniques in fatigue signal editing problem

    SciTech Connect

    Nopiah, Z. M.; Osman, M. H.; Baharin, N.; Abdullah, S.

    2015-02-03

    Success in fatigue signal editing is determined by the level of length reduction without compromising statistical constraints. A great reduction rate can be achieved by removing small amplitude cycles from the recorded signal. The long recorded signal sometimes renders the cycle-to-cycle editing process daunting. This has encouraged researchers to focus on the segment-based approach. This paper discusses joint application of the Running Damage Extraction (RDE) technique and single constrained Genetic Algorithm (GA) in fatigue signal editing optimisation.. In the first section, the RDE technique is used to restructure and summarise the fatigue strain. This technique combines the overlapping window and fatigue strain-life models. It is designed to identify and isolate the fatigue events that exist in the variable amplitude strain data into different segments whereby the retention of statistical parameters and the vibration energy are considered. In the second section, the fatigue data editing problem is formulated as a constrained single optimisation problem that can be solved using GA method. The GA produces the shortest edited fatigue signal by selecting appropriate segments from a pool of labelling segments. Challenges arise due to constraints on the segment selection by deviation level over three signal properties, namely cumulative fatigue damage, root mean square and kurtosis values. Experimental results over several case studies show that the idea of solving fatigue signal editing within a framework of optimisation is effective and automatic, and that the GA is robust for constrained segment selection.

  18. The fatigue in workers of Iran Central Iron Ore Company in Yazd.

    PubMed

    Halvani, Golam Hossein; Zare, Mohsen; Hobobati, Hamid

    2009-01-01

    To evaluate fatigue, sub-dimensions, and job satisfaction among workers of Iran Central Iron Ore Co., and obtain the relationship between them. In a cross-sectional study, fatigue and the dimensionality were measured using Iranian version of Piper Fatigue Scale questionnaire (PFS). Job satisfaction was estimated with the job satisfaction scale (JSS) as well. The score of severe fatigue in four sub-scale/dimensions and total fatigue scores were: 11.9, 15.2, 11.3, 10.8 and 10.6%, respectively. Furthermore, there was significant difference between total fatigue and all its sub-dimensions in relation to job satisfaction of workers. Fatigue has caused job dissatisfaction of participants in our study, therefore we should note that the nature of fatigue may affect the psychological aspects of industrial workforce and can be harmful for business activities.

  19. Limited oxygen diffusion accelerates fatigue development in mouse skeletal muscle

    PubMed Central

    Zhang, Shi-Jin; Bruton, Joseph D; Katz, Abram; Westerblad, Håkan

    2006-01-01

    Isolated whole skeletal muscles fatigue more rapidly than isolated single muscle fibres. We have now employed this difference to study mechanisms of skeletal muscle fatigue. Isolated whole soleus and extensor digitorum longus (EDL) muscles were fatigued by repeated tetanic stimulation while measuring force production. Neither application of 10 mm lactic acid nor increasing the [K+] of the bath solution from 5 to 10 mm had any significant effect on the rate of force decline during fatigue induced by repeated brief tetani. Soleus muscles fatigued slightly faster during continuous tetanic stimulation in 10 mm[K+]. Inhibition of mitochondrial respiration with cyanide resulted in a faster fatigue development in both soleus and EDL muscles. Single soleus muscle fibres were fatigued by repeated tetani while measuring force and myoplasmic free [Ca2+] ([Ca2+]i). Under control conditions, the single fibres were substantially more fatigue resistant than the whole soleus muscles; tetanic force at the end of a series of 100 tetani was reduced by about 10% and 50%, respectively. However, in the presence of cyanide, fatigue developed at a similar rate in whole muscles and single fibres, and tetanic force at the end of fatiguing stimulation was reduced by ∼80%. The force decrease in the presence of cyanide was associated with a ∼50% decrease in tetanic [Ca2+]i, compared with an increase of ∼20% without cyanide. In conclusion, lactic acid or [K+] has little impact on fatigue induced by repeated tetani, whereas hypoxia speeds up fatigue development and this is mainly due to an impaired Ca2+ release from the sarcoplasmic reticulum. PMID:16455685

  20. Brain Tumors and Fatigue

    MedlinePlus

    ... tiredness. You may experience a profound lack of energy that can come on suddenly and bring dramatic ... to manage the severity. Respect the Fatigue The energy you’re accustomed to having has been transferred ...

  1. Chronic Fatigue Syndrome

    MedlinePlus

    ... of fatigue. Think "alternative." Acupuncture, reiki, massage, stretching, yoga, and t'ai chi seem to help many ... not beginning therapy — and therapies like the stress-management techniques and graded exercise previously mentioned have been ...

  2. Revised estimates of the ocean energy cycle and the key role of the western boundary in the APE to KE conversion due to high latitude cooling

    NASA Astrophysics Data System (ADS)

    Tailleux, Remi

    2014-05-01

    The ocean energy cycle is a key aspect of the ocean circulation, and has been traditionally framed in terms of Lorenz (1955) theory of available potential energy. However, the latest available observational estimate of the ocean energy cycle is due to Oort and Peixoto (1994) and is now very dated. Moreover, the latter estimate relies on the so-called Lorenz quasi-geostrophic approximation, which is known to be very inaccurate. Oort and Peixoto also neglected the internal energy contribution to the total available potential energy, which is now understood to be far from negligible, and to account for up to 40 percent of the total APE. The purpose of this work is to revisit observational estimates of the ocean energy cycle by taking advantage of a newly developed APE framework, as well as of the many new available observational products for temperature, salinity and surface buoyancy fluxes. In contrast to previous frameworks, our APE framework (Tailleux, 2013) relies on a physically well defined local APE definition, which is valid for a binary Boussinesq or fully compressible fluid with an arbitrary nonlinear equation of state. As part of our approach, we also developed a new fast and accurate way to construct Lorenz reference state of minimum potential energy, based on using the joint probability distribution function for temperature and salinity. Results will be presented for a variety of observational products, as well as for the ECCO2 ocean state estimate. The role of the deep western boundary as the place where the APE created by high latitude is converted into kinetic energy (KE) as part of driving the Atlantic meridional overturning circulation will be emphasized. References: Tailleux, R., 2013: Available potential energy density for a multicomponent Boussinesq fluid with arbitrary nonlinear equation of state.J. Fluid Mech., 735,499-518. Sijp, W., J.M.Gregory, R. Tailleux, P. Spence, 2012: The key role of the western boundary in linking the AMOC strength to

  3. Fatigue - Multiple Languages

    MedlinePlus

    ... हिन्दी) Japanese (日本語) Korean (한국어) Polish (polski) Russian (Русский) Somali (Af-Soomaali ) Spanish (español) Ukrainian (українська ) ... English Fatigue - polski (Polish) PDF American Cancer Society Russian (Русский) Expand Section Cancer Related Fatigue - Русский (Russian) ...

  4. Fracture and Fatigue

    DTIC Science & Technology

    1988-04-01

    fracture. The main additional categories of crack growth are elastic-plastic crack growth, fatigue crack growth, and crack growth as affected by...FRACTURE AND FATIGUE R. 0. RITCHIE W. W. GERBERICH J. H. UNDERWOOD DTIC AM ELECTE JUL 1 11988 APRIL 1988 FH US ARMY ARMAMENT RESEARCH, DEVELOPMENT AND...other authorized documents. N The use of trade name(s) and/or manufacturer (s) does not constitute an official indorsement or approval. DESTRUCTION NOTICE

  5. Micromechanics of Fatigue.

    DTIC Science & Technology

    1992-06-01

    recalled. Application of the derived tools to Apha-Two- Titanium Aluminide Aliov is made with a first series of strain controlled fatigue tests the locally...accumulation, and, multiaxial fatigue. In section 6, application is performed on the Alpha-Two- Titanium Alum:Aide Alloy.With a first serie of strain controlled ...tests needed for the identification of the model are described in the following figures. Test n’l is a classical tensile test strain controlled 1 = 0

  6. BIOMARKERS for CHRONIC FATIGUE

    PubMed Central

    Broderick, Gordon; Fletcher, Mary Ann

    2012-01-01

    Fatigue that persists for 6 months or more is termed chronic fatigue. Chronic fatigue (CF) in combination with a minimum of 4 of 8 symptoms and the absence of diseases that could explain these symptoms, constitute the case definition for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). Inflammation, immune system activation, autonomic dysfunction, impaired functioning in the hypothalamic-pituitary-adrenal axis, and neuroendocrine dysregulation have all been suggested as root causes of fatigue. The identification of objective markers consistently associated with CFS/ME is an important goal in relation to diagnosis and treatment, as the current case definitions are based entirely on physical signs and symptoms. This review is focused on the recent literature related to biomarkers for fatigue associated with CFS/ME and, for comparison, those associated with other diseases. These markers are distributed across several of the body’s core regulatory systems. A complex construct of symptoms emerges from alterations and/or dysfunctions in the nervous, endocrine and immune systems. We propose that new insight will depend on our ability to develop and deploy an integrative profiling of CFS/ME pathogenesis at the molecular level. Until such a molecular signature is obtained efforts to develop effective treatments will continue to be severely limited. PMID:22732129

  7. Fatigue and multiple sclerosis.

    PubMed

    Béthoux, F

    2006-07-01

    Even if the definition and pathophysiology of fatigue in multiple sclerosis (MS) are still debated, and despite the scarcity of objective markers correlated with the subjective sensation of fatigue, a review of the literature shows the importance of its detection and management, and allows one to propose therapeutic strategies. Fatigue is not only the most frequently reported symptom in MS, but also a frequent source of activity and participation limitations, psychological distress, and impairment of quality of life. Its management, which must be initiated early, is based on a comprehensive evaluation of its characteristics and consequences (sometimes with the use of scales such as the Fatigue Severity Scale and the Modified Fatigue Impact Scale), and on the identification of many potential contributing factors (psychological disorders, sleep disturbances, pain, infections and other comorbidities, medications, and deconditioning). Rehabilitative interventions are essential to the treatment of fatigue. Beyond the traditional energy conservation strategies and cooling techniques, several randomized controlled studies have demonstrated the positive impact of aerobic exercise. Medications are partially beneficial, and with the exception of amantadine, their efficacy has not been confirmed by randomized double-blind trials.

  8. Fretting Fatigue with Cylindrical-On-Flat Contact: Crack Nucleation, Crack Path and Fatigue Life

    PubMed Central

    Noraphaiphipaksa, Nitikorn; Manonukul, Anchalee; Kanchanomai, Chaosuan

    2017-01-01

    Fretting fatigue experiments and finite element analysis were carried out to investigate the influence of cylindrical-on-flat contact on crack nucleation, crack path and fatigue life of medium-carbon steel. The location of crack nucleation was predicted using the maximum shear stress range criterion and the maximum relative slip amplitude criterion. The prediction using the maximum relative slip amplitude criterion gave the better agreement with the experimental result, and should be used for the prediction of the location of crack nucleation. Crack openings under compressive bulk stresses were found in the fretting fatigues with flat-on-flat contact and cylindrical-on-flat contacts, i.e., fretting-contact-induced crack openings. The crack opening stress of specimen with flat-on-flat contact was lower than those of specimens with cylindrical-on-flat contacts, while that of specimen with 60-mm radius contact pad was lower than that of specimen with 15-mm radius contact pad. The fretting fatigue lives were estimated by integrating the fatigue crack growth curve from an initial propagating crack length to a critical crack length. The predictions of fretting fatigue life with consideration of crack opening were in good agreement with the experimental results. PMID:28772522

  9. Regional distribution of fatiguing illnesses in the United States: a pilot study.

    PubMed

    Bierl, Cynthia; Nisenbaum, Rosane; Hoaglin, David C; Randall, Bonnie; Jones, Ann-Britt; Unger, Elizabeth R; Reeves, William C

    2004-02-04

    BACKGROUND: Chronic fatigue syndrome (CFS) is a debilitating illness with no known cause or effective therapy. Population-based epidemiologic data on CFS prevalence are critical to put CFS in a realistic context for public health officials and others responsible for allocating resources. METHODS: We conducted a pilot random-digit-dialing survey to estimate the prevalence of fatiguing illnesses in different geographic regions and in urban and rural populations of the United States. This report focuses on 884 of 7,317 respondents 18 to 69 years old. Fatigued (440) and randomly selected non-fatigued (444) respondents completed telephone questionnaires concerning fatigue, other symptoms, and medical history. RESULTS: We estimated 12,186 per 100,000 persons 18 to 69 years of age suffered from fatigue lasting for at least 6 months (chronic fatigue), and 1,197 per 100,000 described an illness that, though lacking clinical evaluation, met criteria for CFS (CFS-like). Chronic fatigue and CFS-like illness were more common in rural than in urban populations, although the differences were not significant. The prevalence of these fatiguing illnesses did not differ meaningfully among the four regions surveyed, and no significant geographic trends were observed. CONCLUSIONS: This investigation estimated that nearly 2.2 million American adults suffer from CFS-like illness. The study also suggested the need to focus future investigations of fatigue on populations with lower incomes and less education. There was no evidence for regional differences in the occurrence of fatiguing illnesses.

  10. Chronic Fatigue Syndrome (CFS): Treating the Most Disruptive Symptoms First

    MedlinePlus

    ... to those symptoms have been investigated and excluded. Fatigue Due to Sleep Problems Most CFS patients have ... stronger stimulants can lead to the push-crash cycle (do too much, crash, rest, start to feel ...

  11. Fatigue in frail elderly people.

    PubMed

    Toye, Christine; White, Kate; Rooksby, Karen

    2006-05-01

    Many frail older people are likely to suffer from fatigue, but tools to measure fatigue in this population are lacking. Stage one of this study explored and described the experiences of fatigue of 12 older people from Australian residential aged care facilities. Themes identified were pacing yourself, battling on, hitting rock bottom, feeling safe, and moving on. Findings indicated that, with support, frail elders may be able to manage fatigue effects themselves. A measure of fatigue was developed from stage one findings, with reference to the literature. In stage two of the study, the Frail Elder Fatigue Assessment Tool was subjected to panel review, piloting, and refinement. The refined tool comprises 20 items in three subscales: fatigue effects; fatigue resources; and adaptation to fatigue. Further work is required to establish the tool's psychometric properties, but it should then be useful for both research and clinical assessment purposes.

  12. Statistical summaries of fatigue data for design purposes

    NASA Technical Reports Server (NTRS)

    Wirsching, P. H.

    1983-01-01

    Two methods are discussed for constructing a design curve on the safe side of fatigue data. Both the tolerance interval and equivalent prediction interval (EPI) concepts provide such a curve while accounting for both the distribution of the estimators in small samples and the data scatter. The EPI is also useful as a mechanism for providing necessary statistics on S-N data for a full reliability analysis which includes uncertainty in all fatigue design factors. Examples of statistical analyses of the general strain life relationship are presented. The tolerance limit and EPI techniques for defining a design curve are demonstrated. Examples usng WASPALOY B and RQC-100 data demonstrate that a reliability model could be constructed by considering the fatigue strength and fatigue ductility coefficients as two independent random variables. A technique given for establishing the fatigue strength for high cycle lives relies on an extrapolation technique and also accounts for "runners." A reliability model or design value can be specified.

  13. Fatigue in Parkinson's disease: report from a mutidisciplinary symposium

    PubMed Central

    Friedman, Joseph H; Beck, James C; Chou, Kelvin L; Clark, Gracia; Fagundes, Christopher P; Goetz, Christopher G; Herlofson, Karen; Kluger, Benzi; Krupp, Lauren B; Lang, Anthony E; Lou, Jao-Shin; Marsh, Laura; Newbould, Anne; Weintraub, Daniel

    2016-01-01

    Fatigue is a severe problem for many people living with Parkinson's disease (PD). Best estimates suggest that more than 50% of patients experience this debilitating symptom. Little is known about its etiology or treatment, making the understanding of fatigue a true unmet need. As part of the Parkinson's Disease Foundation Community Choice Research Program, patients, caregivers, and scientists attended a symposium on fatigue on 16 and 17 October 2014. We present a summary of that meeting, reviewing what is known about the diagnosis and treatment of fatigue, its physiology, and what we might learn from multiple sclerosis (MS), depression, and cancer—disorders in which fatigue figures prominently too. We conclude with focused recommendations to enhance our understanding and treatment of this prominent problem in PD. PMID:27239558

  14. Life Estimation of Hip Joint Prosthesis

    NASA Astrophysics Data System (ADS)

    Desai, C.; Hirani, H.; Chawla, A.

    2014-11-01

    Hip joint is one of the largest weight-bearing structures in the human body. In the event of a failure of the natural hip joint, it is replaced with an artificial hip joint, known as hip joint prosthesis. The design of hip joint prosthesis must be such so as to resist fatigue failure of hip joint stem as well as bone cement, and minimize wear caused by sliding present between its head and socket. In the present paper an attempt is made to consider both fatigue and wear effects simultaneously in estimating functional-life of the hip joint prosthesis. The finite element modeling of hip joint prosthesis using HyperMesh™ (version 9) has been reported. The static analysis (load due to the dead weight of the body) and dynamic analysis (load due to walking cycle) have been described. Fatigue life is estimated by using the S-N curve of individual materials. To account for progressive wear of hip joint prosthesis, Archard's wear law, modifications in socket geometry and dynamic analysis have been used in a sequential manner. Using such sequential programming reduction in peak stress has been observed with increase in wear. Finally life is estimated on the basis of socket wear.

  15. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, N. K.; Swanson, G.

    2002-01-01

    High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297

  16. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, N. K.; Swanson, G.

    2002-01-01

    High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297

  17. An attempt to estimate the economic value of the loss of human life due to landslide and flood events in Italy

    NASA Astrophysics Data System (ADS)

    Salvati, Paola; Bianchi, Cinzia; Hussin, Haydar; Guzzetti, Fausto

    2013-04-01

    Landslide and flood events in Italy cause wide and severe damage to buildings and infrastructure, and are frequently involved in the loss of human life. The cost estimates of past natural disasters generally refer to the amount of public money used for the restoration of the direct damage, and most commonly do not account for all disaster impacts. Other cost components, including indirect losses, are difficult to quantify and, among these, the cost of human lives. The value of specific human life can be identified with the value of a statistical life (VLS), defined as the value that an individual places on a marginal change in their likelihood of death This is different from the value of an actual life. Based on information of fatal car accidents in Italy, we evaluate the cost that society suffers for the loss of life due to landslide and flood events. Using a catalogue of fatal landslide and flood events, for which information about gender and age of the fatalities is known, we determine the cost that society suffers for the loss of their life. For the purpose, we calculate the economic value in terms of the total income that the working-age population involved in the fatal events would have earned over the course of their life. For the computation, we use the pro-capita income calculated as the ratio between the GDP and the population value in Italy for each year, since 1980. Problems occur for children and retired people that we decided not to include in our estimates.

  18. Improving Fatigue Performance of AHSS Welds

    SciTech Connect

    Feng, Zhili; Yu, Xinghua; Erdman, III, Donald L.; Wang, Yanli; Kelly, Steve; Hou, Wenkao; Yan, Benda; Wang, Zhifeng; Yu, Zhenzhen; Liu, Stephen

    2015-03-01

    Reported herein is technical progress on a U.S. Department of Energy CRADA project with industry cost-share aimed at developing the technical basis and demonstrate the viability of innovative in-situ weld residual stresses mitigation technology that can substantially improve the weld fatigue performance and durability of auto-body structures. The developed technology would be costeffective and practical in high-volume vehicle production environment. Enhancing weld fatigue performance would address a critical technology gap that impedes the widespread use of advanced high-strength steels (AHSS) and other lightweight materials for auto body structure light-weighting. This means that the automotive industry can take full advantage of the AHSS in strength, durability and crashworthiness without the concern of the relatively weak weld fatigue performance. The project comprises both technological innovations in weld residual stress mitigation and due-diligence residual stress measurement and fatigue performance evaluation. Two approaches were investigated. The first one was the use of low temperature phase transformation (LTPT) weld filler wire, and the second focused on novel thermo-mechanical stress management technique. Both technical approaches have resulted in considerable improvement in fatigue lives of welded joints made of high-strength steels. Synchrotron diffraction measurement confirmed the reduction of high tensile weld residual stresses by the two weld residual stress mitigation techniques.

  19. Polarization fatigue of organic ferroelectric capacitors

    PubMed Central

    Zhao, Dong; Katsouras, Ilias; Li, Mengyuan; Asadi, Kamal; Tsurumi, Junto; Glasser, Gunnar; Takeya, Jun; Blom, Paul W. M.; de Leeuw, Dago M.

    2014-01-01

    The polarization of the ferroelectric polymer P(VDF-TrFE) decreases upon prolonged cycling. Understanding of this fatigue behavior is of great technological importance for the implementation of P(VDF-TrFE) in random-access memories. However, the origin of fatigue is still ambiguous. Here we investigate fatigue in thin-film capacitors by systematically varying the frequency and amplitude of the driving waveform. We show that the fatigue is due to delamination of the top electrode. The origin is accumulation of gases, expelled from the capacitor, under the impermeable top electrode. The gases are formed by electron-induced phase decomposition of P(VDF-TrFE), similar as reported for inorganic ferroelectric materials. When the gas barrier is removed and the waveform is adapted, a fatigue-free ferroelectric capacitor based on P(VDF-TrFE) is realized. The capacitor can be cycled for more than 108 times, approaching the programming cycle endurance of its inorganic ferroelectric counterparts. PMID:24861542

  20. Creep-fatigue interaction in aircraft gas turbine components by simulation and testing at scaled temperatures

    NASA Astrophysics Data System (ADS)

    Sabour, Mohammad Hossein

    Advanced gas turbine engines, which use hot section airfoil cooling, present a wide range of design problems. The frequencies of applied loads and the natural frequencies of the blade also are important since they have significant effects on failure of the component due to fatigue phenomenon. Due to high temperature environment the thermal creep and fatigue are quite severe. One-dimensional creep model, using ANSYS has been formulated in order to predict the creep life of a gas turbine engine blade. Innovative mathematical models for the prediction of the operating life of aircraft components, specifically gas turbine blades, which are subjected to creep-fatigue at high temperatures, are proposed. The components are modeled by FEM, mathematically, and using similitude principles. Three models have been suggested and evaluated numerically and experimentally. Using FEM method for natural frequencies causes phenomena such as curve veering which is studied in more detail. The simulation studies on the life-limiting modes of failure, as well as estimating the expected lifetime of the blade, using the proposed models have been carried out. Although the scale model approach has been used for quite some time, the thermal scaling has been used in this study for the first time. The only thermal studies in literature using scaling for structures is by NASA in which materials of both the prototype and the model are the same, but in the present study materials also are different. The finite element method is employed to model the structure. Because of stress redistribution due to the creep process, it is necessary to include a full inelastic creep step in the finite element formulation. Otherwise over-conservative creep life predictions will be estimated if only the initial elastic stresses are considered. The experimental investigations are carried out in order to validate the models. The main contributions in the thesis are: (1) Using similitude theory for life prediction of

  1. Estimation of the collective ionizing dose in the Portuguese population for the years 2011 and 2012, due to nuclear medicine exams.

    PubMed

    Costa, F; Teles, P; Nogueira, A; Barreto, A; Santos, A I; Carvalho, A; Martins, B; Oliveira, C; Gaspar, C; Barros, C; Neves, D; Costa, D; Rodrigues, E; Godinho, F; Alves, F; Cardoso, G; Cantinho, G; Conde, I; Vale, J; Santos, J; Isidoro, J; Pereira, J; Salgado, L; Rézio, M; Vieira, M; Simãozinho, P; Almeida, P; Castro, R; Parafita, R; Pintão, S; Lúcio, T; Reis, T; Vaz, P

    2015-01-01

    In 2009-2010 a Portuguese consortium was created to implement the methodologies proposed by the Dose Datamed II (DDM2) project, aiming to collect data from diagnostic X-ray and nuclear medicine (NM) procedures, in order to determine the most frequently prescribed exams and the associated ionizing radiation doses for the Portuguese population. The current study is the continuation of this work, although it focuses only on NM exams for the years 2011 and 2012. The annual frequency of each of the 28 selected NM exams and the average administered activity per procedure was obtained by means of a nationwide survey sent to the 35 NM centres in Portugal. The results show a reduction of the number of cardiac exams performed in the last two years compared with 2010, leading to a reduction of the annual average effective dose of Portuguese population due to NM exams from 0.08 mSv ± 0.017 mSv/caput to 0.059 ± 0.011 mSv/caput in 2011 and 0.054 ± 0.011 mSv/caput in 2012. Portuguese total annual average collective effective dose due to medical procedures was estimated to be 625.6 ± 110.9 manSv in 2011 and 565.1 ± 117.3 manSv in 2012, a reduction in comparison with 2010 (840.3 ± 183.8 manSv). The most frequent exams and the ones that contributed the most for total population dose were the cardiac and bone exams, although a decrease observed in 2011 and in 2012 was verified. The authors intend to perform this study periodically to identify trends in the annual Portuguese average effective dose and to help to raise awareness about the potential dose optimization. Copyright © 2014 Elsevier España, S.L.U. and SEMNIM. All rights reserved.

  2. FEA Based Tool Life Quantity Estimation of Hot Forging Dies Under Cyclic Thermo-Mechanical Loads

    NASA Astrophysics Data System (ADS)

    Behrens, B.-A.; Bouguecha, A.; Schäfer, F.; Hadifi, T.

    2011-01-01

    Hot forging dies are exposed during service to a combination of cyclic thermo-mechanical, tribological and chemical loads. Besides abrasive and adhesive wear on the die surface, fatigue crack initiation with subsequent fracture is one of the most frequent causes of failure. In order to extend the tool life, the finite element analysis (FEA) may serve as a means for process design and process optimisation. So far the FEA based estimation of the production cycles until initial cracking is limited as tool material behaviour due to repeated loading is not captured with the required accuracy. Material models which are able to account for cyclic effects are not verified for the fatigue life predictions of forging dies. Furthermore fatigue properties from strain controlled fatigue tests of relevant hot work steels are to date not available to allow for a close-to-reality fatigue life prediction. Two industrial forging processes, where clear fatigue crack initiation has been observed are considered for a fatigue analysis. For this purpose the relevant tool components are modelled with elasto-plastic material behaviour. The predicted sites, where crack initiation occurs, agree with the ones observed on the real die component.

  3. Some aspects of thermomechanical fatigue of AISI 304L stainless steel; Part 1: Creep-fatigue damage

    SciTech Connect

    Zauter, R. ); Christ, H.J. . Inst. of Materials Technology); Mughrabi, H. . Inst. for Materials Science)

    1994-02-01

    Thermomechanical fatigue (TMF) tests on the austenitic stainless steel AISI 304L have been conducted under true' plastic-strain control in vacuum. This report considers the damage occurring during TMF loading. It is shown how the temperature interval and the phasing (in phase, out-of-phase) determine the mechanical response and the lifetime of the specimens. If creep-fatigue interaction takes place during in-phase cycling, the damage occurs inside the material, leading creep-induced damage, and no lifetime reduction occurs, even if the material is exposed periodically to temperature in the creep regime. A formula is proposed which allows prediction of the failure mode, depending on whether creep-fatigue damage occurs or not. At a given strain rate, the formula is able to estimate the temperature of transition between pure fatigue and creep-fatigue damage.

  4. Understanding and Counteracting Fatigue in Flight Crews

    NASA Technical Reports Server (NTRS)

    Mallis, Melissa; Neri, David; Rosekind, Mark; Gander, Philippa; Caldwell, John; Graeber, Curtis

    2007-01-01

    The materials included in the collection of documents describe the research of the NASA Ames Fatigue Countermeasures Group (FCG), which examines the extent to which fatigue, sleep loss, and circadian disruption affect flight-crew performance. The group was formed in 1980 in response to a Congressional request to examine a possible safety problem of uncertain magnitude due to transmeridian flying and a potential problem due to fatigue in association with various factors found in air-transport operations and was originally called the Fatigue/Jet Lag Program. The goals of the FCG are: (1) the development and evaluation of strategies for mitigating the effects of sleepiness and circadian disruption on pilot performance levels; (2) the identification and evaluation of objective approaches for the prediction of alertness changes in flight crews; and (3) the transfer and application of research results to the operational field via classes, workshops, and safety briefings. Some of the countermeasure approaches that have been identified to be scientifically valid and operationally relevant are brief naps (less than 40 min) in the cockpit seat and 7-min activity breaks, which include postural changes and ambulation. Although a video-based alertness monitor based on slow eyelid closure shows promise in other operational environments, research by the FCG has demonstrated that in its current form at the time of this reporting, it is not feasible to implement it in the cockpit. Efforts also focus on documenting the impact of untreated fatigue on various types of flight operations. For example, the FCG recently completed a major investigation into the effects of ultra-long-range flights (20 continuous hours in duration) on the alertness and performance of pilots in order to establish a baseline set of parameters against which the effectiveness of new ultra-long-range fatigue remedies can be judged.

  5. Recovery from supraspinal fatigue is slowed in old adults after fatiguing maximal isometric contractions.

    PubMed

    Hunter, Sandra K; Todd, Gabrielle; Butler, Jane E; Gandevia, Simon C; Taylor, Janet L

    2008-10-01

    This study compared the contribution of supraspinal fatigue to muscle fatigue in old and young adults. Transcranial magnetic stimulation (TMS) of motor cortex was used to assess voluntary activation during maximal voluntary contractions (MVCs) of elbow flexor muscles in 17 young adults (25.5 +/- 3.6 yr; mean +/- SD) and 7 old adults (73.0 +/- 3.3 yr). Subjects performed a fatigue task involving six sustained MVCs (22-s duration, separated by 10 s). Young adults exhibited greater reductions in maximal voluntary torque (67 +/- 15% of baseline) than the old (37 +/- 6%; P < 0.001). Increments in torque (superimposed twitch) generated by TMS during sustained MVCs increased for the young and old (P < 0.001) but were larger for the old adults at the start of the sustained contractions and during recovery (P < 0.05). Voluntary activation was less for the old adults at the start of some sustained contractions and during recovery (P = 0.02). Motor-evoked potential area increased similarly with age during the fatiguing task but was greater for the old adults than young during recovery. Silent period duration lengthened less for the old adults during the fatigue task. At the end of the fatiguing task, peak relaxation rate of muscle fibers had declined more in the young than the old adults. The greater endurance with age is largely due to a difference in mechanisms located within the muscle. However, recovery from the fatiguing exercise is impaired for old adults because of greater supraspinal fatigue than in the young.

  6. Influence of Fatigue in Neuromuscular Control of Spinal Stability

    PubMed Central

    Granata, Kevin P.; Slota, Greg P.; Wilson, Sara E.

    2006-01-01

    Lifting-induced fatigue may influence neuromuscular control of spinal stability. Stability is primarily controlled by muscle recruitment, active muscle stiffness, and reflex response. Fatigue has been observed to affect each of these neuromuscular parameters and may therefore affect spinal stability. A biomechanical model of spinal stability was implemented to evaluate the effects of fatigue on spinal stability. The model included a 6-degree-of-freedom representation of the spine controlled by 12 deformable muscles from which muscle recruitment was determined to simultaneously achieve equilibrium and stability. Fatigue-induced reduction in active muscle stiffness necessitated increased antagonistic cocontraction to maintain stability resulting in increased spinal compression with fatigue. Fatigueinduced reduction in force-generating capacity limited the feasible set of muscle recruitment patterns, thereby restricting the estimated stability of the spine. Electromyographic and trunk kinematics from 21 healthy participants were recorded during sudden-load trials in fatigued and unfatigued states. Empirical data supported the model predictions, demonstrating increased antagonistic cocontraction during fatigued exertions. Results suggest that biomechanical factors including spinal load and stability should be considered when performing ergonomic assessments of fatiguing lifting tasks. Potential applications of this research include a biomechanical tool for the design of administrative ergonomic controls in manual materials handling industries. PMID:15151156

  7. Prediction of residual fatigue life using nonlinear ultrasound

    NASA Astrophysics Data System (ADS)

    Amura, Mikael; Meo, Michele

    2012-04-01

    Prediction of fatigue life of components during service is an on-going and unsolved challenge for the NDT and structural health monitoring community. It has been demonstrated by a number of researchers that nonlinear guided waves or the acoustic nonlinear signature of fatigued cracked material provides clear signs of the progressive fatigue damage in the material, unlike linear guided waves. However, even with nonlinear acoustic-ultrasound methods there is a necessity to compare the current nonlinear feature to a previously measured cracked material state to assess the absolute residual fatigue life. In this paper, a new procedure based on the measurement of the second-order acoustic nonlinearity is presented which is able to assess the fatigue life of a metallic component without the need of a baseline. The Nazarov-Sutin crack nonlinearity equation and the Paris law are combined in order to obtain an analytical solution able to evaluate the theoretical second-order quadratic nonlinear parameters as a function of the crack growth and fatigue life that evolve during cyclic loading in metals. The model makes the assumption that the crack surface topology has variable geometrical parameters. The method was tested on aluminum alloy specimens AA2024-T351, containing fatigue fracture of different sizes, and excellent correlation was obtained between the theoretical and measured second-order nonlinear parameter. Then, it was demonstrated clearly that by measuring the nonlinear parameters it is possible to estimate crack size and fatigue life. Finally, advantages and limitations of the procedure are discussed.

  8. Estimation of Effective Transmission Loss Due to Subtropical Hydrometeor Scatters using a 3D Rain Cell Model for Centimeter and Millimeter Wave Applications

    NASA Astrophysics Data System (ADS)

    Ojo, J. S.; Owolawi, P. A.

    2014-12-01

    The problem of hydrometeor scattering on microwave radio communication down links continues to be of interest as the number of the ground and earth space terminals continually grows The interference resulting from the hydrometeor scattering usually leads to the reduction in the signal-to-noise ratio ( SNR) at the affected terminal and at worst can even end up in total link outage. In this paper, an attempt has been made to compute the effective transmission loss due to subtropical hydrometeors on vertically polarized signals in Earth-satellite propagation paths in the Ku, Ka and V band frequencies based on the modified Capsoni 3D rain cell model. The 3D rain cell model has been adopted and modified using the subtropical log-normal distributions of raindrop sizes and introducing the equivalent path length through rain in the estimation of the attenuation instead of the usual specific attenuation in order to account for the attenuation of both wanted and unwanted paths to the receiver. The co-channels, interference at the same frequency is very prone to the higher amount of unwanted signal at the elevation considered. The importance of joint transmission is also considered.

  9. Estimation of annual effective dose due to natural radioactive elements in ingestion of foodstuffs in tin mining area of Jos-Plateau, Nigeria.

    PubMed

    Jibiri, N N; Farai, I P; Alausa, S K

    2007-01-01

    Soils and food crops from a former tin mining location in a high background radiation area on the Jos-Plateau, Nigeria were collected and analyzed by gamma spectrometry to measure their contents of 40K, 238U and 232Th. As well as collecting samples, in situ dose rates on farms were measured using a precalibrated survey meter. Activity concentrations determined in food crops were compared with the local food derivatives or diets to investigate the possible removal or addition of radionuclides during food preparation by cooking or other means. Potassium-40 was found to contribute the highest activity in all the food products. The activity concentration of 40K, 238U and 232Th in local prepared diets ranged between 60 and 494 Bq kg-1, between BDL and 48 Bq kg-1 and between BDL and 17 Bq kg-1, respectively. The internal effective dose to individuals from the consumption of the food types was estimated on the basis of the measured radionuclide contents in the food crops. It ranged between 0.2 microSv y-1 (beans) and 2164 microSv y-1 (yam) while the annual external gamma effective dose in the farms due to soil radioactivity ranged between 228 microSv and 4065 microSv.

  10. Experimental studies on physical deterioration and electrical fatigue behavior in ferroelectric polymers

    NASA Astrophysics Data System (ADS)

    He, Xiangtong

    Ferroelectric materials are widely used in various electronic applications based upon their excellent electrical bi-stabilities and dielectric performance in response to the applied electric field. They have been utilized to make nonvolatile electronic memories by exploiting the hysteretic behavior and high energy density capacitors in regard to the high capability of electrical energy storage. One critical issue is that the ferroelectrics are required to endure a large number of electrical cycles. A large body of scientific efforts has been devoted to high fatigue failure resistance of ferroelectric-based electronic devices. Fatigue failure of ferroelectric materials still needs to be solved. It is the objective of this work to explore the intrinsic origin of fatigue failure mechanisms. In this study, it was found that electric-field-induced stress relaxation in α-phase poly(vinylidene fluoride) (PVDF) films can be well described by using the Kohlraush function groups, also known as the stretched exponential relaxation function. The electric strength of the dielectric is strongly dependent on its elastic properties due to the electromechanical coupling effect. Our fitting result of the stretched exponent is in accordance with a Weibull cumulative distribution function. This indicates that the elastic properties of insulating polymers are crucial to the capability of electrical energy storage. In ferroelectric materials, the electromechanical coupling may be indicative of the microscopic origin of polarization fatigue. Further experiments were focused on the polarization fatigue in semi-crystalline poly(vinylidene fluoride trifluoroethylene) [P(VDF-TrFE)] copolymers films, whose ferroelectric response is superior to PVDF homopolymer films. Fatigue resistance of normal virgin P(VDF-TrFE) films was compared to that of P(VDF-TrFE) films modulated by using magnetic field. It was shown that normal P(VDF-TrFE) films exhibit a higher fatigue resistance. The artificially

  11. Ratcheting fatigue behavior of Zircaloy-2 at room temperature

    NASA Astrophysics Data System (ADS)

    Rajpurohit, R. S.; Sudhakar Rao, G.; Chattopadhyay, K.; Santhi Srinivas, N. C.; Singh, Vakil

    2016-08-01

    Nuclear core components of zirconium alloys experience asymmetric stress or strain cycling during service which leads to plastic strain accumulation and drastic reduction in fatigue life as well as dimensional instability of the component. Variables like loading rate, mean stress, and stress amplitude affect the influence of asymmetric loading. In the present investigation asymmetric stress controlled fatigue tests were conducted with mean stress from 80 to 150 MPa, stress amplitude from 270 to 340 MPa and stress rate from 30 to 750 MPa/s to study the process of plastic strain accumulation and its effect on fatigue life of Zircaloy-2 at room temperature. It was observed that with increase in mean stress and stress amplitude accumulation of ratcheting strain was increased and fatigue life was reduced. However, increase in stress rate led to improvement in fatigue life due to less accumulation of ratcheting strain.

  12. On high-cycle fatigue of 316L stents.

    PubMed

    Barrera, Olga; Makradi, Ahmed; Abbadi, Mohammed; Azaouzi, Mohamed; Belouettar, Salim

    2014-01-01

    This paper deals with fatigue life prediction of 316L stainless steel cardiac stents. Stents are biomedical devices used to reopen narrowed vessels. Fatigue life is dominated by the cyclic loading due to the systolic and diastolic pressure and the design against premature mechanical failure is of extreme importance. Here, a life assessment approach based on the Dang Van high cycle fatigue criterion and on finite element analysis is applied to explore the fatigue reliability of 316L stents subjected to multiaxial fatigue loading. A finite element analysis of the stent vessel subjected to cyclic pressure is performed to carry out fluctuating stresses and strain at some critical elements of the stent where cracks or complete fracture may occur. The obtained results show that the loading path of the analysed stent subjected to a pulsatile load pressure is located in the safe region concerning infinite lifetime.

  13. Fatigue Crack Growth Monitoring Using Rayleigh-Like Waves

    NASA Astrophysics Data System (ADS)

    Masserey, B.; Fromme, P.

    2010-02-01

    A common problem in aircraft maintenance is the development of fatigue cracks at fasteners due to stress concentration. The use of Rayleigh-like waves for the monitoring of fatigue crack growth at a fastener hole in tensile, aluminum specimens is investigated. Rayleigh-like waves can propagate along the structure and have good sensitivity for the detection of small defects. They are excited in the specimen during fatigue experiments using standard wedge transducers and measured using laser interferometry. Fatigue crack growth during cyclic loading is monitored optically and the changes in the ultrasonic signal caused by crack growth are quantified. The laser measurements show a good sensitivity for the early detection of fatigue damage.

  14. Literature survey on oxidations and fatigue lives at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Liu, H. W.; Oshida, Y.

    1984-01-01

    Nickel-base superalloys are the most complex and the most widely used for high temperature applications such as aircraft engine components. The desirable properties of nickel-base superalloys at high temperatures are tensile strength, thermomechanical fatigue resistance, low thermal expansion, as well as oxidation resistance. At elevated temperature, fatigue cracks are often initiated by grain boundary oxidation, and fatigue cracks often propagate along grain boundaries, where the oxidation rate is higher. Oxidation takes place at the interface between metal and gas. Properties of the metal substrate, the gaseous environment, as well as the oxides formed all interact to make the oxidation behavior of nickel-base superalloys extremely complicated. The important topics include general oxidation, selective oxidation, internal oxidation, grain boundary oxidation, multilayer oxide structure, accelerated oxidation under stress, stress-generation during oxidation, composition and substrate microstructural changes due to prolonged oxidation, fatigue crack initiation at oxidized grain boundaries and the oxidation accelerated fatigue crack propagation along grain boundaries.

  15. Fatigue With Systolic Heart Failure

    PubMed Central

    Fink, Anne M.; Sullivan, Shawna L.; Zerwic, Julie J.; Piano, Mariann R.

    2010-01-01

    Background and Research Objective Fatigue is one of the most prevalent symptoms in persons with systolic heart failure (HF). There remains insufficient information about the physiological and psychosocial underpinnings of fatigue in HF. The specific aims of this study were to (1) determine the psychometric properties of 2 fatigue questionnaires in patients with HF, (2) compare fatigue in patients with HF to published scores of healthy adults and patients with cancer undergoing treatment, and (3) identify the physiological (eg, hemoglobin, B-type natriuretic peptide, body mass index, and ejection fraction) and psychosocial (eg, depressed mood) correlates of fatigue in HF. Subjects and Methods A convenience sample of 87 HF outpatients was recruited from 2 urban medical centers. Patients completed the Fatigue Symptom Inventory, Profile of Mood States, and Short Form-36 Health Survey. Results and Conclusions Patients with HF and patients with cancer reported similar levels of fatigue, and both patient groups reported significantly more fatigue than did healthy adults. Physical functioning and hemoglobin categories explained 30% of the variance in Fatigue Symptom Inventory-Interference Scale scores, whereas depressed mood and physical functioning explained 47% of the variance in Profile of Mood States Fatigue subscale scores. Patients with HF experienced substantial fatigue that is comparable with cancer-related fatigue. Low physical functioning, depressed mood, and low hemoglobin level were associated with HF-related fatigue. PMID:19707101

  16. Fatigue Assessment: Subjective Peer-to-Peer Fatigue Scoring (Reprint)

    DTIC Science & Technology

    2013-10-01

    impor- tant role of fatigue in aviation safety and fl ight perfor- mance, the compelling tasks of predicting dangerous fatigued states and quantifying...complex fl ight environment. Indeed, even a precise defi nition of fatigue has been somewhat recondite. It is often stratifi ed into acute versus...Medicine x Vol. 84, No. 10 x October 2013 PEER-TO-PEER FATIGUE SCORING — GAYDOS ET AL. broad and complex skill sets required for fl ight safety

  17. Thermal fatigue of beryllium

    SciTech Connect

    Deksnis, E.; Ciric, D.; Falter, H.

    1995-09-01

    Thermal fatigue life of S65c beryllium castellated to a geometry 6 x 6 x (8-10)mm deep has been tested for steady heat fluxes of 3 MW/m{sup 2} to 5 MW/m{sup 2} and under pulsed heat fluxes (10-20 MW/m{sup 2}) for which the time averaged heat flux is 5 MW/m{sup 2}. These tests were carried out in the JET neutral beam test facility A test sequence with peak surface temperatures {le} 600{degrees}C produced no visible fatigue cracks. In the second series of tests, with T{sub max} {le} 750{degrees}C evidence for fatigue appeared after a minimum of 1350 stress cycles. These fatigue data are discussed in view of the observed lack of thermal fatigue in JET plasma operations with beryllium PFC. JET experience with S65b and S65c is reviewed; recent operations with {Phi} = 25 MW/m{sup 2} and sustained melting/resolidification are also presented. The need for a failure criterion for finite element analyses of Be PFC lifetimes is discussed.

  18. Prestraining and Its Influence on Subsequent Fatigue Life

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.; Mcgaw, Michael A.; Kalluri, Sreeramesh

    1995-01-01

    An experimental program was conducted to study the damaging effects of tensile and compressive prestrains on the fatigue life of nickel-base, Inconel 718 superalloy at room temperature. To establish baseline fatigue behavior, virgin specimens with a solid uniform gage section were fatigued to failure under fully-reversed strain-control. Additional specimens were prestrained to 2 percent, 5 percent, and 10 percent (engineering strains) in the tensile direction and to 2 percent (engineering strain) in the compressive direction under stroke-control, and were subsequently fatigued to failure under fully-reversed strain-control. Experimental results are compared with estimates of remaining fatigue lives (after prestraining) using three life prediction approaches: (1) the Linear Damage Rule; (2) the Linear Strain and Life Fraction Rule; and (3) the nonlinear Damage Curve Approach. The Smith-Watson-Topper parameter was used to estimate fatigue lives in the presence of mean stresses. Among the cumulative damage rules investigated, best remaining fatigue life predictions were obtained with the nonlinear Damage Curve Approach.

  19. Acoustic fatigue life prediction for nonlinear structures with multiple resonant modes

    NASA Technical Reports Server (NTRS)

    Miles, R. N.

    1992-01-01

    This report documents an effort to develop practical and accurate methods for estimating the fatigue lives of complex aerospace structures subjected to intense random excitations. The emphasis of the current program is to construct analytical schemes for performing fatigue life estimates for structures that exhibit nonlinear vibration behavior and that have numerous resonant modes contributing to the response.

  20. Acoustic fatigue life prediction for nonlinear structures with multiple resonant modes

    NASA Astrophysics Data System (ADS)

    Miles, R. N.

    1992-03-01

    This report documents an effort to develop practical and accurate methods for estimating the fatigue lives of complex aerospace structures subjected to intense random excitations. The emphasis of the current program is to construct analytical schemes for performing fatigue life estimates for structures that exhibit nonlinear vibration behavior and that have numerous resonant modes contributing to the response.

  1. Saccadic eye movement metrics reflect surgical residents' fatigue.

    PubMed

    Di Stasi, Leandro L; McCamy, Michael B; Macknik, Stephen L; Mankin, James A; Hooft, Nicole; Catena, Andrés; Martinez-Conde, Susana

    2014-04-01

    Little is known about the effects of surgical residents' fatigue on patient safety. We monitored surgical residents' fatigue levels during their call day using (1) eye movement metrics, (2) objective measures of laparoscopic surgical performance, and (3) subjective reports based on standardized questionnaires. Prior attempts to investigate the effects of fatigue on surgical performance have suffered from methodological limitations, including inconsistent definitions and lack of objective measures of fatigue, and nonstandardized measures of surgical performance. Recent research has shown that fatigue can affect the characteristics of saccadic (fast ballistic) eye movements in nonsurgical scenarios. Here we asked whether fatigue induced by time-on-duty (~24 hours) might affect saccadic metrics in surgical residents. Because saccadic velocity is not under voluntary control, a fatigue index based on saccadic velocity has the potential to provide an accurate and unbiased measure of the resident's fatigue level. We measured the eye movements of members of the general surgery resident team at St. Joseph's Hospital and Medical Center (Phoenix, AZ) (6 males and 6 females), using a head-mounted video eye tracker (similar configuration to a surgical headlight), during the performance of 3 tasks: 2 simulated laparoscopic surgery tasks (peg transfer and precision cutting) and a guided saccade task, before and after their call day. Residents rated their perceived fatigue level every 3 hours throughout their 24-hour shift, using a standardized scale. Time-on-duty decreased saccadic velocity and increased subjective fatigue but did not affect laparoscopic performance. These results support the hypothesis that saccadic indices reflect graded changes in fatigue. They also indicate that fatigue due to prolonged time-on-duty does not result necessarily in medical error, highlighting the complicated relationship among continuity of care, patient safety, and fatigued providers. Our data

  2. Low-cycle thermal fatigue

    NASA Technical Reports Server (NTRS)

    Halford, G. R.

    1986-01-01

    A state-of-the-art review is presented of the field of thermal fatigue. Following a brief historical review, the concept is developed that thermal fatigue can be viewed as processes of unbalanced deformation and cracking. The unbalances refer to dissimilar mechanisms occurring in opposing halves of thermal fatigue loading and unloading cycles. Extensive data summaries are presented and results are interpreted in terms of the unbalanced processes involved. Both crack initiation and crack propagation results are summarized. Testing techniques are reviewed, and considerable discussion is given to a technique for thermal fatigue simulation, known as the bithermal fatigue test. Attention is given to the use of isothermal life prediction methods for the prediction of thermal fatigue lives. Shortcomings of isothermally-based life prediction methods are pointed out. Several examples of analyses and thermal fatigue life predictions of high technology structural components are presented. Finally, numerous dos and don'ts relative to design against thermal fatigue are presented.

  3. An indentation fatigue strength law

    NASA Astrophysics Data System (ADS)

    Xu, Baoxing; Yonezu, Akio; Chen, Xi

    2010-05-01

    Indentation fatigue, where a cyclic load is applied on the sample via an indenter, emerges as an alternative approach for measuring the fatigue properties of materials. We have carried out indentation fatigue tests on a poly(vinyl chloride) (PVC) bulk material, as well as on TiN and NiP films/coatings deposited on SUS304 steel substrates, and demonstrate that a simple power-law relationship can be established between the indentation load amplitude and number of cycles to failure. Such a law is very similar to the conventional fatigue strength law obtained from uniaxial tests. The agreement between the fatigue stress exponents obtained by uniaxial and indentation fatigue tests suggests the potential applicability of the indentation fatigue technique for extracting the fatigue properties of materials.

  4. Relationship between fatigue and photosensitivity.

    PubMed

    Shigihara, Yoshihito; Tanaka, Masaaki; Watanabe, Yasuyoshi

    2010-01-01

    It is considered that photosensitivity is one of the most important factors to cause video-game epilepsy. Since photosensitivity is thought to cause various signs of hypersensitivity in the central nervous system and hypersensitivity is believed to be related to fatigue, whether fatigue is associated with photosensitivity was determined. The study group consisted of 68 healthy medical students attending Osaka City University Graduate School of Medicine. They completed questionnaires dealing with fatigue (Chalder Fatigue Scale) and photosensitivity. On simple regression analyses, fatigue score was positively associated with photosensitivity score. Similarly, on multiple regression analyses adjusted for age, gender, and sleeping hours, fatigue score was positively associated with photosensitivity score. Fatigue is associated with photosensitivity. Our findings provide new perspectives on fatigue.

  5. Chronic Fatigue Syndrome (CFS): Symptoms

    MedlinePlus

    ... please visit this page: About CDC.gov . Chronic Fatigue Syndrome (CFS) Share Compartir Symptoms On this Page ... Symptoms What's the Clinical Course of CFS? Chronic fatigue syndrome can be misdiagnosed or overlooked because its ...

  6. Estimation of excess mortality due to long-term exposure to PM2.5 in Japan using a high-resolution model for present and future scenarios

    NASA Astrophysics Data System (ADS)

    Goto, Daisuke; Ueda, Kayo; Ng, Chris Fook Sheng; Takami, Akinori; Ariga, Toshinori; Matsuhashi, Keisuke; Nakajima, Teruyuki

    2016-09-01

    Particulate matter with a diameter of less than 2.5 μm, known as PM2.5, can affect human health, especially in elderly people. Because of the imminent aging of society in the near future in most developed countries, the human health impacts of PM2.5 must be evaluated. In this study, we used a global-to-regional atmospheric transport model to simulate PM2.5 in Japan with a high-resolution stretched grid system (∼10 km for the high-resolution model, HRM) for the present (the 2000) and the future (the 2030, as proposed by the Representative Concentrations Pathway 4.5, RCP4.5). We also used the same model with a low-resolution uniform grid system (∼100 km for the low-resolution model, LRM). These calculations were conducted by nudging meteorological fields obtained from an atmosphere-ocean coupled model and providing emission inventories used in the coupled model. After correcting for bias, we calculated the excess mortality due to long-term exposure to PM2.5 among the elderly (over 65 years old) based on different minimum PM2.5 concentration (MINPM) levels to account for uncertainty using the simulated PM2.5 distributions to express the health effect as a concentration-response function. As a result, we estimated the excess mortality for all of Japan to be 31,300 (95% confidence intervals: 20,700 to 42,600) people in 2000 and 28,600 (95% confidence intervals: 19,000 to 38,700) people in 2030 using the HRM with a MINPM of 5.8 μg/m3. In contrast, the LRM resulted in underestimates of approximately 30% (for PM2.5 concentrations in the 2000 and 2030), approximately 60% (excess mortality in the 2000) and approximately 90% (excess mortality in 2030) compared to the HRM results. We also found that the uncertainty in the MINPM value, especially for low PM2.5 concentrations in the future (2030) can cause large variability in the estimates, ranging from 0 (MINPM of 15 μg/m3 in both HRM and LRM) to 95,000 (MINPM of 0 μg/m3 in HRM) people.

  7. Methylphenidate for Fatigue in Ambulatory Men with Prostate Cancer

    PubMed Central

    Roth, Andrew J.; Nelson, Christian; Rosenfeld, Barry; Scher, Howard; Slovin, Susan; Morris, Michael; Arauz, Gabrielle; Breitbart, William

    2013-01-01

    Purpose Fatigue is a highly prevalent and clinically significant symptom of advanced prostate cancer. To date, however, there are no published controlled trials of interventions for fatigue in men with prostate cancer. Method This six-week, randomized, double-blind, placebo-controlled design, evaluated the efficacy of methylphenidate to treat fatigue in prostate cancer patients. Inclusion criteria included men with advanced prostate cancer and the presence of moderate to severe fatigue. Patients with major depression, hypothyroidism, uncontrolled hypertension, arrhythmia or anemia were excluded. Fatigue levels, blood pressure, pulse and other safety concerns were monitored regularly. Results Thirty-two subjects were randomized to methylphenidate (N=16) or placebo (N=16). Brief Fatigue Inventory (BFI) total scores significantly decreased for both groups, however the methylphenidate group, as compared to placebo, reported greater decrease on BFI severity scores (p=.03) and a trend toward greater decrease on BFI total scores (p=.07). A significantly greater number of subjects in the methylphenidate group vs. the placebo group demonstrated clinically significant improvement in fatigue on total BFI scores (7/10 vs. 3/13) and BFI severity scores (8/10 vs. 3/13). Importantly, six subjects in the methylphenidate group discontinued due to increased blood pressure or tachycardia. There were no serious adverse events. Conclusions Methylphenidate is effective in treating fatigue in men with prostate cancer; however, oncologists need to monitor for possible pulse and blood pressure elevations. PMID:20665492

  8. Fatigue related changes in electromyographic coherence between synergistic hand muscles.

    PubMed

    Kattla, Shashikala; Lowery, Madeleine M

    2010-04-01

    The aim of this study was to examine coherence between surface electromyographic (EMG) signals from two index finger flexor muscles, the first dorsal interosseous (FDI) and flexor digitorum superficialis (FDS), during and immediately following sustained, fatiguing isometric contraction. Coherence was observed between the FDI and FDS EMG signals in the tremor (8-12 Hz), beta (15-35 Hz) and gamma (35-60 Hz) bands in all subjects. A significant increase in EMG-EMG coherence in the beta and gamma frequency bands was observed immediately following the fatiguing contraction. No significant difference was observed in the tremor band coherence before and after fatigue. Coherence was observed between EMG and force in the tremor band during both the pre- and post-fatigue contractions and a significant increase in the FDI EMG-force coherence post-fatigue was observed. It is suggested that the increase in beta and gamma band coherence with fatigue may be due to increased levels of corticomotoneuronal drive to both muscles. Alternatively, the increased EMG-EMG coherence may reflect an increased contribution of peripheral afferents to coupling across the muscle with fatigue. Although the functional significance is not clear, the increase in coherence may help to overcome reduced motoneuron excitability with fatigue, to bind together different sensorimotor elements or to coordinate force generation across muscles in a more synergistic manner as the force generating capacity of the muscle is decreased.

  9. Effect of electrostimulation training-detraining on neuromuscular fatigue mechanisms.

    PubMed

    Jubeau, Marc; Zory, Raphaël; Gondin, Julien; Martin, Alain; Maffiuletti, Nicola A

    2007-08-31

    The aim of this study was to evaluate the effects of neuromuscular electrical stimulation (NMES) training and subsequent detraining on neuromuscular fatigue mechanisms. Ten young healthy men completed one NMES fatigue protocol before and after a NMES training program of 4 weeks and again after 4 weeks of detraining. Muscle fatigue (maximal voluntary torque loss), central fatigue (activation failure), and peripheral fatigue (transmission failure and contractile failure) of the plantar flexor muscles were assessed by using a series of electrically evoked and voluntary contractions with concomitant electromyographic and torque recordings. At baseline, maximal voluntary torque decreased significantly with fatigue (P<0.001), due to both activation and transmission failure. After detraining, maximal voluntary torque loss was significantly reduced (P<0.05). In the same way, the relative decrease in muscle activation after training and detraining was significantly lower compared to baseline values (P<0.05). Short-term NMES training-detraining of the plantar flexor muscles significantly reduced the muscle fatigue associated to one single NMES exercise session. This was mainly attributable to a reduction in activation failure, i.e., lower central fatigue, probably as a result of subject's accommodation to pain and discomfort during NMES.

  10. Mean stress effects in biaxial fatigue of Inconel 718

    SciTech Connect

    Socie, D.F.; Shield, T.W.

    1984-07-01

    Biaxial fatigue tests were conducted on Inconel 718 thin-walled tubular specimens to quantify the effect of mean stress. The specimens were loaded in combined tension and torsion in strain control at room temperature. Fatigue lives ranged from 3000 to 15,000 cycles depending on the mean stress. These data were correlated with a parameter based on the maximum plastic shear strain amplitude, normal strain amplitude and mean normal stress on the plane of maximum shear strain amplitude. This parameter was combined with the Coffin-Manson equation for estimating fatigue lives. Observations of the cracking behavior show that mean stress affects the rate of crack growth and distribution of cracks.

  11. Notched Fatigue Behavior of PEEK

    PubMed Central

    Murphy, JE; Brinkman, JG; Kurtz, SM; Rimnac, CM

    2013-01-01

    Poly(ether-ether-ketone) (PEEK) has been used as a load bearing orthopaedic implant material with clinical success. All of the orthopaedic applications contain stress concentrations (notches) in their design; however, little work has been done to examine the fatigue behavior of PEEK in the presence of a notch. This work examines both stress-life (SN) fatigue behavior and the fracture behavior of unfilled PEEK under tension tension loading in circumferentially grooved round bar specimens with different elastic stress concentration factors. It was found that the majority of the loading was elastic in nature, and that there was only a small portion on the lifetime where there was a detectable change in structural behavior prior to gross fracture. Fractographic analysis via SEM further elucidated the potential fracture micromechanisms. Additional analysis was conducted to estimate the percent of the lifetime spent in crack initiation vs propagation, and it was found that the specimens spent the majority of the time in the crack initiation phase. PMID:20864160

  12. Fatigue and fracture overview

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.

    1986-01-01

    The accomplishments achieved under the isotropic creep-fatigue crack initiation life prediction program are summarized. A sizeable creep-fatigue crack initiation data base was generated on the nickel-base superalloy, B-1900. Companion constitutive modeling programs have also generated extensive data bases on the same heat of material. The crack initiation results have formed the basis of a new approach to creep-fatigue life prediction. The term Cyclic Damage Accumulation (CDA) was coined for the method, which was evaluated under isothermal, uniaxial conditions. Stringent laboratory verification experiments were used to test the accuracy of the method. Considering the quite limited material property data needed to evaluate the constants in the approach, the prediction accuracy is acceptable. At the expense of the larger data base required, Lewis developed total strain- strainrange partitioning method (TS-SRP) is capable of a higher degree of accuracy.

  13. Fatigue and Barkhausen effect

    NASA Astrophysics Data System (ADS)

    Tong, Wei

    Piezomagnetism designates a change in the magnetization of materials induced by mechanical actions such as tension or compression. The type of Barkhausen effect that occurs in this work consists of sudden, discontinuous jumps in a material's magnetization that appear in response to smooth (continuous) stress variations. A series of strain controlled fatigue tests with an alternating sinusoidal waveform were carried out to study the relationship between the endurance limit and the Barkhausen effect. Results of fatigue tests on steel specimens exhibiting Barkhausen pulses at various stages are reported and a threshold-crossing analysis is applied to the test results. These studies show that when the fatigue limit is approached, the Barkhausen pulses become, in general, more intense in amplitude and quantity than at other stress levels. A hypothetical mechanism is proposed that relates the intensity of the Barkhausen response to the inception of micro-cracking and rearrangements of the mechanical lattice at the microscopic level.

  14. Effect of Microstructural Banding on the Fatigue Behavior of Induction-Hardened 4140 Steel

    NASA Astrophysics Data System (ADS)

    Hayne, M. L.; Anderson, P. I.; Findley, K. O.; Van Tyne, C. J.

    2013-08-01

    The fatigue behavior of induction-hardened calcium-treated 4140 steel with three different case depths was evaluated using rotating bending fatigue tests. The as-received microstructure of the steel was banded and the orientation of microstructural banding with respect to the fatigue specimen was varied. Due to the inclusion shape control resulting from the calcium additions, inclusions in the steel were not elongated in the direction of the banding. It was found that microstructure banding does not have a significant influence on the fatigue properties of the steel tested. Furthermore, the fatigue limit increase with case depth is primarily related to the bending stress near the location of crack nucleation.

  15. Estimating Parallax Error Due to Orbital Motion for HST/WFC3 Spatial Scan Observations of 19 Long-period Classical Cepheids

    NASA Astrophysics Data System (ADS)

    Anderson, Richard I.; Casertano, Stefano; Riess, Adam G.

    2017-01-01

    We employ the Hubble Space Telescope's Wide Field Camera 3 (HST/WFC3) in spatial scanning mode to measure 30 - 40μas parallax of 19 classical Cepheids in the Milky Way with the aim of improving the calibration of the cosmic distance scale (Riess et al. 2014; Casertano et al. 2016). The measured parallaxes are an order of magnitude more precise than parallaxes from the first Gaia data release and thus furthermore provide important cross-checks for Gaia data processing.Here we present our work aimed at estimating the parallax error due to orbital motion caused by undetected companion stars (Anderson et al. 2016). We have secured more than 1600 high-precision radial velocity (RV) measurements of the 19 long-period (Ppuls > 9d) Cepheids in our sample using ground-based telescopes on both hemispheres to investigate the presence of spectroscopic companions. We model the RV variability together with orbital motion using a grid of input orbital periods, Porb. We determine upper limits on the (unsigned) projected parallax error induced by hypothetical companions using the orbital configuration upper limits determined by modeling RV data. We thus show that our HST/WFC3 parallax measurements are subject to an error of less than 2% in parallax (i.e., typically less than ±7μas) for 16 stars in the sample, and < 4% for two Cepheids with fewer RV observations. For YZ Carinae, however, we correct the previously published orbital solution and show that the astrometric model must take into account orbital motion to avoid significant (approx. ±100μas) parallax error.We have further investigated long-timescale (Porb > 10yr) orbital motion using literature data and RV templates based on our new data. We thus discover new evidence for RV signals due to long-term orbital motion for 4 Cepheids and critically assess putative evidence for spectroscopic binarity previously reported based on data of much lesser quality. We caution that astrometric measurements of binaries with Porb on

  16. Fatigue 󈨛. Volume 2,

    DTIC Science & Technology

    1987-06-01

    Sci.,12,1g78,64 (6) Antolovich ,S.D.,Rosa,E.and Pineau,A.,Mat.Sci.Eng.,47,1981,47 (7)Bricknell,R.H.and Woodford,D.A.,Metall.Trans.,A12,1981,425 (8...M. Rddhakrishnan, Trans. ASME, J. Engr. Matls. & Tech., 1983, vol. 105, p. 273. (16) J. P. Bailon and S. 0. Antolovich , in FATIGUE MECHANISMS...time t = time (min) th = hold-time period (min) Oc = creep fraction damage OF = fatigue fraction damage REFERENCES (1) Antolovich , S.D. and Zamrik, S

  17. Estimates of net infiltration in arid basins and potential impacts on recharge and solute flux due to land use and vegetation change

    NASA Astrophysics Data System (ADS)

    Robertson, Wendy Marie; Sharp, John M.

    2015-03-01

    Human impacts on land use and vegetation in arid basins have, in some regions, altered infiltration, recharge, and groundwater chemistry. However, some modeling approaches currently used do not account for these effects. In the Trans-Pecos region of Texas the presence of modern water, increasing groundwater NO3- concentrations, and vadose zone cores flushed of naturally accumulated solutes belie the notion that basin groundwater is unaffected by overlying land use and vegetation change. Recharge to the Trans-Pecos basins is spatially and temporally variable, and due to human impacts it has likely changed since pre-western settlement time (circa 1850s). By using the INFIL 3.0.1 model, a spatially distributed model of net infiltration, the volume and spatial distribution of net infiltration was examined for two basins, Wild Horse/Michigan Flats and Lobo/Ryan Flats, with model simulations designed to examine the effects of irrigated agriculture and human impacts on vegetation. Model results indicate that recharge to the basins is not limited to mountain-front zones and discrete features (i.e., alluvial channels), rather, irrigation return flow contributes an estimated 6.3 × 107 m3 (408 mm) of net infiltration over 40 yrs and net infiltration on the basin floors could contribute between 7% and 11.5% of annual basin recharge. Model results also indicate that net infiltration may be higher under current vegetation regimes than in pre-western settlement conditions; the removal of thick dense grasslands in INFIL model simulations enhanced net infiltration by 48% or more. Results from distributed models (like INFIL) improve upon scientific understanding of the links between vegetation regime and hydrological processes; this is important for the sustainable management of arid basin aquifers in Texas and elsewhere.

  18. Fatigue and fatigue crack growth processes in hard tissues: The importance of age and surface integrity

    NASA Astrophysics Data System (ADS)

    Majd, Hessam

    With the progressive increase in partially and fully dentate seniors, fracture has become an increasingly common form of restored tooth failure. Dentin undergoes progressive changes in microstructure with patient age, and studies are now suggesting that there is a reduction in fatigue strength and fatigue crack growth resistance of this tissue. This dissertation explores aging of dentin, the influence of flaws that are introduced during restorative processes on the fatigue properties of dentin, and proposes models for characterizing the damage initiation and growth process during fatigue of dentin. Results from this investigation show that the fatigue crack growth properties (Paris Law parameters (C, m) andDeltaKth) of human dentin undergo the most significant changes at a patient age of 42 years. Based on the fatigue crack growth responses, three age groups were established including young (age≤33), aged (34≤age ≤49) and old (50≤age) patients for further analysis. There were significant differences in the initiation and growth behavior between the tissues of patients from the three age groups. With regards to the influence of restorative processes, there was no influence on the quasi-static responses of dentin. However, the endurance limit of dentin treated with the dental burs (28 MPa) and abrasive air jet (35 MPa) were approximately 36% and 20% lower than that of the control (44 MPa), respectively. Both cutting processes caused a significant reduction (p≤0.0001) in fatigue strength. An accumulative damage model was developed to characterize fatigue of the control and bur treated dentin as well as provide a model for fatigue life prediction. The damage models were derived as a function of number of loading cycles (N), and ratio of applied stress to ultimate strength (r). The developed models provide estimations for the initial state of damage, the state of damage during the life, as well as the damage accumulation rate for cyclic loading of dentin

  19. Bending stresses in spherically hollow ball bearing and fatigue experiments

    NASA Technical Reports Server (NTRS)

    Nypan, L. J.; Coe, H. H.; Parker, R. J.

    1975-01-01

    Spherically hollow balls of 21.7, 50.0, and 56.5 percent mass reduction were operated in ball bearings and in a five-ball fatigue tester with differing outcomes. Available theoretical and experimental treatments of stresses in spherically hollow balls are reviewed and compared. Bending stresses are estimated for these spherically hollow balls to better understand the differences in ball bearing and fatigue test experience.

  20. Aircrew Fatigue during Extended Transport, Tactical and Command Post Operations

    DTIC Science & Technology

    1983-11-01

    USAF School of Aerospace Medicine Aerospace Medical Divislon (APSC) Brooks Air Force aise, Texas 78235 MMRlf-r{tings of subjective fatigue and sleep... Medicine (UBAPSRN) has used a variety of psychobiological measures to evaluate crew fatigue in both air- borne and ground operations. The measures...the mission-day (Table 4). Because of missing data, beet -estimates of means were calculated for the various com- parisons, resulting in two sets of

  1. The Effect of Osteoporosis Treatments on Fatigue Properties of Cortical Bone Tissue.

    PubMed

    Brock, Garry R; Chen, Julia T; Ingraffea, Anthony R; MacLeay, Jennifer; Pluhar, G Elizabeth; Boskey, Adele L; van der Meulen, Marjolein C H

    2015-06-01

    Bisphosphonates are commonly prescribed for treatment of osteoporosis. Long-term use of bisphosphonates has been correlated to atypical femoral fractures (AFF). AFFs arise from fatigue damage to bone tissue that cannot be repaired due to pharmacologic treatments. Despite fatigue being the primary damage mechanism of AFFs, the effects of osteoporosis treatments on fatigue properties of cortical bone are unknown. To examine if fatigue-life differences occur in bone tissue after different pharmacologic treatments for osteoporosis, we tested bone tissue from the femurs of sheep given a metabolic acidosis diet to induce osteoporosis, followed by treatment with a selective estrogen reception modulator (raloxifene), a bisphosphonate (alendronate or zoledronate), or parathyroid hormone (teriparatide, PTH). Beams of cortical bone tissue were created and tested in four-point bending fatigue to failure. Tissues treated with alendronate had reduced fatigue life and less modulus loss at failure compared to other treatments, while tissue treated with PTH had a prolonged fatigue life. No loss of fatigue life occurred with zoledronate treatment despite its greater binding affinity and potency compared to alendronate. Tissue mineralization measured by microCT did not explain the differences seen in fatigue behavior. Increased fatigue life with PTH suggests that current treatment methods for AFF could have beneficial effects for restoring fatigue life. These results indicate that fatigue life differs with each type of osteoporosis treatment.

  2. Influence of axle-wheel interface on ultrasonic testing of fatigue cracks in wheelset.

    PubMed

    Makino, Kazunari; Biwa, Shiro

    2013-01-01

    For the ultrasonic testing at the wheel seat of railway axles, quantitative investigation of the reflection and transmission phenomena at the axle-wheel interface is important. This paper describes the influence of the axle-wheel interface on the ultrasonic testing of a fatigue crack in a wheelset by applying the spring interface model. The normal and tangential stiffnesses were identified experimentally for an as-manufactured wheelset at the normal incidence, and the reflection coefficient for the shear-wave oblique incidence was calculated. A parametric study was performed to clarify the influence of these interfacial stiffnesses on the incident-angle dependence of the reflection coefficient. The calculated reflection coefficient at the incident angle of 45° qualitatively explained the relative echo-height decrease due to the presence of a wheel observed experimentally for a wheelset in fatigue loading by rotating bending. The quantitative difference between the experimental and calculated results was considered to be due to the reduction of the effective interference of shrink fit by the wear at the axle-wheel interface during the fatigue loading as well as by the applied bending moment. For the estimated relative echo-height decrease to agree with the experimental results, the interfacial stiffnesses were found to be smaller than the values identified for the as-manufactured wheelset by a factor of 0.5-0.7. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. The Effect of Structural Quality on Fatigue Life in 319 Aluminum Alloy Castings

    NASA Astrophysics Data System (ADS)

    Özdeş, Hüseyin; Tiryakioğlu, Murat

    2016-12-01

    Tensile and fatigue life data for 319 aluminum alloy from seventeen datasets reported in four independent studies from the literature have been reanalyzed. Analysis of fatigue life data involved mean stress correction for different R ratios used in fatigue testing, inclusion of survival (runout) data along with failure data, as well as volumetric correction for Weibull distributions for different specimen sizes used in these studies. Tensile data have been transformed into the structural quality index, Q T, which is used as a measure of the structural quality of castings. A distinct relationship has been observed between the expected fatigue life and mean quality index. Moreover, fatigue strengt