Science.gov

Sample records for failure investigation 1983-2009

  1. Genesis Failure Investigation Report

    NASA Technical Reports Server (NTRS)

    Klein, John

    2004-01-01

    The-Genesis mission to collect solar-wind samples and return them to Earth for detailed analysis proceeded successfully for 3.5 years. During reentry on September 8, 2004, a failure in the entry, descent and landing sequence resulted in a crash landing of the Genesis sample return capsule. This document describes the findings of the avionics sub-team that supported the accident investigation of the JPL Failure Review Board.

  2. ACIS Door Failure Investigation and Mitigation Procedures

    NASA Technical Reports Server (NTRS)

    Podgorski, William A.; Tice, Neil W.; Plucinsky, Paul P.

    2000-01-01

    NASA's Chandra X-ray Observatory (formerly AXAF) was launched on July 23, 1999 and is currently in orbit performing scientific studies. Chandra is the third of NASA's Great Observatories to be launched, following the Hubble Space Telescope and the Compton Gamma Ray Observatory. One of four primary science instruments on Chandra, and one of only two focal plane instruments, is the Advanced CCD Imaging Spectrometer, or ACIS. The ACIS focal plane and Optical Blocking Filter (OBF) must be launched under vacuum, so a tightly sealed, functioning door and venting subsystem were implemented. The door was opened two and one-half weeks after launch (after most out-gassing of composite materials) and allowed X-rays to be imaged by the ACIS CCD's in the focal plane. A failure of this door to open on-orbit would have eliminated all ACIS capabilities, severely degrading mission science. During the final pre-flight thermal-vacuum test of the fully integrated Chandra Observatory at TRW, the ACIS door failed to open when commanded to do so. This paper describes the efforts, under considerable time pressure, by NASA, its contractors and outside review teams to investigate the failure and to develop modified hardware and procedures which would correct the problem. Of interest is the fact that the root cause of the test failure was never clearly identified despite massive effort. We ultimately focussed on hardware and procedures designed to mitigate the effects of potential, but unproven, failure modes. We describe a frequent real-world engineering situation in which one must proceed on the best basis possible in the absence of the complete set of facts.

  3. Analytical investigation of solid rocket nozzle failure

    NASA Technical Reports Server (NTRS)

    Mccoy, K. E.; Hester, J.

    1985-01-01

    On April 5, 1983, an Inertial Upper Stage (IUS) spacecraft experienced loss of control during the burn of the second of two solid rocket motors. The anomaly investigation showed the cause to be a malfunction of the solid rocket motor. This paper presents a description of the IUS system, a failure analysis summary, an account of the thermal testing and computer modeling done at Marshall Space Flight Center, a comparison of analysis results with thermal data obtained from motor static tests, and describes some of the design enhancement incorporated to prevent recurrence of the anomaly.

  4. Everyday Attention Failures: An Individual Differences Investigation

    ERIC Educational Resources Information Center

    Unsworth, Nash; McMillan, Brittany D.; Brewer, Gene A.; Spillers, Gregory J.

    2012-01-01

    The present study examined individual differences in everyday attention failures. Undergraduate students completed various cognitive ability measures in the laboratory and recorded everyday attention failures in a diary over the course of a week. The majority of attention failures were failures of distraction or mind wandering in educational…

  5. Materials investigation of STS-3 parachute failure

    NASA Technical Reports Server (NTRS)

    Nichols, R. L.

    1983-01-01

    Main parachute, No. 2 of SRB A-12 on STS-3, sustained damage during deployment or initial inflation that resulted in its collapse and failure to sustain load. During an investigation of the materials from this parachute, optical and scanning electron microscope analyses were conducted. This examination identified stains and abrasions on vent lines that appear to have been a result of friction contact with its flotation bag lanyard. Mechanical testing of the vent band indicated a reduction in strength of 37 percent obviously due to structural overload, heat, and ocean water exposure. It is concluded from this and other available data that entanglement of parachutes No. 1 and No. 2 during deployment caused adequate structural damage to main parachute No. 2 to render it unable to carry load.

  6. Everyday attention failures: an individual differences investigation.

    PubMed

    Unsworth, Nash; McMillan, Brittany D; Brewer, Gene A; Spillers, Gregory J

    2012-11-01

    The present study examined individual differences in everyday attention failures. Undergraduate students completed various cognitive ability measures in the laboratory and recorded everyday attention failures in a diary over the course of a week. The majority of attention failures were failures of distraction or mind wandering in educational contexts (in class or while studying). Latent variable techniques were used to perform analyses, and the results suggested that individual differences in working memory capacity and attention control were related to some but not all everyday attention failures. Furthermore, everyday attention failures predicted SAT scores and partially accounted for the relation between cognitive abilities and SAT scores. These results provide important evidence for individual differences in everyday attention failures as well as for the ecological validity of laboratory measures of working memory capacity and attention control.

  7. Cumberland last stage blade failure investigation

    SciTech Connect

    Puri, A.; Lam, T.

    1995-12-31

    TVA`s Cumberland plant has two sister units which are rated 1,300 MW each, and have been in service since 1973. Five other units in the United States share the identical design and configuration as the Cumberland machines, and have a similar operating history. Relying on a cross compound design, these machines have an HP turbine and two LP turbines in line A, an IP turbine and two LP turbines in line B. The four double flow LP turbines are identical in design. The L-0 stage is comprised of 71 free standing blades, each of which measures 30 inches from hub to tip. On December 3, 1993, Unit 1 experienced an in-service catastrophic failure. Subsequent inspection revealed that blade {number_sign}35 in the L-0 stage, LP1 turbine end of A line had failed in the airfoil near the platform. The separation of blade {number_sign}35 caused a revere rotor unbalance which resulted in extensive consequential damage to all the components in the A line rotor train. To manage the forced outage and minimize the unit downtime the plant needed to establish (a) a list of immediate actions to restore the damaged unit and return it back into service and (b) the long term actions which should be taken to ensure the reliability of both the damaged machine and its sister unit. A key issue included within this decision making process was to identify the root cause of failure of blade {number_sign}35. By relying on the EPRI BLADE{trademark} program, TVA was able to initiate a technical investigation in parallel with the repair efforts being performed with the cooperation of the Original Equipment Manufacturers (OEM). Based on the technical detail generated in part with BLADE, and supplemented with a series of additional tests and studies, TVA was able to bring Unit 1 back into service and reduce the downtime by 58 days, and thereby save an estimated $25.55 million towards the purchase of replacement power.

  8. 49 CFR 193.2515 - Investigations of failures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... GAS FACILITIES: FEDERAL SAFETY STANDARDS Operations § 193.2515 Investigations of failures. (a) Each... Administrator or relevant state agency under the pipeline safety laws (49 U.S.C. 60101 et seq.) investigates...

  9. ISS Fiber Optic Failure Investigation Root Cause Report

    NASA Technical Reports Server (NTRS)

    Leidecker, Henning; Plante, Jeannette

    2000-01-01

    In August of 1999, Boeing Corporation (Boeing) engineers began investigating failures of optical fiber being used on International Space Station flight hardware. Catastrophic failures of the fiber were linked to a defect in the glass fiber. Following several meetings of Boeing and NASA engineers and managers, Boeing created and led an investigation team, which examined the reliability of the cable installed in the U.S. Lab. NASA Goddard Space Flight Center's Components Technologies and Radiation Effects Branch (GSFC) led a team investigating the root cause of the failures. Information was gathered from: regular telecons and other communications with the investigation team, investigative trips to the cable distributor's plant, the cable manufacturing plant and the fiber manufacturing plant (including a review of build records), destructive and non-destructive testing, and expertise supplied by scientists from Dupont, and Lucent-Bell Laboratories. Several theories were established early on which were not able to completely address the destructive physical analysis and experiential evidence. Lucent suggested hydrofluoric acid (HF) etching of the glass and successfully duplicated the "rocket engine" defect. Strength testing coupled with examination of the low strength break sites linked features in the polyimide coating with latent defect sites. The information provided below explains what was learned about the susceptibility of the pre-cabled fiber to failure when cabled as it was for Space Station and the nature of the latent defects.

  10. Changes in dental caries and oral hygiene among 7-8 year-old schoolchildren in different regions of Lithuania 1983-2009.

    PubMed

    Matulaitiene, Zivilė Kristina; Zemaitiene, Migle; Zemgulyte, Sandra; Milciuviene, Simona

    2012-01-01

    The objectives of this study were to evaluate and compare the changes of the dental caries prevalence and severity of 7 to 8 year old schoolchildren in six Lithuanian regions over the past 26 years (1983-2009) and to propose recommendations based on the results of the study. The study is based on the analysis of data, containing 576 cases of children examined in 1983 and comparison with data containing 531 cases added in 2009. The studies were conducted in the same six regions of Lithuania among the children from 7 to 8 years of age. For the study of children the WHO oral assessment methodology was used (WHO Basic methods 1997). Severity of dental caries was described by df-t and DMF-T index. The average of individual df-t and DMF-T indices was calculated for all subjects and sorted by gender. Oral hygiene status was evaluated by applying the simplified Green-Vermilion index-OHI-S (1964) The prevalence of primary dental caries among the children 7 to 8 years of age was 92.4% in 1983 and 88.7% (p=0.43) in 2009. The prevalence of permanent dental caries decreased from 49.6% in 1983 to 29.7% (p<0.001) in 2009. Mean df-t score decreased from 4.9±3.4 in 1983 to 4.1±2.7 in 2009 and DMF-T index decreased from 1.1±1.7 in 1983 to 0.5±1.0 in 2009 (p<0.001). The OHI-S index was not significantly different during 1983-2009. In the period of last 26 years a tendency towards the decrease in the prevalence and severity of dental caries was observed. That could be related to the frequent using of the toothpastes with fluoride, as well as implementation of the caries prevention program with sealants among the children of that age. The poor oral hygiene and comparatively high caries prevalence in schoolchildren show that it is still necessary to improve preventive measures in Lithuania.

  11. 29 CFR 502.21 - Failure to cooperate with investigations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Failure to cooperate with investigations. 502.21 Section 502.21 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR DIVISION, DEPARTMENT OF LABOR... SECTION 218 OF THE IMMIGRATION AND NATIONALITY ACT (SUSPENDED 6-29-2009) Enforcement of Work...

  12. Investigation of valve failure problems in LWR power plants

    SciTech Connect

    1980-04-01

    An analysis of component failures from information in the computerized Nuclear Safety Information Center (NSIC) data bank shows that for both PWR and BWR plants the component category most responsible for approximately 19.3% of light water reactor (LWR) power plant shutdowns. This investigation by Burns and Roe, Inc. shows that the greatest cause of shutdowns in LWRs due to valve failures is leakage from valve stem packing. Both BWR plants and PWR plants have stem leakage problems (BWRs, 21% and PWRs, 34%).

  13. Investigation of capacitor failures in an automated external defibrillator.

    PubMed

    Tan, K-S; Hinberg, I

    2002-09-01

    Over the past 2 years, the Canadian Medical Devices Bureau has received a number of reports of capacitor failures on the high voltage board of an automated external defibrillator. Twenty-five cases of broken capacitor leads were found during routine preventive maintenance by the biomedical engineering staff of the institutions reporting the incidents. The Bureau has carried out a laboratory investigation to determine the effect of missing capacitors on the energy delivered by the defibrillator and to assess whether these capacitor failures represent a significant risk to patients. Our findings indicate that the automated external defibrillator will not perform acceptably with two broken capacitors. They further suggest that, during preventive maintenance, operators should use a defibrillator analyser to measure the delivered energy output rather than using the internal energy measurement circuit within the automated external defibrillator. PMID:12394622

  14. 49 CFR 192.617 - Investigation of failures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS... operator shall establish procedures for analyzing accidents and failures, including the selection...

  15. 49 CFR 192.617 - Investigation of failures.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS... operator shall establish procedures for analyzing accidents and failures, including the selection...

  16. 49 CFR 192.617 - Investigation of failures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS... operator shall establish procedures for analyzing accidents and failures, including the selection...

  17. 49 CFR 192.617 - Investigation of failures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS... operator shall establish procedures for analyzing accidents and failures, including the selection...

  18. 49 CFR 192.617 - Investigation of failures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS... operator shall establish procedures for analyzing accidents and failures, including the selection...

  19. Investigation of rainfall infiltration and slope failure using numerical model

    NASA Astrophysics Data System (ADS)

    Lin, H.; Chang, K.; Wen, J.

    2012-12-01

    This research simulated the real condition of the rain period at Ping Ding Village, Yunlin, Taiwan using FEMWATER and STABLE PRO in order to investigate the effects of infiltration on landslide behavior. We established a three-dimensional numerical groundwater model (FEMWATER) to simulate water infiltration and flow during the rain period in Ping Ding Village, estimated water content of the soil layer, and used STABLEPRO to analysis the stability of the slope. The aim of the research was to investigate the influence of infiltration on the slope instability. According to the results of sensitivity analysis, we found the pressure head of Layer-2 was affected by every parameter discussed in this research. And the affect from the Layer-1 and the Layer-3 also played an important role on pressure head of the Layer-2. According to the numerical simulation of rainfall infiltration, the simulation result on the borehole BH02 was satisfied (L1=0.013, L2=0.021, COR=0.997). The result of slope stability analysis showed that the B-B' profile had lower safety factor (0.989) which indicated higher potential of slope failure. The history records also sustained the result of our study. However, the A-A' profile had higher safety (1.142) factor than B-B' profile.

  20. Genesis failure investigation report : JPL Failure Review Board, Avionics Sub-Team

    NASA Technical Reports Server (NTRS)

    Klein, John; Manning, Rob; Barry, Ed; Donaldson, Jim; Rivellini, Tom; Battel, Steven; Savino, Joe; Lee, Wayne; Dalton, Jerry; Underwood, Mark; Surampudi, Rao; Accord, Arden; Perkins, Dave; Barrow, Kirk; Wilson, Bob

    2004-01-01

    On January 7, 2001, the Genesis spacecraft lifted off from Cape Canaveral. Its mission was to collect solar wind samples and return those samples to Earth for detailed analysis by scientists. The mission proceeded successfully for three-and-a-half years. On September 8, 2004, the spacecraft approached Earth, pointed the Sample Return Capsule (SRC) at its entry target, and then fired pyros that jettisoned the SRC. The SRC carried the valuable samples collected over the prior 29 months. The SRC also contained the requisite hardware (mechanisms, parachutes, and electronics) to manage the process of entry, descent, and landing (EDL). After entering Earthas atmosphere, the SRC was expected to open a drogue parachute. This should have been followed by a pyro event to release the drogue chute, and then by a pyro event to deploy the main parachute at an approximate elevation of 6.7 kilometers. As the SRC descended to the Utah landing site, helicopters were in position to capture the SRC before the capsule touched down. On September 8, 2004, observers of the SRCas triumphant return became concerned as the NASA announcer fell silent, and then became even more alarmed as they watched the spacecraft tumble as it streaked across the sky. Long-distance cameras clearly showed that the drogue parachute had not deployed properly. On September 9, 2004, General Eugene Tattini, Deputy Director of the Jet Propulsion Laboratory formed a Failure Review Board (FRB). This board was charged with investigating the cause of the Genesis mishap in close concert with the NASA Mishap Investigation Board (MIB). The JPL-FRB was populated with experts from within and external to the Jet Propulsion Laboratory. The JPL-FRB participated with the NASA-MIB through all phases of the investigation, working jointly and concurrently as one team to discover the facts of the mishap.

  1. Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

    SciTech Connect

    Kim, Jihoon; Moridis, George

    2014-11-01

    We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

  2. Investigation of Tantalum Wet Slug Capacitor Failures in the Apollo Telescope Mount Charger Battery Regulator Modules

    NASA Technical Reports Server (NTRS)

    Williams, J. F.; Wiedeman, D. H.

    1973-01-01

    This investigation describes the capacitor failures and to identify the cause of the failure mechanism. Early failures were thought to have happened because of age and/or abuse since the failed capacitors were dated 1967. It is shown that all 1967 capacitors were replaced with 1972 capacitors.

  3. Morpheus 1.5A Lander Failure Investigation Results

    NASA Technical Reports Server (NTRS)

    Munday, Steve; Olansen, John

    2013-01-01

    On August 9th, 2012, the Morpheus 1.5 Vertical Testbed (VTB) crashed during Free Flight 2 (FF2) at KSC SLF, resulting in the loss of 1.5 VTB hardware. JSC/KSC Morpheus team immediately executed the pre-rehearsed Emergency Action Plan to protect personnel and property, so damage was limited to 1.5 VTB hardware. JSC/KSC Morpheus team secured data and mapped & recovered debris. Project had pre-declared loss of VTB to be a test failure, not a mishap.

  4. Investigation of failure to separate an Inconel 718 frangible nut

    NASA Technical Reports Server (NTRS)

    Hoffman, William C., III; Hohmann, Carl

    1994-01-01

    The 2.5-inch frangible nut is used in two places to attach the Space Shuttle Orbiter to the External Tank. It must be capable of sustaining structural loads and must also separate into two pieces upon command. Structural load capability is verified by proof loading each flight nut, while ability to separate is verified on a sample of a production lot. Production lots of frangible nuts beginning in 1987 experienced an inability to reliably separate using one of two redundant explosive boosters. The problems were identified in lot acceptance tests, and the cause of failure has been attributed to differences in the response of the Inconel 718. Subsequent tests performed on the frangible nuts resulted in design modifications to the nuts along with redesign of the explosive booster to reliably separate the frangible nut. The problem history along with the design modifications to both the explosive booster and frangible nut are discussed in this paper. Implications of this failure experience impact any pyrotechnic separation system involving fracture of materials with respect to design margin control and lot acceptance testing.

  5. A near-miss management system architecture for the forensic investigation of software failures.

    PubMed

    Bella, M A Bihina; Eloff, J H P

    2016-02-01

    Digital forensics has been proposed as a methodology for doing root-cause analysis of major software failures for quite a while. Despite this, similar software failures still occur repeatedly. A reason for this is the difficulty of obtaining detailed evidence of software failures. Acquiring such evidence can be challenging, as the relevant data may be lost or corrupt following a software system's crash. This paper proposes the use of near-miss analysis to improve on the collection of evidence for software failures. Near-miss analysis is an incident investigation technique that detects and subsequently analyses indicators of failures. The results of a near-miss analysis investigation are then used to detect an upcoming failure before the failure unfolds. The detection of these indicators - known as near misses - therefore provides an opportunity to proactively collect relevant data that can be used as digital evidence, pertaining to software failures. A Near Miss Management System (NMS) architecture for the forensic investigation of software failures is proposed. The viability of the proposed architecture is demonstrated through a prototype.

  6. Investigation of failure mechanisms in integrated vacuum circuits

    NASA Technical Reports Server (NTRS)

    Rosengreen, A.

    1972-01-01

    The fabrication techniques of integrated vacuum circuits are described in detail. Data obtained from a specially designed test circuit are presented. The data show that the emission observed in reverse biased devices is due to cross-talk between the devices and can be eliminated by electrostatic shielding. The lifetime of the cathodes has been improved by proper activation techniques. None of the cathodes on life test has shown any sign of failure after more than 3500 hours. Life tests of triodes show a decline of anode current by a factor of two to three after a few days. The current recovers when the large positive anode voltage (100 V) has been removed for a few hours. It is suggested that this is due to trapped charges in the sapphire substrate. Evidence of the presence of such charges is given, and a model of the charge distribution is presented consistent with the measurements. Solution of the problem associated with the decay of triode current may require proper treatment of the sapphire surface and/or changes in the deposition technique of the thin metal films.

  7. Student Failure in First Year Modules in the Biosciences: An Interview Based Investigation

    ERIC Educational Resources Information Center

    Scott, Jon; Graal, Maria

    2007-01-01

    Undergraduate retention is a major concern for universities and first year failure is a significant contributor to the overall statistics for non-progression. This report describes an interview-based investigation of students' perceptions for the reasons underlying their failure in 1st and 2nd semester modules. The most commonly cited reasons were…

  8. Failure Investigation of Radiant Platen Superheater Tube of Thermal Power Plant Boiler

    NASA Astrophysics Data System (ADS)

    Ghosh, D.; Ray, S.; Mandal, A.; Roy, H.

    2015-04-01

    This paper highlights a case study of typical premature failure of a radiant platen superheater tube of 210 MW thermal power plant boiler. Visual examination, dimensional measurement and chemical analysis, are conducted as part of the investigations. Apart from these, metallographic analysis and fractography are also conducted to ascertain the probable cause of failure. Finally it has been concluded that the premature failure of the super heater tube can be attributed to localized creep at high temperature. The corrective actions has also been suggested to avoid this type of failure in near future.

  9. 49 CFR 193.2515 - Investigations of failures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ....2515 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY LIQUEFIED NATURAL... operator shall investigate the cause of each explosion, fire, or LNG spill or leak which results in:...

  10. 49 CFR 193.2515 - Investigations of failures.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ....2515 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY LIQUEFIED NATURAL... operator shall investigate the cause of each explosion, fire, or LNG spill or leak which results in:...

  11. 49 CFR 193.2515 - Investigations of failures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ....2515 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY LIQUEFIED NATURAL... operator shall investigate the cause of each explosion, fire, or LNG spill or leak which results in:...

  12. 49 CFR 193.2515 - Investigations of failures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ....2515 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY LIQUEFIED NATURAL... operator shall investigate the cause of each explosion, fire, or LNG spill or leak which results in:...

  13. A simulator investigation of engine failure compensation for powered-lift STOL aircraft

    NASA Technical Reports Server (NTRS)

    Nieuwenhuijse, A. W.; Franklin, J. A.

    1974-01-01

    A piloted simulator investigation of various engine failure compensation concepts for powered-lift STOL aircraft was carried out at the Ames Research Center. The purpose of this investigation was to determine the influence of engine failure compensation on recovery from an engine failure during the landing approach and on the precision of the STOL landing. The various concepts include: (1) cockpit warning lights to cue the pilot of an engine failure, (2) programmed thrust and roll trim compensation, (3) thrust command and (4) flight-path stabilization. The aircraft simulated was a 150 passenger four-engine, externally blown flap civil STOL transport having a 90 psf wing loading and a .56 thrust to weight ratio. Results of the simulation indicate that the combination of thrust command and flight-path stabilization offered the best engine-out landing performance in turbulence and did so over the entire range of altitudes for which engine failures occurred.

  14. Investigation into Cause of High Temperature Failure of Boiler Superheater Tube

    NASA Astrophysics Data System (ADS)

    Ghosh, D.; Ray, S.; Roy, H.; Shukla, A. K.

    2015-04-01

    The failure of the boiler tubes occur due to various reasons like creep, fatigue, corrosion and erosion. This paper highlights a case study of typical premature failure of a final superheater tube of 210 MW thermal power plant boiler. Visual examination, dimensional measurement, chemical analysis, oxide scale thickness measurement, microstructural examination are conducted as part of the investigations. Apart from these investigations, sulfur print, Energy Dispersive spectroscopy (EDS) and X ray diffraction analysis (XRD) are also conducted to ascertain the probable cause of failure of final super heater tube. Finally it has been concluded that the premature failure of the super heater tube can be attributed to the combination of localized high tube metal temperature and loss of metal from the outer surface due to high temperature corrosion. The corrective actions have also been suggested to avoid this type of failure in near future.

  15. When the biological indicator is positive: investigating autoclave failures.

    PubMed

    Bryce, E A; Roberts, F J; Clements, B; MacLean, S

    1997-09-01

    A series of positive biological indicators in steam autoclaves from different hospital departments within the same building were traced to blocked steam traps on building condensate lines. The steps taken during the investigation and a protocol for management of positive biological indicators are described. PMID:9309439

  16. Numerical investigations of rib fracture failure models in different dynamic loading conditions.

    PubMed

    Wang, Fang; Yang, Jikuang; Miller, Karol; Li, Guibing; Joldes, Grand R; Doyle, Barry; Wittek, Adam

    2016-01-01

    Rib fracture is one of the most common thoracic injuries in vehicle traffic accidents that can result in fatalities associated with seriously injured internal organs. A failure model is critical when modelling rib fracture to predict such injuries. Different rib failure models have been proposed in prediction of thorax injuries. However, the biofidelity of the fracture failure models when varying the loading conditions and the effects of a rib fracture failure model on prediction of thoracic injuries have been studied only to a limited extent. Therefore, this study aimed to investigate the effects of three rib failure models on prediction of thoracic injuries using a previously validated finite element model of the human thorax. The performance and biofidelity of each rib failure model were first evaluated by modelling rib responses to different loading conditions in two experimental configurations: (1) the three-point bending on the specimen taken from rib and (2) the anterior-posterior dynamic loading to an entire bony part of the rib. Furthermore, the simulation of the rib failure behaviour in the frontal impact to an entire thorax was conducted at varying velocities and the effects of the failure models were analysed with respect to the severity of rib cage damages. Simulation results demonstrated that the responses of the thorax model are similar to the general trends of the rib fracture responses reported in the experimental literature. However, they also indicated that the accuracy of the rib fracture prediction using a given failure model varies for different loading conditions.

  17. Development Testing and Subsequent Failure Investigation of a Spring Strut Mechanism

    NASA Technical Reports Server (NTRS)

    Dervan, Jared; Robertson, Brandan; Staab, Lucas; Culberson, Michael; Pellicciotti, Joseph

    2014-01-01

    The NASA Engineering and Safety Center (NESC) and Lockheed Martin (LM) performed random vibration testing on a single spring strut development unit to assess its ability to withstand qualification level random vibration environments. Failure of the strut while exposed to random vibration resulted in a follow-on failure investigation, design changes, and additional development tests. This paper focuses on the results of the failure investigations referenced in detail in the NESC final report [1] including identified lessons learned to aid in future design iterations of the spring strut and to help other mechanism developers avoid similar pitfalls.

  18. Development Testing and Subsequent Failure Investigation of a Spring Strut Mechanism

    NASA Technical Reports Server (NTRS)

    Dervan, Jared; Robertson, Brandon; Staab, Lucas; Culberson, Michael; Pellicciotti, Joseph

    2014-01-01

    The NASA Engineering and Safety Center (NESC) and Lockheed Martin (LM) performed random vibration testing on a single spring strut development unit to assess its ability to withstand qualification level random vibration environments. Failure of the strut while exposed to random vibration resulted in a follow-on failure investigation, design changes, and additional development tests. This paper focuses on the results of the failure investigations referenced in detail in the NESC final report including identified lessons learned to aid in future design iterations of the spring strut and to help other mechanism developers avoid similar pitfalls.

  19. Mechanistic failure mode investigation and resolution of parvovirus retentive filters.

    PubMed

    LaCasse, Daniel; Lute, Scott; Fiadeiro, Marcus; Basha, Jonida; Stork, Matthew; Brorson, Kurt; Godavarti, Ranga; Gallo, Chris

    2016-07-01

    Virus retentive filters are a key product safety measure for biopharmaceuticals. A simplistic perception is that they function solely based on a size-based particle removal mechanism of mechanical sieving and retention of particles based on their hydrodynamic size. Recent observations have revealed a more nuanced picture, indicating that changes in viral particle retention can result from process pressure and/or flow interruptions. In this study, a mechanistic investigation was performed to help identify a potential mechanism leading to the reported reduced particle retention in small virus filters. Permeate flow rate or permeate driving force were varied and analyzed for their impact on particle retention in three commercially available small virus retentive filters. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:959-970, 2016.

  20. An investigation of theories of failure for ceramic matrix composites

    NASA Technical Reports Server (NTRS)

    Hemann, John H.

    1995-01-01

    This final report is comprised of the abstract of a masters thesis research grant. The abstract of the thesis, 'An Investigation of Acoustic Emission Techniques for the Discrimination of Damage Mechanisms in Ceramic Matrix Composites', is as follows: In order to further advance the understanding of the mechanical behavior of ceramic matrix composites (CMS's), acoustic emission (AE) techniques were implemented to monitor and identify damage mechanisms in CMC's under tensile loading. In addition to real-time AE monitoring techniques, a data acquisition system was developed and implemented in order to capture AE waveforms resulting from stress-induced damage. Waveforms were inspected for multiple events, separated in distinct events, and then analyzed to determine waveform characteristics in the time and frequency domains. Waveform characteristics included peak amplitude, event duration, MARSE, energy, and dominant and centroidal frequency. In addition to conventional methods for determining a damage discrimination criteria, a study of the distribution and correlation of the waveform characteristics criteria and a study of the distribution and correlation of the waveform characteristics were performed to aid in the determination of a damage discrimination criteria. The damage discrimination criteria was tested for 'uniqueness', i.e., the effectiveness of the criteria to identify and monitor damage independent of the stress-strain relationship. Insitu radiography was used to substantiate the damage accumulation. A simulation test was also performed over the loading history to study the changes in the waveform characteristics of the system response from a constant excitation. This thesis demonstrates the use of waveform analysis to study the AE activity resulting from stress-induced damage in CMC's in conjunction with other nondestructive evaluation techniques to investigate the mechanical behavior of CMC's.

  1. An Investigation of the Ability to Recover from Transients Following Failures for Single-Pilot Rotorcraft

    NASA Technical Reports Server (NTRS)

    Mansur, M. Hossein; Schroeder, Jeffery A.

    1988-01-01

    A moving-base simulation was conducted to investigate a pilot's ability to recover from transients following single-axis hard-over failures of the flight-control system. The investigation was performed in conjunction with a host simulation that examined the influence of control modes on a single pilot's ability to perform various mission elements under high-workload conditions. The NASA Ames large-amplitude-motion Vertical Motion Simulator (VMS) was utilized, and the experimental variables were the failure axis, the severity of the failure, and the airspeed at which the failure occurred. Other factors, such as pilot workload and terrain and obstacle proximity at the time of failure, were kept as constant as possible within the framework of the host simulation task scenarios. No explicit failure warnings were presented to the pilot. Data from the experiment are shown, and pilot ratings are compared with the proposed handling-qualities requirements for military rotorcraft. Results indicate that the current proposed failure transient requirements may need revision.

  2. Investigating Deformation and Failure Mechanisms in Nanoscale Multilayer Metallic Composites

    SciTech Connect

    Zbib, Hussein M; Bahr, David F

    2014-10-22

    Over the history of materials science there are many examples of materials discoveries that have made superlative materials; the strongest, lightest, or toughest material is almost always a goal when we invent new materials. However, often these have been a result of enormous trial and error approaches. A new methodology, one in which researchers design, from the atoms up, new ultra-strong materials for use in energy applications, is taking hold within the science and engineering community. This project focused on one particular new classification of materials; nanolaminate metallic composites. These materials, where two metallic materials are intimately bonded and layered over and over to form sheets or coatings, have been shown over the past decade to reach strengths over 10 times that of their constituents. However, they are not yet widely used in part because while extremely strong (they don’t permanently bend), they are also not particularly tough (they break relatively easily when notched). Our program took a coupled approach to investigating new materials systems within the laminate field. We used computational materials science to explore ways to institute new deformation mechanisms that occurred when a tri-layer, rather than the more common bi-layer system was created. Our predictions suggested that copper-nickel or copper-niobium composites (two very common bi-layer systems) with layer thicknesses on the order of 20 nm and then layered 100’s of times, would be less tough than a copper-nickel-niobium metallic composite of similar thicknesses. In particular, a particular mode of permanent deformation, cross-slip, could be activated only in the tri-layer system; the crystal structure of the other bi-layers would prohibit this particular mode of deformation. We then experimentally validated this predication using a wide range of tools. We utilized a DOE user facility, the Center for Integrated Nanotechnology (CINT), to fabricate, for the first time, these

  3. Lessons Learned from Recent Failure and Incident Investigations of Composite Structures

    NASA Technical Reports Server (NTRS)

    Ransom, J. B.; Glaessgen, E. H.; Raju, L. S.; Knight, N. F., Jr.; Reeder, J. R.

    2008-01-01

    During the past few decades, NASA Langley Research Center (LaRC) has supported several large-scale failure and incident investigations and numerous requests for engineering consultations. Although various extenuating circumstances contributed to each of these incidents, in all cases, the failure resulted from accumulation and/or propagation of damage that reduced the load carrying capability of the structure to a level below that which was needed to sustain structural loads. A brief overview of various failure and incident investigations supported by LaRC, including some of the computational and experimental methodologies that have been applied, is presented. An important outcome of many of these failure and incident investigations is the development of an improved understanding of not only the state-of-the-art in experimental and analytical methods but also the state-of-the-art in the design and manufacturing processes that may contribute to such failures. In order to provide insight into such large-scale investigations, a series of lessons learned were captured. Awareness of these lessons learned is highly beneficial to engineers involved in similar investigations. Therefore, it is prudent that the lessons learned are disseminated such that they can be built upon in other investigations and in ensuing research and development activities.

  4. 16 CFR 1605.11 - Remedies for failure to permit authorized investigations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Remedies for failure to permit authorized investigations. 1605.11 Section 1605.11 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS INVESTIGATIONS, INSPECTIONS AND INQUIRIES PURSUANT TO THE FLAMMABLE FABRICS...

  5. 16 CFR 1605.11 - Remedies for failure to permit authorized investigations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Remedies for failure to permit authorized investigations. 1605.11 Section 1605.11 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS INVESTIGATIONS, INSPECTIONS AND INQUIRIES PURSUANT TO THE FLAMMABLE FABRICS...

  6. 16 CFR 1605.11 - Remedies for failure to permit authorized investigations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Remedies for failure to permit authorized investigations. 1605.11 Section 1605.11 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS INVESTIGATIONS, INSPECTIONS AND INQUIRIES PURSUANT TO THE FLAMMABLE FABRICS...

  7. 16 CFR 1605.11 - Remedies for failure to permit authorized investigations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Remedies for failure to permit authorized investigations. 1605.11 Section 1605.11 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS INVESTIGATIONS, INSPECTIONS AND INQUIRIES PURSUANT TO THE FLAMMABLE FABRICS...

  8. 16 CFR 1605.11 - Remedies for failure to permit authorized investigations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Remedies for failure to permit authorized investigations. 1605.11 Section 1605.11 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FLAMMABLE FABRICS ACT REGULATIONS INVESTIGATIONS, INSPECTIONS AND INQUIRIES PURSUANT TO THE FLAMMABLE FABRICS...

  9. Investigation of a Modified 9Cr-1Mo (P91) Pipe Failure

    SciTech Connect

    Klueh, Ronald L; Shingledecker, John P

    2006-04-01

    A modified 9Cr-1Mo feedwater (condensate) line at an Eastman Chemical Company plant failed in January 2005. The line was in continuous service since start-up December 2001 until failure. The Plant Superintendent estimated there were three thermal cycles since start-up, although there may have been as many as 25 thermal cycles during commissioning. Normal operating temperature was 325 F (163 C) and pressure was 1762 psig. The line was steam traced with the tracing activated only when ambient outdoor temperature dropped to 40 F (5 C). A modified 9Cr-1Mo steel (P91) pipe failure in a feedwater line in a chemical plant was investigated. The failure occurred in the vicinity of an elbow produced with socket welds of the pipe to the elbow. Based on metallography and hardness measurements, it was concluded that failure occurred because of an improper post-weld heat treatment of the socket weldment.

  10. Failure detection and isolation investigation for strapdown skew redundant tetrad laser gyro inertial sensor arrays

    NASA Technical Reports Server (NTRS)

    Eberlein, A. J.; Lahm, T. G.

    1976-01-01

    The degree to which flight-critical failures in a strapdown laser gyro tetrad sensor assembly can be isolated in short-haul aircraft after a failure occurrence has been detected by the skewed sensor failure-detection voting logic is investigated along with the degree to which a failure in the tetrad computer can be detected and isolated at the computer level, assuming a dual-redundant computer configuration. The tetrad system was mechanized with two two-axis inertial navigation channels (INCs), each containing two gyro/accelerometer axes, computer, control circuitry, and input/output circuitry. Gyro/accelerometer data is crossfed between the two INCs to enable each computer to independently perform the navigation task. Computer calculations are synchronized between the computers so that calculated quantities are identical and may be compared. Fail-safe performance (identification of the first failure) is accomplished with a probability approaching 100 percent of the time, while fail-operational performance (identification and isolation of the first failure) is achieved 93 to 96 percent of the time.

  11. Diagnosis of patients with chronic heart failure in primary care: usefulness of history, examination, and investigations.

    PubMed Central

    Khunti, K; Baker, R; Grimshaw, G

    2000-01-01

    Chronic heart failure is a common clinical syndrome that may have different causes. Its incidence and prevalence are predicted to rise substantially over the next 10 years. There are therefore major consequences for resource provision, especially in primary care, where most patients are managed. Chronic heart failure is a serious condition with high morbidity and mortality. There is good evidence to show that treatment with angiotensin-converting enzyme (ACE) inhibitors in patients with left ventricular systolic dysfunction improves symptoms and signs, slows progression of heart failure, reduces hospitalisation rates, and improves survival. Despite this evidence, primary care studies show that patients with heart failure are incorrectly diagnosed and inadequately treated. Most patients present in general practice, and because effective treatment relies on a correct diagnosis, this is a key step in the appropriate management of heart failure. The aim of this paper is to review the evidence about the usefulness of signs, symptoms, and investigations in diagnosing heart failure in primary care. To identify relevant studies for this review, four strategies were used: a MEDLINE search from 1993 to January 1998 using the diagnosis search filter; a MEDLINE search from 1993 to January 1998 using the guideline search filter to locate published heart failure guidelines; a search for review articles in the Cochrane Library; and a check of references in the studies identified. The search terms included MeSH terms and the keywords 'heart failure' and 'diagnosis'. All searches were limited to humans and English language articles. Studies were included in this review on the basis of quality and relevance to primary care. The review shows that symptoms and signs are important because they alert clinicians to the possibility of heart failure as a diagnosis. However, they are not sufficiently specific for confirming left ventricular systolic dysfunction. From the evidence available

  12. An investigation of gear mesh failure prediction techniques. M.S. Thesis - Cleveland State Univ.

    NASA Technical Reports Server (NTRS)

    Zakrajsek, James J.

    1989-01-01

    A study was performed in which several gear failure prediction methods were investigated and applied to experimental data from a gear fatigue test apparatus. The primary objective was to provide a baseline understanding of the prediction methods and to evaluate their diagnostic capabilities. The methods investigated use the signal average in both the time and frequency domain to detect gear failure. Data from eleven gear fatigue tests were recorded at periodic time intervals as the gears were run from initiation to failure. Four major failure modes, consisting of heavy wear, tooth breakage, single pits, and distributed pitting were observed among the failed gears. Results show that the prediction methods were able to detect only those gear failures which involved heavy wear or distributed pitting. None of the methods could predict fatigue cracks, which resulted in tooth breakage, or single pits. It is suspected that the fatigue cracks were not detected because of limitations in data acquisition rather than in methodology. Additionally, the frequency response between the gear shaft and the transducer was found to significantly affect the vibration signal. The specific frequencies affected were filtered out of the signal average prior to application of the methods.

  13. University Students' Metacognitive Failures in Mathematical Proving Investigated Based on the Framework of Assimilation and Accommodation

    ERIC Educational Resources Information Center

    Huda, Nizlel; Subanji; Nusantar, Toto; Susiswo; Sutawidjaja, Akbar; Rahardjo, Swasono

    2016-01-01

    This study aimed to determine students' metacognitive failure in Mathematics Education Program of FKIP in Jambi University investigated based on assimilation and accommodation Mathematical framework. There were 35 students, five students did not answer the question, three students completed the questions correctly and 27 students tried to solve…

  14. Investigation of static and cyclic bearing failure mechanisms for GR/EP laminates

    NASA Technical Reports Server (NTRS)

    Walter, R. W.; Tuttle, M. M.

    1992-01-01

    Static, cyclic load (fatigue), and residual strength testing of graphite-epoxy (GR/EP) and aluminum pin bearing joints was completed to study bearing failure mechanisms. Parameters investigated included static strength, failure mode, fatigue life, hole growth, joint stiffness, and residual strength. Comparative evaluation of these results show that the MIL-HDBK-5 convention for the definition of bearing strength can be used for GR/EP materials while maintaining the same, or improved, level of structural integrity shown for metal joints.

  15. Bovine respiratory disease research (1983-2009).

    PubMed

    Fulton, Robert W

    2009-12-01

    Bovine respiratory disease (BRD) research has provided significant understanding of the disease over the past 26 years. Modern research tools that have been used include monoclonal antibodies, genomics, polymerase chain reaction, immunohistochemistry (IHC), DNA vaccines and viral vectors coding for immunogens. Emerging/reemerging viruses and new antigenic strains of viruses and bacteria have been identified. Methods of detection and the role for cattle persistently infected bovine viral diarrhea virus (BVDV) were identified; viral subunits, cellular components and bacterial products have been characterized. Product advances have included vaccines for bovine respiratory syncytial virus, Mannheimia haemolytica and Pasteurella multocida; the addition of BVDV2 to the existing vaccines and new antibiotics. The role of Mycoplasma spp., particularly Mycoplasma bovis in BRD, has been more extensively studied. Bovine immunology research has provided more specific information on immune responses, T cell subsets and cytokines. The molecular and genetic basis for viral-bacterial synergy in BRD has been described. Attempts have been made to document how prevention of BRD by proper vaccination and management prior to exposure to infectious agents can minimize disease and serve as economic incentives for certified health programs. PMID:20003649

  16. NEESROCK: A Physical and Numerical Modeling Investigation of Seismically Induced Rock-Slope Failure

    NASA Astrophysics Data System (ADS)

    Applegate, K. N.; Wartman, J.; Keefer, D. K.; Maclaughlin, M.; Adams, S.; Arnold, L.; Gibson, M.; Smith, S.

    2013-12-01

    Worldwide, seismically induced rock-slope failures have been responsible for approximately 30% of the most significant landslide catastrophes of the past century. They are among the most common, dangerous, and still today, least understood of all seismic hazards. Seismically Induced Rock-Slope Failure: Mechanisms and Prediction (NEESROCK) is a major research initiative that fully integrates physical modeling (geotechnical centrifuge) and advanced numerical simulations (discrete element modeling) to investigate the fundamental mechanisms governing the stability of rock slopes during earthquakes. The research is part of the National Science Foundation-supported Network for Earthquake Engineering Simulation Research (NEES) program. With its focus on fractures and rock materials, the project represents a significant departure from the traditional use of the geotechnical centrifuge for studying soil, and pushes the boundaries of physical modeling in new directions. In addition to advancing the fundamental understanding of the rock-slope failure process under seismic conditions, the project is developing improved rock-slope failure assessment guidelines, analysis procedures, and predictive tools. Here, we provide an overview of the project, present experimental and numerical modeling results, discuss special considerations for the use of synthetic rock materials in physical modeling, and address the suitability of discrete element modeling for simulating the dynamic rock-slope failure process.

  17. An investigation of mechanical behavior and failure mechanisms of composite T-joints with transverse stitching

    NASA Astrophysics Data System (ADS)

    Stickler, Patrick Bickford

    2001-07-01

    A new low cost damage tolerant method of joining load-bearing composite structures using two-dimensional dry fabric preforms with transverse stitching and a novel fiber insertion process with resin transfer molding has recently been developed, however, knowledge of strength prediction and failure mechanisms is not well understood. In this investigation, fundamental knowledge of T-joint mechanical behavior was developed through detailed experimental, numerical, and post failure analyses. Experiments were conducted under flexure, tension, and shear loads and failed specimens were examined to discern failure modes. T-joint constituent elastic and strength properties were experimentally determined. Elastic properties were used as input to the finite element analysis and strength properties were used as limiting values in the T-joint failure analysis. Linear elastic, nonlinear elastic, and progressive damage finite element models were developed under each load condition. T-joint numerical models are shown to predict experimental behavior through ultimate load. Damage accumulation was characterized based on experimental, numerical, and post failure analyses. A parametric finite element analysis was conducted and design curves were derived to demonstrate the effect of varying key T-joint interface parameters on mechanical behavior under each load condition. Results of this research enable the application of T-joints with transverse stitching to future products and predictive finite element models developed herein reduce the structural testing required to validate these designs.

  18. Forensic engineering: applying materials and mechanics principles to the investigation of product failures.

    PubMed

    Hainsworth, S V; Fitzpatrick, M E

    2007-06-01

    Forensic engineering is the application of engineering principles or techniques to the investigation of materials, products, structures or components that fail or do not perform as intended. In particular, forensic engineering can involve providing solutions to forensic problems by the application of engineering science. A criminal aspect may be involved in the investigation but often the problems are related to negligence, breach of contract, or providing information needed in the redesign of a product to eliminate future failures. Forensic engineering may include the investigation of the physical causes of accidents or other sources of claims and litigation (for example, patent disputes). It involves the preparation of technical engineering reports, and may require giving testimony and providing advice to assist in the resolution of disputes affecting life or property.This paper reviews the principal methods available for the analysis of failed components and then gives examples of different component failure modes through selected case studies.

  19. Full-Field Strain Methods for Investigating Failure Mechanisms in Triaxial Braided Composites

    NASA Technical Reports Server (NTRS)

    Littell, Justin D.; Binienda, Wieslaw K.; Goldberg, Robert K.; Roberts, Gary D.

    2008-01-01

    Recent advancements in braiding technology have led to commercially viable manufacturing approaches for making large structures with complex shape out of triaxial braided composite materials. In some cases, the static load capability of structures made using these materials has been higher than expected based on material strength properties measured using standard coupon tests. A more detailed investigation of deformation and failure processes in large-unit-cell-size triaxial braid composites is needed to evaluate the applicability of standard test methods for these materials and to develop alternative testing approaches. This report presents some new techniques that have been developed to investigate local deformation and failure using digital image correlation techniques. The methods were used to measure both local and global strains during standard straight-sided coupon tensile tests on composite materials made with 12- and 24-k yarns and a 0 /+60 /-60 triaxial braid architecture. Local deformation and failure within fiber bundles was observed and correlations were made between these local failures and global composite deformation and strength.

  20. Failure Investigation of a Cage Suspension Gear Chain used in Coal Mines

    NASA Astrophysics Data System (ADS)

    Ghosh, Debashis; Dutta, Shamik; Shukla, Awdhesh Kumar; Roy, Himadri

    2015-09-01

    This investigation is primarily aimed to examine the probable causes of in-service failure of cage suspension gear chain used in coal mines. Preliminary visual examination, dimensional measurement, chemical analysis, magnetic particle inspection and estimation of mechanical properties are necessary supplement to this investigation. Optical microscopic analysis along with scanning electron microscopy examinations are carried out to understand the metallurgical reasons for failure. The visual examination and magnetic particle investigations reveal presence of fissure cracks at weld joint for both un-failed and failed end link chain. The average hardness value has been found to increase gradually with the distance from the weld interface. The macro and microstructural examinations of the samples prepared from both failed and un-failed specimens depict presence of continuous as well as aligned linear inclusions randomly distributed along with decarburized layer at weld interface/fusion zone. Fractographic examination shows flat fracture covering major portion of cross-section, which is surrounded by a narrow annular metallic fracture surface having a texture different from that of the remaining surface. Fracture mechanics principles have been used to study the fatigue crack growth rate in both weld region and base region of the un-failed gear chain material. Detailed stress analyses are also carried out to evaluate the stress generated along the chain periphery. Finally, it is concluded that presence of serious weld defect due to use of improper welding parameters/procedure caused failure of the end links of the investigated chain link.

  1. Impact failure of MHW fuel sphere MHFT 65: report on interagency task force investigation and SRL evaluation of failure, November 1979-February 1980

    SciTech Connect

    Taylor, D.H.

    1981-06-01

    Following a safety verification impact test failure of a Multi-Hundred Watt (MHW) fuel sphere made at Savannah River Plant, from which 2.1 g of /sup 238/PuO/sub 2/ escaped containment, the Department of Energy organized a task force to investigate the cause of the test failure and to assess the failure probability of MHW fuel made at SRP. The task force described a two-part failure mechanism: embrittlement of the iridium containment shell by phosphorus which may have been picked up from the fuel; and large shear strains in the iridium caused by shearing or push-through of large chunks of fuel. Because the likelihood of push-through in this failure model depends on preexisting cracks in the fuel and their orientation to the impact face, the probability of further impact failures could not be easily assessed. From independent analysis of the available data at the Savannah River Laboratory, we concluded that the impact failure was caused by phosphorus embrittlement of the iridium, and breaching during impact of the graphite impact shell surrounding and cushioning the iridium-clad fuel. Excessive strain in the iridium is caused by extrusion of the iridium into the breach. This model predicts that impact failure is essentially independent of pre-existing cracks in the fuel and that SRP fuel, upon impact, should have no more failures than previously used fuel made at Mound Facility. Impact data to date indicate that SRP fuel clad in DOP-26 iridium cladding actually has fewer impact failures than earlier fuel clad in undoped iridium at MF.

  2. A Numerical Investigation of CFRP-Steel Interfacial Failure with Material Point Method

    SciTech Connect

    Shen Luming; Faleh, Haydar; Al-Mahaidi, Riadh

    2010-05-21

    The success of retrofitting steel structures by using the Carbon Fibre Reinforced Polymers (CFRP) significantly depends on the performance and integrity of CFRP-steel joint and the effectiveness of the adhesive used. Many of the previous numerical studies focused on the design and structural performance of the CFRP-steel system and neglected the mechanical responses of adhesive layer, which results in the lack of understanding in how the adhesive layer between the CFRP and steel performs during the loading and failure stages. Based on the recent observation on the failure of CFRP-steel bond in the double lap shear tests, a numerical approach is proposed in this study to simulate the delamination process of CFRP sheet from steel plate using the Material Point Method (MPM). In the proposed approach, an elastoplasticity model with a linear hardening and softening law is used to model the epoxy layer. The MPM, which does not employ fixed mesh-connectivity, is employed as a robust spatial discretization method to accommodate the multi-scale discontinuities involved in the CFRP-steel bond failure process. To demonstrate the potential of the proposed approach, a parametric study is conducted to investigate the effects of bond length and loading rates on the capacity and failure modes of CFRP-steel system. The evolution of the CFRP-steel bond failure and the distribution of stress and strain along bond length direction will be presented. The simulation results not only well match the available experimental data but also provide a better understanding on the physics behind the CFRP sheet delamination process.

  3. A Numerical Investigation of CFRP-Steel Interfacial Failure with Material Point Method

    NASA Astrophysics Data System (ADS)

    Shen, Luming; Faleh, Haydar; Al-Mahaidi, Riadh

    2010-05-01

    The success of retrofitting steel structures by using the Carbon Fibre Reinforced Polymers (CFRP) significantly depends on the performance and integrity of CFRP-steel joint and the effectiveness of the adhesive used. Many of the previous numerical studies focused on the design and structural performance of the CFRP-steel system and neglected the mechanical responses of adhesive layer, which results in the lack of understanding in how the adhesive layer between the CFRP and steel performs during the loading and failure stages. Based on the recent observation on the failure of CFRP-steel bond in the double lap shear tests [1], a numerical approach is proposed in this study to simulate the delamination process of CFRP sheet from steel plate using the Material Point Method (MPM). In the proposed approach, an elastoplasticity model with a linear hardening and softening law is used to model the epoxy layer. The MPM [2], which does not employ fixed mesh-connectivity, is employed as a robust spatial discretization method to accommodate the multi-scale discontinuities involved in the CFRP-steel bond failure process. To demonstrate the potential of the proposed approach, a parametric study is conducted to investigate the effects of bond length and loading rates on the capacity and failure modes of CFRP-steel system. The evolution of the CFRP-steel bond failure and the distribution of stress and strain along bond length direction will be presented. The simulation results not only well match the available experimental data but also provide a better understanding on the physics behind the CFRP sheet delamination process.

  4. Application of dynamic fracture mechanics to the investigation of catastrophic failure in aircraft structures

    NASA Astrophysics Data System (ADS)

    Chow, Benjamin Bin

    A dynamic fracture mechanics approach to the estimation of the residual strength of aircraft structures is presented. The dependence of the dynamic crack initiation toughness of aluminum 2024-T3 on loading rate is first studied experimentally. Based on the experimental results and on established dynamic fracture mechanic concepts, a fracture mechanics based failure model is established and is used to estimate the residual strength of aircraft structures. A methodology to determine residual strength of dynamically loaded structures based on global structural analysis coupled with local finite element analysis is introduced. Local finite element calculations were performed for different loading rates to simulate the conditions encountered in an explosively loaded aircraft fuselage. The results from the analyses were then used in conjunction with the experimental results for the dynamic fracture toughness of a 2024-T3 aluminum alloy as a function of loading rate, KdIC vs. K˙d(t), to determine the time to failure, tf, for a given loading rate. A failure envelope, sf vs. ṡ , based on the failure model and finite element analysis, is presented for the different cases and the implications for the residual strength of aircraft structures is discussed. Mixed mode dynamic crack initiation in aluminum 2024-T3 alloy is investigated by combining experiments with numerical simulations. The optical technique of coherent gradient sensing (CGS) and a strain gage method are employed to study the evolution of the mixed mode stress intensity factors. The dynamic mixed mode failure envelope is obtained using the crack initiation data from the experiments at a nominal loading rate of 7 x 105 MPam/s . Numerical simulations of the experiments are conducted to both help in designing the experiments and to validate the results of the experiments. The numerical simulations show good correlation with the experimental results.

  5. Development Testing and Subsequent Failure Investigation of a Spring Strut Mechanism

    NASA Technical Reports Server (NTRS)

    Dervan, Jared; Robertson, Brandon; Staab, Lucas; Culberson, Michael

    2014-01-01

    Commodities are transferred between the Multi-Purpose Crew Vehicle (MPCV) crew module (CM) and service module (SM) via an external umbilical that is driven apart with spring-loaded struts after the structural connection is severed. The spring struts must operate correctly for the modules to separate safely. There was no vibration testing of strut development units scoped in the MPCV Program Plan; therefore, any design problems discovered as a result of vibration testing would not have been found until the component qualification. The NASA Engineering and Safety Center (NESC) and Lockheed Martin (LM) performed random vibration testing on a single spring strut development unit to assess its ability to withstand qualification level random vibration environments. Failure of the strut while exposed to random vibration resulted in a follow-on failure investigation, design changes, and additional development tests. This paper focuses on the results of the failure investigations including identified lessons learned and best practices to aid in future design iterations of the spring strut and to help other mechanism developers avoid similar pitfalls.

  6. Investigation of a Shock Absorber for Safeguard of Fuel Assemblies Failure

    SciTech Connect

    Karalevicius, Renatas; Dundulis, Gintautas; Rimkevicius, Sigitas; Uspuras, Eugenijus

    2006-07-01

    The Ignalina NPP has two reactors. The Unit 1 was shut down, therefore the special equipment was designed for transportation of the fuel from Unit 1 to Unit 2. The fuel-loaded basket can drop during transportation. The special shock absorber was designed in order to avoid failure of fuel assemblies during transportation. In case of drop of fuel loaded basket, the failure of fuel assemblies can occur. This shock absorber was studied by scaled experiments at Lithuanian Energy Institute. Static and dynamic investigations of shock absorber are presented in this paper, including dependency of axial force versus axial compression. The finite element codes BRIGADE/Plus and ABAQUS/Explicit were used for analysis. Static simulation was used to optimize the dimensions of shock absorber. Dynamic analysis shows that shock absorber is capable to withstand the dynamic load for successful force suppression function in case of an accident. (authors)

  7. A clinical investigation of the effects of omission of pumice prophylaxis on band and bond failure.

    PubMed

    Barry, G R

    1995-08-01

    One hundred and twelve first molar bands and 614 directly bonded brackets on incisor, canine, and premolar teeth were included in a clinical trail to investigate the importance of omission of pumice prophylaxis at the time of banding and bonding, on their possible subsequent failure. Half of the sample were selected for the non-pumiced test groups using a random number allocation method, the remaining pumiced teeth acting as control groups. Two etch times were used for the direct bonding part of the study, 15 and 60 seconds, with non-pumiced test and pumiced control groups included within both etch-time groups. Results showed no statistical difference in the failure rate of attachments in either test or control groups during the course of treatment. The different etch times had no significant effects in the direct bonding part of the study.

  8. Project Morpheus: Morpheus 1.5A Lander Failure Investigation Results

    NASA Technical Reports Server (NTRS)

    Devolites, Jennifer L.; Olansen, Jon B.; Munday, Stephen R.

    2013-01-01

    On August 9, 2012 the Morpheus 1.5A vehicle crashed shortly after lift off from the Kennedy Space Center. The loss was limited to the vehicle itself which was pre-declared to be a test failure and not a mishap. The Morpheus project is demonstrating advanced technologies for in space and planetary surface vehicles including: autonomous flight control, landing site hazard identification and safe site selection, relative surface and hazard navigation, precision landing, modular reusable flight software, and high performance, non-toxic, cryogenic liquid Oxygen and liquid Methane integrated main engine and attitude control propulsion system. A comprehensive failure investigation isolated the fault to the Inertial Measurement Unit (IMU) data path to the flight computer. Several improvements have been identified and implemented for the 1.5B and 1.5C vehicles.

  9. Results of investigations of failures of geothermal direct-use well pumps

    SciTech Connect

    Culver, G.

    1994-12-01

    Failures of 13 geothermal direct-use well pumps were investigated and information obtained about an additional 5 pumps that have been in service up to 23 years, but have not failed. Pumps with extra long lateral and variable-speed drives had the highest correlation with reduced time in service. There appears to be at least circumstantial evidence that recirculation may be a cause of reduced pump life. If recirculation is a cause of pump failures, pump specifiers will need to be more aware of minimum flow conditions as well as maximum flow conditions when specifying pumps. Over-sizing pumps and the tendency to specify pumps with high flow and low Net Positive Suction Head (NPSH) could lead to increased problems with recirculation.

  10. Full-field Strain Methods for Investigating Failure Mechanisms in Triaxial Braided Composites

    NASA Technical Reports Server (NTRS)

    Littell, Justin D.; Binienda, Wieslaw K.; Goldberg, Robert K.; Roberts, Gary D.

    2008-01-01

    Composite materials made with triaxial braid architecture and large tow size carbon fibers are beginning to be used in many applications, including composite aircraft and engine structures. Recent advancements in braiding technology have led to commercially viable manufacturing approaches for making large structures with complex shape. Although the large unit cell size of these materials is an advantage for manufacturing efficiency, the fiber architecture presents some challenges for materials characterization, design, and analysis. In some cases, the static load capability of structures made using these materials has been higher than expected based on material strength properties measured using standard coupon tests. A potential problem with using standard tests methods for these materials is that the unit cell size can be an unacceptably large fraction of the specimen dimensions. More detailed investigation of deformation and failure processes in large unit cell size triaxial braid composites is needed to evaluate the applicability of standard test methods for these materials and to develop alternative testing approaches. In recent years, commercial equipment has become available that enables digital image correlation to be used on a more routine basis for investigation of full field 3D deformation in materials and structures. In this paper, some new techniques that have been developed to investigate local deformation and failure using digital image correlation techniques are presented. The methods were used to measure both local and global strains during standard straight-sided coupon tensile tests on composite materials made with 12 and 24 k yarns and a 0/+60/-60 triaxial braid architecture. Local deformation and failure within fiber bundles was observed, and this local failure had a significant effect on global stiffness and strength. The matrix material had a large effect on local damage initiation for the two matrix materials used in this investigation

  11. Investigation of pump and pump switch failures in rainwater harvesting systems

    NASA Astrophysics Data System (ADS)

    Moglia, Magnus; Gan, Kein; Delbridge, Nathan; Sharma, Ashok K.; Tjandraatmadja, Grace

    2016-07-01

    Rainwater harvesting is an important technology in cities that can contribute to a number of functions, such as sustainable water management in the face of demand growth and drought as well as the detention of rainwater to increase flood protection and reduce damage to waterways. The objective of this article is to investigate the integrity of residential rainwater harvesting systems, drawing on the results of the field inspection of 417 rainwater systems across Melbourne that was combined with a survey of householders' situation, maintenance behaviour and attitudes. Specifically, the study moves beyond the assumption that rainwater systems are always operational and functional and draws on the collected data to explore the various reasons and rates of failure associated with pumps and pump switches, leaving for later further exploration of the failure in other components such as the collection area, gutters, tank, and overflows. To the best of the authors' knowledge, there is no data like this in academic literature or in the water sector. Straightforward Bayesian Network models were constructed in order to analyse the factors contributing to various types of failures, including system age, type of use, the reason for installation, installer, and maintenance behaviour. Results show that a number of issues commonly exist, such as failure of pumps (5% of systems), automatic pump switches that mediate between the tank and reticulated water (9% of systems), and systems with inadequate setups (i.e. no pump) limiting their use. In conclusion, there appears to be a lack of enforcement or quality controls in both installation practices by sometimes unskilled contractors and lack of ongoing maintenance checks. Mechanisms for quality control and asset management are required, but difficult to promote or enforce. Further work is needed into how privately owned assets that have public benefits could be better managed.

  12. Large-scale density functional theory investigation of failure modes in ZnO nanowires.

    PubMed

    Agrawal, Ravi; Paci, Jeffrey T; Espinosa, Horacio D

    2010-09-01

    Electromechanical and photonic properties of semiconducting nanowires depend on their strain states and are limited by their extent of deformation. A fundamental understanding of the mechanical response of individual nanowires is therefore essential to assess system reliability and to define the design space of future nanowire-based devices. Here we perform a large-scale density functional theory (DFT) investigation of failure modes in zinc oxide (ZnO) nanowires. Nanowires as large as 3.6 nm in diameter with 864 atoms were investigated. The study reveals that pristine nanowires can be elastically deformed to strains as high as 20%, prior to a phase transition leading to fracture. The current study suggests that the phase transition predicted at approximately 10% strain in pristine nanowires by the Buckingham pairwise potential (BP) is an artifact of approximations inherent in the BP. Instead, DFT-based energy barrier calculations suggest that defects may trigger heterogeneous phase transition leading to failure. Thus, the difference previously reported between in situ electron microscopy tensile experiments (brittle fracture) and atomistic simulations (phase transition and secondary loading) (Agrawal, R.; Peng, B.; Espinosa, H. D. Nano Lett. 2009, 9 (12), 4177-2183) is elucidated. PMID:20726573

  13. Investigation of an outbreak of measles: failure to vaccinate or vaccine failure in a community of predominantly fishermen in Kerala.

    PubMed

    Nujum, Zinia T; Varghese, Sara

    2015-01-01

    Measles outbreaks continue to occur in developing countries. This study attempted to explore the context of an outbreak of measles in a community of predominantly fishermen in Kerala to find out whether the outbreak was the result of a failure to vaccinate or failure of the vaccine itself. A cross sectional study was conducted in Mukkola village of Thiruvananthapuram district, Kerala, India. A total of 215 children of ages between 9 and 35 months were studied. Documented evidence of measles vaccination was available only in 71.6% (65.57-77.62) of the children. The risk factors for not being immunized against measles were being third or higher in birth order and having: a father whose occupation is fishing, low family income, lower parental education, Muslim religion and poor knowledge regarding measles and its vaccine. Of the 215 children studied, 43 had a history of measles. Thirty percent of these 43 children were younger than the age of vaccination. Unvaccinated children, children third or higher in birth order and children of families with more than 5 members had a significantly higher risk of contracting measles. Vaccine effectiveness was 76.6% (95% CI: 75.96-77.99). The prevalence of missed vaccination opportunities was found to be 15.8% (34/215). Even with the relatively low vaccine effectiveness, this outbreak could have been prevented by higher vaccination coverage. Lowering the age at administration of the first dose of measles vaccine needs to be considered. Effective utilization of opportunities for vaccination could enhance coverage and prevent outbreaks in the future.

  14. An accelerated failure time model for investigating pedestrian crossing behavior and waiting times at signalized intersections.

    PubMed

    Yang, Xiaobao; Abdel-Aty, Mohamed; Huan, Mei; Peng, Yichuan; Gao, Ziyou

    2015-09-01

    The waiting process is crucial to pedestrians in the street-crossing behavior. Once pedestrians terminate their waiting behavior during the red light period, they would cross against the red light and put themselves in danger. A joint hazard-based duration model is developed to investigate the effect of various covariates on pedestrian crossing behavior and to estimate pedestrian waiting times at signalized intersections. A total of 1181 pedestrians approaching the intersections during red light periods were observed in Beijing, China. Pedestrian crossing behaviors are classified into immediate crossing behavior and waiting behavior. The probability and effect of various covariates for pedestrians' immediate crossing behavior are identified by a logit model. Four accelerated failure time duration models based on the exponential, Weibull, lognormal and log-logistic distributions are proposed to examine the significant risk factors affecting duration times for pedestrians' waiting behavior. A joint duration model is developed to estimate pedestrian waiting times. Moreover, unobserved heterogeneity is considered in the proposed model. The results indicate that the Weibull AFT model with shared frailty is appropriate for modelling pedestrian waiting durations. Failure to account for heterogeneity would significantly underestimate the effects of covariates on waiting duration times. The proposed model provides a better understanding of pedestrian crossing behavior and more accurate estimation of pedestrian waiting times. It may be applicable in traffic system analysis in developing countries with high flow of mixed traffic.

  15. Triggers for the Collapse of Ice Shelves in Antarctica: Investigating Compressive Arch Failure with Numerical Models

    NASA Astrophysics Data System (ADS)

    Huth, A.; Smith, B. E.

    2015-12-01

    Antarctic ice shelves restrain, or buttress, grounded ice from flowing freely into the ocean by redistributing the force of the ice flow to pinning points (ice rises) at the ice front and shear margins at adjacent bay walls. This buttressing process typically defines a 'compressive arch' in the strain rate-field of the ice shelf, where the smallest principal component transitions from compressive inland of the arch to extensive seaward of the arch. If the compressive arch is breached due to iceberg calving at the ice front or thinning at the shear margins, the ice shelf will retreat irreversibly to a new stable configuration or collapse entirely. This retreat can compromise ice shelf buttressing, resulting in sea-level rise and ocean freshening as grounded ice flows unrestricted into the ocean. Here, we investigate the dynamics of compressive arch failure using Larsen C ice shelf as a test case for a larger study that will include several other ice shelves and projections for sea-level rise. We use satellite observations to develop a steady state model of Larsen C in Elmer/ICE, a finite element ice sheet/ice flow software package. We run calving and thinning simulations to determine the conditions needed to trigger ice shelf retreat via compressive arch failure and discuss the likelihood of these scenarios occurring in relation to extrapolations of current melt profiles and calving trends.

  16. Development of a GIS-based failure investigation system for highway soil slopes

    NASA Astrophysics Data System (ADS)

    Ramanathan, Raghav; Aydilek, Ahmet H.; Tanyu, Burak F.

    2015-06-01

    A framework for preparation of an early warning system was developed for Maryland, using a GIS database and a collective overlay of maps that highlight highway slopes susceptible to soil slides or slope failures in advance through spatial and statistical analysis. Data for existing soil slope failures was collected from geotechnical reports and field visits. A total of 48 slope failures were recorded and analyzed. Six factors, including event precipitation, geological formation, land cover, slope history, slope angle, and elevation were considered to affect highway soil slope stability. The observed trends indicate that precipitation and poor surface or subsurface drainage conditions are principal factors causing slope failures. 96% of the failed slopes have an open drainage section. A majority of the failed slopes lie in regions with relatively high event precipitation ( P>200 mm). 90% of the existing failures are surficial erosion type failures, and only 1 out of the 42 slope failures is deep rotational type failure. More than half of the analyzed slope failures have occurred in regions having low density land cover. 46% of failures are on slopes with slope angles between 20° and 30°. Influx of more data relating to failed slopes should give rise to more trends, and thus the developed slope management system will aid the state highway engineers in prudential budget allocation and prioritizing different remediation projects based on the literature reviewed on the principles, concepts, techniques, and methodology for slope instability evaluation (Leshchinsky et al., 2015).

  17. Comparison Between Corrosion Behavior of Copper and Stainless Steel 90° Elbow and Failure Investigation of 90° Copper Elbow

    NASA Astrophysics Data System (ADS)

    Fouad, Mohamed Ahmed; Zewail, Taghreed Mohamed; Amine, Nieven Abbas; El-Tawail, Yehia Ahmed

    2016-06-01

    Frequently found in elbow, erosion failures may lead to the leakage of pipes and even damage the whole system. Erosion is a form of material degradation that involves electrochemical corrosion and mechanical wear processes encountered on the surface of metal pipes. Research on the erosion-corrosion mechanism indicates that the erosion mainly results from the interactions between the elbow surface and the fluid traveling along the surface. Corrosion behavior of 90° copper and stainless steel elbow was studied. Scanning electron microscopy was processed on the 90° copper elbow to show the surface morphology of the failed copper elbow. Failure investigation was carried out on 90° copper elbow to determine failure location and failure causes.

  18. Numerical investigations of failure in EB-PVD thermal barrier coating systems

    NASA Astrophysics Data System (ADS)

    Glynn, Michael L.

    Thermal barrier coating (TBC) systems are used in high temperature applications in turbine engines. TBCs are applied on superalloy substrates and are multilayered coatings comprised of a metallic bond coat, a thermally grown oxide (TGO) and a ceramic top coat. They provide thermal protection for the superalloy substrate and are considered to hold the greatest potential for increased operating temperatures. Failure of the TBC system most commonly occurs as a result of large scale buckling and spallation. The buckling is a consequence of many small-scale delaminations that arise in the top coat above local imperfections in the TGO, and durability of the TBC system is governed by a sequence of crack nucleation, propagation and coalescence. The numerical investigations that are employed in this dissertation are used to determine the stress development near the imperfections and are based on microstructural observations and measured material properties of TBC test buttons supplied by GE Aircraft Engines. The test buttons were subject to thermal cycling at GE and cycled to different percentages of TBC life. Numerical simulations of two different types of TBC tests are used to show that the top coat out-of-plane stress increases with a decrease of the substrate radius of curvature and a decrease in the heating rate. An inherent scaling parameter in the TBC system is identified and used to demonstrate that the stress developed in the top coat is governed by the evolution of an imperfection in the TGO. The effect of a martensitic phase transformation in the bond coat, related to a change in bond coat chemistry, is shown to significantly increase the top coat out-of-plane tensile stress. Finally, a subsurface crack is simulated in the top coat and used to determine the influence of the bond coat on failure of the TBC system. While the bond coat inelastic properties are the most important factors in determining the extent of the crack opening displacement, the bond coat

  19. Investigation of component failure rates for pulsed versus steady state tokamak operation

    SciTech Connect

    Cadwallader, L.C.

    1992-07-01

    This report presents component failure rate data sources applicable to magnetic fusion systems, and defines multiplicative factors to adjust these data for specific use on magnetic fusion experiment designs. The multipliers address both long pulse and steady state tokamak operation. Thermal fatigue and radiation damage are among the leading reasons for large multiplier values in pulsed operation applications. Field failure rate values for graphite protective tiles are presented, and beryllium tile failure rates in laboratory testing are also given. All of these data can be used for reliability studies, safety analyses, design tradeoff studies, and risk assessments.

  20. Investigation of extrusion failures of PTFE-based gaskets in chemical plant service

    SciTech Connect

    Winter, J.R.; Keywood, S.S.

    1996-12-01

    PTFE-based gaskets in chemical plant service typically fail in an extrusion mode, sometimes referred to as blowout. Test work previously published by Monsanto indicated that correctly installed PTFE-based gaskets have pressure performance far exceeding system pressure ratings. These results have since been confirmed by extensive testing at the Montreal based Ecole Polytechnique Tightness Testing and Research Laboratory (TTRL), funded by a consortium of gasket users and manufacturers. With the knowledge that properly installed gaskets can withstand system pressures in excess of 1,000 psig [6,894 kPa], failures at two chemical plants were re-examined. This analysis indicates that extrusion type failures can be caused by excessive internal pressures, associated with sections of pipe having an external source of heat coincident with a blocked flow condition. This results in high system pressures which explain the extrusion type failures observed. The paper discusses details of individual failures and examines methods to prevent them. Other causes for extrusion failures are reviewed, with a recommendation that stronger gasket materials not be utilized to correct problems until it is verified that excessive pressure build-up is not the problem. Also summarized are the requirements for proper installation to achieve the potential blowout resistance found in these gaskets.

  1. Elephant butte powerplant investigation of permanent magnet generator corrosion and bearing failures. Project notes 8450-97-07. Technical memo

    SciTech Connect

    Price, P.; Atwater, P.

    1997-04-01

    This investigation and report were initiated in response to a request to determine causes for excessive corrosion and premature bearing failures on the Woodward Permanent Magnet Generator (PMG) on the three main generating units at Elephant Butte. All three main generating units were rewound using epoxy-type insulating materials between 1989 and 1991. Plant personnel reported that corrosion and failure rates seemed to accelerate after the new stator windings were installed. This report documents field testing conducted the week of March 10, 1997, to determine if stray electrical currents/voltages were causing the problems. Electrical field test results indicate that accelerated PMG bearing failure and corrosion were not caused by stray voltages or current. Tests were conducted on the main shaft in the turbine pit and on the PMG shaft and housing located atop the exciter shaft.

  2. Investigation of control law reconfigurations to accommodate a control element failure on a commercial airplane

    NASA Technical Reports Server (NTRS)

    Ostroff, A. J.; Hueschen, R. M.

    1984-01-01

    The ability of a pilot to reconfigure the control surfaces on an airplane after a failure, allowing the airplane to recover to a safe condition, becomes more difficult with increasing airplane complexity. Techniques are needed to stabilize and control the airplane immediately after a failure, allowing the pilot more time to make longer range decisions. This paper presents a baseline design of a discrete multivariable control law using four controls for the longitudinal channel of a B-737. Non-reconfigured and reconfigured control laws are then evaluated, both analytically and by means of a digital airplane simulation, for three individual control element failures (stabilizer, elevator, spoilers). The simulation results are used to evaluate the effectiveness of the control reconfiguration on tracking ability during the approach and landing phase of flight with severe windshear and turbulence disturbing the airplane dynamics.

  3. A percolative approach to investigate electromigration failure in printed Ag structures

    NASA Astrophysics Data System (ADS)

    Zhao, Zhao; Mamidanna, Avinash; Lefky, Christopher; Hildreth, Owen; Alford, T. L.

    2016-09-01

    The ease of fabrication and wide application of printed microelectronics are driving advances in reactive inks. The long-term performance of structures printed using reactive ink is important for their application in microelectronics. In this study, silver lines are printed with low-temperature, self-reducing, silver-diamine based ink. The electromigration failure of the printed silver is first studied using Black's equation. However, due to the porous nature of the printed Ag line, Black's equation is not the best fit for predicting the lifetime, this is because Black's equation does not take into account morphology-induced current crowding. We find that the resistivity of the printed Ag lines can be described (as a function of void fraction) by percolation theory. In addition, we also demonstrate that the failure lifetimes of the printed Ag can be predicted quite well by a percolative model of failure.

  4. Investigations of the Failure in Boilers Economizer Tubes Used in Power Plants

    NASA Astrophysics Data System (ADS)

    Moakhar, Roozbeh Siavash; Mehdipour, Mehrad; Ghorbani, Mohammad; Mohebali, Milad; Koohbor, Behrad

    2013-09-01

    In this study, failure of a high pressure economizer tube of a boiler used in gas-Mazut combined cycle power plants was studied. Failure analysis of the tube was accomplished by taking into account visual inspection, thickness measurement, and hardness testing as well as microstructural observations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Optical microscopy images indicate that there is no phase transformation during service, and ferrite-pearlite remained. The results of XRD also revealed Iron sulfate (FeSO4) and Iron hydroxide sulfate (FeOH(SO4)) phases formed on the steel surface. A considerable amount of Sulfur was also detected on the outer surface of the tube by EDS analysis. Dew-point corrosion was found to be the principal reason for the failure of the examined tube while it has been left out-of-service.

  5. Predicting Success, Preventing Failure: An Investigation of the California High School Exit Exam

    ERIC Educational Resources Information Center

    Zau, Andrew C.; Betts, Julian R.

    2008-01-01

    Many educators, parents, and policymakers continue to call for reforms to the California High School Exit Exam (CAHSEE), citing concern about the 10 percent of California students who do not graduate because of their failure to pass the test. By law, current funding for tutoring those at risk of failing the CAHSEE is targeted at those in grade 12…

  6. Investigation of a fatigue failure in a stainless steel femoral plate.

    PubMed

    Marcomini, J B; Baptista, C A R P; Pascon, J P; Teixeira, R L; Reis, F P

    2014-10-01

    Surgical implants are exposed to severe working conditions and therefore a wide range of failure mechanisms may occur, including fatigue, corrosion, wear, fretting and combinations of them. The mechanical failures of metallic implants may also be influenced by several other factors, including the design, material, manufacturing, installation, postoperative complications and misuse. An 83-year-old patient suffered an oblique femoral shaft fracture due to a fall at home. A stainless steel locking compression plate (LCP) employed in the fracture reduction failed after four months and was sent back to the producer. A second LCP of the same type was implanted and also failed after six months. A failure analysis of the second femoral LCP is performed in this paper. The results demonstrate that poor material quality was decisive to the failure. The chemical analysis revealed a high P content in the steel, which is not in accordance to the standards. A combination of factors lead to LCP fracture and these include: brittle crack initiation due to phosphorus, segregation at grain boundaries, crack propagation due to cyclic loading and final fast fracture favored by the loss of ductility due to cold work. PMID:25023519

  7. Failure Investigation for QP Steel Sheets under uniaxial and Equal-Biaxial Tension Conditions

    NASA Astrophysics Data System (ADS)

    Zou, Danqing; Li, Shuhui; He, Ji; Cui, Ronggao

    2016-08-01

    The Quenching and Partitioning (QP) steel sheet is new generation material to induce phase transformation for plasticity in forming vehicle parts. The phase transformation is strongly stress state dependent behavior in experiments, which should affect the failure timing and limit strain in forming processes. In this paper, Nakajima test with QP980 and DP1000 steel sheets under equal-biaxial loading condition is performed for failure behavior. X-ray diffraction (XRD) is adopted to obtain the volume fraction of retained austenite (fA). Digital Image Correlation (DIC) is used to record the surface strain field and its evolution during equal-biaxial tension deformation. The same level Dual Phase (DP) steel is also employed for the purpose of comparison. The results show that phase transformation in QP steel gives small impact on failure strain under equal biaxial tension condition which is contradicted with our understanding. It suggests that failure behavior under uniaxial tension of QP980 is strongly phase transformation dependent. But it shows almost independent under equal biaxial tension condition.

  8. Are Success and Failure Experiences Equally Motivational? An Investigation of Regulatory Focus and Feedback

    ERIC Educational Resources Information Center

    Shu, Tse-Mei; Lam, Shui-fong

    2011-01-01

    The present study extended regulatory focus theory (Idson & Higgins, 2000) to an educational setting and attempted to identify individuals with high motivation after both success and failure feedback. College students in Hong Kong (N = 180) participated in an experiment with a 2 promotion focus (high vs. low) x 2 prevention focus (high vs. low) x…

  9. Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1983-01-01

    Results of an ongoing research program into the reliability of terrestrial solar cells are presented. Laboratory accelerated testing procedures are used to identify failure/degradation modes which are then related to basic physical, chemical, and metallurgical phenomena. In the most recent tests, ten different types of production cells, both with and without encapsulation, from eight different manufacturers were subjected to a variety of accelerated tests. Results indicated the presence of a number of hitherto undetected failure mechanisms, including Schottky barrier formation at back contacts and loss of adhesion of grid metallization. The mechanism of Schottky barrier formation is explained by hydrogen, formed by the dissociation of water molecules at the contact surface, diffusing to the metal semiconductor interface. This same mechanism accounts for the surprising increase in sensitivity to accelerated stress conditions that was observed in some cells when encapsulated.

  10. Preliminary investigation of cardiopulmonary function in stroke patients with stable heart failure and exertional dyspnea

    PubMed Central

    Liaw, Mei-Yun; Wang, Lin-Yi; Pong, Ya-Ping; Tsai, Yu-Chin; Huang, Yu-Chi; Yang, Tsung-Hsun; Lin, Meng-Chih

    2016-01-01

    Abstract The aim of this study was to investigate the relationships between pulmonary function, respiratory muscle strength, perceived dyspnea, degree of fatigue, and activity of daily living with motor function and neurological status in stroke patients with stable congestive heart failure (CHF). This was a cohort study in a tertiary care medical center. Stroke patients with CHF and exertional dyspnea (New York Heart Association class I–III) were recruited. The baseline characteristics included duration of disease, Brunnstrom stage, spirometry, resting heart rate, resting oxyhemoglobin saturation (SpO2), maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), Borg scale, fatigue scale, and Barthel index. A total of 47 stroke patients (24 males, 23 females, mean age 65.9 ± 11.5 years) were included. The average Brunnstrom stages of affected limbs were 3.6 ± 1.3 over the proximal parts and 3.5 ± 1.4 over the distal parts of upper limbs, and 3.9 ± 0.9 over lower limbs. The average forced vital capacity (FVC) was 2.0 ± 0.8 L, with a predicted FVC% of 67.9 ± 18.8%, forced expiratory volume in the first second (FEV1) of 1.6 ± 0.7 L, predicted FEV1% of 70.6 ± 20.1%, FEV1/FVC of 84.2 ± 10.5%, and maximum mid-expiratory flow of 65.4 ± 29.5%. The average MIP and MEP were −52.9 ± 33.3 cmH2O and 60.8 ± 29.0 cmH2O, respectively. The Borg scale was 1.5 ± 0.8. MIP was negatively associated with the average Brunnstrom stage of the proximal (r = −0.318, P < 0.05) and distal (r = −0.391, P < 0.01) parts of the upper extremities and lower extremities (r = −0.288, P < 0.05), FVC (r = −0.471, P < 0.01), predicted FVC% (r = −0.299, P < 0.05), and FEV1 (r = −0.397, P < 0.01). MEP was positively associated with average Brunnstrom stage of the distal area of the upper extremities (r = 0.351, P < 0.05), FVC (r = 0.526, P < 0

  11. Investigation of fatigue failure of a stainless steel orthopedic implant device

    NASA Astrophysics Data System (ADS)

    Sivakumar, M.; Kamachi Mudali, U.; Rajeswari, S.

    1994-02-01

    An orthopedic implant (rush nail) fractured in a patient at a location that corresponded to the site of a prior fracture of the bone (right femur). The crack propagation in the implant proceeded from both sides of the nail, and the final fracture occurred by ductile shear in the midsection of the nail. Dimple structures and tear ridges between fatigue striation patches were observed on the fractured surface. Moreover, the device fractured within a short period of use. Contrary to post-procedure instructions, the patient placed the body’s full weight on the implanted leg at least once, perhaps twice, causing overload-induced fatigue failure of the implant.

  12. What causes an icy fault to slip? Investigating strike-slip failure conditions on Ganymede at Dardanus and Tiamat Sulcus.

    NASA Astrophysics Data System (ADS)

    Cameron, M. E.; Smith-Konter, B. R.; Burkhard, L. M.; Collins, G. C.; Seifert, F.; Pappalardo, R. T.

    2015-12-01

    Ganymede exhibits two geologically distinct terrains known as dark and light (grooved) terrain. The mechanism for a transition from dark to light terrain remains unclear; however, inferences of strike-slip faulting and distributed shear zones suggest that strike-slip tectonism may be important to the structural development of Ganymede's surface and in this transition. Here we investigate the role of tidal stresses on Ganymede in the formation and evolution of strike-slip structures in both dark and grooved terrains. Using numerical code SatStress, we calculate both diurnal and non-synchronous rotation (NSR) tidal stresses at Ganymede's surface. Specifically, we investigate the role of fault friction and orbital eccentricity in the development of ~45 km of right-lateral offset at Dardanus Sulcus and a possible case of <10 km of right-lateral offset at Tiamat Sulcus. We compute Coulomb failure conditions for these target fractures and consider tidal stress scenarios for both present eccentricity (0.0013) and possible past high (~0.05) eccentricity of Ganymede. We find that while diurnal stresses are not large enough to support strike-slip failure at present or past eccentricities, models that include both diurnal and NSR stress readily generate shear and normal stress magnitudes that could give rise to shear failure. Results for a past high eccentricity assuming a low coefficient of friction (μf = 0.2) suggest shear failure is possible down to depths of 1-2 km along both Dardanus and Tiamat. For a high coefficient of friction (μf = 0.6), failure is limited to about 1 km depth at Dardanus and Tiamat, although confined to small episodic slip windows for the latter. Moreover, our models predict a right-lateral sense of slip, in agreement with inferred offset observed at both regions. Based on these results, we infer that past shear failure on Ganymede is possible when NSR is a driving stress mechanism. We complement this study with a detailed morphological mapping of

  13. Investigation of Mechanisms of Blade Failure of Forged Hastalloy B and Cast Stellite 21 Turbine Blades in Turbojet Engine

    NASA Technical Reports Server (NTRS)

    Yaker, C; Robards, C F; Garrett, F B

    1951-01-01

    An investigation was conducted to study the mechanisms of blade failure of forged Hastelloy B and cast Stellite 21. The blades were mounted in a 16-25-6 alloy rotor and subjected to 20-minute cycles consisting of 15 minutes at rated speed and approximately 5 minutes at idle. The first failures of the Hastelloy B and Stellite 21 blades were probably the result of excessive vibratory stresses and occurred after 14.25 and 16.75 hours, respectively. After 28.75 hours of operation, all but 3 of the original 25 Hastelloy B blades had either failed or contained stress-rupture-type cracks and four of the original 27 Stellite 21 blades contained stress-rupture-type cracks.

  14. Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1984-01-01

    Research on the reliability of terrestrial solar cells was performed to identify failure/degradation modes affecting solar cells and to relate these to basic physical, chemical, and metallurgical phenomena. Particular concerns addressed were the reliability attributes of individual single crystalline, polycrystalline, and amorphous thin film silicon cells. Results of subjecting different types of crystalline cells to the Clemson accelerated test schedule are given. Preliminary step stress results on one type of thin film amorphous silicon (a:Si) cell indicated that extraneous degradation modes were introduced above 140 C. Also described is development of measurement procedures which are applicable to the reliability testing of a:Si solar cells as well as an approach to achieving the necessary repeatability of fabricating a simulated a:Si reference cell from crystalline silicon photodiodes.

  15. Circuit breaker operation and potential failure modes during an earthquake: a preliminary investigation

    SciTech Connect

    Lambert, H.E.

    1984-04-09

    This study addresses the effect of a strong-motion earthquake on circuit breaker operation. It focuses on the loss of offsite power (LOSP) transient caused by a strong-motion earthquake at the Zion Nuclear Power Plant. This report also describes the operator action necessary to prevent core melt if the above circuit breaker failure modes occur simultaneously on three 4.16 KV buses. Numerous circuit breakers important to plant safety, such as circuit breakers to diesel generators and engineered safety systems, (ESS), must open and/or close during this transient while strong motion is occurring. Nearly 500 electrical drawings were examined to address the effects of earthquakes on circuit breaker operation. Due to the complexity of the problem, this study is not intended to be definitive but serves as a focusing tool for further work. 5 references, 9 figures, 3 tables.

  16. An investigation into the role of plastic failure in crater modification

    NASA Technical Reports Server (NTRS)

    Mckinnon, W. B.

    1978-01-01

    The mechanical stability of an impact crater is analyzed in this paper via a quasi-static, axisymmetric slip line theory of plasticity. The yield model incorporated is Mohr-Coulomb and a simplified rectangular profile is used for the transient cavity. The degree of stability (or instability) is described as a function of internal friction angle, depth/diameter ratio, and a dimensionless parameter. To match the observed slumping of large lunar craters the cohesion strength of the lunar surface material must be low (less than 20 bars) and the angle of internal friction must be less than 2 deg. It is not implausible that these failure strength characteristics are realized by freshly shocked rock.

  17. Investigations of micromechanical and failure mechanisms of toughened thermoplastics by electron microscopy

    SciTech Connect

    Michler, G.H.; Starke, J.U.

    1996-12-31

    The competitive influence of particle diameter and interparticle distance on the toughening mechanism was studied in various thermoplastics. The morphology, deformation, and fracture properties were also investigated.

  18. Centrifuge model tests of rainfall-induced slope failures for the investigation of the initiation conditions

    NASA Astrophysics Data System (ADS)

    Matziaris, Vasileios; Marshall, Alec; Yu, Hai-Sui

    2015-04-01

    Rainfall-induced landslides are very common natural disasters which cause damage to properties and infrastructure and may result in the loss of human lives. These phenomena often take place in unsaturated soil slopes and are triggered by the saturation of the soil profile, due to rain infiltration, which leads to a loss of shear strength. The aim of this study is to determine rainfall thresholds for the initiation of landslides under different initial conditions. Model tests of rainfall-induced landslides are conducted in the Nottingham Centre for Geomechanics 50g-T geotechnical centrifuge. Initially unsaturated plane-strain slope models made with fine silica sand are prepared at varying densities at 1g and accommodated within a climatic chamber which provides controlled environmental conditions. During the centrifuge flight at 60g, rainfall events of varying intensity and duration are applied to the slope models causing the initiation of slope failure. The impact of soil state properties and rainfall characteristics on the landslide initiation process are discussed. The variation of pore water pressures within the slope before, during and after simulated rainfall events is recorded using miniature pore pressure transducers buried in the soil model. Slope deformation is determined by using a high-speed camera and digital image analysis techniques.

  19. Quality Assurance in Software Development: An Exploratory Investigation in Software Project Failures and Business Performance

    ERIC Educational Resources Information Center

    Ichu, Emmanuel A.

    2010-01-01

    Software quality is perhaps one of the most sought-after attributes in product development, however; this goal is unattained. Problem factors in software development and how these have affected the maintainability of the delivered software systems requires a thorough investigation. It was, therefore, very important to understand software…

  20. Development of KSC program for investigating and generating field failure rates. Volume 1: Summary and overview

    NASA Technical Reports Server (NTRS)

    Bean, E. E.; Bloomquist, C. E.

    1972-01-01

    A summary of the KSC program for investigating the reliability aspects of the ground support activities is presented. An analysis of unsatisfactory condition reports (RC), and the generation of reliability assessment of components based on the URC are discussed along with the design considerations for attaining reliable real time hardware/software configurations.

  1. The Failure of Inquiry: Preparing Science Teachers with an Authentic Investigation

    ERIC Educational Resources Information Center

    Lustick, David

    2009-01-01

    This mixed methodology action research study examined the impact of a curricular innovation designed to provide an authentic science inquiry learning experience for 15 secondary science teacher candidates enrolled in a master's level initial certification program. The class investigated the question "How can peak autumn color in New England be…

  2. Failure Investigation of an Intra-Manifold Explosion in a Horizontally-Mounted 870 lbf Reaction Control Thruster

    NASA Technical Reports Server (NTRS)

    Durning, Joseph G., III; Westover, Shayne C.; Cone, Darren M.

    2011-01-01

    In June 2010, an 870 lbf Space Shuttle Orbiter Reaction Control System Primary Thruster experienced an unintended shutdown during a test being performed at the NASA White Sands Test Facility. Subsequent removal and inspection of the thruster revealed permanent deformation and misalignment of the thruster valve mounting plate. Destructive evaluation determined that after three nominal firing sequences, the thruster had experienced an energetic event within the fuel (monomethylhydrazine) manifold at the start of the fourth firing sequence. The current understanding of the phenomenon of intra-manifold explosions in hypergolic bipropellant thrusters is documented in literature where it is colloquially referred to as a ZOT. The typical ZOT scenario involves operation of a thruster in a gravitational field with environmental pressures above the triple point pressure of the propellants. Post-firing, when the thruster valves are commanded closed, there remains a residual quantity of propellant in both the fuel and oxidizer (nitrogen tetroxide) injector manifolds known as the "dribble volume". In an ambient ground test configuration, these propellant volumes will drain from the injector manifolds but are impeded by the local atmospheric pressure. The evacuation of propellants from the thruster injector manifolds relies on the fluids vapor pressure to expel the liquid. The higher vapor pressure oxidizer will evacuate from the manifold before the lower vapor pressure fuel. The localized cooling resulting from the oxidizer boiling during manifold draining can result in fuel vapor migration and condensation in the oxidizer passage. The liquid fuel will then react with the oxidizer that enters the manifold during the next firing and may produce a localized high pressure reaction or explosion within the confines of the oxidizer injector manifold. The typical ZOT scenario was considered during this failure investigation, but was ultimately ruled out as a cause of the explosion

  3. Investigation of the Alexander L. Kielland failure-metallurgical and fracture analysis

    SciTech Connect

    Almar-Naess, A.; Haagensen, P.J.; Lian, B.; Moan, T.; Simonsen, T.

    1984-03-01

    On March 27, 1980, the semi-submersible platform Alexander L. Kielland broke down in a storm in the North Sea, resulting in a loss of 123 lives. The investigation subsequently performed by the inquiry commission showed that one of the lower tubular bracings had failed by fatigue. As a result, the vertical leg attached to it was torn off, and the platform capsized. The fatigue fracture had started from a double fillet weld joining a 0.325-m tubular attachment to the bracing. The fillet welds were partially cracked in the early history of the platform due to lammelar tearing. Cumulative damage calculations indicated that the design fatigue life of the bracing was inadequate.

  4. Investigation of failure modes in fiber-reinforced ceramic-matrix composites. Master's thesis

    SciTech Connect

    Moschler, J.W.

    1988-12-01

    This experimental study was conducted to investigate the damage progression in fiber-reinforced ceramic-matrix composites under tensile loading. As part of this study, the effect of the residual stresses at the fiber-matrix interface on damage progression was evaluated. Composite samples were fabricated from silicon carbide fibers and borosilicate glass matrices. Each glass had a different coefficient of thermal expansion than the fiber and through the variation of this mismatch, the residual stresses at the fiber-matrix interface were varied resulting in different bonding conditions at the fiber-matrix interface. The mechanical properties of the composites were measured using a servo-hydraulic mechanical testing machine. During these tests, transverse strain reversal was observed that is believed to be caused by axial matrix cracks and fiber-matrix debonding. Tensile tests were conducted on the composites using a constant-load straining device in which damage progression was observed using an optical microscope.

  5. Failure Investigation & Design Optimization of a Photo-Multiplier Tube Assembly Under Thermal Loading

    NASA Technical Reports Server (NTRS)

    Dahya, Kevin

    2004-01-01

    Analysis of GLAST ACD Photo-Multiplier Tube (PMT) assembly under thermal loading demonstrates that the glass tube experiences high stresses due to Coefficient of Thermal Expansion mismatch, as well as increased stress due to high stiffness and incompressibility of potting compound. Further investigation shows adverse loading effects due to the magnetic shield, a thin piece of steel wrapped around the PMT. This steel, Mu Metal, contained an overlap region that directly attributed to crack propagation in the outside surface of the tube. Sensitivities to different configurations were studied to reduce the stress and provide a more uniform loading throughout the PMT to ensure mission success. Studies indicate substituting a softer and more compressible potting compound and moving the Mu metal from the glass tube to the outside wall of the aluminum housing yields lower stress.

  6. Failure of the Ingard-Myers boundary condition for a lined duct: an experimental investigation.

    PubMed

    Renou, Ygaäl; Aurégan, Yves

    2011-07-01

    This paper deals with experimental investigation of the lined wall boundary condition in flow duct applications such as aircraft engine systems or automobile mufflers. A first experiment, based on a microphone array located in the liner test section, is carried out in order to extract the axial wavenumbers with the help of an "high-accurate" singular value decomposition Prony-like algorithm. The experimental axial wavenumbers are then used to provide the lined wall impedance for both downstream and upstream acoustic propagation by means of a straightforward impedance education method involving the classical Ingard-Myers boundary condition. The results show that the Ingard-Myers boundary condition fails to predict with accuracy the acoustic behavior in a lined duct with flow. An effective lined wall impedance, valid whatever the direction of acoustic propagation, can be suitably found from experimental axial wavenumbers and a modified version of the Ingard-Myers condition with the form inspired from a previous theoretical study [Aurégan et al., J. Acoust. Soc. Am. 109, 59-64 (2001)]. In a second experiment, the scattering matrix of the liner test section is measured and is then compared to the predicted scattering matrix using the multimodal approach and the lined wall impedances previously deduced. A large discrepancy is observed between the measured and the predicted scattering coefficients that confirms the poor accuracy provided from the Ingard-Myers boundary condition widely used in lined duct applications. PMID:21786877

  7. Investigation of Pathogenic Genes in Peri-Implantitis from Implant Clustering Failure Patients: A Whole-Exome Sequencing Pilot Study

    PubMed Central

    Lee, Soohyung; Kim, Ji-Young; Hwang, Jihye; Kim, Sanguk; Lee, Jae-Hoon; Han, Dong-Hoo

    2014-01-01

    Peri-implantitis is a frequently occurring gum disease linked to multi-factorial traits with various environmental and genetic causalities and no known concrete pathogenesis. The varying severity of peri-implantitis among patients with relatively similar environments suggests a genetic aspect which needs to be investigated to understand and regulate the pathogenesis of the disease. Six unrelated individuals with multiple clusterization implant failure due to severe peri-implantitis were chosen for this study. These six individuals had relatively healthy lifestyles, with minimal environmental causalities affecting peri-implantitis. Research was undertaken to investigate pathogenic genes in peri-implantitis albeit with a small number of subjects and incomplete elimination of environmental causalities. Whole-exome sequencing was performed on collected saliva samples via self DNA collection kit. Common variants with minor allele frequencies (MAF) > = 0.05 from all control datasets were eliminated and variants having high and moderate impact and loss of function were used for comparison. Gene set enrichment analysis was performed to reveal functional groups associated with the genetic variants. 2,022 genes were left after filtering against dbSNP, the 1000 Genomes East Asian population, and healthy Korean randomized subsample data (GSK project). 175 (p-value <0.05) out of 927 gene sets were obtained via GSEA (DAVID). The top 10 was chosen (p-value <0.05) from cluster enrichment showing significance of cytoskeleton, cell adhesion, and metal ion binding. Network analysis was applied to find relationships between functional clusters. Among the functional groups, ion metal binding was located in the center of all clusters, indicating dysfunction of regulation in metal ion concentration might affect cell morphology or cell adhesion, resulting in implant failure. This result may demonstrate the feasibility of and provide pilot data for a larger research project aimed at

  8. Simulation and Mechanistic Investigation of the Arrhythmogenic Role of the Late Sodium Current in Human Heart Failure

    PubMed Central

    Trenor, Beatriz; Cardona, Karen; Gomez, Juan F.; Rajamani, Sridharan; Ferrero, Jose M.; Belardinelli, Luiz; Saiz, Javier

    2012-01-01

    Heart failure constitutes a major public health problem worldwide. The electrophysiological remodeling of failing hearts sets the stage for malignant arrhythmias, in which the role of the late Na+ current (INaL) is relevant and is currently under investigation. In this study we examined the role of INaL in the electrophysiological phenotype of ventricular myocytes, and its proarrhythmic effects in the failing heart. A model for cellular heart failure was proposed using a modified version of Grandi et al. model for human ventricular action potential that incorporates the formulation of INaL. A sensitivity analysis of the model was performed and simulations of the pathological electrical activity of the cell were conducted. The proposed model for the human INaL and the electrophysiological remodeling of myocytes from failing hearts accurately reproduce experimental observations. The sensitivity analysis of the modulation of electrophysiological parameters of myocytes from failing hearts due to ion channels remodeling, revealed a role for INaL in the prolongation of action potential duration (APD), triangulation of the shape of the AP, and changes in Ca2+ transient. A mechanistic investigation of intracellular Na+ accumulation and APD shortening with increasing frequency of stimulation of failing myocytes revealed a role for the Na+/K+ pump, the Na+/Ca2+ exchanger and INaL. The results of the simulations also showed that in failing myocytes, the enhancement of INaL increased the reverse rate-dependent APD prolongation and the probability of initiating early afterdepolarizations. The electrophysiological remodeling of failing hearts and especially the enhancement of the INaL prolong APD and alter Ca2+ transient facilitating the development of early afterdepolarizations. An enhanced INaL appears to be an important contributor to the electrophysiological phenotype and to the dysregulation of [Ca2+]i homeostasis of failing myocytes. PMID:22427860

  9. Heart Failure

    MedlinePlus

    ... version of this page please turn Javascript on. Heart Failure What is Heart Failure? In heart failure, the heart cannot pump enough ... failure often experience tiredness and shortness of breath. Heart Failure is Serious Heart failure is a serious and ...

  10. What causes an icy fault to slip? Investigating the depth and frictional conditions for tidally driven Coulomb failure along major strike-slip faults of Europa and Ganymede

    NASA Astrophysics Data System (ADS)

    Cameron, Marissa E.; Smith-Konter, Bridget R.; Pappalardo, Robert T.

    2014-11-01

    The surfaces of Europa and Ganymede display strike-slip fractures, presumably arising from a combination of global and local stress sources. To better understand the role of tidal stress sources and implications for strike-slip faulting on these icy bodies, we investigate the relationship between shear and normal stresses at several major fault zones: Agenor Linea, Rhadamanthys Linea, Agave/Asterius Lineae, and Astypalaea Linea (on Europa), and Dardanus Sulcus (on Ganymede). Assuming tidal diurnal and non-synchronous rotation (NSR) stresses as plausible mechanisms for strike-slip tectonism, here we investigate the mechanics of Coulomb shear failure. We consider a range of friction coefficients (µf = 0.2 - 0.6) and fault depths (0 - 6 km) to evaluate how failure predictions vary between the satellites and as a function of depth, ice friction, geographic location, and fault geometry. Assuming present-day orbital eccentricities, our results indicate that the conditions for failure at depth are not met for any of the fault systems if subject to diurnal stresses only. Alternatively, models that include both diurnal and NSR stresses readily generate stress magnitudes that could permit shear failure. On Europa, shear failure is easily activated and failure extends to depths ranging from 3 - 6 km when a low coefficient of friction (µf = 0.2) is assumed. On Ganymede, failure is limited to even shallower depths (< 2 km). A high coefficient of friction (µf = 0.6) limits failure depths to < 3 km on Europa faults and discourages strike-slip faulting completely on Ganymede. Based on these results, we infer that the conditions for shear failure are potentially met along at least these five studied systems, and possibly others in the outer solar system, if NSR is adopted as a driving stress mechanism and the coefficient of friction is low.

  11. Vibrational and thermal characterisation of a new chiral drug under investigation for the therapy of congestive heart failure

    NASA Astrophysics Data System (ADS)

    Taddei, Paola; Torreggiani, Armida; Fini, Giancarlo

    2002-12-01

    Racemic (5,6-bis 2-methyl propanoic acid-1,2,3,4-tetrahydro-naphtalen-2-yl)-methylammonium chloride, CHF-1035, under clinical investigation for the treatment of congestive heart failure, was here characterised by Raman and IR spectroscopies coupled with thermal analysis (thermogravimetry and differential scanning calorimetry). These techniques proved suitable for investigating the presence of different polymorphic forms, their relative stability and interconversion tendency in relation to industrial manufacturing processes undergone by the drug (i.e. grinding, compression, heating). Crystallisation experiments were carried out and two different CHF-1035 polymorphic forms were identified. Both grinding and heating revealed to cause a polymorphic transformation of the drug crystal form. It was hypothesised that a change in molecular packing occurs in the drug by effect of both treatments. The possible sources of polymorphism were identified in the -OCOCH(CH 3) groups and in the saturated ring. The non-ground sample showed two endothermic transitions; since they are reversible and not due to desolvation processes the system is probably enantiotropic.

  12. Investigation of stainless steel clad fuel rod failures and fuel performance in the Connecticut Yankee Reactor. Final report

    SciTech Connect

    Pasupathi, V.; Klingensmith, R. W.

    1981-11-01

    Significant levels of fuel rod failures were observed in the batch 8 fuel assemblies of the Connecticut Yankee reactor. Failure of 304 stainless steel cladding in a PWR environment was not expected. Therefore a detailed poolside and hot cell examination program was conducted to determine the cause of failure and identify differences between batch 8 fuel and previous batches which had operated without failures. Hot cell work conducted consisted of detailed nondestructive and destructive examination of fuel rods from batches 7 and 8. The results indicate that the batch 8 failure mechanism was stress corrosion cracking initiating on the clad outer surface. The sources of cladding stresses are believed to be (a) fuel pellet chips wedged in the cladding gap, (b) swelling of highly nondensifying batch 8 fuel and (c) potentially harmful effects of a power change event that occurred near the end of the second cycle of irradiation for batch 8.

  13. In-Situ AFM Investigation of Solid Electrolyte Interphase Formation and Failure Mechanisms in Lithium -Ion Batteries

    NASA Astrophysics Data System (ADS)

    Mueller, Thomas; Kumar, Ravi; Tokranov, Anton; Huang, Teddy; Li, Chunzeng; Xiao, Xingcheng; Sheldon, Brian

    The formation and evolution of the solid electrolyte interphase (SEI) is critical for lifetime and performance of lithium-ion batteries (LIBs), particularly for LIBs with high energy density materials such as silicon. Si has almost ten time theoretical specific capacity vs graphite, but its volume changes during cycling (up to 400%) put enormous strains on the SEI layer, resulting in continuous capacity loss. In this study we report in situ atomic force microscopy (AFM) investigation on the formation and failure mechanisms of SEI layer using patterned Si island structures. Due to the shear lag effect, patterned Si islands go through lateral expansion and Contraction, putting the SEI layer in tension and compression during lithiation and delithiation, respectively. Experimentally, we performed the studies in a glovebox with <1 ppm O2 and H2O, using PeakForce Tapping to image the extremely fragile SEI layer. We show for the first time the in operando cracking of SEI layer. To understand the mechanics of the SEI layer, the critical strain for cracking was derived from a progression of the AFM images. Our studies provide new insight into SEI formation, evolution and its mechanical response, and offer guidance to tailor passivation layers for optimal performance.

  14. Analysis of 7- X 10-foot high speed wind tunnel shaft loads in support of fan blade failure investigation

    NASA Technical Reports Server (NTRS)

    Faison, Richard W.

    1987-01-01

    This is a report of the investigation of the High-Speed 7- X 10-Foot Wind Tunnel at NASA Langley Research Center, which experienced a catastrophic failure of all 18 Sitka spruce fan blades during operation at 0.8 Mach number on 2 July 1985. The High-Speed Tunnel, a closed-circuit/single-return atmospheric wind tunnel, had been operated since 1945 to support a wide range of subsonic aerodynamic tests and studies. The failed blade set had been in use since 1975. In addition to blade loss, the most significant damage was a bent main drive shaft for a total estimated damage loss of 1.7 million dollars. An analysis of the natural frequency characteristics as well as loads, reactions, stresses, and deflections of the fan drive system resulting from steady-state and dynamic loads due to unbalance was performed. Transient load cases were simulated by step input and ramp input loading functions intended to simulate the loss of one to nine blades (maximum unbalance forces).

  15. Investigation of drilling failure of Well A1, E-Field, onshore Niger Delta, Nigeria, using 3-D seismic data

    NASA Astrophysics Data System (ADS)

    Akinmosin, A.; Oladele, S.; Oriade, O. F.

    2016-02-01

    This study aimed at investigating reasons for failure of Well A1 that is surrounded by hydrocarbon discoveries in onshore Niger delta with a view to propose optimal location for a new well through interpretation of new 3-D seismic data. Sands encountered by Well A1 were delineated and tied to seismic. Structural closure was mapped and reservoirs at various depths were stacked and sectioned. Porosity, Net to Gross, and Gross Rock Volume of the reservoirs were computed. Well A1 was correlated to a nearby Well K4 and a good correlation was observed. A fault assisted multi reservoirs Prospect-E with south-westerly shift with depth was delineated on the hanging wall of structure building E-Fault whose closing contours is expected to trap hydrocarbon. Petrophysical properties of the reservoirs range from fair to good. Well A1 either perforated prospect-E beneath the oil water contact, completely missed prospect-E or punctured the wet foot wall of E-fault. Consequently, Well A1 could not impact the objective sands and only able to produce water. Well A1 failed because of wrong surface positioning which unsuccessfully targeted the shifting reservoirs. A successful exploratory well in E-Field would be a gently south-westerly deviated well whose vertical section would encounter the shallower sands and deviated section targeting the deeper sands with surface location at about 1 km southeast of Well A1.

  16. Investigating internal architecture effect in plastic deformation and failure for TPMS-based scaffolds using simulation methods and experimental procedure.

    PubMed

    Kadkhodapour, J; Montazerian, H; Raeisi, S

    2014-10-01

    Rapid prototyping (RP) has been a promising technique for producing tissue engineering scaffolds which mimic the behavior of host tissue as properly as possible. Biodegradability, agreeable feasibility of cell growth, and migration parallel to mechanical properties, such as strength and energy absorption, have to be considered in design procedure. In order to study the effect of internal architecture on the plastic deformation and failure pattern, the architecture of triply periodic minimal surfaces which have been observed in nature were used. P and D surfaces at 30% and 60% of volume fractions were modeled with 3∗3∗ 3 unit cells and imported to Objet EDEN 260 3-D printer. Models were printed by VeroBlue FullCure 840 photopolymer resin. Mechanical compression test was performed to investigate the compressive behavior of scaffolds. Deformation procedure and stress-strain curves were simulated by FEA and exhibited good agreement with the experimental observation. Current approaches for predicting dominant deformation mode under compression containing Maxwell's criteria and scaling laws were also investigated to achieve an understanding of the relationships between deformation pattern and mechanical properties of porous structures. It was observed that effect of stress concentration in TPMS-based scaffolds resultant by heterogeneous mass distribution, particularly at lower volume fractions, led to a different behavior from that of typical cellular materials. As a result, although more parameters are considered for determining dominant deformation in scaling laws, two mentioned approaches could not exclusively be used to compare the mechanical response of cellular materials at the same volume fraction. PMID:25175253

  17. Canadian Cardiovascular Society Consensus Conference guidelines on heart failure – 2008 update: Best practices for the transition of care of heart failure patients, and the recognition, investigation and treatment of cardiomyopathies

    PubMed Central

    Arnold, J Malcolm O; Howlett, Jonathan G; Ducharme, Anique; Ezekowitz, Justin A; Gardner, Martin J; Giannetti, Nadia; Haddad, Haissam; Heckman, George A; Isaac, Debra; Jong, Philip; Liu, Peter; Mann, Elizabeth; McKelvie, Robert S; Moe, Gordon W; Svendsen, Anna M; Tsuyuki, Ross T; O’Halloran, Kelly; Ross, Heather J; Sequeira, Errol J; White, Michel

    2008-01-01

    Heart failure is a clinical syndrome that normally requires health care to be provided by both specialists and nonspecialists. This is advantageous because patients benefit from complementary skill sets and experience, but can present challenges in the development of a common, shared treatment plan. The Canadian Cardiovascular Society published a comprehensive set of recommendations on the diagnosis and management of heart failure in January 2006, and on the prevention, management during intercurrent illness or acute decompensation, and use of biomarkers in January 2007. The present update builds on those core recommendations. Based on feedback obtained through a national program of heart failure workshops during 2006 and 2007, several topics were identified as priorities because of the challenges they pose to health care professionals. New evidence-based recommendations were developed using the structured approach for the review and assessment of evidence that was adopted and previously described by the Society. Specific recommendations and practical tips were written for best practices during the transition of care of heart failure patients, and the recognition, investigation and treatment of some specific cardiomyopathies. Specific clinical questions that are addressed include: What information should a referring physician provide for a specialist consultation? What instructions should a consultant provide to the referring physician? What processes should be in place to ensure that the expectations and needs of each physician are met? When a cardiomyopathy is suspected, how can it be recognized, how should it be investigated and diagnosed, how should it be treated, when should the patient be referred, and what special tests are available to assist in the diagnosis and treatment? The goals of the present update are to translate best evidence into practice, apply clinical wisdom where evidence for specific strategies is weaker, and aid physicians and other health

  18. Acoustic Emission Investigation of Rolling/Sliding Contact Fatigue Failure of NiCr-Cr3C2 Coating

    NASA Astrophysics Data System (ADS)

    Guolu, Li; Zhonglin, Xu; Tianshun, Dong; Haidou, Wang; Jinhai, Liu; Jiajie, Kang

    2016-08-01

    NiCr-Cr3C2 coating was fabricated using supersonic plasma spraying technology. Subsequently, rolling/sliding contact fatigue (R/SCF) testing was carried out, using acoustic emission (AE) technology to monitor the failure process. The results showed that R/SCF consists of three failure modes, namely abrasion, spalling, and delamination. Abrasion is the main failure mode, but delamination is the most severe. The AE monitoring results indicated that the R/SCF failure process is composed of normal contact, crack initiation, crack propagation, and material removal stages. The frequency of each stage was analyzed by fast Fourier transform, revealing a peak frequency for each stage mainly distributed from 200 to 250 kHz.

  19. Acoustic Emission Investigation of Rolling/Sliding Contact Fatigue Failure of NiCr-Cr3C2 Coating

    NASA Astrophysics Data System (ADS)

    Guolu, Li; Zhonglin, Xu; Tianshun, Dong; Haidou, Wang; Jinhai, Liu; Jiajie, Kang

    2016-10-01

    NiCr-Cr3C2 coating was fabricated using supersonic plasma spraying technology. Subsequently, rolling/sliding contact fatigue (R/SCF) testing was carried out, using acoustic emission (AE) technology to monitor the failure process. The results showed that R/SCF consists of three failure modes, namely abrasion, spalling, and delamination. Abrasion is the main failure mode, but delamination is the most severe. The AE monitoring results indicated that the R/SCF failure process is composed of normal contact, crack initiation, crack propagation, and material removal stages. The frequency of each stage was analyzed by fast Fourier transform, revealing a peak frequency for each stage mainly distributed from 200 to 250 kHz.

  20. Development of KSC program for investigating and generating field failure rates. Reliability handbook for ground support equipment

    NASA Technical Reports Server (NTRS)

    Bloomquist, C. E.; Kallmeyer, R. H.

    1972-01-01

    Field failure rates and confidence factors are presented for 88 identifiable components of the ground support equipment at the John F. Kennedy Space Center. For most of these, supplementary information regarding failure mode and cause is tabulated. Complete reliability assessments are included for three systems, eight subsystems, and nine generic piece-part classifications. Procedures for updating or augmenting the reliability results are also included.

  1. Diagnostic investigation of porcine periweaning failure-to-thrive syndrome: lack of compelling evidence linking to common porcine pathogens.

    PubMed

    Huang, Yanyun; Gauvreau, Henry; Harding, John

    2012-01-01

    Porcine periweaning failure-to-thrive syndrome (PFTS), an increasingly recognized syndrome in the swine industry of North America, is characterized by the anorexia of nursery pigs noticeable within 1 week of weaning, and progressive loss of body condition and lethargy during the next 1-2 weeks. Morbidity caused by PFTS is moderate, but case fatality is high. The etiology of PFTS is presently unknown and may include infectious agent(s), noninfectious factors, or both. PFTS was identified in a high health status farm with good management in early 2007. A diagnostic investigation was undertaken to identify the pathological lesions of, and infectious agents associated with, pigs demonstrating typical clinical signs. Affected (PFTS-SICK) and unaffected (PFTS-HLTHY) pigs from an affected farm, and unaffected pigs from 2 unaffected farms, were examined. The most prevalent lesions in PFTS-SICK pigs were superficial lymphocytic fundic gastritis, atrophic enteritis, superficial colitis, lymphocytic and neutrophilic rhinitis, mild nonsuppurative meningoencephalitis, and thymic atrophy. Rotavirus A and Betacoronavirus 1 (Porcine hemagglutinating encephalomyelitis virus) were identified only in PFTS-SICK pigs, but the significance of the viruses is uncertain because PFTS is not consistent with the typical presentation following infection by these pathogens. Porcine reproductive and respiratory syndrome virus, Porcine circovirus-2, Influenza A virus, Alphacoronavirus 1 (Transmissible gastroenteritis virus), Torque teno virus 1, Brachyspira hyodysenteriae, and Brachyspira pilosicoli were not identified in PFTS-SICK pigs. Suid herpesvirus 2 (Porcine cytomegalovirus), Porcine enteric calicivirus, Torque teno virus 2, pathogenic Escherichia coli, and coccidia were detected in both PFTS-SICK and PFTS-HLTHY pigs. It was concluded that there is a lack of compelling evidence that PFTS is caused by any of these pathogens.

  2. An Experimental Investigation into Failure and Localization Phenomena in the Extension to Shear Fracture Transition in Rock

    NASA Astrophysics Data System (ADS)

    Choens, R. C., II; Chester, F. M.; Bauer, S. J.; Flint, G. M.

    2014-12-01

    Fluid-pressure assisted fracturing can produce mesh and other large, interconnected and complex networks consisting of both extension and shear fractures in various metamorphic, magmatic and tectonic systems. Presently, rock failure criteria for tensile and low-mean compressive stress conditions is poorly defined, although there is accumulating evidence that the transition from extension to shear fracture with increasing mean stress is continuous. We report on the results of experiments designed to document failure criteria, fracture mode, and localization phenomena for several rock types (sandstone, limestone, chalk and marble). Experiments were conducted in triaxial extension using a necked (dogbone) geometry to achieve mixed tension and compression stress states with local component-strain measurements in the failure region. The failure envelope for all rock types is similar, but are poorly described using Griffith or modified Griffith (Coulomb or other) failure criteria. Notably, the mode of fracture changes systematically from pure extension to shear with increase in compressive mean stress and display a continuous change in fracture orientation with respect to principal stress axes. Differential stress and inelastic strain show a systematic increase with increasing mean stress, whereas the axial stress decreases before increasing with increasing mean stress. The stress and strain data are used to analyze elastic and plastic strains leading to failure and compare the experimental results to predictions for localization using constitutive models incorporating on bifurcation theory. Although models are able to describe the stability behavior and onset of localization qualitatively, the models are unable to predict fracture type or orientation. Constitutive models using single or multiple yield surfaces are unable to predict the experimental results, reflecting the difficulty in capturing the changing micromechanisms from extension to shear failure. Sandia

  3. Wind-Turbine Gear-Box Roller-Bearing Premature-Failure Caused by Grain-Boundary Hydrogen Embrittlement: A Multi-physics Computational Investigation

    NASA Astrophysics Data System (ADS)

    Grujicic, M.; Chenna, V.; Galgalikar, R.; Snipes, J. S.; Ramaswami, S.; Yavari, R.

    2014-11-01

    To help overcome the problem of horizontal-axis wind-turbine (HAWT) gear-box roller-bearing premature-failure, the root causes of this failure are currently being investigated using mainly laboratory and field-test experimental approaches. In the present work, an attempt is made to develop complementary computational methods and tools which can provide additional insight into the problem at hand (and do so with a substantially shorter turn-around time). Toward that end, a multi-physics computational framework has been developed which combines: (a) quantum-mechanical calculations of the grain-boundary hydrogen-embrittlement phenomenon and hydrogen bulk/grain-boundary diffusion (the two phenomena currently believed to be the main contributors to the roller-bearing premature-failure); (b) atomic-scale kinetic Monte Carlo-based calculations of the hydrogen-induced embrittling effect ahead of the advancing crack-tip; and (c) a finite-element analysis of the damage progression in, and the final failure of a prototypical HAWT gear-box roller-bearing inner raceway. Within this approach, the key quantities which must be calculated using each computational methodology are identified, as well as the quantities which must be exchanged between different computational analyses. The work demonstrates that the application of the present multi-physics computational framework enables prediction of the expected life of the most failure-prone HAWT gear-box bearing elements.

  4. Multi-spectral investigation of bulk and facet failures in high-power single emitters at 980 nm

    NASA Astrophysics Data System (ADS)

    Yanson, Dan; Levy, Moshe; Shamay, Moshe; Cohen, Shalom; Shkedy, Lior; Berk, Yuri; Tessler, Renana; Klumel, Genadi; Rappaport, Noam; Karni, Yoram

    2013-03-01

    Reliable single emitters delivering >10W in the 9xx nm spectral range, are common building blocks for fiber laser pumps. As facet passivation techniques can suppress or delay catastrophic optical mirror damage (COMD) extending emitter reliability into hundreds of thousands of hours, other, less dominant, failure modes such as intra-chip catastrophic optical bulk damage (COBD) become apparent. Based on our failure statistics in high current operation, only ~52% of all failures can be attributed to COMD. Imaging through a window opened in the metallization on the substrate (n) side of a p-side down mounted emitter provides valuable insight into both COMD and COBD failure mechanisms. We developed a laser ablation process to define a window on the n-side of an InGaAs/AlGaAs 980nm single emitter that is overlaid on the pumped 90μm stripe on the p-side. The ablation process is compatible with the chip wire-bonding, enabling the device to be operated at high currents with high injection uniformity. We analyzed both COMD and COBD failed emitters in the electroluminescence and mid-IR domains supported by FIB/SEM observation. The ablated devices revealed branching dark line patterns, with a line origin either at the facet center (COMD case) or near the stripe edge away from the facet (COBD case). In both cases, the branching direction is always toward the rear facet (against the photon density gradient), with SEM images revealing a disordered active layer structure. Absorption levels between 0.22eV - 0.55eV were observed in disordered regions by FT-IR spectroscopy. Temperature mapping of a single emitter in the MWIR domain was performed using an InSb detector. We also report an electroluminescence study of a single emitter just before and after failure.

  5. Developmental problems and their solution for the Space Shuttle main engine alternate liquid oxygen high-pressure turbopump: Anomaly or failure investigation the key

    NASA Technical Reports Server (NTRS)

    Ryan, R.; Gross, L. A.

    1995-01-01

    The Space Shuttle main engine (SSME) alternate high-pressure liquid oxygen pump experienced synchronous vibration and ball bearing life problems that were program threatening. The success of the program hinged on the ability to solve these development problems. The design and solutions to these problems are engirded in the lessons learned and experiences from prior programs, technology programs, and the ability to properly conduct failure or anomaly investigations. The failure investigation determines the problem cause and is the basis for recommending design solutions. For a complex problem, a comprehensive solution requires that formal investigation procedures be used, including fault trees, resolution logic, and action items worked through a concurrent engineering-multidiscipline team. The normal tendency to use an intuitive, cut-and-try approach will usually prove to be costly, both in money and time and will reach a less than optimum, poorly understood answer. The SSME alternate high-pressure oxidizer turbopump development has had two complex problems critical to program success: (1) high synchronous vibrations and (2) excessive ball bearing wear. This paper will use these two problems as examples of this formal failure investigation approach. The results of the team's investigation provides insight into the complexity of the turbomachinery technical discipline interacting/sensitivities and the fine balance of competing investigations required to solve problems and guarantee program success. It is very important to the solution process that maximum use be made of the resources that both the contractor and Government can bring to the problem in a supporting and noncompeting way. There is no place for the not-invented-here attitude. The resources include, but are not limited to: (1) specially skilled professionals; (2) supporting technologies; (3) computational codes and capabilities; and (4) test and manufacturing facilities.

  6. Developmental problems and their solution for the Space Shuttle main engine alternate liquid oxygen high-pressure turbopump: Anomaly or failure investigation the key

    NASA Astrophysics Data System (ADS)

    Ryan, R.; Gross, L. A.

    1995-05-01

    The Space Shuttle main engine (SSME) alternate high-pressure liquid oxygen pump experienced synchronous vibration and ball bearing life problems that were program threatening. The success of the program hinged on the ability to solve these development problems. The design and solutions to these problems are engirded in the lessons learned and experiences from prior programs, technology programs, and the ability to properly conduct failure or anomaly investigations. The failure investigation determines the problem cause and is the basis for recommending design solutions. For a complex problem, a comprehensive solution requires that formal investigation procedures be used, including fault trees, resolution logic, and action items worked through a concurrent engineering-multidiscipline team. The normal tendency to use an intuitive, cut-and-try approach will usually prove to be costly, both in money and time and will reach a less than optimum, poorly understood answer. The SSME alternate high-pressure oxidizer turbopump development has had two complex problems critical to program success: (1) high synchronous vibrations and (2) excessive ball bearing wear. This paper will use these two problems as examples of this formal failure investigation approach. The results of the team's investigation provides insight into the complexity of the turbomachinery technical discipline interacting/sensitivities and the fine balance of competing investigations required to solve problems and guarantee program success. It is very important to the solution process that maximum use be made of the resources that both the contractor and Government can bring to the problem in a supporting and noncompeting way. There is no place for the not-invented-here attitude. The resources include, but are not limited to: (1) specially skilled professionals; (2) supporting technologies; (3) computational codes and capabilities; and (4) test and manufacturing facilities.

  7. Kidney Failure

    MedlinePlus

    ... if You Have Kidney Disease Kidney Failure Expand Dialysis Kidney Transplant Preparing for Kidney Failure Treatment Choosing Not to Treat with Dialysis or Transplant Paying for Kidney Failure Treatment Contact ...

  8. Investigations into the tensile failure of doubly-convex cylindrical tablets under diametral loading using finite element methodology.

    PubMed

    Podczeck, Fridrun; Drake, Kevin R; Newton, J Michael

    2013-09-15

    In the literature various solutions exist for the calculation of the diametral compression tensile strength of doubly-convex tablets and each approach is based on experimental data obtained from single materials (gypsum, microcrystalline cellulose) only. The solutions are represented by complex equations and further differ for elastic and elasto-plastic behaviour of the compacts. The aim of this work was to develop a general equation that is applicable independently of deformation behaviour and which is based on simple tablet dimensions such as diameter and total tablet thickness only. With the help of 3D-FEM analysis the tensile failure stress of doubly-convex tables with central cylinder to total tablet thickness ratios W/D between 0.06 and 0.50 and face-curvature ratios D/R between 0.25 and 1.85 were evaluated. Both elastic and elasto-plastic deformation behaviour were considered. The results of 80 individual simulations were combined and showed that the tensile failure stress σt of doubly-convex tablets can be calculated from σt=(2P/πDW)(W/T)=2P/πDT with P being the failure load, D the diameter, W the central cylinder thickness, and T the total thickness of the tablet. This equation converts into the standard Brazilian equation (σt=2P/πDW) when W equals T, i.e. is equally valid for flat cylindrical tablets. In practice, the use of this new equation removes the need for complex measurements of tablet dimensions, because it only requires values for diameter and total tablet thickness. It also allows setting of standards for the mechanical strength of doubly-convex tablets. The new equation holds both for elastic and elasto-plastic deformation behaviour of the tablets under load. It is valid for all combinations of W/D-ratios between 0.06 and 0.50 with D/R-ratios between 0.00 and 1.85 except for W/D=0.50 in combination with D/R-ratios of 1.85 and 1.43 and for W/D-ratios of 0.40 and 0.30 in combination with D/R=1.85. FEM-analysis indicated a tendency to

  9. Experimental and Numerical Investigation into the Effect of Strain Rate Changes on Failure of AA7075 at the Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Zand, H.; Zhalehfar, F.; Vafaeesefat, A.

    2016-08-01

    This paper represents the temperature-dependent study which is performed on AA7075. This was performed through the application of deep drawing experiments at high temperature of 250, 300, 350, 400, 450 and 500°C and different forming speeds. FEM study is applied at room and 300 and 400 0C temperature with different strain rates. Softening model is used to model the thermo-mechanical constitutive equation. Forming limit curve models (based on M-K model) were used in the analysis of simulation results in order to predict the onset of necking. Simulation results were compared with experimental data to evaluate the accuracy of onset of necking simulation and failure location prediction

  10. Investigation of heat transfer in zirconium potassium perchlorate at low temperature: A study of the failure mechanism of the NASA standard initiator

    NASA Technical Reports Server (NTRS)

    Varghese, Philip L.

    1989-01-01

    The objective of this work was to study the reasons for the failure of pyrotechnic initiators at very low temperatures (10 to 100 K). A two-dimensional model of the NASA standard initiator was constructed to model heat transfer from the electrically heated stainless steel bridgewire to the zirconium potassium perchlorate explosive charge and the alumina charge cup. Temperature dependent properties were used in the model to simulate initiator performance over a wide range of initial temperatures (10 to 500 K). A search of the thermophysical property data base showed that pure alumina has a very high thermal conductivity at low temperatures. It had been assumed to act as a thermal insulator in all previous analyses. Rapid heat transfer from the bridgewire to the alumina at low initial temperatures was shown to cause failure of the initiators if the wire did not also make good contact with the zirconium potassium perchlorate charge. The mode is able to reproduce the results of the tests that had been conducted to investigate the cause for failure. It also provides an explanation for previously puzzling results and suggests simple design changes that will increase reliability at very low initial temperatures.

  11. Investigation of Macroscopic Brittle Creep Failure Caused by Microcrack Growth Under Step Loading and Unloading in Rocks

    NASA Astrophysics Data System (ADS)

    Li, Xiaozhao; Shao, Zhushan

    2016-07-01

    The growth of subcritical cracks plays an important role in the creep of brittle rock. The stress path has a great influence on creep properties. A micromechanics-based model is presented to study the effect of the stress path on creep properties. The microcrack model of Ashby and Sammis, Charles' Law, and a new micro-macro relation are employed in our model. This new micro-macro relation is proposed by using the correlation between the micromechanical and macroscopic definition of damage. A stress path function is also introduced by the relationship between stress and time. Theoretical expressions of the stress-strain relationship and creep behavior are derived. The effects of confining pressure on the stress-strain relationship are studied. Crack initiation stress and peak stress are achieved under different confining pressures. The applied constant stress that could cause creep behavior is predicted. Creep properties are studied under the step loading of axial stress or the unloading of confining pressure. Rationality of the micromechanics-based model is verified by the experimental results of Jinping marble. Furthermore, the effects of model parameters and the unloading rate of confining pressure on creep behavior are analyzed. The coupling effect of step axial stress and confining pressure on creep failure is also discussed. The results provide implications on the deformation behavior and time-delayed rockburst mechanism caused by microcrack growth on surrounding rocks during deep underground excavations.

  12. Exploratory Investigation of Failure Mechanisms in Transition Regions between Solid Laminates and X-cor(registered tm) Truss Sandwich

    NASA Technical Reports Server (NTRS)

    OBrien, T. Kevin; Paris, Isabelle L.

    2004-01-01

    Small sub-component specimens consisting of solid laminates at the ends that transition to X-cor(R) truss sandwich in the center, were tested in a combination of three point bending, uni-axial tension, and combined tension and bending. The failure process in the transition region was documented for each loading using digital video and high-resolution cameras. For the 3-point bending tests, most of the deformation occurred in the solid laminate regions on either end of the specimen. Some pin debonding from the skin of the X-cor(R) truss sandwich was observed in the transition region and was accompanied by audible "pings" throughout the loading. Tension loaded specimens failed in the sandwich skin in the middle of the gage length, accompanied by separation of the sandwich core from the back skin and by delamination between the top skin and bottom skin at the transition region. The pinging associated with pin debonding occurred as the load was increased. However, the frequency of the pinging exceeded any visual observations of pin debonding in the video of the transition region. For specimens tested in combined tension and bending, the greatest amount of pinging occurred during initial application of the axial load. High-resolution images in the transition region indicated that the pinging corresponded to pins debonding and buckling due to the through-thickness Poisson contraction of the specimen. This buckling continued to a much smaller extent as the transverse load was applied.

  13. A Pharmacogenetic Investigation of Intravenous Furosemide in Decompensated Heart Failure: A Meta-Analysis of 3 Clinical Trials

    PubMed Central

    de Denus, Simon; Rouleau, Jean L; Mann, Douglas L.; Huggins, Gordon S.; Cappola, Thomas P.; Shah, Svati H.; Keleti, Julianna; Zada, Yassamin Feroz; Provost, Sylvie; Bardhadi, Amina; Phillips, Michael S.; Normand, Valérie; Mongrain, Ian; Dubé, Marie-Pierre

    2016-01-01

    We conducted a meta-analysis of pharmacogenomic substudies of three randomized trials conducted in patients with decompensated heart failure (HF) which were led by National Heart Lung and Blood Institute (NHLBI)-funded HF Network to test the hypothesis that candidate genes modulate net fluid loss and weight change in patients with decompensated HF treated with a furosemide-based diuretic regimen. Although none of the genetic variants previously shown to modulate the effects of loop diuretics in healthy individuals were associated with net fluid loss after 72 hours of treatment, a set of rare variants in the APOL1 gene, which codes for apolipoprotein L1 (P= 0.0005 in the random effects model) was associated with this endpoint. Moreover, a common variant in the multidrug resistance protein-4 coding gene (ABCC4, rs17268282) was associated with weight loss with furosemide use (P = 0.0001). Our results suggest that both common and rare genetic variants modulate the response to a furosemide-based diuretic regimen in patients with decompensated HF. PMID:26927285

  14. A poroplastic model of mature fault cores with biphasic pore fluids to investigate the role of gas on the onset of fault failure

    NASA Astrophysics Data System (ADS)

    Maury, V.; Fitzenz, D. D.; Piau, J.

    2011-12-01

    A poroplastic model of mature fault cores with biphasic pore fluids to investigate the role of gas on the onset of fault failure The effects of a rapid access of a fault to a source of overpressured fluids on effective stress and failure criterion have been recognized for a long time (Quattrocchi 1999), resulting in a decrease of the effective stress. We concentrate here on the case of the appearance/disappearance of gas in the pore fluid, and its effects on the loading path (Maury et al., 2011). Indeed, gas can appear continuously in a fault zone through dilatant deformation of the zones adjacent to the core fault (Kuo, 2006 ), due to fluid depressurization and degassing. Other source of gas e.g., mantle degasing (Miller et al, 2004), devolitization of coal or other organic matter during frictional sliding (O'Hara et al, 2006), may be remote, and diffuse through a fracture network, or local. Gas in a fault core reduces the Skempton's coefficient to almost 0, the total stress increase during tectonic loading induces a larger increase in effective stress than when pore fluid is fully liquid saturated, thus changing dramatically the loading path for that fault. Not only is failure delayed, but the shear stress at failure increases significantly. Before gas disappearance, the fault might not be critically stressed. However, a subsequent disappearance of gas may lead to failure for small increments of normal and shear stress: apparently strong faults can fail in response to small stress changes. Dilatant failure envelopes are often assumed for localized faults, whereas end-cap envelopes are usually used in association with compaction bands. Here we investigate a poroplastic model for mature fault cores acknowledging that these can be dilatant/contractant according to the state of stress at the plasticity criterion contact. We therefore use a Cam-Clay model as a first approximation. This model enables us to monitor the stability behavior and compute the jumps in stress

  15. Investigating the reasons for the failure of palaeointensity experiments: a study on historical lava flows from Mt. Etna (Italy)

    NASA Astrophysics Data System (ADS)

    Calvo, Manuel; Prévot, Michel; Perrin, Mireille; Riisager, Janna

    2002-04-01

    A refined palaeointensity experiment, accompanied by rock-magnetic studies, has been carried out on six lava flows from 1910 and 1928 from Mt. Etna. The purpose of the study was to try to understand why these very young basaltic flows are generally unable to provide a correct estimate of the magnitude of the ambient magnetic field during flow cooling. Susceptibility versus temperature curves and ore microscopic studies show that 3 types of magnetic minerals (phases `h ', `m ' and `l') are present in these flows, some samples containing a single largely dominant magnetic phase while others contain a mixture of several phases. Phase `h ' is a thermally stable, near magnetite phase resulting from titanomagnetite oxyexsolution. Phase `l' is a thermally stable titanomagnetite with a Curie temperature of approximately 200°C. Phase `m ' is a titanomagnetite phase of Curie temperature between 450-490°C which is unstable at temperatures above 400°C. In addition to the usual reliability checks of the Thellier method (NRM-TRM linearity, pTRM checks), our palaeointensity experiments included additional heating allowing determination of the MD or PSD-SD character of each pTRM and determination of CRM or transdomain remanences possibly acquired during heating. From the 28 samples studied 20 provide a linear NRM-TRM plot over about 1/4 or more of total NRM. However, only six of them, all containing near-magnetite as a single phase, display positive pTRM checks. Nevertheless, these six samples yield a mean palaeointensity of about 52 μT, which exceeds the real field palaeomagnitude (42 μT) by some 25 per cent. The reasons for this almost-total failure of palaeointensity experiments are diverse. For samples with a dominant `l' phase, pTRMs present a behaviour typical of large MD grains, with as much as 1/3 of remanence with unblocking temperatures exceeding the blocking range. No CRM is acquired. Yet a remanence does develop during heating in a field (followed by cooling in

  16. Failure Mechanism analysis of rainfall-induced landslide at Pingguang Stream in Taiwan: Mapping, Investigation, and Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Kai; Lee, Ching-Fang; Lo, Chia-Ming; Chiu, Chun-Jung

    2015-04-01

    On September 15, 2012, torrential storm carried by the peripheral circulation of Typhoon Sanba and the northeast monsoon induced a translational landslide near Pingguang Road in Xindian District of New Taipei City, Taiwan. The total volume of the landslide was approximately 162,000 m^3. The sliding mass destroyed two houses across the stream and formed a landslide dam at the toe of the slope, constricting the stream. In this study, remote sensing images and LiDAR scanning were interpreted, and conducted onsite surveys to obtain material parameters, and performed simulations using the discrete element method to reconstruction the post event, in order to elucidate the mechanisms involved in the landslide process. Survey results revealed complex geological conditions with wide spreading tension cracks at source area. This facilitated the infiltration of surface runoff into weak surfaces and raised groundwater levels. Once the shear strength falls below a critical value, failure surface will occur along the stratum boundary. The results of numerical simulation reveal that at 80 sec after the Pingguang Stream landslide began, a maximum deposition depth of 20 m had been reached. The sliding mass cut off the stream and pushed the stream flow roughly 35 m to the southeast. Because the slope materials surrounding the study area and the landslide-inducing mechanisms are similar, the top of the slopes to the northwest of the study area require monitoring immediately. In addition to filling in the tension cracks, drainage facilities should be constructed to prevent further landslides. Keywords: translational landslide, onsite survey, discrete element method, mechanism, landslide process

  17. Experimental Investigation of Secondary Flow Structures Downstream of a Model Type IV Stent Failure in a 180° Curved Artery Test Section.

    PubMed

    Bulusu, Kartik V; Plesniak, Michael W

    2016-01-01

    The arterial network in the human vasculature comprises of ubiquitously present blood vessels with complex geometries (branches, curvatures and tortuosity). Secondary flow structures are vortical flow patterns that occur in curved arteries due to the combined action of centrifugal forces, adverse pressure gradients and inflow characteristics. Such flow morphologies are greatly affected by pulsatility and multiple harmonics of physiological inflow conditions and vary greatly in size-strength-shape characteristics compared to non-physiological (steady and oscillatory) flows (1 - 7). Secondary flow structures may ultimately influence the wall shear stress and exposure time of blood-borne particles toward progression of atherosclerosis, restenosis, sensitization of platelets and thrombosis (4 - 6, 8 - 13). Therefore, the ability to detect and characterize these structures under laboratory-controlled conditions is precursor to further clinical investigations. A common surgical treatment to atherosclerosis is stent implantation, to open up stenosed arteries for unobstructed blood flow. But the concomitant flow perturbations due to stent installations result in multi-scale secondary flow morphologies (4 - 6). Progressively higher order complexities such as asymmetry and loss in coherence can be induced by ensuing stent failures vis-à-vis those under unperturbed flows (5). These stent failures have been classified as "Types I-to-IV" based on failure considerations and clinical severity (14). This study presents a protocol for the experimental investigation of the complex secondary flow structures due to complete transverse stent fracture and linear displacement of fractured parts ("Type IV") in a curved artery model. The experimental method involves the implementation of particle image velocimetry (2C-2D PIV) techniques with an archetypal carotid artery inflow waveform, a refractive index matched blood-analog working fluid for phase-averaged measurements (15 - 18

  18. Experimental Investigation of Secondary Flow Structures Downstream of a Model Type IV Stent Failure in a 180° Curved Artery Test Section.

    PubMed

    Bulusu, Kartik V; Plesniak, Michael W

    2016-07-19

    The arterial network in the human vasculature comprises of ubiquitously present blood vessels with complex geometries (branches, curvatures and tortuosity). Secondary flow structures are vortical flow patterns that occur in curved arteries due to the combined action of centrifugal forces, adverse pressure gradients and inflow characteristics. Such flow morphologies are greatly affected by pulsatility and multiple harmonics of physiological inflow conditions and vary greatly in size-strength-shape characteristics compared to non-physiological (steady and oscillatory) flows (1 - 7). Secondary flow structures may ultimately influence the wall shear stress and exposure time of blood-borne particles toward progression of atherosclerosis, restenosis, sensitization of platelets and thrombosis (4 - 6, 8 - 13). Therefore, the ability to detect and characterize these structures under laboratory-controlled conditions is precursor to further clinical investigations. A common surgical treatment to atherosclerosis is stent implantation, to open up stenosed arteries for unobstructed blood flow. But the concomitant flow perturbations due to stent installations result in multi-scale secondary flow morphologies (4 - 6). Progressively higher order complexities such as asymmetry and loss in coherence can be induced by ensuing stent failures vis-à-vis those under unperturbed flows (5). These stent failures have been classified as "Types I-to-IV" based on failure considerations and clinical severity (14). This study presents a protocol for the experimental investigation of the complex secondary flow structures due to complete transverse stent fracture and linear displacement of fractured parts ("Type IV") in a curved artery model. The experimental method involves the implementation of particle image velocimetry (2C-2D PIV) techniques with an archetypal carotid artery inflow waveform, a refractive index matched blood-analog working fluid for phase-averaged measurements (15 - 18

  19. Experimental investigation of the failure envelope of unidirectional carbon-epoxy composite under high strain rate transverse and off-axis tensile loading

    NASA Astrophysics Data System (ADS)

    Kuhn, Peter; Ploeckl, Marina; Koerber, Hannes

    2015-09-01

    The mechanical response of the carbon-epoxy material system HexPly IM7-8552 was investigated under transverse tension and combined transverse tension / in-plane shear loading at quasi-static and dynamic strain rates. The dynamic tests of the transverse tension and off-axis tension specimens were carried out on a split-Hopkinson tension bar system, while the quasi-static reference tests were performed on a standard electro-mechanical testing machine. Digital image correlation was used for data reduction at both strain rate regimes. For the high rate tests, the strain rate in loading direction was adjusted to reach approximately the same strain rate value in the fracture plane for each specimen. The measured axial strengths were transformed from the global coordinate system into the combined transverse tension-shear stress space of the material coordinate system and compared with the Puck Mode A criterion for inter-fibre failure. A good correlation between the experimental data and the predicted failure envelopes was found for both investigated strain rate regimes.

  20. Novel experimental methods for investigating high speed friction of titanium-aluminum-vanadium/tool steel interface and dynamic failure of extrinsically toughened DRA composites

    NASA Astrophysics Data System (ADS)

    Irfan, Mohammad Abdulaziz

    Dynamic deformation, flow, and failure are integral parts of all dynamic processes in materials. Invariably, dynamic failure also involves the relative sliding of one component of the material over the other. Advances in elucidation of these failure mechanisms under high loading rates has been of great interest to scientists working in this area. The need to develop new dynamic mechanical property tests for materials under well characterized and controllable loading conditions has always been a challenge to experimentalists. The current study focuses on the development of two experimental methods to study some aspects of dynamic material response. The first part focuses on the development of a single stage gas gun facility for investigating high-speed metal to metal interfacial friction with applications to high speed machining. During the course of this investigation a gas gun was designed and built capable of accelerating projectiles upto velocities of 1 km/s. Using this gas gun pressure-shear plate impact friction experiments were conducted to simulate conditions similar to high speed machining at the tool-workpiece interface. The impacting plates were fabricated from materials representing the tribo-pair of interest. Accurate measurements of the interfacial tractions, i.e. the normal pressure and the frictional stress at the tribo-pair interface, and the interfacial slip velocity could be made by employing laser interferometry. Normal pressures of the order of 1-2 MPa were generated and slipping velocities of the order of 50 m/s were obtained. In order to illustrate the structure of the constitutive law governing friction, the study included experimental investigation of frictional response to step changes in normal pressure and interfacial shear stress. The results of these experiments indicate that sliding resistance for Ti6Al4V/CH steel interface is much lower than measured under quasi-static sliding conditions. Also the temperature at the interface strongly

  1. Respiratory Failure

    MedlinePlus

    Respiratory failure happens when not enough oxygen passes from your lungs into your blood. Your body's organs, ... brain, need oxygen-rich blood to work well. Respiratory failure also can happen if your lungs can' ...

  2. Numerical Investigation of Seismically Induced Rock Mass Fatigue as a Mechanism Contributing to the Progressive Failure of Deep-Seated Landslides

    NASA Astrophysics Data System (ADS)

    Gischig, Valentin; Preisig, Giona; Eberhardt, Erik

    2016-06-01

    The importance of earthquakes in triggering catastrophic failure of deep-seated landslides has long been recognized and is well documented in the literature. However, seismic waves do not only act as a trigger mechanism. They also contribute to the progressive failure of large rock slopes as a fatigue process that is highly efficient in deforming and damaging rock slopes. Given the typically long recurrence time and unpredictability of earthquakes, field-based investigations of co-seismic rock slope deformations are difficult. We present here a conceptual numerical study that demonstrates how repeated earthquake activity over time can destabilize a relatively strong rock slope by creating and propagating new fractures until the rock mass is sufficiently weakened to initiate catastrophic failure. Our results further show that the damage and displacement induced by a certain earthquake strongly depends on pre-existing damage. In fact, the damage history of the slope influences the earthquake-induced displacement as much as earthquake ground motion characteristics such as the peak ground acceleration. Because seismically induced fatigue is: (1) characterized by low repeat frequency, (2) represents a large amplitude damage event, and (3) weakens the entire rock mass, it differs from other fatigue processes. Hydro-mechanical cycles, for instance, occur at higher repeat frequencies (i.e., annual cycles), lower amplitude, and only affect limited parts of the rock mass. Thus, we also compare seismically induced fatigue to seasonal hydro-mechanical fatigue. While earthquakes can progressively weaken even a strong, competent rock mass, hydro-mechanical fatigue requires a higher degree of pre-existing damage to be effective. We conclude that displacement rates induced by hydro-mechanical cycling are indicative of the degree of pre-existing damage in the rock mass. Another indicator of pre-existing damage is the seismic amplification pattern of a slope; frequency

  3. Investigation of the cross-ship comparison monitoring method of failure detection in the HIMAT RPRV. [digital control techniques using airborne microprocessors

    NASA Technical Reports Server (NTRS)

    Wolf, J. A.

    1978-01-01

    The Highly maneuverable aircraft technology (HIMAT) remotely piloted research vehicle (RPRV) uses cross-ship comparison monitoring of the actuator RAM positions to detect a failure in the aileron, canard, and elevator control surface servosystems. Some possible sources of nuisance trips for this failure detection technique are analyzed. A FORTRAN model of the simplex servosystems and the failure detection technique were utilized to provide a convenient means of changing parameters and introducing system noise. The sensitivity of the technique to differences between servosystems and operating conditions was determined. The cross-ship comparison monitoring method presently appears to be marginal in its capability to detect an actual failure and to withstand nuisance trips.

  4. The histological investigation of gingiva from patients with chronic renal failure, renal transplants, and periodontitis: a light and electron microscopic study.

    PubMed

    Yamalik, N; Delilbasi, L; Gülay, H; Cağlayan, F; Haberal, M; Cağlayan, G

    1991-12-01

    The clinical and histological appearance of gingiva was evaluated in renal transplant recipients (RTR) receiving immunosuppressive drugs, in patients with chronic renal failure (CRF) undergoing hemodialysis, and systemically healthy individuals with periodontitis. Although the amount of bacterial plaque accumulation was similar among the groups (P greater than 0.05), the gingival inflammation was significantly less in RTR when compared to the other 2 groups (P less than 0.05). In light microscopic investigation the overall appearance of the connective tissue was similar in all of the groups. A mononuclear cell infiltration was present in all of the specimens; however, the number of inflammatory cells in patients with periodontitis was significantly higher than the other 2 groups (P less than 0.05). Prominent epithelial changes in the superficial layers of the oral epithelium; i.e., areas showing desquamation-like appearance, were noticed in patients with CRF. In electron microscopic investigation, fibroblasts and plasma cells with well-developed granular endoplasmic reticulum were found in connective tissue in RTR patients. In patients with CRF, epithelial cells presented swollen granular endoplasmic reticulum cisternae resembling vacuoles, indicating the presence of degeneration. It was suggested that with the use of immunosuppressive drugs the response to bacterial plaque did not diminish completely. PMID:1765936

  5. Lunar Base Life Support Failures

    NASA Technical Reports Server (NTRS)

    Jones, Harry W.

    2009-01-01

    Dynamic simulation of the lunar outpost habitat life support was undertaken to investigate the impact of life support failures and to investigate responses. Some preparatory static analysis for the Lunar Outpost life support model, an earlier version of the model, and an investigation into the impact of Extravehicular Activity (EVA) were reported previously. (Jones, 2008-01-2184, 2008-01-2017) The earlier model was modified to include possible resupply delays, power failures, recycling system failures, and atmosphere and other material storage failures. Most failures impact the lunar outpost water balance and can be mitigated by reducing water usage. Food solids, nitrogen can be obtained only by resupply from Earth. The most time urgent failure is a lass of carbon dioxide removal capability. Life support failures might be survivable if effective operational solutions are provided in the system design.

  6. A Study to Compare the Failure Rates of Current Space Shuttle Ground Support Equipment with the New Pathfinder Equipment and Investigate the Effect that the Proposed GSE Infrastructure Upgrade Might Have to Reduce GSE Infrastructure Failures

    NASA Technical Reports Server (NTRS)

    Kennedy, Barbara J.

    2004-01-01

    The purposes of this study are to compare the current Space Shuttle Ground Support Equipment (GSE) infrastructure with the proposed GSE infrastructure upgrade modification. The methodology will include analyzing the first prototype installation equipment at Launch PAD B called the "Pathfinder". This study will begin by comparing the failure rate of the current components associated with the "Hardware interface module (HIM)" at the Kennedy Space Center to the failure rate of the neW Pathfinder components. Quantitative data will be gathered specifically on HIM components and the PAD B Hypergolic Fuel facility and Hypergolic Oxidizer facility areas which has the upgraded pathfinder equipment installed. The proposed upgrades include utilizing industrial controlled modules, software, and a fiber optic network. The results of this study provide evidence that there is a significant difference in the failure rates of the two studied infrastructure equipment components. There is also evidence that the support staff for each infrastructure system is not equal. A recommendation to continue with future upgrades is based on a significant reduction of failures in the new' installed ground system components.

  7. Preliminary results: Root cause investigation of orbital anomalies and failures in NASA standard 50 ampere-hour nickel-cadmium batteries

    NASA Technical Reports Server (NTRS)

    Toft, Mark R.

    1993-01-01

    Two lots of NASA standard 50 A.H. Ni-Cd battery cells, manufactured by Gates Aerospace Batteries and built into batteries by McDonnell Douglas, have experienced significant performance problems. The two lots were used on the Compton Gamma Ray Observatory and the Upper Atmosphere Research Satellite. Both of these satellites are Low Earth Orbital (LEO) satellites containing batteries on a parallel bus charged to NASA standard V/T curves using a NASA standard power regulator. The following preliminary conclusions were reached: (1) several plate and cell parameters have migrated within their spec limits over the years (in some cases, from one extreme to the other); (2) several parametric relationships, not generally monitored and therefore not under specification control, have also migrated over the years; (3) many of these changes appear to have taken place as a natural consequence of changes in GE/GAB materials and processes; (4) several of these factors may be 'conspiring' to aggravate known cell failure mechanisms (factors such as heavier plate, less teflon and/or less-uniform teflon, and less electrolyte) but all are still in spec (where specs exist); (5) the weight of the evidence collected to characterize the anomalies and to characterize the negative electrode itself, strongly suggests that alterations to the structure, composition, uniformity, and efficiency of the negative electrode are at the heart of the battery performance problems currently being experienced; and (6) further investigation at all levels (plate, cell, battery, and system) continues to be warranted.

  8. Testicular failure

    MedlinePlus

    ... LH . Your doctor may also order a semen analysis to examine the number of healthy sperm you are producing. Sometimes, an ultrasound of the testes will be ordered. Testicular failure and low testosterone level may be hard to ...

  9. Development of KSC program for investigating and generating field failure rates. Volume 2: Recommended format for reliability handbook for ground support equipment

    NASA Technical Reports Server (NTRS)

    Bloomquist, C. E.; Kallmeyer, R. H.

    1972-01-01

    Field failure rates and confidence factors are presented for 88 identifiable components of the ground support equipment at the John F. Kennedy Space Center. For most of these, supplementary information regarding failure mode and cause is tabulated. Complete reliability assessments are included for three systems, eight subsystems, and nine generic piece-part classifications. Procedures for updating or augmenting the reliability results presented in this handbook are also included.

  10. SSC 17-meter dipole magnet DD000Z test results and investigation of coil failure: The report of the {open_quotes}Z{close_quotes} Committee

    SciTech Connect

    Coombes, R.; Mirk, K.; Tompkins, J.; Zbasnik, J.; Lundy, R.; Schneider, W.; Wanderer, P.

    1988-03-01

    Following the failure of the lower inner coil of magnet DD000Z on November 3, 1987, a committee was formed on November 11 and given the following charges: `To review the events leading up to and including the failure of the coils of magnet DD000Z. The intent of the review will be to determine the cause of the failure and to make recommendations to reduce the likelihood of such failures in the future. Given the fact that this is the first long magnet to be disassembled, the committee may uncover leads which point to other opportunities for improvement. The committee should follow up on these leads. The committee should prepare a plan to serve as an initial guide for the disassembly and provide guidance as the disassembly progresses.` The committee held its first meeting at FNAL on 17 and 18 Nov to review the record of events leading up to the failure and to establish an initial disassembly procedure. This was followed by further meetings at FNAL, BNL, and CDG, leading to this final report. Committee activities included interviewing personnel who had been involved in the design, assembly and testing of DD000Z, reviewing all documents relating to the magnet and its failure, and participating in and providing guidance during the disassembly. The intention of the committee was to report factual findings, to consider well founded hypotheses, not to consider conjecture and to avoid speculation.

  11. Heart failure.

    PubMed

    2014-12-15

    Essential facts Heart failure affects about 900,000 people in the UK. The condition can affect people of all ages, but it is more common in older people, with more than half of all patients over the age of 75. It is caused by the heart failing to pump enough blood around the body at the right pressure, usually because the heart muscle has become too weak or stiff to work properly. Acute heart failure, which occurs when symptoms develop quickly, is the leading cause of hospital admission in people over 65. PMID:25492766

  12. Heart Failure

    MedlinePlus

    ... of breath Common causes of heart failure are coronary artery disease, high blood pressure and diabetes. It is more common in people who are 65 years old or older, African Americans, people who are ... treatments fail. NIH: National Heart, Lung, and Blood Institute

  13. Emotional reactions to success and failure of collective action as predictors of future action intentions: a longitudinal investigation in the context of student protests in Germany.

    PubMed

    Tausch, Nicole; Becker, Julia C

    2013-09-01

    This research examined how emotional responses to success and failure of collective action relate to willingness to engage in collective action in the future. It was hypothesized that both pride (in relation to a success) and anger (in response to failure) would motivate future collective action. Findings are reported from a two-wave longitudinal study (N= 98) in the context of student protests against tuition fees in Germany, which was conducted before and after collective action had resulted in both a success and a failure. While anger positively predicted action intentions, over and above baseline action intentions, pride exerted a significant indirect effect on action intentions via increased efficacy perceptions, over and above baseline efficacy and action intentions. Politicized identification positively predicted the intensity of both pride and anger and baseline group efficacy positively predicted the intensity of anger. The theoretical and practical implications of these findings are discussed. PMID:22694314

  14. Investigating Clinical Failure of Bone Grafting through a Window at the Femoral Head Neck Junction Surgery for the Treatment of Osteonecrosis of the Femoral Head

    PubMed Central

    Sun, Wei; Zhao, Dingyan; Gao, Fuqiang; Su, Yangming; Li, Zirong

    2016-01-01

    Aims This study aimed to analyze the clinical factors related to the failure of bone grafting through a window at the femoral head-neck junction. Methods In total, 119 patients (158 hips) underwent bone grafting for treatment of avascular necrosis of the femoral head. The patients were classified by their ARCO staging and CJFH classification. All patients were clinically and radiographically followed up every three months during the first year and every six months in the following year. The clinical follow-up comprised determination of pre- and postoperative Harris hip scores, while serial AP, frog lateral radiographs, and CT scan were used for the radiographic follow-up. Results The clinical failure of bone grafting was observed in 40 patients. The clinical failure rates in patients belonging to ARCO stage II period, IIIa, and III (b + c) were 25.9%, 16.2%, and 61.5%, respectively, while those in patients belonging to (C + M + L1) type and L2, L3 type disease groups were 1.7%, 38.9%, and 39%, respectively. The clinical failure rates in patients aged below 40 and those aged 40 and over were 20.5% and 39.0%, respectively (all P < 0.05). Conclusion Disease type, disease stage, and patient age are risk factors for failure of bone graft surgery. Patients belonging to ARCO stage II and IIIa showed a good overall response rate, while patients belonging to ARCO stage IIIb and IIIc and those with necrotic lesions involving the lateral pillar (L2 and L3 type) showed high surgical failure rates. PMID:27285821

  15. A stability analysis of semi-cohesive streambanks with CONCEPTS: Coupling field and laboratory investigations to quantify the onset of fluvial erosion and mass failure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The overarching goal of this study is to perform a comprehensive bank stability analysis that is phenomenologically sound by considering both mass failure and fluvial erosion. The nature of this study is twofold. First, field and experimental analysis is conducted to generate data for channel cross-...

  16. Common Cause Failure Modeling

    NASA Technical Reports Server (NTRS)

    Hark, Frank; Britton, Paul; Ring, Rob; Novack, Steven D.

    2015-01-01

    Common Cause Failures (CCFs) are a known and documented phenomenon that defeats system redundancy. CCFS are a set of dependent type of failures that can be caused by: system environments; manufacturing; transportation; storage; maintenance; and assembly, as examples. Since there are many factors that contribute to CCFs, the effects can be reduced, but they are difficult to eliminate entirely. Furthermore, failure databases sometimes fail to differentiate between independent and CCF (dependent) failure and data is limited, especially for launch vehicles. The Probabilistic Risk Assessment (PRA) of NASA's Safety and Mission Assurance Directorate at Marshall Space Flight Center (MFSC) is using generic data from the Nuclear Regulatory Commission's database of common cause failures at nuclear power plants to estimate CCF due to the lack of a more appropriate data source. There remains uncertainty in the actual magnitude of the common cause risk estimates for different systems at this stage of the design. Given the limited data about launch vehicle CCF and that launch vehicles are a highly redundant system by design, it is important to make design decisions to account for a range of values for independent and CCFs. When investigating the design of the one-out-of-two component redundant system for launch vehicles, a response surface was constructed to represent the impact of the independent failure rate versus a common cause beta factor effect on a system's failure probability. This presentation will define a CCF and review estimation calculations. It gives a summary of reduction methodologies and a review of examples of historical CCFs. Finally, it presents the response surface and discusses the results of the different CCFs on the reliability of a one-out-of-two system.

  17. Common Cause Failure Modeling

    NASA Technical Reports Server (NTRS)

    Hark, Frank; Britton, Paul; Ring, Rob; Novack, Steven D.

    2016-01-01

    Common Cause Failures (CCFs) are a known and documented phenomenon that defeats system redundancy. CCFS are a set of dependent type of failures that can be caused by: system environments; manufacturing; transportation; storage; maintenance; and assembly, as examples. Since there are many factors that contribute to CCFs, the effects can be reduced, but they are difficult to eliminate entirely. Furthermore, failure databases sometimes fail to differentiate between independent and CCF (dependent) failure and data is limited, especially for launch vehicles. The Probabilistic Risk Assessment (PRA) of NASA's Safety and Mission Assurance Directorate at Marshal Space Flight Center (MFSC) is using generic data from the Nuclear Regulatory Commission's database of common cause failures at nuclear power plants to estimate CCF due to the lack of a more appropriate data source. There remains uncertainty in the actual magnitude of the common cause risk estimates for different systems at this stage of the design. Given the limited data about launch vehicle CCF and that launch vehicles are a highly redundant system by design, it is important to make design decisions to account for a range of values for independent and CCFs. When investigating the design of the one-out-of-two component redundant system for launch vehicles, a response surface was constructed to represent the impact of the independent failure rate versus a common cause beta factor effect on a system's failure probability. This presentation will define a CCF and review estimation calculations. It gives a summary of reduction methodologies and a review of examples of historical CCFs. Finally, it presents the response surface and discusses the results of the different CCFs on the reliability of a one-out-of-two system.

  18. Investigation of the design and static behavior of cylindrical tubular composite adhesive joints utilizing the finite element method and stress-based failure theories

    NASA Astrophysics Data System (ADS)

    Lambert, Michael D.

    2011-12-01

    The stress and strength behavior of cylindrical tubular adhesive joints composed of dissimilar materials was explored. This was accomplished with the finite element method (FEM) and stress-based failure theories. Also, it was shown how a design of experiments (DOE) based method can be used to objectively organize the process of optimizing joint strength by using stress-based failure criteria. The finite element program used in this work was written in-house from scratch to implement the FEM for the purpose of solving both axisymmetric and three-dimensional linear elastic governing equations of static equilibrium. The formulation of the three-dimensional model is presented, and the required operations to arrive to the axisymmetric model are also presented. The axisymmetric model is two dimensional, capable of using four and eight node quadrilateral elements. However, only four node elements are used because a mesh of eight node elements requires more memory and increased mesh refinement. The three-dimensional model is capable of using eight and twenty node brick elements, but only eight node brick elements are used for the same reason. Both of the axisymmetric and three-dimensional models calculate the nodal displacements, strains, stress values for each material, and strength values for each material. The external static loads can be individually applied, or coupled together. The outputs seem to be most useful for interpretation when plotted through-the-thickness (TTT) and along-the-length (ATL) of the joint or tube. Outputs are valid only for materials that behave linearly elastic up to (or near) failure, and the stress-based failure criteria are used to define that limit. A small laboratory-sized joint was modeled to look at the theoretical stress and strength distributions plotted along-the-length of the joint at different radial locations. These stress and strength distributions can be correlated to the type of load being applied because of unique or prominent

  19. Vamistor resistor investigation

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Results are presented of the failure investigation conducted on resistors produced by the Vamistor Divison, Wagner Electric Corporation. This failure investigation included; failure analyses, chemical and metallurgical analyses, failure mechanism studies, seal leak analyses, and nondestructive stress tests. The data, information, conclusions, and recommendation can be helpful in assessing current usage of these resistors.

  20. Structural failures: Causes, prevention, and misinterpretation

    SciTech Connect

    Barsom, J.M. )

    1993-07-01

    This article presents a few observations on causes and prevention of failures in structural and equipment components that are related to the initiation and propagation of fatigue cracks. Some of these observations are illustrated by using actual failures. Also, the article presents a discussion of some common misconceptions and misinterpretations that have led to incorrect conclusions in failure investigations.

  1. Investigating a TELEmedicine solution to improve MEDication adherence in chronic Heart Failure (TELEMED-HF): study protocol for a randomized controlled trial

    PubMed Central

    2011-01-01

    Background Frequent rehospitalisations and poorer survival chances in heart failure (HF) patients may partly be explained by poor medication adherence. There are multiple medication-related reasons for suboptimal adherence, but psychological reasons may also be important. A novel TELEmonitoring device may improve MEDication adherence in HF patients (TELEMED-HF). TELEMED-HF is a randomized, controlled clinical intervention trial designed to examine (1) the efficacy and cost-efficiency of an electronic medication adherence support system in improving and monitoring HF patients' medication adherence; (2) the effect of medication adherence on hospitalizations and health care consumption; as well as on (3) clinical characteristics, and Quality of Life (QoL); and (4) clinical, sociodemographic, and psychological determinants of medication adherence. Methods/Design Consecutive patients with chronic, systolic HF presenting to the outpatient clinic of the TweeSteden Hospital, The Netherlands, will be approached for study participation and randomly assigned (1:1) following blocked randomization procedures to the intervention (n = 200) or usual care arm (n = 200). Patients in the intervention arm use the medication support device for six months in addition to usual care. Post-intervention, patients return to usual care only and all patients participate in four follow-up occasions over 12 months. Primary endpoints comprise objective and subjective medication adherence, healthcare consumption, number of hospitalizations, and cost-effectiveness. Secondary endpoints include disease severity, physical functioning, and QoL. Discussion The TELEMED-HF study will provide us a comprehensive understanding of medication adherence in HF patients, and will show whether telemonitoring is effective and cost-efficient in improving adherence and preventing hospitalization in HF patients. Trial registration number NCT01347528. PMID:21999637

  2. Acute kidney failure

    MedlinePlus

    Kidney failure; Renal failure; Renal failure - acute; ARF; Kidney injury - acute ... There are many possible causes of kidney damage. They include: ... cholesterol (cholesterol emboli) Decreased blood flow due to very ...

  3. What Is Heart Failure?

    MedlinePlus

    ... page from the NHLBI on Twitter. What Is Heart Failure? Heart failure is a condition in which the heart can' ... force. Some people have both problems. The term "heart failure" doesn't mean that your heart has stopped ...

  4. Heart failure - medicines

    MedlinePlus

    CHF - medicines; Congestive heart failure - medicines; Cardiomyopathy - medicines; HF - medicines ... You will need to take most of your heart failure medicines every day. Some medicines are taken ...

  5. Periodontitis in Chronic Heart Failure.

    PubMed

    Fröhlich, Hanna; Herrmann, Kristina; Franke, Jennifer; Karimi, Alamara; Täger, Tobias; Cebola, Rita; Katus, Hugo A; Zugck, Christian; Frankenstein, Lutz

    2016-08-01

    Periodontal disease has been associated with an increased risk of cardiovascular events. The purpose of our study was to investigate whether a correlation between periodontitis and chronic heart failure exists, as well as the nature of the underlying cause. We enrolled 71 patients (mean age, 54 ± 13 yr; 56 men) who had stable chronic heart failure; all underwent complete cardiologic and dental evaluations. The periodontal screening index was used to quantify the degree of periodontal disease. We compared the findings to those in the general population with use of data from the 4th German Dental Health Survey. Gingivitis, moderate periodontitis, and severe periodontitis were present in 17 (24%), 17 (24%), and 37 (52%) patients, respectively. Severe periodontitis was more prevalent among chronic heart failure patients than in the general population. In contrast, moderate periodontitis was more prevalent in the general population (P <0.00001). The severity of periodontal disease was not associated with the cause of chronic heart failure or the severity of heart failure symptoms. Six-minute walking distance was the only independent predictor of severe periodontitis. Periodontal disease is highly prevalent in chronic heart failure patients regardless of the cause of heart failure. Prospective trials are warranted to clarify the causal relationship between both diseases. PMID:27547136

  6. Periodontitis in Chronic Heart Failure.

    PubMed

    Fröhlich, Hanna; Herrmann, Kristina; Franke, Jennifer; Karimi, Alamara; Täger, Tobias; Cebola, Rita; Katus, Hugo A; Zugck, Christian; Frankenstein, Lutz

    2016-08-01

    Periodontal disease has been associated with an increased risk of cardiovascular events. The purpose of our study was to investigate whether a correlation between periodontitis and chronic heart failure exists, as well as the nature of the underlying cause. We enrolled 71 patients (mean age, 54 ± 13 yr; 56 men) who had stable chronic heart failure; all underwent complete cardiologic and dental evaluations. The periodontal screening index was used to quantify the degree of periodontal disease. We compared the findings to those in the general population with use of data from the 4th German Dental Health Survey. Gingivitis, moderate periodontitis, and severe periodontitis were present in 17 (24%), 17 (24%), and 37 (52%) patients, respectively. Severe periodontitis was more prevalent among chronic heart failure patients than in the general population. In contrast, moderate periodontitis was more prevalent in the general population (P <0.00001). The severity of periodontal disease was not associated with the cause of chronic heart failure or the severity of heart failure symptoms. Six-minute walking distance was the only independent predictor of severe periodontitis. Periodontal disease is highly prevalent in chronic heart failure patients regardless of the cause of heart failure. Prospective trials are warranted to clarify the causal relationship between both diseases.

  7. Periodontitis in Chronic Heart Failure

    PubMed Central

    Fröhlich, Hanna; Herrmann, Kristina; Franke, Jennifer; Karimi, Alamara; Täger, Tobias; Cebola, Rita; Katus, Hugo A.; Zugck, Christian

    2016-01-01

    Periodontal disease has been associated with an increased risk of cardiovascular events. The purpose of our study was to investigate whether a correlation between periodontitis and chronic heart failure exists, as well as the nature of the underlying cause. We enrolled 71 patients (mean age, 54 ± 13 yr; 56 men) who had stable chronic heart failure; all underwent complete cardiologic and dental evaluations. The periodontal screening index was used to quantify the degree of periodontal disease. We compared the findings to those in the general population with use of data from the 4th German Dental Health Survey. Gingivitis, moderate periodontitis, and severe periodontitis were present in 17 (24%), 17 (24%), and 37 (52%) patients, respectively. Severe periodontitis was more prevalent among chronic heart failure patients than in the general population. In contrast, moderate periodontitis was more prevalent in the general population (P <0.00001). The severity of periodontal disease was not associated with the cause of chronic heart failure or the severity of heart failure symptoms. Six-minute walking distance was the only independent predictor of severe periodontitis. Periodontal disease is highly prevalent in chronic heart failure patients regardless of the cause of heart failure. Prospective trials are warranted to clarify the causal relationship between both diseases. PMID:27547136

  8. Cascaded failures in weighted networks.

    PubMed

    Mirzasoleiman, Baharan; Babaei, Mahmoudreza; Jalili, Mahdi; Safari, Mohammadali

    2011-10-01

    Many technological networks can experience random and/or systematic failures in their components. More destructive situations can happen if the components have limited capacity, where the failure in one of them might lead to a cascade of failures in other components, and consequently break down the structure of the network. In this paper, the tolerance of cascaded failures was investigated in weighted networks. Three weighting strategies were considered including the betweenness centrality of the edges, the product of the degrees of the end nodes, and the product of their betweenness centralities. Then, the effect of the cascaded attack was investigated by considering the local weighted flow redistribution rule. The capacity of the edges was considered to be proportional to their initial weight distribution. The size of the survived part of the attacked network was determined in model networks as well as in a number of real-world networks including the power grid, the internet in the level of autonomous system, the railway network of Europe, and the United States airports network. We found that the networks in which the weight of each edge is the multiplication of the betweenness centrality of the end nodes had the best robustness against cascaded failures. In other words, the case where the load of the links is considered to be the product of the betweenness centrality of the end nodes is favored for the robustness of the network against cascaded failures.

  9. Respiratory failure in diabetic ketoacidosis

    PubMed Central

    Konstantinov, Nikifor K; Rohrscheib, Mark; Agaba, Emmanuel I; Dorin, Richard I; Murata, Glen H; Tzamaloukas, Antonios H

    2015-01-01

    Respiratory failure complicating the course of diabetic ketoacidosis (DKA) is a source of increased morbidity and mortality. Detection of respiratory failure in DKA requires focused clinical monitoring, careful interpretation of arterial blood gases, and investigation for conditions that can affect adversely the respiration. Conditions that compromise respiratory function caused by DKA can be detected at presentation but are usually more prevalent during treatment. These conditions include deficits of potassium, magnesium and phosphate and hydrostatic or non-hydrostatic pulmonary edema. Conditions not caused by DKA that can worsen respiratory function under the added stress of DKA include infections of the respiratory system, pre-existing respiratory or neuromuscular disease and miscellaneous other conditions. Prompt recognition and management of the conditions that can lead to respiratory failure in DKA may prevent respiratory failure and improve mortality from DKA. PMID:26240698

  10. Advanced Heart Failure

    MedlinePlus

    ... High Blood Pressure Tools & Resources Stroke More Advanced Heart Failure Updated:Oct 8,2015 When heart failure (HF) ... content was last reviewed on 04/06/2015. Heart Failure • Home • About Heart Failure • Causes and Risks for ...

  11. Investigation of failure mechanisms in silicon based half cells during the first cycle by micro X-ray tomography and radiography

    NASA Astrophysics Data System (ADS)

    Sun, Fu; Markötter, Henning; Dong, Kang; Manke, Ingo; Hilger, Andre; Kardjilov, Nikolay; Banhart, John

    2016-07-01

    Two proof-of-concept batteries were designed and prepared for X-ray microtomography and radiography characterizations to investigate the degradation mechanisms of silicon (Si) based half cells during the first cycle. It is highlighted here for the first time that, apart from the significant volume expansion-induced pulverization, the electrochemical "deactivation" mechanism contributes significantly to the capacity loss during the first charge process. In addition, the unexpected electrochemically inactive Si particles are also believed to substantially decrease the energy density due to the inefficient utilization of loaded active material. These unexpected findings, which cannot be deduced from macroscopic electrochemical characterizations, expand the inherent explanations for performance deterioration of Si-anode material based lithium ion batteries (LIBs) and emphasize the vital value of microscopic techniques in revealing the correlation between macroscopic electrode structure and the overall electrochemical performance.

  12. Wind Turbine Failures - Tackling current Problems in Failure Data Analysis

    NASA Astrophysics Data System (ADS)

    Reder, M. D.; Gonzalez, E.; Melero, J. J.

    2016-09-01

    The wind industry has been growing significantly over the past decades, resulting in a remarkable increase in installed wind power capacity. Turbine technologies are rapidly evolving in terms of complexity and size, and there is an urgent need for cost effective operation and maintenance (O&M) strategies. Especially unplanned downtime represents one of the main cost drivers of a modern wind farm. Here, reliability and failure prediction models can enable operators to apply preventive O&M strategies rather than corrective actions. In order to develop these models, the failure rates and downtimes of wind turbine (WT) components have to be understood profoundly. This paper is focused on tackling three of the main issues related to WT failure analyses. These are, the non-uniform data treatment, the scarcity of available failure analyses, and the lack of investigation on alternative data sources. For this, a modernised form of an existing WT taxonomy is introduced. Additionally, an extensive analysis of historical failure and downtime data of more than 4300 turbines is presented. Finally, the possibilities to encounter the lack of available failure data by complementing historical databases with Supervisory Control and Data Acquisition (SCADA) alarms are evaluated.

  13. An investigation of dynamic failure events in steels using full field high-speed infrared thermography and high-speed photography

    NASA Astrophysics Data System (ADS)

    Guduru, Pradeep R.

    An infrared (IR) imaging system has been developed for measuring the temperature increase during the dynamic deformation of materials. The system consists of an 8 x 8 HgCdTe focal plane array, each with its own preamplifier. Outputs from all 64 signals are simultaneously acquired and held using a bank of track and hold amplifiers. An array of eight 8:1 multiplexers then routes the signals to eight 10MHz digitizers, acquiring data from each row of detectors in parallel. The maximum rate is one million frames per second. Crack tip temperature rise during dynamic deformation is known to alter the fracture mechanisms and consequently the fracture toughness of a material. However, no direct experimental measurements have ever been made to determine the same because of limited diagnostic tools. By transcending the existing experimental limitations, this investigation presents detailed, real time evolution of the transient crack tip temperature fields in two different steels (C300 and HY100 steels), using the 2-D high speed IR camera. The crack tip temperature rise at initiation in C300 steel was found to be about 55K. In case of HY100, which is a highly ductile steel, the crack tip temperature rise was above 200K and was seen to be a strong function of loading rate. HRR elastic-plastic singular field has been used to extract J integral evolution from the measured temperature field. An experimental investigation has been conducted to study the initiation and propagation characteristics of dynamic shear bands in C300 maraging steel. Pre-fatigued single edge notched specimens were impacted on the edge under the notch to produce shear dominated mixed mode stress fields. The optical technique of coherent gradient sensing (CGS) was employed to study the evolution of the mixed mode stress intensity factors. Simultaneously, a newly developed high speed IR camera was employed to obtain the temperature field evolution during the initiation and propagation of the shear bands. The

  14. An investigation of the stable orientations of orthorhombic particles in a thin film and their effect on its critical failure pressure.

    PubMed

    Morris, G; Neethling, S J; Cilliers, J J

    2011-09-01

    The effects of shape and contact angle on the behaviour of orthorhombic particles at an interface and in thin films were investigated using Surface Evolver. It is shown that the energetically stable orientations of the particle change with its aspect ratio. Long, wide, flat particles with low contact angles are more stable in flat orientations, i.e. with two faces parallel to the flat film surface. More cubic particles with higher contact angles are more stable in twisted orientations, where the opposite sides of the film can be drawn together at the sharp edges of the particle. The combination of contact angle and orientation has been found to have a large effect on the capillary pressure required to rupture the film. A film containing a particle in a flat orientation will rupture at a capillary pressure up to three times greater than one containing an identical particle in a twisted orientation. Wider, flatter particles with low contact angles stabilise thin liquid films to a greater extent than cubic particles with high contact angles.

  15. Failure Analysis at the Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Salazar, Victoria L.; Wright, Clara

    2010-01-01

    History has shown that failures occur in every engineering endeavor, and what we learn from those failures contributes to the knowledge base to safely complete future missions. The necessity of failure analysis is at its apex at the end of one aged program (i.e. Shuttle) and at the beginning of a new and untested program (i.e. Constellation). The information that we gain through failure analysis corrects the deficiencies in the current vehicle to make the next generation of vehicles more efficient and safe. The Failure Analysis and Materials Evaluation section in the Materials Science Division at the Kennedy Space Center performs metallurgical, mechanical, electrical, and non-metallic failure analysis and accident investigations on both flight hardware and ground support equipment (GSE) for the Shuttle, International Space Station, Constellation, and Launch Services Programs. This presentation will explore a variety of failure case studies at KSC and the lessons learned that can be applied in future programs.

  16. Failure Analysis at the Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Salazar, Victoria L.; Wright, M. Clara

    2010-01-01

    History has shown that failures occur in every engineering endeavor, and what we learn from those failures contributes to the knowledge base to safely complete future missions. The necessity of failure analysis is at its apex at the end of one aged program and at the beginning of a new and untested program. The information that we gain through failure analysis corrects the deficiencies in the current vehicle to make the next generation of vehicles more efficient and safe. The Failure Analysis and Materials Evaluation Branch in the Materials Science Division at the Kennedy Space Center performs metallurgical, mechanical, electrical, and non-metallic materials failure analyses and accident investigations on both flight hardware and ground support equipment for the Space Shuttle, International Space Station, Constellation, and Launch Services Programs. This paper will explore a variety of failure case studies at the Kennedy Space Center and the lessons learned that can be applied in future programs.

  17. Contraceptive failure in China.

    PubMed

    Wang, Duolao

    2002-09-01

    This study examines patterns and differentials of contraceptive failure rates by method and characteristics of users, using the Chinese Two-per-Thousand Fertility Survey data. The results show that contraceptive failure rates for modern methods including sterilization are some of the highest in the world. The first year failure rates are 4.2% for male sterilization, 0.7% for female sterilization, 10.3% for IUD, 14.5% for pill, and 19.0% for condom. There are also some differentials in contraceptive failure rates by users' sociodemographic and fertility characteristics. Contraceptive failure rate declines with women's age for all reversible methods. Rural women have higher sterilization, IUD, and condom contraceptive failure rates than urban women. Women with two or more children have a higher failure rate for sterilization methods but have lower failure rates for other methods.

  18. Electrostatic Discharge (ESD) Failures in Thin Film Resistors

    NASA Technical Reports Server (NTRS)

    Hull, Scott M.

    1999-01-01

    Field failures of nichrome thin film resistors have been investigated recently for several pieces of space flight hardware. These failures have involved resistance shifts ranging from a few percent to complete open circuits. Failure analysis and duplication of these failures have revealed that the failures were caused by electrostatic discharge. The failure characteristics and the circuit conditions necessary for failure have been studied for several types of thin film resistors including nichrome and tantalum nitride resistive elements. The effects of latent damage and resistive pattern design will also be discussed.

  19. In Support of Failure

    ERIC Educational Resources Information Center

    Carr, Allison

    2013-01-01

    In this essay, I propose a concerted effort to begin devising a theory and pedagogy of failure. I review the discourse of failure in Western culture as well as in composition pedagogy, ultimately suggesting that failure is not simply a judgement or indication of rank but is a relational, affect-bearing concept with tremendous relevance to…

  20. Ammonia tank failure

    SciTech Connect

    Sweat, M.E.

    1983-04-01

    An ammonia tank failure at Hawkeye Chemical of Clinton, Iowa is discussed. The tank was a double-wall, 27,000 metric-ton tank built in 1968 and commissioned in December 1969. The paper presented covers the cause of the failure, repair, and procedural changes made to prevent recurrence of the failure. (JMT)

  1. Failure models for textile composites

    NASA Technical Reports Server (NTRS)

    Cox, Brian

    1995-01-01

    The goals of this investigation were to: (1) identify mechanisms of failure and determine how the architecture of reinforcing fibers in 3D woven composites controlled stiffness, strength, strain to failure, work of fracture, notch sensitivity, and fatigue life; and (2) to model composite stiffness, strength, and fatigue life. A total of 11 different angle and orthogonal interlock woven composites were examined. Composite properties depended on the weave architecture, the tow size, and the spatial distributions and strength of geometrical flaws. Simple models were developed for elastic properties, strength, and fatigue life. A more complicated stochastic model, called the 'Binary Model,' was developed for damage tolerance and ultimate failure. These 3D woven composites possessed an extraordinary combination of strength, damage tolerance, and notch insensitivity.

  2. Failure models for textile composites

    SciTech Connect

    Cox, B.

    1995-08-01

    The goals of this investigation were to: (1) identify mechanisms of failure and determine how the architecture of reinforcing fibers in 3D woven composites controlled stiffness, strength, strain to failure, work of fracture, notch sensitivity, and fatigue life; and (2) to model composite stiffness, strength, and fatigue life. A total of 11 different angle and orthogonal interlock woven composites were examined. Composite properties depended on the weave architecture, the tow size, and the spatial distributions and strength of geometrical flaws. Simple models were developed for elastic properties, strength, and fatigue life. A more complicated stochastic model, called the `Binary Model,` was developed for damage tolerance and ultimate failure. These 3D woven composites possessed an extraordinary combination of strength, damage tolerance, and notch insensitivity.

  3. The failure of earthquake failure models

    USGS Publications Warehouse

    Gomberg, J.

    2001-01-01

    In this study I show that simple heuristic models and numerical calculations suggest that an entire class of commonly invoked models of earthquake failure processes cannot explain triggering of seismicity by transient or "dynamic" stress changes, such as stress changes associated with passing seismic waves. The models of this class have the common feature that the physical property characterizing failure increases at an accelerating rate when a fault is loaded (stressed) at a constant rate. Examples include models that invoke rate state friction or subcritical crack growth, in which the properties characterizing failure are slip or crack length, respectively. Failure occurs when the rate at which these grow accelerates to values exceeding some critical threshold. These accelerating failure models do not predict the finite durations of dynamically triggered earthquake sequences (e.g., at aftershock or remote distances). Some of the failure models belonging to this class have been used to explain static stress triggering of aftershocks. This may imply that the physical processes underlying dynamic triggering differs or that currently applied models of static triggering require modification. If the former is the case, we might appeal to physical mechanisms relying on oscillatory deformations such as compaction of saturated fault gouge leading to pore pressure increase, or cyclic fatigue. However, if dynamic and static triggering mechanisms differ, one still needs to ask why static triggering models that neglect these dynamic mechanisms appear to explain many observations. If the static and dynamic triggering mechanisms are the same, perhaps assumptions about accelerating failure and/or that triggering advances the failure times of a population of inevitable earthquakes are incorrect.

  4. Failure analyses of composite bolted joints

    NASA Technical Reports Server (NTRS)

    Wilson, D. W.; Gillespie, J. W.; York, J. L.; Pipes, R. B.

    1980-01-01

    The complex failure behavior exhibited by bolted joints of graphite epoxy (Hercules AS/3501) was investigated for the net tension, bearing and shearout failure modes using combined analytical and experimental techniques. Plane stress, linear elastic, finite element methods were employed to determine the two dimensional state of stress resulting from a loaded hole in a finite width, semiinfinite strip. The stresses predicted by the finite element method were verified by experiment to lend credence to the analysis. The influence of joint geometric parameters on the state of stress and resultant strength of the joint was also studied. The resulting functional relationships found to exist between bolted joint strength and the geometric parameters, were applied in the formulation of semiempirical strength models for the basic failure modes. A point stress failure criterion was successfully applied as the failure criterion for the net tension and shearout failure modes.

  5. Light water reactor lower head failure analysis

    SciTech Connect

    Rempe, J.L.; Chavez, S.A.; Thinnes, G.L.

    1993-10-01

    This document presents the results from a US Nuclear Regulatory Commission-sponsored research program to investigate the mode and timing of vessel lower head failure. Major objectives of the analysis were to identify plausible failure mechanisms and to develop a method for determining which failure mode would occur first in different light water reactor designs and accident conditions. Failure mechanisms, such as tube ejection, tube rupture, global vessel failure, and localized vessel creep rupture, were studied. Newly developed models and existing models were applied to predict which failure mechanism would occur first in various severe accident scenarios. So that a broader range of conditions could be considered simultaneously, calculations relied heavily on models with closed-form or simplified numerical solution techniques. Finite element techniques-were employed for analytical model verification and examining more detailed phenomena. High-temperature creep and tensile data were obtained for predicting vessel and penetration structural response.

  6. Failure of Non-Circular Composite Cylinders

    NASA Technical Reports Server (NTRS)

    Hyer, M. W.

    2004-01-01

    In this study, a progressive failure analysis is used to investigate leakage in internally pressurized non-circular composite cylinders. This type of approach accounts for the localized loss of stiffness when material failure occurs at some location in a structure by degrading the local material elastic properties by a certain factor. The manner in which this degradation of material properties takes place depends on the failure modes, which are determined by the application of a failure criterion. The finite-element code STAGS, which has the capability to perform progressive failure analysis using different degradation schemes and failure criteria, is utilized to analyze laboratory scale, graphite-epoxy, elliptical cylinders with quasi-isotropic, circumferentially-stiff, and axially-stiff material orthotropies. The results are divided into two parts. The first part shows that leakage, which is assumed to develop if there is material failure in every layer at some axial and circumferential location within the cylinder, does not occur without failure of fibers. Moreover before fibers begin to fail, only matrix tensile failures, or matrix cracking, takes place, and at least one layer in all three cylinders studied remain uncracked, preventing the formation of a leakage path. That determination is corroborated by the use of different degradation schemes and various failure criteria. Among the degradation schemes investigated are the degradation of different engineering properties, the use of various degradation factors, the recursive or non-recursive degradation of the engineering properties, and the degradation of material properties using different computational approaches. The failure criteria used in the analysis include the noninteractive maximum stress criterion and the interactive Hashin and Tsai-Wu criteria. The second part of the results shows that leakage occurs due to a combination of matrix tensile and compressive, fiber tensile and compressive, and inplane

  7. Role of failure-mechanism identification in accelerated testing

    NASA Technical Reports Server (NTRS)

    Hu, J. M.; Barker, D.; Dasgupta, A.; Arora, A.

    1993-01-01

    Accelerated life testing techniques provide a short-cut method to investigate the reliability of electronic devices with respect to certain dominant failure mechanisms that occur under normal operating conditions. However, accelerated tests have often been conducted without knowledge of the failure mechanisms and without ensuring that the test accelerated the same mechanism as that observed under normal operating conditions. This paper summarizes common failure mechanisms in electronic devices and packages and investigates possible failure mechanism shifting during accelerated testing.

  8. Loess failure in northeast Afghanistan

    NASA Astrophysics Data System (ADS)

    Shroder, John F.; Schettler, Megan Jensen; Weihs, Brandon J.

    Mass movements in northeastern Afghanistan include large-scale rockslides and complex slope failures, as well as failures in loess. The loess region in northeastern Afghanistan occurs in the Badakhshan and Takhar provinces and was likely created by dust blown to the east from the Karakum Desert and the alluvial plains of northern Afghanistan. This loessic dust was deposited against the Hindu Kush mountain range which rises up along the eastern half of Afghanistan as a result of transpressional tectonism. It overlies less permeable crystalline and sedimentary bedrocks such as Triassic granite, Proterozoic gneiss, and Miocene and Pliocene clastics in the area with the largest concentration of slope failures. Thirty-four loess slides and flows were mapped and analyzed using remote satellite imagery over digital elevation models on Google Earth™. This source enabled location, classification, and measurement of failures. Findings revealed that most failed slopes faced north, west, and northwest. This trend can be explained possibly as different moisture contents resulting from the primarily westerly wind direction, which may cause more precipitation to be deposited on west-facing slopes, and sun position during the hottest part of the day. Additionally, the easterly rising Hindu Kush range may cause more slope area to face west in the study region. Other contributing factors could be the very high seismicity of the area, which may cause rapid dry fluidized loess flows, and landscape modification by humans. Several loess slope failures appear to be generated by water concentration through irrigation ditches and possible rutted tire tracks, which can create tunneling between the loess and its less permeable bedrock. Causes and effects of loess failure in Afghanistan need to be investigated in more depth. Further study may lead to the adoption of more sustainable and safe farming practices and more informed housing locations, which may prevent loss of property, crop, and

  9. Duralumin - Defects and Failures

    NASA Technical Reports Server (NTRS)

    Nelson, WM

    1927-01-01

    It is proposed in this paper to identify some of the defects and failures in duralumin most frequently encountered by the aircraft industry with a view to indicate their importance. The defects and failures in duralumin may be classified into the following groups: 1) defects produced during manufacture; 2) defects produced during fabrication; 3) corrosion and erosion; and 4) fatigue failures. Only the first two will be covered in this report.

  10. ATM CMG bearing failure analysis

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The cause or causes for the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2) were investigated. Skylab telemetry data were reviewed and presented in the form of parameter distributions. The theory that the problems were caused by marginal bearing lubrication was studied along with the effects of orbital conditions on lubricants. Bearing tests were performed to investigate the effect of lubricant or lack of lubricant in the ATM CMG bearings and the dispersion and migration of the lubricant. The vacuum and weightless conditions of space were simulated in the bearing tests. Analysis of the results of the tests conducted points to inadequate lubrication as the predominant factor causing the failure of ATM CMG S/N 5 (Skylab 1) and the anomalies associated with ATM CMG S/N 6 (Skylab 2).

  11. Ampoule Failure System

    NASA Technical Reports Server (NTRS)

    Watring, Dale A. (Inventor); Johnson, Martin L. (Inventor)

    1996-01-01

    An ampoule failure system for use in material processing furnaces comprising a containment cartridge and an ampoule failure sensor. The containment cartridge contains an ampoule of toxic material therein and is positioned within a furnace for processing. An ampoule failure probe is positioned in the containment cartridge adjacent the ampoule for detecting a potential harmful release of toxic material therefrom during processing. The failure probe is spaced a predetermined distance from the ampoule and is chemically chosen so as to undergo a timely chemical reaction with the toxic material upon the harmful release thereof. The ampoule failure system further comprises a data acquisition system which is positioned externally of the furnace and is electrically connected to the ampoule failure probe so as to form a communicating electrical circuit. The data acquisition system includes an automatic shutdown device for shutting down the furnace upon the harmful release of toxic material. It also includes a resistance measuring device for measuring the resistance of the failure probe during processing. The chemical reaction causes a step increase in resistance of the failure probe whereupon the automatic shutdown device will responsively shut down the furnace.

  12. Immune mediated liver failure

    PubMed Central

    Wang, Xiaojing; Ning, Qin

    2014-01-01

    Liver failure is a clinical syndrome of various etiologies, manifesting as jaundice, encephalopathy, coagulopathy and circulatory dysfunction, which result in subsequent multiorgan failure. Clinically, liver failure is classified into four categories: acute, subacute, acute-on-chronic and chronic liver failure. Massive hepatocyte death is considered to be the core event in the development of liver failure, which occurs when the extent of hepatocyte death is beyond the liver regenerative capacity. Direct damage and immune-mediated liver injury are two major factors involved in this process. Increasing evidence has suggested the essential role of immune-mediated liver injury in the pathogenesis of liver failure. Here, we review the evolved concepts concerning the mechanisms of immune-mediated liver injury in liver failure from human and animal studies. Both innate and adaptive immunity, especially the interaction of various immune cells and molecules as well as death receptor signaling system are discussed. In addition, we highlight the concept of “immune coagulation”, which has been shown to be related to the disease progression and liver injury exacerbation in HBV related acute-on-chronic liver failure. PMID:26417328

  13. Physicists and failure

    NASA Astrophysics Data System (ADS)

    Raheem, Ruby; zilch, Mortimer

    2015-08-01

    In reply to a post on the physicsworld.com blog about the central role of failure in physics (“Success, failure and women in physics”, 10 June, http://ow.ly/O8kvR; see also “Failing better,” Editorial, July p15).

  14. A failure recovery planning prototype for Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Hammen, David G.; Kelly, Christine M.

    1991-01-01

    NASA is investigating the use of advanced automation to enhance crew productivity for Space Station Freedom in numerous areas, including failure management. A prototype is described that uses various advanced automation techniques to generate courses of action whose intents are to recover from a diagnosed failure, and to do so within the constraints levied by the failure and by Freedom's configuration and operating conditions.

  15. Generalized energy failure criterion.

    PubMed

    Qu, R T; Zhang, Z J; Zhang, P; Liu, Z Q; Zhang, Z F

    2016-01-01

    Discovering a generalized criterion that can predict the mechanical failure of various different structural materials is one of ultimate goals for scientists in both material and mechanics communities. Since the first study on the failure criterion of materials by Galileo, about three centuries have passed. Now we eventually find the "generalized energy criterion", as presented here, which appears to be one universal law for various different kinds of materials. The validity of the energy criterion for quantitatively predicting the failure is experimentally confirmed using a metallic glass. The generalized energy criterion reveals the competition and interaction between shear and cleavage, the two fundamental inherent failure mechanisms, and thus provides new physical insights into the failure prediction of materials and structural components. PMID:26996781

  16. Acute Decompensated Heart Failure

    PubMed Central

    Joseph, Susan M.; Cedars, Ari M.; Ewald, Gregory A.; Geltman, Edward M.; Mann, Douglas L.

    2009-01-01

    Hospitalizations for acute decompensated heart failure are increasing in the United States. Moreover, the prevalence of heart failure is increasing consequent to an increased number of older individuals, as well as to improvement in therapies for coronary artery disease and sudden cardiac death that have enabled patients to live longer with cardiovascular disease. The main treatment goals in the hospitalized patient with heart failure are to restore euvolemia and to minimize adverse events. Common in-hospital treatments include intravenous diuretics, vasodilators, and inotropic agents. Novel pharmaceutical agents have shown promise in the treatment of acute decompensated heart failure and may simplify the treatment and reduce the morbidity associated with the disease. This review summarizes the contemporary management of patients with acute decompensated heart failure. PMID:20069075

  17. Generalized energy failure criterion

    PubMed Central

    Qu, R. T.; Zhang, Z. J.; Zhang, P.; Liu, Z. Q.; Zhang, Z. F.

    2016-01-01

    Discovering a generalized criterion that can predict the mechanical failure of various different structural materials is one of ultimate goals for scientists in both material and mechanics communities. Since the first study on the failure criterion of materials by Galileo, about three centuries have passed. Now we eventually find the “generalized energy criterion”, as presented here, which appears to be one universal law for various different kinds of materials. The validity of the energy criterion for quantitatively predicting the failure is experimentally confirmed using a metallic glass. The generalized energy criterion reveals the competition and interaction between shear and cleavage, the two fundamental inherent failure mechanisms, and thus provides new physical insights into the failure prediction of materials and structural components. PMID:26996781

  18. Common Cause Failure Modeling: Aerospace Versus Nuclear

    NASA Technical Reports Server (NTRS)

    Stott, James E.; Britton, Paul; Ring, Robert W.; Hark, Frank; Hatfield, G. Spencer

    2010-01-01

    Aggregate nuclear plant failure data is used to produce generic common-cause factors that are specifically for use in the common-cause failure models of NUREG/CR-5485. Furthermore, the models presented in NUREG/CR-5485 are specifically designed to incorporate two significantly distinct assumptions about the methods of surveillance testing from whence this aggregate failure data came. What are the implications of using these NUREG generic factors to model the common-cause failures of aerospace systems? Herein, the implications of using the NUREG generic factors in the modeling of aerospace systems are investigated in detail and strong recommendations for modeling the common-cause failures of aerospace systems are given.

  19. Progressive failure of structures

    NASA Technical Reports Server (NTRS)

    Khozeimeh, K.; Toridis, G. T. G.; Zanganeh, S. E.

    1978-01-01

    A procedure is presented for determining the nonlinear behavior of structures subjected to extreme loading and the possibility of development of potential for progressive failure. The methodology takes into account the effect of both material and geometric nonlinearities. At a given stage of analysis, the individual components of the structure are checked against predetermined failure criteria. Subsequently, the failing components are removed and the modified structure is analyzed for overall failure. Examples, obtained from a computer program based on the proposed procedure, showing the applicability of the method are presented.

  20. Damage mechanics - failure modes

    SciTech Connect

    Krajcinovic, D.; Vujosevic, M.

    1996-12-31

    The present study summarizes the results of the DOE sponsored research program focused on the brittle failure of solids with disordered microstructure. The failure is related to the stochastic processes on the microstructural scale; namely, the nucleation and growth of microcracks. The intrinsic failure modes, such as the percolation, localization and creep rupture, are studied by emphasizing the effect of the micro-structural disorder. A rich spectrum of physical phenomena and new concepts that emerges from this research demonstrates the reasons behind the limitations of traditional, deterministic, and local continuum models.

  1. Failure of Viral Shells

    NASA Astrophysics Data System (ADS)

    Klug, William S.; Bruinsma, Robijn F.; Michel, Jean-Philippe; Knobler, Charles M.; Ivanovska, Irena L.; Schmidt, Christoph F.; Wuite, Gijs J. L.

    2006-12-01

    We report a combined theoretical and experimental study of the structural failure of viral shells under mechanical stress. We find that discontinuities in the force-indentation curve associated with failure should appear when the so-called Föppl von Kármán (FvK) number exceeds a critical value. A nanoindentation study of a viral shell subject to a soft-mode instability, where the stiffness of the shell decreases with increasing pH, confirms the predicted onset of failure as a function of the FvK number.

  2. Incidence trends in head and neck squamous cell carcinoma in Slovenia, 1983-2009: role of human papillomavirus infection.

    PubMed

    Strojan, Primož; Zadnik, Vesna; Šifrer, Robert; Lanišnik, Boštjan; Didanović, Vojislav; Jereb, Sara; Poljak, Mario; Kocjan, Boštjan J; Gale, Nina

    2015-12-01

    An increase in the incidence of oropharyngeal squamous cell carcinoma (OPSCC) was observed in several population-based registries and has been attributed to human papillomavirus (HPV) infection. In the present study, we aimed to assess the contribution of HPV infection to the burden of mucosal head and neck squamous cell carcinoma (HNSCC) in Slovenia. For this purpose, data from the nationwide Cancer Registry of Slovenia for cases diagnosed between 1983 and 2009 were analyzed to determine time trends of age-adjusted incidence rates and survival in terms of annual percentage change (APC) for HNSCC in potentially HPV-related and HPV-unrelated sites. In addition, determination of p16 protein, HPV DNA and E6/E7 mRNA was performed in a cohort of OPSCC patients identified from the prospective database for the years 2007-2008. In total, 2,862 cases of HNSCC in potentially HPV-related sites and 7,006 cases in potentially HPV-unrelated sites were identified with decreased incidence observed over the time period in both groups (-0.58; 95 % CI -1.28 to -0.13 and -0.90; 95 % CI -1.23 to -0.57). Regardless of the group, incidence trends for both genders showed a significant decrease in men and increase in women. In a cohort of 99 OPSCC patients diagnosed between 2007 and 2008, 20 (20.2 %) patients had HPV positive tumors and exhibited a superior outcome compared to HPV-negative patients. In conclusion, results of the epidemiologic and histopathologic study confirmed that HPV infection had no major impact on the incidence trends in the Slovenian patients with HNSCC and, specifically, OPSCC during the studied period.

  3. Hyperkalemia in Heart Failure.

    PubMed

    Sarwar, Chaudhry M S; Papadimitriou, Lampros; Pitt, Bertram; Piña, Ileana; Zannad, Faiez; Anker, Stefan D; Gheorghiade, Mihai; Butler, Javed

    2016-10-01

    Disorders of potassium homeostasis can potentiate the already elevated risk of arrhythmia in heart failure. Heart failure patients have a high prevalence of chronic kidney disease, which further heightens the risk of hyperkalemia, especially when renin-angiotensin-aldosterone system inhibitors are used. Acute treatment for hyperkalemia may not be tolerated in the long term. Recent data for patiromer and sodium zirconium cyclosilicate, used to treat and prevent high serum potassium levels on a more chronic basis, have sparked interest in the treatment of hyperkalemia, as well as the potential use of renin-angiotensin-aldosterone system inhibitors in patients who were previously unable to take these drugs or tolerated only low doses. This review discusses the epidemiology, pathophysiology, and outcomes of hyperkalemia in heart failure; provides an overview of traditional and novel ways to approach management of hyperkalemia; and discusses the need for further research to optimally treat heart failure.

  4. Hyperkalemia in Heart Failure.

    PubMed

    Sarwar, Chaudhry M S; Papadimitriou, Lampros; Pitt, Bertram; Piña, Ileana; Zannad, Faiez; Anker, Stefan D; Gheorghiade, Mihai; Butler, Javed

    2016-10-01

    Disorders of potassium homeostasis can potentiate the already elevated risk of arrhythmia in heart failure. Heart failure patients have a high prevalence of chronic kidney disease, which further heightens the risk of hyperkalemia, especially when renin-angiotensin-aldosterone system inhibitors are used. Acute treatment for hyperkalemia may not be tolerated in the long term. Recent data for patiromer and sodium zirconium cyclosilicate, used to treat and prevent high serum potassium levels on a more chronic basis, have sparked interest in the treatment of hyperkalemia, as well as the potential use of renin-angiotensin-aldosterone system inhibitors in patients who were previously unable to take these drugs or tolerated only low doses. This review discusses the epidemiology, pathophysiology, and outcomes of hyperkalemia in heart failure; provides an overview of traditional and novel ways to approach management of hyperkalemia; and discusses the need for further research to optimally treat heart failure. PMID:27687200

  5. What Causes Heart Failure?

    MedlinePlus

    ... the heart, leading to heart failure. High Blood Pressure Blood pressure is the force of blood pushing against the ... weaken your heart and lead to plaque buildup. Blood pressure is considered high if it stays at or ...

  6. Heart failure - tests

    MedlinePlus

    CHF - tests; Congestive heart failure - tests; Cardiomyopathy - tests; HF - tests ... An echocardiogram (Echo) is a test that uses sound waves to create a moving picture of the heart. The picture is much more detailed than a plain ...

  7. Types of Heart Failure

    MedlinePlus

    ... to be made. Here we delve into the importance of shared decision making. This content was last ... heart failure. Popular Articles 1 Understanding Blood Pressure Readings 2 Sodium and Salt 3 Low Blood Pressure ...

  8. Classes of Heart Failure

    MedlinePlus

    ... to be made. Here we delve into the importance of shared decision making. HF Resources For Life ... heart failure. Popular Articles 1 Understanding Blood Pressure Readings 2 Sodium and Salt 3 Low Blood Pressure ...

  9. Common Cause Failure Modeling

    NASA Technical Reports Server (NTRS)

    Hark, Frank; Britton, Paul; Ring, Robert; Novack, Steven

    2015-01-01

    Space Launch System (SLS) Agenda: Objective; Key Definitions; Calculating Common Cause; Examples; Defense against Common Cause; Impact of varied Common Cause Failure (CCF) and abortability; Response Surface for various CCF Beta; Takeaways.

  10. Kidney (Renal) Failure

    MedlinePlus

    ... renal function using ureteral stenting, nephrostomy, surgery or dialysis. What is kidney (renal) failure? How is kidney ... as a urinary stent or kidney stone removal. Dialysis , including hemodialysis and peritoneal dialysis: These procedures remove ...

  11. What Causes Respiratory Failure?

    MedlinePlus

    ... easily move oxygen into your blood and remove carbon dioxide from your blood (gas exchange). This can cause a low oxygen level or high carbon dioxide level, or both, in your blood. Respiratory failure ...

  12. Decompensated heart failure

    PubMed Central

    Mangini, Sandrigo; Pires, Philippe Vieira; Braga, Fabiana Goulart Marcondes; Bacal, Fernando

    2013-01-01

    ABSTRACT Heart failure is a disease with high incidence and prevalence in the population. The costs with hospitalization for decompensated heart failure reach approximately 60% of the total cost with heart failure treatment, and mortality during hospitalization varies according to the studied population, and could achieve values of 10%. In patients with decompensated heart failure, history and physical examination are of great value for the diagnosis of the syndrome, and also can help the physician to identify the beginning of symptoms, and give information about etiology, causes and prognosis of the disease. The initial objective of decompensated heart failure treatment is the hemodynamic and symptomatic improvement preservation and/or improvement of renal function, prevention of myocardial damage, modulation of the neurohormonal and/or inflammatory activation and control of comorbidities that can cause or contribute to progression of the syndrome. According to the clinical-hemodynamic profile, it is possible to establish a rational for the treatment of decompensated heart failure, individualizing the proceedings to be held, leading to reduction in the period of hospitalization and consequently reducing overall mortality. PMID:24136770

  13. Troponins in heart failure.

    PubMed

    Omland, T; Røsjø, H; Giannitsis, E; Agewall, S

    2015-03-30

    The signs and symptoms of heart failure are frequently unspecific and correlate poorly with objective indices of cardiac function. Objective assessment of cardiac function by echocardiography or other imaging modalities also correlate poorly with symptomatic status and functional capacity. Accordingly, there is a need for circulating biomarkers that can provide incremental diagnostic and prognostic information to the existing armamentarium of tests. The introduction of more sensitive assays that allow determination of very low circulating concentrations of the myofibrillar proteins cardiac troponin I and T has not only resulted in improved diagnostic accuracy in the setting of acute coronary syndromes. The high sensitivity assays have also shown that cardiac troponins are frequently found chronically circulating in a variety of acute and chronic, cardiac and non-cardiac disease conditions, including acute heart failure and chronic symptomatic and asymptomatic left ventricular dysfunction. Cardiac troponin I and T provide may provide clinically useful prognostic information both concerning the future risk of developing heart failure in asymptomatic subjects and the risk of fatal events and hospital admissions in those with already established heart failure This review summarizes current literature on the clinical performance and utility of cardiac troponin measurements as diagnostic and prognostic tools in patients with symptomatic heart failure, as well as in those with asymptomatic left ventricular dysfunction, and clinical phenotypes at high risk for developing heart failure, including stable coronary artery disease, left ventricular hypertrophy, and aortic stenosis.

  14. Pathophysiology of Heart Failure.

    PubMed

    Tanai, Edit; Frantz, Stefan

    2015-12-15

    Heart failure is considered an epidemic disease in the modern world affecting approximately 1% to 2% of adult population. It presents a multifactorial, systemic disease, in which--after cardiac injury--structural, neurohumoral, cellular, and molecular mechanisms are activated and act as a network to maintain physiological functioning. These coordinated, complex processes lead to excessive volume overload, increased sympathetic activity, circulation redistribution, and result in different, parallel developing clinical signs and symptoms. These signs and symptoms sum up to an unspecific clinical picture; thus invasive and noninvasive diagnostic tools are used to get an accurate diagnosis and to specify the underlying cause. The most important, outcome determining factor in heart failure is its constant progression. Constant optimizing of pharmatherapeutical regimes, novel targets, and fine regulation of these processes try to keep these compensatory mechanisms in a physiological range. Beside pharmacological therapy, interventional and surgical therapy options give new chances in the management of heart failure. For the optimization and establishment of these and novel therapeutical approaches, complete and comprehensive understanding of the underlying mechanisms is essentially needed. Besides diagnosis and treatment, efforts should be made for better prevention in heart failure by treatment of risk factors, or identifying and following risk groups. This summary of the pathophysiology of heart failure tries to give a compact overview of basic mechanisms and of the novel unfolding, progressive theory of heart failure to contribute to a more comprehensive knowledge of the disease.

  15. Pathophysiology of Heart Failure.

    PubMed

    Tanai, Edit; Frantz, Stefan

    2015-01-01

    Heart failure is considered an epidemic disease in the modern world affecting approximately 1% to 2% of adult population. It presents a multifactorial, systemic disease, in which--after cardiac injury--structural, neurohumoral, cellular, and molecular mechanisms are activated and act as a network to maintain physiological functioning. These coordinated, complex processes lead to excessive volume overload, increased sympathetic activity, circulation redistribution, and result in different, parallel developing clinical signs and symptoms. These signs and symptoms sum up to an unspecific clinical picture; thus invasive and noninvasive diagnostic tools are used to get an accurate diagnosis and to specify the underlying cause. The most important, outcome determining factor in heart failure is its constant progression. Constant optimizing of pharmatherapeutical regimes, novel targets, and fine regulation of these processes try to keep these compensatory mechanisms in a physiological range. Beside pharmacological therapy, interventional and surgical therapy options give new chances in the management of heart failure. For the optimization and establishment of these and novel therapeutical approaches, complete and comprehensive understanding of the underlying mechanisms is essentially needed. Besides diagnosis and treatment, efforts should be made for better prevention in heart failure by treatment of risk factors, or identifying and following risk groups. This summary of the pathophysiology of heart failure tries to give a compact overview of basic mechanisms and of the novel unfolding, progressive theory of heart failure to contribute to a more comprehensive knowledge of the disease. PMID:26756631

  16. Seasonal factors influencing the failure of buried water reticulation pipes.

    PubMed

    Gould, S J F; Boulaire, F A; Burn, S; Zhao, X L; Kodikara, J K

    2011-01-01

    While the use of environmental factors in the analysis and prediction of failures of buried reticulation pipes in cold environments has been the focus of extensive work, the same cannot be said for failures occurring on pipes in other (non-freezing) environments. A novel analysis of pipe failures in such an environment is the subject of this paper. An exploratory statistical analysis was undertaken, identifying a peak in failure rates during mid to late summer. This peak was found to correspond to a peak in the rate of circumferential failures, whilst the rate of longitudinal failures remained constant. Investigation into the effect of climate on failure rates revealed that the peak in failure rates occurs due to differential soil movement as the result of shrinkage in expansive soils. PMID:22049766

  17. Life Support with Failures and Variable Supply

    NASA Technical Reports Server (NTRS)

    Jones, Harry

    2010-01-01

    The life support system for long duration missions will recycle oxygen and water to reduce the material resupply mass from Earth. The impact of life support failures was investigated by dynamic simulation of a lunar outpost habitat life support model. The model was modified to simulate resupply delays, power failures, recycling system failures, and storage failures. Many failures impact the lunar outpost water supply directly or indirectly, depending on the water balance and water storage. Failure effects on the water supply are reduced if Extra Vehicular Activity (EVA) water use is low and the water supply is ample. Additional oxygen can be supplied by scavenging unused propellant or by production from regolith, but the amounts obtained can vary significantly. The requirements for oxygen and water can also vary significantly, especially for EVA. Providing storage buffers can improve efficiency and reliability, and minimize the chance of supply failing to meet demand. Life support failures and supply variations can be survivable if effective solutions are provided by the system design

  18. Technology integration box beam failure study

    NASA Technical Reports Server (NTRS)

    Shuart, Mark J.; Ambur, Damodar R.; Davis, D. D., Jr.; Davis, R. C.; Farley, G. L.; Lotts, C. G.; Wang, J. T.

    1992-01-01

    The objective of this paper is to describe current results from an on-going study of the mechanisms that led to the failure of the TIBB. Experimental and analytical results are presented. Experimental results include load, strain, and deflection data for the TIBB (Technology Integration Box Beam). An analytical investigation was conducted to compliment the experimental investigation and to gain additional insight into the TIBB structural response. Analytical results include strain and deflection results from a global analysis of the TIBB. A local analysis of the failure region is being completed. These analytical results are validated through comparisons with the experimental results from the TIBB tests. The experimental and analytical results from the TIBB tests are used to determine a sequence of events that may have resulted in failure of the TIBB. A potential cause of failure is high stresses in a stiffener runout region. Typical analytical results are presented for a stiffener runout specimen that is being defined to simulate the TIBB failure mechanisms. The results of this study are anticipated to provide better understanding of potential failure mechanisms in composite aircraft structures, to lead to future design improvements, and to identify needed analytical tools for design and analysis.

  19. Apollo 15 main-parachute failure

    NASA Technical Reports Server (NTRS)

    Arabian, D. D.; Mechelay, J. E.

    1972-01-01

    In the investigation of the failure of one of the three main parachutes of the Apollo 15 spacecraft, which collapsed at approximately 1825 meters after operating properly from deployment at 3050 meters, three conditions considered to be possible causes of the failure were produced. The suspect conditions were the proximity of the forward heat shield that passed the spacecraft at approximately 1825 meters, the dumping of the reaction control system hypergolic propellants at approximately 1825 meters, and the failing of a riser link found on a recovered parachute. (The failed parachute was not recovered). The remaining two parachutes functioned as planned and averted a catastrophic failure. The conclusions concerning the cause of the failure are discussed.

  20. SAW Sensor for Fastener Failure Detection

    NASA Technical Reports Server (NTRS)

    Wilson, W. C.; Rogge, M. D.; Fisher, B.; Roller, M. J.; Malocha, D. M.

    2010-01-01

    The proof of concept for using surface acoustic wave (SAW) strain sensors in the detection of aircraft fastener failures is demonstrated. SAW sensors were investigated because they have the potential for the development of passive wireless systems. The SAW devices employed four orthogonal frequency coding (OFC) spread spectrum reflectors in two banks on a high temperature piezoelectric substrate. Three SAW devices were attached to a cantilever panel with removable side stiffeners. Damage in the form of fastener failure was simulated by removal of bolts from the side stiffeners. During testing, three different force conditions were used to simulate static aircraft structural response under loads. The design of the sensor, the panel arrangement and the panel testing results are reported. The results show that the sensors successfully detected single fastener failure at distances up to 54.6 cm from the failure site under loaded conditions.

  1. Weld failure detection

    DOEpatents

    Pennell, William E.; Sutton, Jr., Harry G.

    1981-01-01

    Method and apparatus for detecting failure in a welded connection, particrly applicable to not readily accessible welds such as those joining components within the reactor vessel of a nuclear reactor system. A preselected tag gas is sealed within a chamber which extends through selected portions of the base metal and weld deposit. In the event of a failure, such as development of a crack extending from the chamber to an outer surface, the tag gas is released. The environment about the welded area is directed to an analyzer which, in the event of presence of the tag gas, evidences the failure. A trigger gas can be included with the tag gas to actuate the analyzer.

  2. BIOASSAY VESSEL FAILURE ANALYSIS

    SciTech Connect

    Vormelker, P

    2008-09-22

    Two high-pressure bioassay vessels failed at the Savannah River Site during a microwave heating process for biosample testing. Improper installation of the thermal shield in the first failure caused the vessel to burst during microwave heating. The second vessel failure is attributed to overpressurization during a test run. Vessel failure appeared to initiate in the mold parting line, the thinnest cross-section of the octagonal vessel. No material flaws were found in the vessel that would impair its structural performance. Content weight should be minimized to reduce operating temperature and pressure. Outer vessel life is dependent on actual temperature exposure. Since thermal aging of the vessels can be detrimental to their performance, it was recommended that the vessels be used for a limited number of cycles to be determined by additional testing.

  3. Judicial failure to thrive.

    PubMed

    Stern, H P; Casey, P H

    1984-06-01

    The case of a toddler who developed nonorganic failure to thrive during the course of a custody determination is reported. The child demonstrated physical, emotional, and developmental aspects of failure to thrive. These signs correlated with custody ordered by the judge, during which time the child's care was alternated between parents. The symptoms resolved when the child was in the hospital and when provided stable care by his grandmother. With the increasing frequency of divorce, failure to thrive resulting from judicial decisions will probably increase. Physicians should monitor these children carefully in order to prevent serious psychosocial complications. The judicial system should expedite custody decisions, availing itself of information in child development. PMID:6736261

  4. Common Cause Failure Modes

    NASA Technical Reports Server (NTRS)

    Wetherholt, Jon; Heimann, Timothy J.; Anderson, Brenda

    2011-01-01

    High technology industries with high failure costs commonly use redundancy as a means to reduce risk. Redundant systems, whether similar or dissimilar, are susceptible to Common Cause Failures (CCF). CCF is not always considered in the design effort and, therefore, can be a major threat to success. There are several aspects to CCF which must be understood to perform an analysis which will find hidden issues that may negate redundancy. This paper will provide definition, types, a list of possible causes and some examples of CCF. Requirements and designs from NASA projects will be used in the paper as examples.

  5. Failure detection and identification

    NASA Technical Reports Server (NTRS)

    Massoumnia, Mohammad-Ali; Verghese, George C.; Willsky, Alan S.

    1989-01-01

    Using the geometric concept of an unobservability subspace, a solution is given to the problem of detecting and identifying control system component failures in linear, time-invariant systems. Conditions are developed for the existence of a causal, linear, time-invariant processor that can detect and uniquely identify a component failure, first for the case where components can fail simultaneously, and then for the case where they fail only one at a time. Explicit design algorithms are provided when these conditions are satisfied. In addition to time-domain solvability conditions, frequency-domain interpretations of the results are given, and connections are drawn with results already available in the literature.

  6. Causal Attributions for Failure and the Effect of Gender among Moroccan EFL University Learners

    ERIC Educational Resources Information Center

    Zohri, Abdelaziz

    2011-01-01

    This paper reports a study that sought to investigate Moroccan university learners' perceptions of failure. 333 subjects studying English at university ranked their perceptions of failure in a Causal Attribution Scale of University Failure (CASUF). The results show that Moroccan learners attribute their failure to teachers' attitude, effort,…

  7. Living with Heart Failure

    MedlinePlus

    ... should be. This includes advice on daily activities, work, leisure time, sex, and exercise. Your level of activity will depend on the stage of your heart failure (how severe it is). Keep all of your ... to get tests and lab work. Your doctor needs the results of these tests ...

  8. Failure Free Reading.

    ERIC Educational Resources Information Center

    Education Commission of the States, Denver, CO.

    This paper provides an overview of Failure Free Reading, a program with the primary goal of providing a basic understanding of the reading process to students in grades K-12 with pronounced reading difficulty and move them into traditional reading programs. The program is targeted to and most effective with at-risk and English as a Second Language…

  9. Designing for Productive Failure

    ERIC Educational Resources Information Center

    Kapur, Manu; Bielaczyc, Katerine

    2012-01-01

    In this article, we describe the design principles undergirding "productive failure" (PF; M. Kapur, 2008). We then report findings from an ongoing program of research on PF in mathematical problem solving in 3 Singapore public schools with significantly different mathematical ability profiles, ranging from average to lower ability. In the 1st…

  10. Premature Ovarian Failure

    MedlinePlus

    Premature ovarian failure (POF) is when a woman's ovaries stop working before she is 40. POF is different from premature menopause. With premature menopause, ... be a disease, surgery, chemotherapy, or radiation. With POF, some women still have occasional periods. They may ...

  11. Preventing Early Learning Failure.

    ERIC Educational Resources Information Center

    Sornson, Bob, Ed.

    Noting that thousands of young children with the capacity to experience school success do not because they are unprepared for school learning activities, have experienced physical or emotional setbacks that cause them to be at risk for early learning failure, have never experienced limits on their behavior, or have mild sensory or motor deficits,…

  12. Explaining Jewish Student Failure.

    ERIC Educational Resources Information Center

    Schoem, David

    1982-01-01

    Ethnographic study of a suburban Jewish afternoon school suggests that students' failure to meet school behavior and learning standards occurred because they did not value or understand the rewards made available to them through the school and because their means of achieving status mobility had shifted away from the Jewish school. (Author/GC)

  13. Learning from Failures.

    ERIC Educational Resources Information Center

    Saffran, Murray

    1991-01-01

    Describes mistakes made in trying to change the Nutrition and Digestion section of a medical biochemistry course. Author tried to make the section student taught and reports nine mistakes including the following: ignoring active opposition of colleagues, failure to assess the receptivity of the class to a new form of teaching, and overestimating…

  14. Large Rock Slope Failures Induced by Recent Earthquakes

    NASA Astrophysics Data System (ADS)

    Aydan, Ö.

    2016-06-01

    Recent earthquakes caused many large-scale rock slope failures. The scale and impact of rock slope failures are very large, and the form of failure differs depending upon the geological structures of slopes. First, the author briefly describes some model experiments to investigate the effects of shaking or faulting due to earthquakes on rock slopes. Then, fundamental characteristics of the rock slope failures induced by the earthquakes are described and evaluated according to some empirical and theoretical models. Furthermore, the observations for slope failures in relation to earthquake magnitude and epicenter or hypocenter distance were compared with several empirical relations available in the literature. Some of major rock slope failures induced by earthquakes are selected, and the post-failure motions are simulated and compared with observations. In addition, the effects of tsunamis on rock slopes in view of observations in the reconnaissances of the recent mega-earthquakes are explained and are discussed.

  15. Civil aircraft accident investigation.

    PubMed

    Haines, Daniel

    2013-01-01

    This talk reviews some historic aircraft accidents and some more recent. It reflects on the division of accident causes, considering mechanical failures and aircrew failures, and on aircrew training. Investigation results may lead to improved aircraft design, and to appropriate crew training. PMID:24057309

  16. Carbon Fiber Strand Tensile Failure Dynamic Event Characterization

    NASA Technical Reports Server (NTRS)

    Johnson, Kenneth L.; Reeder, James

    2016-01-01

    There are few if any clear, visual, and detailed images of carbon fiber strand failures under tension useful for determining mechanisms, sequences of events, different types of failure modes, etc. available to researchers. This makes discussion of physics of failure difficult. It was also desired to find out whether the test article-to-test rig interface (grip) played a part in some failures. These failures have nothing to do with stress rupture failure, thus representing a source of waste for the larger 13-00912 investigation into that specific failure type. Being able to identify or mitigate any competing failure modes would improve the value of the 13-00912 test data. The beginnings of the solution to these problems lay in obtaining images of strand failures useful for understanding physics of failure and the events leading up to failure. Necessary steps include identifying imaging techniques that result in useful data, using those techniques to home in on where in a strand and when in the sequence of events one should obtain imaging data.

  17. Buckling failures in insect exoskeletons.

    PubMed

    Parle, Eoin; Herbaj, Simona; Sheils, Fiona; Larmon, Hannah; Taylor, David

    2016-02-01

    Thin walled tubes are often used for load-bearing structures, in nature and in engineering, because they offer good resistance to bending and torsion at relatively low weight. However, when loaded in bending they are prone to failure by buckling. It is difficult to predict the loading conditions which cause buckling, especially for tubes whose cross sections are not simple shapes. Insights into buckling prevention might be gained by studying this phenomenon in the exoskeletons of insects and other arthropods. We investigated the leg segments (tibiae) of five different insects: the locust (Schistocerca gergaria), American cockroach (Periplaneta americana), death's head cockroach (Blaberus discoidalis), stick insect (Parapachymorpha zomproi) and bumblebee (Bombus terrestris audax). These were tested to failure in cantilever bending and modelled using finite element analysis (FEA). The tibiae of the locust and the cockroaches were found to be approximately circular in shape. Their buckling loads were well predicted by linear elastic FEA, and also by one of the analytical solutions available in the literature for elastic buckling. The legs of the stick insect are also circular in cross section but have several prominent longitudinal ridges. We hypothesised that these ridges might protect the legs against buckling but we found that this was not the case: the loads necessary for elastic buckling were not reached in practice because yield occurred in the material, causing plastic buckling. The legs of bees have a non-circular cross section due to a pollen-carrying feature (the corbicula). We found that this did not significantly affect their resistance to buckling. Our results imply that buckling is the dominant failure mode in the tibia of insects; it likely to be a significant consideration for other arthropods and any organisms with stiff exoskeletons. The interactions displayed here between material properties and cross sectional geometry may provide insights for the

  18. Satellite failures revisited

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-12-01

    In January 1994, the two geostationary satellites known as Anik-E1 and Anik-E2, operated by Telesat Canada, failed one after the other within 9 hours, leaving many northern Canadian communities without television and data services. The outage, which shut down much of the country's broadcast television for hours and cost Telesat Canada more than $15 million, generated significant media attention. Lam et al. used publicly available records to revisit the event; they looked at failure details, media coverage, recovery effort, and cost. They also used satellite and ground data to determine the precise causes of those satellite failures. The researchers traced the entire space weather event from conditions on the Sun through the interplanetary medium to the particle environment in geostationary orbit.

  19. Diastolic heart failure.

    PubMed

    Gary, Rebecca; Davis, Leslie

    2008-01-01

    Diastolic heart failure (DHF) is estimated to occur in 40% to 50% of patients with heart failure. Evidence suggests that DHF is primarily a cardiogeriatric syndrome that increases from approximately 1% at age 50 years to 10% or more at 80 years. DHF is also more likely to occur in older women who are hypertensive or diabetic. Although survival is better in patients with DHF compared with systolic heart failure, mortality rates for patients with DHF are four times higher than those for healthy, community-dwelling older adults. The increase in DHF is anticipated to continue during the next several decades largely because of the aging of the population; increase in risk factors associated with hypertension, diabetes, and obesity; and ongoing technologic advances in the treatment of cardiovascular disease. Few clinical trials have evaluated therapy in this population, so evidence about the effectiveness of treatment strategies for DHF is limited. Future research should target novel interventions that specifically target patients with DHF who are typically older and female, and experience exertional intolerance and have a considerably reduced quality of life.

  20. Factors Influencing Academic Failure of University Students

    ERIC Educational Resources Information Center

    Khan, Yousaf Ali; Ahamad, Zahoor; Kousar, Sadia

    2013-01-01

    There was a close link between education and development. Education played a vital role in human capital formation. Academic failure from university was a problem that had became a serious concern for higher education institutions. This study presented the result of a recent investigation at the University of Gujrat that attempted to identify the…

  1. A novel needleless liquid jet injection methodology for improving direct cardiac gene delivery: An optimization of parameters, AAV mediated therapy and investigation of host responses in ischemic heart failure

    NASA Astrophysics Data System (ADS)

    Fargnoli, Anthony Samuel

    Heart disease remains the leading cause of mortality and morbidity worldwide, with 22 million new patients diagnosed annually. Essentially, all present therapies have significant cost burden to the healthcare system, yet fail to increase survival rates. One key employed strategy is the genetic reprogramming of cells to increase contractility via gene therapy, which has advanced to Phase IIb Clinical Trials for advanced heart failure patients. It has been argued that the most significant barrier preventing FDA approval are resolving problems with safe, efficient myocardial delivery, whereby direct injection in the infarct and remote tissue areas is not clinically feasible. Here, we aim to: (1) Improve direct cardiac gene delivery through the development of a novel liquid jet device approach (2) Compare the new method against traditional IM injection with two different vector constructions and evaluate outcome (3) Evaluate the host response resulting from both modes of direct cardiac injection, then advance a drug/gene combination with controlled release nanoparticle formulations.

  2. Heart Failure Society of America

    MedlinePlus

    ... Review Course in Advanced Heart Failure and Transplant Cardiology is now available OnDemand! Monday, August 29, 2016! ... than expected, and the FDA... European Society of Cardiology – Heart Failure 2017 October 11, 2016 ESC: Heart ...

  3. Failure Analysis for Improved Reliability

    NASA Technical Reports Server (NTRS)

    Sood, Bhanu

    2016-01-01

    Outline: Section 1 - What is reliability and root cause? Section 2 - Overview of failure mechanisms. Section 3 - Failure analysis techniques (1. Non destructive analysis techniques, 2. Destructive Analysis, 3. Materials Characterization). Section 4 - Summary and Closure

  4. Synergistic Failure of BWR Internals

    SciTech Connect

    Ware, Arthur Gates; Chang, T-Y

    1999-10-01

    Boiling Water Reactor (BWR) core shrouds and other reactor internals important to safety are experiencing intergranular stress corrosion cracking (IGSCC). The United States Nuclear Regulatory Commission has followed the problem, and as part of its investigations, contracted with the Idaho National Engineering and Environmental Laboratory to conduct a risk assessment. The overall project objective is to assess the potential consequences and risks associated with the failure of IGSCC-susceptible BWR vessel internals, with specific consideration given to potential cascading and common mode effects. An initial phase has been completed in which background material was gathered and evaluated, and potential accident sequences were identified. A second phase is underway to perform a simplified, quantitative probabilistic risk assessment on a representative high-power BWR/4. Results of the initial study conducted on the jet pumps show that any cascading failures would not result in a significant increase in the core damage frequency. The methodology is currently being extended to other major reactor internals components.

  5. Heart failure prognostic model.

    PubMed

    Axente, L; Sinescu, C; Bazacliu, G

    2011-05-15

    Heart failure (HF) is a common, costly, disabling and deadly syndrome. Heart failure is a progressive disease characterized by high prevalence in society, significantly reducing physical and mental health, frequent hospitalization and high mortality (50% of the patients survive up to 4 years after the diagnosis, the annual mortality varying from 5% to 75%). The purpose of this study is to develop a prognostic model with easily obtainable variables for patients with heart failure. METHODS AND RESULTS. Our lot included 101 non-consecutive hospitalized patients with heart failure diagnosis. It included 49.5% women having the average age of 71.23 years (starting from 40 up to 91 years old) and the roughly estimated period for monitoring was 35.1 months (5-65 months). Survival data were available for all patients and the median survival duration was of 44.0 months. A large number of variables (demographic, etiologic, co morbidity, clinical, echocardiograph, ECG, laboratory and medication) were evaluated. We performed a complex statistical analysis, studying: survival curve, cumulative hazard, hazard function, lifetime distribution and density function, meaning residual life time, Ln S (t) vs. t and Ln(H) t vs. Ln (t). The Cox multiple regression model was used in order to determine the major factors that allow the forecasting survival and their regression coefficients: age (0.0369), systolic blood pressure (-0.0219), potassium (0.0570), sex (-0.3124) and the acute myocardial infarction (0.2662). DISCUSSION. Our model easily incorporates obtainable variables that may be available in any hospital, accurately predicting survival of the heart failure patients and enables risk stratification in a few hours after the patients' presentation. Our model is derived from a sample of patients hospitalized in an emergency department of cardiology, some with major life-altering co morbidities. The benefit of being aware of the prognosis of these patients with high risk is extremely

  6. Reconfigurable control of aircraft undergoing sensor and actuator failures

    NASA Astrophysics Data System (ADS)

    Bajpai, Gaurav

    2001-07-01

    Significant number of fatal aircraft accidents in recent years have been linked to component failures. With the predicted increase in air traffic these numbers are likely to increase. With reduction of fatal accidents as motivation, this dissertation investigates design of fault tolerant control systems for aircrafts undergoing sensor and/or actuator failures. Given that the nominal controller may perform inadequately in the event of sensors and/or actuator failure, the feasible approach for such a control scheme is to predesign various controllers anticipating these failures and then switching to an appropriate controller when the failure occurs. This is enabled by the available redundancy in sensing and actuation and allows the system to perform adequately even when these failures occur. The predesign of controllers for sensor and actuator failures is considered. Sensor failures are easily accommodated if certain detectability conditions are met. However, the predesign for actuator failures is not trivial as the position at which the actuators fail is not known a priori. It is shown that this problem can be tackled by reducing it to the classical control problem of disturbance decoupling, in which, the functional control enables the steady state output of dynamical system to reject any disturbance due to the failed actuators. For linear systems, conditions for existence of a controller capable of accommodating these failures can be understood in geometric terms and calculations are linked to solvability of coupled matrix equations. Although control design for aircrafts is done using linear techniques, failures can cause excursions into nonlinear regimes due to ensuing changes in the flight conditions. This dissertation also uses the recent results in the nonlinear regulator theory to address actuator failures in nonlinear systems. The utility of design techniques is illustrated using flight control examples with failures. The symbolic computational tools are

  7. Detecting servo failures with software

    NASA Technical Reports Server (NTRS)

    Lew, D.; Quam, R.

    1979-01-01

    Program detects hardware failure in servosystems by comparing actual servo valve position with predictions of software model. In addition, system will also pick up most computer input/output failures. Process presents faster and more reliable results than previous failure detection methods.

  8. Planning Ahead: Advanced Heart Failure

    MedlinePlus

    ... Pressure Tools & Resources Stroke More Planning Ahead: Advanced Heart Failure Updated:Aug 24,2016 An important part of ... content was last reviewed on 04/16/2015. Heart Failure • Home • About Heart Failure • Causes and Risks for ...

  9. Your Heart Failure Healthcare Team

    MedlinePlus

    ... High Blood Pressure Tools & Resources Stroke More Your Heart Failure Healthcare Team Updated:Mar 25,2016 Patients with ... to the Terms and Conditions and Privacy Policy Heart Failure • Home • About Heart Failure • Causes and Risks for ...

  10. Degradation and Failure Characteristics of NPP Containment Protective Coating Systems

    SciTech Connect

    Sindelar, R.L.

    2000-12-01

    A research program to investigate the performance and potential for failure of Service Level I coating systems used in nuclear power plant containment is in progress. The research activities are aligned to address phenomena important to cause failure as identified by the industry coatings expert panel.

  11. Capillary and elastic failure of particle-stabilized droplets

    NASA Astrophysics Data System (ADS)

    Samudrala, Nivi; Sarfati, Raphael; Nam, Jin; Dufresne, Eric

    2015-11-01

    Colloidal surfactants robustly stabilize fluid interfaces against spontaneous phase separation. Like molecular surfactants, they improve the thermodynamic and kinetic stability of the interface. Here, we investigate the mechanical stability of particle-stabilized droplets using micro-pipette aspiration. We observe two distinct modes of failure. In capillary failure, fluid is pulled through the gaps between the particles. In elastic failure, the particle-laden interface buckles like an elastic shell. We explore the impact of the fluid surface tension and particle interactions on these two modes of failure.

  12. Code System to Calculate Pressure Vessel Failure Probabilities.

    2001-03-27

    Version 00 OCTAVIA (Operationally Caused Transients And Vessel Integrity Analysis) calculates the probability of pressure vessel failure from operationally-caused pressure transients which can occur in a pressurized water reactor (PWR). For specified vessel and operating environment characteristics the program computes the failure pressure at which the vessel will fail for different-sized flaws existing in the beltline and the probability of vessel failure per reactor year due to the flaw. The probabilities are summed over themore » various flaw sizes to obtain the total vessel failure probability. Sensitivity studies can be performed to investigate different vessel or operating characteristics in the same computer run.« less

  13. A bulge-induced dehydration failure mode of nanocomposite hydrogel

    NASA Astrophysics Data System (ADS)

    Tang, Jingda; Yu, Zejun; Sun, Youyi; Pei, Yongmao; Fang, Daining

    2013-10-01

    Since hydrogels are very soft and usually weak in swollen state, they pose unique challenges to traditional mechanical experiments. The mechanical property of nanocomposite poly(N-isopropylacrylamide) hydrogel was characterized by the bulge test in this investigation. A dehydration failure phenomenon of the hydrogel was found and the failure mechanism was presented. A criterion is proposed that when strain reaches the threshold, water molecules migrate out of the polymer networks and the dehydration failure occurs. The critical strain keeps constant for orifices with different diameters. This failure mode can be applied in the controllable release of drugs.

  14. Chronic sublethal stress causes bee colony failure.

    PubMed

    Bryden, John; Gill, Richard J; Mitton, Robert A A; Raine, Nigel E; Jansen, Vincent A A

    2013-12-01

    Current bee population declines and colony failures are well documented yet poorly understood and no single factor has been identified as a leading cause. The evidence is equivocal and puzzling: for instance, many pathogens and parasites can be found in both failing and surviving colonies and field pesticide exposure is typically sublethal. Here, we investigate how these results can be due to sublethal stress impairing colony function. We mathematically modelled stress on individual bees which impairs colony function and found how positive density dependence can cause multiple dynamic outcomes: some colonies fail while others thrive. We then exposed bumblebee colonies to sublethal levels of a neonicotinoid pesticide. The dynamics of colony failure, which we observed, were most accurately described by our model. We argue that our model can explain the enigmatic aspects of bee colony failures, highlighting an important role for sublethal stress in colony declines.

  15. Chronic sublethal stress causes bee colony failure.

    PubMed

    Bryden, John; Gill, Richard J; Mitton, Robert A A; Raine, Nigel E; Jansen, Vincent A A

    2013-12-01

    Current bee population declines and colony failures are well documented yet poorly understood and no single factor has been identified as a leading cause. The evidence is equivocal and puzzling: for instance, many pathogens and parasites can be found in both failing and surviving colonies and field pesticide exposure is typically sublethal. Here, we investigate how these results can be due to sublethal stress impairing colony function. We mathematically modelled stress on individual bees which impairs colony function and found how positive density dependence can cause multiple dynamic outcomes: some colonies fail while others thrive. We then exposed bumblebee colonies to sublethal levels of a neonicotinoid pesticide. The dynamics of colony failure, which we observed, were most accurately described by our model. We argue that our model can explain the enigmatic aspects of bee colony failures, highlighting an important role for sublethal stress in colony declines. PMID:24112478

  16. Chronic sublethal stress causes bee colony failure

    PubMed Central

    Bryden, John; Gill, Richard J; Mitton, Robert A A; Raine, Nigel E; Jansen, Vincent A A; Hodgson, David

    2013-01-01

    Current bee population declines and colony failures are well documented yet poorly understood and no single factor has been identified as a leading cause. The evidence is equivocal and puzzling: for instance, many pathogens and parasites can be found in both failing and surviving colonies and field pesticide exposure is typically sublethal. Here, we investigate how these results can be due to sublethal stress impairing colony function. We mathematically modelled stress on individual bees which impairs colony function and found how positive density dependence can cause multiple dynamic outcomes: some colonies fail while others thrive. We then exposed bumblebee colonies to sublethal levels of a neonicotinoid pesticide. The dynamics of colony failure, which we observed, were most accurately described by our model. We argue that our model can explain the enigmatic aspects of bee colony failures, highlighting an important role for sublethal stress in colony declines. PMID:24112478

  17. From yield to fracture, failure initiation captured by molecular simulation

    NASA Astrophysics Data System (ADS)

    Brochard, Laurent; Tejada, Ignacio G.; Sab, Karam

    2016-10-01

    While failure of cracked bodies with strong stress concentrations is described by an energy criterion (fracture mechanics), failure of flawless bodies with uniform stresses is captured by a criterion on stress (yielding). In-between those two cases, the problem of failure initiation from flaws that moderately concentrate stresses is debated. In this paper, we propose an investigation of the process of failure initiation at the atomic scale by means of molecular simulations. We first discuss the appropriate scaling conditions to capture initiation, since system sizes that can be simulated by molecular mechanics are strongly limited. Then, we perform a series of molecular simulations of failure of a 2D model material, which exhibits strength and toughness properties that are suitable to capture initiation with systems of reasonable sizes. Transition from fracture failure to yield failure is well characterized. Interestingly, in some specific cases, failure exceeds yield failure which is in contradiction with most initiation theories. This occurs when stress are highly concentrated while little mechanical energy is stored in the material. This observation calls for a theory of initiation which requires that both stress and energy are necessary conditions of failure. Such an approach was proposed by Leguillon (2002). We show that the predictions of this theory are consistent with the molecular simulation results.

  18. Electrophysiological Remodeling in Heart Failure

    PubMed Central

    Wang, Yanggan; Hill, Joseph A.

    2010-01-01

    Heart failure affects nearly 6 million Americans, with a half-million new cases emerging each year. Whereas up to 50% of heart failure patients die of arrhythmia, the diverse mechanisms underlying heart failure-associated arrhythmia are poorly understood. As a consequence, effectiveness of antiarrhythmic pharmacotherapy remains elusive. Here, we review recent advances in our understanding of heart failure-associated molecular events impacting the electrical function of the myocardium. We approach this from an anatomical standpoint, summarizing recent insights gleaned from pre-clinical models and discussing their relevance to human heart failure. PMID:20096285

  19. Failure is an option: Reactions to failure in elementary engineering design projects

    NASA Astrophysics Data System (ADS)

    Johnson, Matthew M.

    Recent reform documents in science education have called for teachers to use epistemic practices of science and engineering researchers to teach disciplinary content (NRC, 2007; NRC, 2012; NGSS Lead States, 2013). Although this creates challenges for classroom teachers unfamiliar with engineering, it has created a need for high quality research about how students and teachers engage in engineering activities to improve curriculum development and teaching pedagogy. While framers of the Next Generation Science Standards (NRC, 2012; NGSS Lead States 2013) focused on the similarities of the practices of science researchers and engineering designers, some have proposed that engineering has a unique set of epistemic practices, including improving from failure (Cunningham & Carlsen, 2014; Cunningham & Kelly, in review). While no one will deny failures occur in science, failure in engineering is thought of in fundamentally different ways. In the study presented here, video data from eight classes of elementary students engaged in one of two civil engineering units were analyzed using methods borrowed from psychology, anthropology, and sociolinguistics to investigate: 1) the nature of failure in elementary engineering design; 2) the ways in which teachers react to failure; and 3) how the collective actions of students and teachers support or constrain improvement in engineering design. I propose new ways of considering the types and causes of failure, and note three teacher reactions to failure: the manager, the cheerleader, and the strategic partner. Because the goal of iteration in engineering is improvement, I also studied improvement. Students only systematically improve when they have the opportunity, productive strategies, and fair comparisons between prototypes. I then investigate the use of student engineering journals to assess learning from the process of improvement after failure. After discussion, I consider implications from this work as well as future research

  20. Steam generator tube failures

    SciTech Connect

    MacDonald, P.E.; Shah, V.N.; Ward, L.W.; Ellison, P.G.

    1996-04-01

    A review and summary of the available information on steam generator tubing failures and the impact of these failures on plant safety is presented. The following topics are covered: pressurized water reactor (PWR), Canadian deuterium uranium (CANDU) reactor, and Russian water moderated, water cooled energy reactor (VVER) steam generator degradation, PWR steam generator tube ruptures, the thermal-hydraulic response of a PWR plant with a faulted steam generator, the risk significance of steam generator tube rupture accidents, tubing inspection requirements and fitness-for-service criteria in various countries, and defect detection reliability and sizing accuracy. A significant number of steam generator tubes are defective and are removed from service or repaired each year. This wide spread damage has been caused by many diverse degradation mechanisms, some of which are difficult to detect and predict. In addition, spontaneous tube ruptures have occurred at the rate of about one every 2 years over the last 20 years, and incipient tube ruptures (tube failures usually identified with leak detection monitors just before rupture) have been occurring at the rate of about one per year. These ruptures have caused complex plant transients which have not always been easy for the reactor operators to control. Our analysis shows that if more than 15 tubes rupture during a main steam line break, the system response could lead to core melting. Although spontaneous and induced steam generator tube ruptures are small contributors to the total core damage frequency calculated in probabilistic risk assessments, they are risk significant because the radionuclides are likely to bypass the reactor containment building. The frequency of steam generator tube ruptures can be significantly reduced through appropriate and timely inspections and repairs or removal from service.

  1. Renal failure in Yemen.

    PubMed

    Al-Rohani, M

    2004-01-01

    Renal failure remains a serious cause of mortality in Yemen. Our region has 1.25 million population and our hospital is the central hospital, which has a nephrology department and performs dialysis for the region. Between January 1998 and December 2002, we admitted 547 patients; including children, with acute renal failure (ARF) and chronic renal failure (CRF). CRF was observed in 400 patients, an incidence of 64 per million per year and a prevalence of 320 per million. ARF occurred in 147 persons with an incidence of 23.5 per million per year and a prevalence of 117.5 patients per million. Of all patients, 72% were adults (age range, 20-60 years) with a male preponderance. As a tropical country, malaria (27.9%), diarrhea (13.6%), and other infectious diseases were the main causes. Next most common were obstructive diseases causing CRF and ARF (26.8% and 12.9%, respectively), mainly urolithiasis, Schistosomiasis, and prostatic enlargement. However the cause of CRF in 57.5% of patients was unknown as most persons presented late with end-stage disease (64.7%), requiring immediate intervention. Other causes, such as hepatorenal syndrome, snake bite, diabetes mellitus, and hypertension, showed low occurrence rates. Patients presented to the hospital mostly in severe uremia and without a clear history of prior medications. The major findings were vomiting, acidosis, and hypertension with serum creatinine values ranging between 2.8-45 mg/dL (mean value, 13.4 mg/dL). Anemia was observed in 80.4% of CRF versus 62.6% of ARF patients. Hypertension prevalence was 65.5% among CRF patients, of whom 25% were in hypertensive crisis, whereas among ARF the prevalence was only 26.5%. PMID:15350475

  2. Renal Failure in Pregnancy.

    PubMed

    Balofsky, Ari; Fedarau, Maksim

    2016-01-01

    Renal failure during pregnancy affects both mother and fetus, and may be related to preexisting disease or develop secondary to diseases of pregnancy. Causes include hypovolemia, sepsis, shock, preeclampsia, thrombotic microangiopathies, and renal obstruction. Treatment focuses on supportive measures, while pharmacologic treatment is viewed as second-line therapy, and is more useful in mitigating harmful effects than treating the underlying cause. When supportive measures and pharmacotherapy prove inadequate, dialysis may be required, with the goal being to prolong pregnancy until delivery is feasible. Outcomes and recommendations depend primarily on the underlying cause.

  3. Sleep and Heart Failure.

    PubMed

    Nelson, Kimberly A; Trupp, Robin J

    2015-12-01

    Sleep deprivation occurs for many reasons but, when chronic in nature, has many consequences for optimal health and performance. Despite its high prevalence, sleep-disordered breathing is underrecognized and undertreated. This is especially true in the setting of heart failure, where sleep-disordered breathing affects more than 50% of patients. Although the optimal strategy to best identify patients is currently unknown, concerted and consistent efforts to support early recognition, diagnosis, and subsequent treatment should be encouraged. Optimization of guideline-directed medical therapy and concurrent treatment of sleep-disordered breathing are necessary to improve outcomes in this complex high-risk population. PMID:26567495

  4. SCADA alarms processing for wind turbine component failure detection

    NASA Astrophysics Data System (ADS)

    Gonzalez, E.; Reder, M.; Melero, J. J.

    2016-09-01

    Wind turbine failure and downtime can often compromise the profitability of a wind farm due to their high impact on the operation and maintenance (O&M) costs. Early detection of failures can facilitate the changeover from corrective maintenance towards a predictive approach. This paper presents a cost-effective methodology to combine various alarm analysis techniques, using data from the Supervisory Control and Data Acquisition (SCADA) system, in order to detect component failures. The approach categorises the alarms according to a reviewed taxonomy, turning overwhelming data into valuable information to assess component status. Then, different alarms analysis techniques are applied for two purposes: the evaluation of the SCADA alarm system capability to detect failures, and the investigation of the relation between components faults being followed by failure occurrences in others. Various case studies are presented and discussed. The study highlights the relationship between faulty behaviour in different components and between failures and adverse environmental conditions.

  5. Advanced Congestive Heart Failure Associated With Disseminated Intravascular Coagulopathy.

    PubMed

    Sarcon, Annahita; Liu, Xiaoli; Ton, David; Haywood, James; Hitchcock, Todd

    2015-01-01

    Background. Disseminated intravascular coagulopathy (DIC) is a complication of an underlying disease and not a primary illness. It is most commonly associated with sepsis, trauma, obstetrical complications, and malignancies. There are very few cases in the literature illustrating the association between DIC and congestive heart failure. Findings. In this report, we present a case of severe congestive heart failure, leading to biventricular thrombi and subsequently DIC. Conclusion. We suggest that the association between congestive heart failure and DIC is an underrecognized one. Congestive heart failure continues to remain a major cause of morbidity and mortality despite advances in medical therapies. Thus far, the precise role of coagulation factors in congestive heart failure is unknown. Further investigations are needed to elucidate the pathophysiology of congestive heart failure and coagulation factors.

  6. A modeling framework for system restoration from cascading failures.

    PubMed

    Liu, Chaoran; Li, Daqing; Zio, Enrico; Kang, Rui

    2014-01-01

    System restoration from cascading failures is an integral part of the overall defense against catastrophic breakdown in networked critical infrastructures. From the outbreak of cascading failures to the system complete breakdown, actions can be taken to prevent failure propagation through the entire network. While most analysis efforts have been carried out before or after cascading failures, restoration during cascading failures has been rarely studied. In this paper, we present a modeling framework to investigate the effects of in-process restoration, which depends strongly on the timing and strength of the restoration actions. Furthermore, in the model we also consider additional disturbances to the system due to restoration actions themselves. We demonstrate that the effect of restoration is also influenced by the combination of system loading level and restoration disturbance. Our modeling framework will help to provide insights on practical restoration from cascading failures and guide improvements of reliability and resilience of actual network systems.

  7. Troubleshooting failed sterilization loads: Process failures and wet packs/loads.

    PubMed

    Seavey, Rose

    2016-05-01

    Sterilization process failures may place patients at risk. It is important that IPs, managers, educators, and staff members responsible for sterilization in health care facilities understand what to do if there is a biological, chemical, or mechanical sterilization monitor failure, or a wet pack. Sterilization process failures occur for many reasons: a malfunctioning sterilizer, user error (eg, incorrect packaging or loading procedures or incorrect cycle selection), poor steam quality, and others. All process failures should be investigated and the root cause of the failure identified. Understanding the possible causes of sterilization process failures and investigating tools for failed loads can help with risk assessment and necessary corrective action.

  8. Troubleshooting failed sterilization loads: Process failures and wet packs/loads.

    PubMed

    Seavey, Rose

    2016-05-01

    Sterilization process failures may place patients at risk. It is important that IPs, managers, educators, and staff members responsible for sterilization in health care facilities understand what to do if there is a biological, chemical, or mechanical sterilization monitor failure, or a wet pack. Sterilization process failures occur for many reasons: a malfunctioning sterilizer, user error (eg, incorrect packaging or loading procedures or incorrect cycle selection), poor steam quality, and others. All process failures should be investigated and the root cause of the failure identified. Understanding the possible causes of sterilization process failures and investigating tools for failed loads can help with risk assessment and necessary corrective action. PMID:27131132

  9. [Cardiac failure in endocrine diseases].

    PubMed

    Hashizume, K

    1993-05-01

    Several endocrine diseases show the symptoms of cardiac failure. Among them, patients with acromegaly show a specific cardiomyopathy which results in a severe left-sided cardiac failure. Hypoparathyroidism also induces cardiac failure, which is resulted from hypocalcemia and low levels of serum parathyroid hormone. In the cases of hypothyroidism, the patients with myxedemal coma show a severe cardiac failure, which is characterized by disturbance of central nervous system, renal function, and cardiac function. In the patients with thyroid crisis (storm), the cardiac failure comes from the great reduction of cardiac output with dehydration. The reduction of circulation volume, observed in the patients with pheochromocytoma easily induces cardiac failure (shock) just after the removal of adrenal tumor. In patients with malignant carcinoid syndrome, right-sided ventricular failure which may be occurred through the actions of biogenic amines is observed. PMID:8331806

  10. Intelligent failure-tolerant control

    NASA Technical Reports Server (NTRS)

    Stengel, Robert F.

    1991-01-01

    An overview of failure-tolerant control is presented, beginning with robust control, progressing through parallel and analytical redundancy, and ending with rule-based systems and artificial neural networks. By design or implementation, failure-tolerant control systems are 'intelligent' systems. All failure-tolerant systems require some degrees of robustness to protect against catastrophic failure; failure tolerance often can be improved by adaptivity in decision-making and control, as well as by redundancy in measurement and actuation. Reliability, maintainability, and survivability can be enhanced by failure tolerance, although each objective poses different goals for control system design. Artificial intelligence concepts are helpful for integrating and codifying failure-tolerant control systems, not as alternatives but as adjuncts to conventional design methods.

  11. Teacher Perceptions of High School Student Failure in the Classroom: Identifying Preventive Practices of Failure Using Critical Incident Technique

    ERIC Educational Resources Information Center

    Kalahar, Kory G.

    2011-01-01

    Student failure is a prominent issue in many comprehensive secondary schools nationwide. Researchers studying error, reliability, and performance in organizations have developed and employed a method known as critical incident technique (CIT) for investigating failure. Adopting an action research model, this study involved gathering and analyzing…

  12. What is the optimal medical management of ischaemic heart failure?

    PubMed

    Cleland, J G; John, J; Dhawan, J; Clark, A

    2001-01-01

    Ischaemic heart disease is probably the most important cause of heart failure. All patients with heart failure may benefit from treatment designed to retard progressive ventricular dysfunction and arrhythmias. Patients with heart failure due to ischaemic heart disease may also, theoretically, benefit from treatments designed to relieve ischaemia and prevent coronary occlusion and from revascularisation. However, there is little evidence to show that effective treatments, such as angiotensin converting enzyme (ACE) inhibitors and beta-blockers, exert different effects in patients with heart failure with or without coronary disease. Moreover, there is no evidence that treatment directed specifically at myocardial ischaemia, whether or not symptomatic, or coronary disease alters outcome in patients with heart failure. Some agents, such as aspirin, designed to reduce the risk of coronary occlusion appear ineffective or harmful in patients with heart failure. There is no evidence, yet, that revascularisation improves prognosis in patients with heart failure, even in patients who are demonstrated to have extensive myocardial hibernation. On current evidence, revascularisation should be reserved for the relief of angina. Large-scale, randomised controlled trials are currently underway investigating the role of specific treatments targeted at coronary syndromes in patients who have heart failure. The CHRISTMAS study is investigating the effects of carvedilol in a large cohort of patients with and without hibernating myocardium. The WATCH study is comparing the efficacy of aspirin, clopidogrel and warfarin. The HEART-UK study is assessing the effect of revascularisation on mortality in patients with heart failure and myocardial hibernation. Smaller scale studies are currently assessing the safety and efficacy of statin therapy in patients with heart failure. Only when the results of these and other studies are known will it be possible to come to firm conclusions about

  13. Scaling of structural failure

    SciTech Connect

    Bazant, Z.P.; Chen, Er-Ping

    1997-01-01

    This article attempts to review the progress achieved in the understanding of scaling and size effect in the failure of structures. Particular emphasis is placed on quasibrittle materials for which the size effect is complicated. Attention is focused on three main types of size effects, namely the statistical size effect due to randomness of strength, the energy release size effect, and the possible size effect due to fractality of fracture or microcracks. Definitive conclusions on the applicability of these theories are drawn. Subsequently, the article discusses the application of the known size effect law for the measurement of material fracture properties, and the modeling of the size effect by the cohesive crack model, nonlocal finite element models and discrete element models. Extensions to compression failure and to the rate-dependent material behavior are also outlined. The damage constitutive law needed for describing a microcracked material in the fracture process zone is discussed. Various applications to quasibrittle materials, including concrete, sea ice, fiber composites, rocks and ceramics are presented.

  14. Telomeres and marrow failure.

    PubMed

    Calado, Rodrigo T

    2009-01-01

    Telomeres, repeat sequences at the ends of chromosomes, are protective chromosomal structures highly conserved from primitive organisms to humans. Telomeres inevitably shorten with every cell cycle, and telomere attrition has been hypothesized to be fundamental to normal senescence of cells, tissues, and organisms. Molecular mechanisms have evolved to maintain their length and protective function; telomerase (TERT) is a reverse transcriptase enzyme that uses an RNA molecule (TERC) as the template to elongate the 3' ends of telomeres. Shelterin is a collection of DNA-binding proteins that cover and protect telomeres. The recent discovery of inherited mutations in genes that function to repair telomeres as etiologic in a range of human diseases, which have clinical manifestations in diverse tissues, including the hematopoietic tissue, suggests that defects in telomere repair and protection can cause organ failure. Dyskeratosis congenita is the prototype of telomere diseases; it is characterized by bone marrow failure, mucocutaneous abnormalities, pulmonary fibrosis, liver cirrhosis, and increased susceptibility to cancer, including acute myeloid leukemia. Aplastic anemia, acute myeloid leukemia, and idiopathic pulmonary fibrosis also are associated with inherited mutations in telomere repair or protection genes. Additionally, telomere defects associate with predisposition to hematologic malignancy and epithelial tumors. Telomere erosion is abnormally rapid in patients with mutations in telomerase genes but also after hematopoietic stem cell transplant, and telomeres are naturally shorter in older individuals-all conditions associated with higher rates of malignant diseases. In human tissue culture, short telomeres produce end-to-end chromosome fusion, nonreciprocal translocations, and aneuploidy.

  15. Fracture, failure, and fragmentation

    SciTech Connect

    Dienes, J.K.

    1984-01-01

    Though continuum descriptions of material behavior are useful for many kinds of problems, particularly those involving plastic flow, a more general approach is required when the failure is likely to involve growth and coalescence of a large number of fractures, as in fragmentation. Failures of this kind appear frequently in rapid dynamic processes such as those resulting from impacts and explosions, particularly in the formation of spall fragments. In the first part of this paper an approach to formulating constitutive relations that accounts for the opening, shear and growth of an ensemble of cracks is discussed. The approach also accounts for plastic flow accompanying fragmentation. The resulting constitutive relations have been incorporated into a Lagrangean computer program. In the second part of this paper a theoretical approach to coalescence is described. The simplest formulation makes use of a linear Liouville equation, with crack growth limited by the mean free path of cracks, assumed constant. This approach allows for an anisotropic distribution of cracks. An alternative approach is also described in which the decrease of the mean free path with increasing crack size is accounted for, but the crack distribution is assumed isotropic. A reduction of the governing Liouville equation to an ordinary differential equation of third order is possible, and the result can be used to determine how mean-free-path decreases with increasing crack size.

  16. Obesity and heart failure.

    PubMed

    De Pergola, Giovanni; Nardecchia, Adele; Giagulli, Vito Angelo; Triggiani, Vincenzo; Guastamacchia, Edoardo; Minischetti, Manuela Castiglione; Silvestris, Franco

    2013-03-01

    Epidemiological studies have recently shown that obesity, and abdominal obesity in particular, is an independent risk factor for the development of heart failure (HF). Higher cardiac oxidative stress is the early stage of heart dysfunction due to obesity, and it is the result of insulin resistance, altered fatty acid and glucose metabolism, and impaired mitochondrial biogenesis. Extense myocyte hypertrophy and myocardial fibrosis are early microscopic changes in patients with HF, whereas circumferential strain during the left ventricular (LV) systole, LV increase in both chamber size and wall thickness (LV hypertrophy), and LV dilatation are the early macroscopic and functional alterations in obese developing heart failure. LV hypertrophy leads to diastolic dysfunction and subendocardial ischemia in obesity, and pericardial fat has been shown to be significantly associated with LV diastolic dysfunction. Evolving abnormalities of diastolic dysfunction may include progressive hypertrophy and systolic dysfunction, and various degrees of eccentric and/or concentric LV hypertrophy may be present with time. Once HF is established, overweight and obese have a better prognosis than do their lean counterparts with the same level of cardiovascular disease, and this phenomenon is called "obesity paradox". It is mainly due to lower muscle protein degradation, brain natriuretic peptide circulating levels and cardio-respiratory fitness than normal weight patients with HF.

  17. Insomnia Self-Management in Heart Failure

    ClinicalTrials.gov

    2016-05-11

    Cardiac Failure; Heart Failure; Congestive Heart Failure; Heart Failure, Congestive; Sleep Initiation and Maintenance Disorders; Chronic Insomnia; Disorders of Initiating and Maintaining Sleep; Fatigue; Pain; Depressive Symptoms; Sleep Disorders; Anxiety

  18. High-Temperature Graphitization Failure of Primary Superheater Tube

    NASA Astrophysics Data System (ADS)

    Ghosh, D.; Ray, S.; Roy, H.; Mandal, N.; Shukla, A. K.

    2015-12-01

    Failure of boiler tubes is the main cause of unit outages of the plant, which further affects the reliability, availability and safety of the unit. So failure analysis of boiler tubes is absolutely essential to predict the root cause of the failure and the steps are taken for future remedial action to prevent the failure in near future. This paper investigates the probable cause/causes of failure of the primary superheater tube in a thermal power plant boiler. Visual inspection, dimensional measurement, chemical analysis, metallographic examination and hardness measurement are conducted as the part of the investigative studies. Apart from these tests, mechanical testing and fractographic analysis are also conducted as supplements. Finally, it is concluded that the superheater tube is failed due to graphitization for prolonged exposure of the tube at higher temperature.

  19. Component failure data handbook

    SciTech Connect

    Gentillon, C.D.

    1991-04-01

    This report presents generic component failure rates that are used in reliability and risk studies of commercial nuclear power plants. The rates are computed using plant-specific data from published probabilistic risk assessments supplemented by selected other sources. Each data source is described. For rates with four or more separate estimates among the sources, plots show the data that are combined. The method for combining data from different sources is presented. The resulting aggregated rates are listed with upper bounds that reflect the variability observed in each rate across the nuclear power plant industry. Thus, the rates are generic. Both per hour and per demand rates are included. They may be used for screening in risk assessments or for forming distributions to be updated with plant-specific data.

  20. Copeptin in Heart Failure.

    PubMed

    Balling, Louise; Gustafsson, Finn

    2016-01-01

    Heart failure (HF) is one of the most common causes of hospitalization and mortality in the modern Western world and an increasing proportion of the population will be affected by HF in the future. Although HF management has improved quality of life and prognosis, mortality remains very high despite therapeutic options. Medical management consists of a neurohormonal blockade of an overly activated neurohormonal axis. No single marker has been able to predict or monitor HF with respect to disease progression, hospitalization, or mortality. New methods for diagnosis, monitoring therapy, and prognosis are warranted. Copeptin, a precursor of pre-provasopressin, is a new biomarker in HF with promising potential. Copeptin has been found to be elevated in both acute and chronic HF and is associated with prognosis. Copeptin, in combination with other biomarkers, could be a useful marker in the monitoring of disease severity and as a predictor of prognosis and survival in HF. PMID:26975969

  1. Failure to control gonorrhoea

    PubMed Central

    Guthe, T.

    1961-01-01

    There is increasing evidence of emerging resistance of the gonococcus to antibiotics, particularly penicillin, but apparent resistance may sometimes be due to concomitant infection with micro-organisms other than the gonococcus, which are not susceptible to this antibiotic. There is also evidence that clinical complications, particularly in the female, are much more frequent than was previously believed to be the case. The incidence of gonorrhoea has increased significantly in many countries in spite of the availability of the ”ideal” drug, penicillin. The reasons for the failure to control gonorrhoea in the individual and in the mass of patients are discussed, taking into account a number of factors relating to emerging drug resistance of the gonococcus, insufficient criteria for diagnosis, the possibility of persistence of infection and increased frequency of reinfection. PMID:13709981

  2. Iridium: failures & successes

    NASA Astrophysics Data System (ADS)

    Christensen, CarissaBryce; Beard, Suzette

    2001-03-01

    This paper will provide an overview of the Iridium business venture in terms of the challenges faced, the successes achieved, and the causes of the ultimate failure of the venture — bankruptcy and system de-orbit. The paper will address technical, business, and policy issues. The intent of the paper is to provide a balanced and accurate overview of the Iridium experience, to aid future decision-making by policy makers, the business community, and technical experts. Key topics will include the history of the program, the objectives and decision-making of Motorola, the market research and analysis conducted, partnering strategies and their impact, consumer equipment availability, and technical issues — target performance, performance achieved, technical accomplishments, and expected and unexpected technical challenges. The paper will use as sources trade media and business articles on the Iridium program, technical papers and conference presentations, Wall Street analyst's reports, and, where possible, interviews with participants and close observers.

  3. Premature ovarian failure.

    PubMed

    Vujović, Svetlana; Ivović, Miomira; Tancić-Gajić, Milina; Marina, Ljiljana; Barać, Marija; Arizanović, Zorana; Nenezić, Ana; Ivanisević, Maja; Micić, Jelena; Sajić, Silvija; Micić, Dragan

    2012-01-01

    Premature ovarian failure (POF) is the occurrence of hypergonadotropic hypoestrogenic amenorrhea in women under the age of forty years. It is idiopathic in 74-90% patients. Known cases can be divided into primary and secondary POF. In primary POF genetic aberrations can involve the X chromosome (monosomy, trisomy, translocations, deletions) or autosomes. Genetic mechanisms include reduced gene dosage and non-specific chromosome effects impairing meiosis, decreasing the pool of primordial follicles and increasing atresia due to apoptosis or failure of follicle maturation. Autoimmune ovarian damage is caused by alteration of T-cell subsets and T-cell mediated injury, increase of autoantibody producing B-cells, a low number of effector/cytotoxic lymphocyte, which decreases the number and activity of natural killer cells. Bilateral oophorectomy, chemotherapy, radiotherapy and infections cause the secondary POF. Symptoms of POF include irritability, nervousness, loss of libido, depression, lack of concentration, hot flushes, weight gaining, dry skin, vaginal dryness, frequent infections etc.The diagnosis is confirmed by the level of FSH of over 40 IU/L and estradiol below 50 pmol/L in women aged below 40 years. Biochemical and other hormonal analysis (free thyroxin, TSH, prolactin, testosterone), karyotype (<30 years of age), ultrasound of the breasts and pelvis are advisable. Optimal therapy is combined estrogen progestagen therapy given in a sequential rhythm, after excluding absolute contraindications. Testosterone can be added to adnexectomized women and those with a low libido. Sequential estrogen progestagen replacement therapy is the first line therapy for ovulation induction in those looking for pregnancy and after that oocyte donation will be advised. Appropriate estro-progestagen therapy improves the quality of life and prevents complications such as cardiovascular diseases, osteoporosis, stroke etc. PMID:23350261

  4. Forecasting the failure of heterogeneous magmas

    NASA Astrophysics Data System (ADS)

    Vasseur, J.; Wadsworth, F. B.; Lavallée, Y.; Bell, A. F.; Main, I. G.; Dingwell, D. B.

    2015-12-01

    Eruption prediction is a long-sought-after goal of volcanology. Yet applying existing techniques retrospectively (hindcasting), we fail to predict events more often than we success. As much of the seismicity associated with intermediate to silicic volcanic eruptions comes from the brittle response of the ascending magma itself, we clearly require a good understanding of the parameters that control the ability to forecast magma failure itself. Here, we present suites of controlled experiments at magmatic temperatures using a range of synthetic magmas to investigate the control of microstructures on the efficacy of forecast models for material failure. We find that the failure of magmas with very little microstructural heterogeneity - such as melts - is very challenging to predict; whereas, the failure of very heterogeneous magmas is always well-predicted. To shed further light on this issue, we provide a scaling law based on the relationship between the microstructural heterogeneity in a magma and the error in the prediction of its failure time. We propose this method be used to elucidate the variable success rate of predicting volcanic predictions. We discuss this scaling in the context of the birth, life and death of structural heterogeneity during magma ascent with specific emphasis on obsidian-forming eruptions such as Chaitèn, 2008. During such eruptions, the repetitive creation and destruction of fractures filled with granular magma, which are thought to be the in situ remnants of seismogenic fracturing itself, are expressions of the life-cycle of heterogeneity in an otherwise coherent, melt-rich magma. We conclude that the next generation of failure forecast tools available to monitoring teams should incorporate some acknowledgment of the magma microstructure and not be solely based on the geophysical signals prior to eruption.

  5. Probabilistic Failure Assessment For Fatigue

    NASA Technical Reports Server (NTRS)

    Moore, Nicholas; Ebbeler, Donald; Newlin, Laura; Sutharshana, Sravan; Creager, Matthew

    1995-01-01

    Probabilistic Failure Assessment for Fatigue (PFAFAT) package of software utilizing probabilistic failure-assessment (PFA) methodology to model high- and low-cycle-fatigue modes of failure of structural components. Consists of nine programs. Three programs perform probabilistic fatigue analysis by means of Monte Carlo simulation. Other six used for generating random processes, characterizing fatigue-life data pertaining to materials, and processing outputs of computational simulations. Written in FORTRAN 77.

  6. Diameter dependent failure current density of gold nanowires

    NASA Astrophysics Data System (ADS)

    Karim, S.; Maaz, K.; Ali, G.; Ensinger, W.

    2009-09-01

    Failure current density of single gold nanowires is investigated in this paper. Single wires with diameters ranging from 80 to 720 nm and length 30 µm were electrochemically deposited in ion track-etched single-pore polycarbonate membranes. The maximum current density was investigated while keeping the wires embedded in the polymer matrix and ramping up the current until failure occurred. The current density is found to increase with diminishing diameter and the wires with a diameter of 80 nm withstand 1.2 × 1012 A m-2 before undergoing failure. Possible reasons for these results are discussed in this paper.

  7. A traffic accident caused by fatigue failure of axle.

    PubMed

    Park, Chan-Seong; Lee, Sang-Hoon; Lee, Kyu-Jung

    2007-09-01

    An investigation of a traffic accident involving a tractor-trailer and a passenger car that were traveling at high speed is presented. The cause was the fracture of a trailer axle. The investigation showed that the fracture was because of the fatigue failure. In addition, cracks were found in the remaining three trailer wheels. Hardness measurements showed that, because of inadequate heat treatment of the metal, they were prone to failure.

  8. Heart failure in South America.

    PubMed

    Bocchi, Edimar Alcides

    2013-05-01

    Continued assessment of temporal trends in mortality and epidemiology of specific heart failure in South America is needed to provide a scientific basis for rational allocation of the limited health care resources, and strategies to reduce risk and predict the future burden of heart failure. The epidemiology of heart failure in South America was reviewed. Heart failure is the main cause of hospitalization based on available data from approximately 50% of the South American population. The main etiologies of heart failure are ischemic, idiopathic dilated cardiomyopathy, valvular, hypertensive and chagasic etiologies. In endemic areas, Chagas heart disease may be responsible by 41% of the HF cases. Also, heart failure presents high mortality especially in patients with Chagas etiology. Heart failure and etiologies associated with heart failure may be responsible for 6.3% of causes of deaths. Rheumatic fever is the leading cause of valvular heart disease. However, a tendency to reduction of HF mortality due to Chagas heart disease from 1985 to 2006, and reduction in mortality due to HF from 1999 to 2005 were observed in selected states in Brazil. The findings have important public health implications because the allocation of health care resources, and strategies to reduce risk of heart failure should also consider the control of neglected Chagas disease and rheumatic fever in South American countries.

  9. Heart Failure in South America

    PubMed Central

    Bocchi, Edimar Alcides

    2013-01-01

    Continued assessment of temporal trends in mortality and epidemiology of specific heart failure in South America is needed to provide a scientific basis for rational allocation of the limited health care resources, and strategies to reduce risk and predict the future burden of heart failure. The epidemiology of heart failure in South America was reviewed. Heart failure is the main cause of hospitalization based on available data from approximately 50% of the South American population. The main etiologies of heart failure are ischemic, idiopathic dilated cardiomyopathy, valvular, hypertensive and chagasic etiologies. In endemic areas, Chagas heart disease may be responsible by 41% of the HF cases. Also, heart failure presents high mortality especially in patients with Chagas etiology. Heart failure and etiologies associated with heart failure may be responsible for 6.3% of causes of deaths. Rheumatic fever is the leading cause of valvular heart disease. However, a tendency to reduction of HF mortality due to Chagas heart disease from 1985 to 2006, and reduction in mortality due to HF from 1999 to 2005 were observed in selected states in Brazil. The findings have important public health implications because the allocation of health care resources, and strategies to reduce risk of heart failure should also consider the control of neglected Chagas disease and rheumatic fever in South American countries. PMID:23597301

  10. Strategies of learning from failure.

    PubMed

    Edmondson, Amy C

    2011-04-01

    Many executives believe that all failure is bad (although it usually provides Lessons) and that Learning from it is pretty straightforward. The author, a professor at Harvard Business School, thinks both beliefs are misguided. In organizational life, she says, some failures are inevitable and some are even good. And successful learning from failure is not simple: It requires context-specific strategies. But first leaders must understand how the blame game gets in the way and work to create an organizational culture in which employees feel safe admitting or reporting on failure. Failures fall into three categories: preventable ones in predictable operations, which usually involve deviations from spec; unavoidable ones in complex systems, which may arise from unique combinations of needs, people, and problems; and intelligent ones at the frontier, where "good" failures occur quickly and on a small scale, providing the most valuable information. Strong leadership can build a learning culture-one in which failures large and small are consistently reported and deeply analyzed, and opportunities to experiment are proactively sought. Executives commonly and understandably worry that taking a sympathetic stance toward failure will create an "anything goes" work environment. They should instead recognize that failure is inevitable in today's complex work organizations.

  11. Public Choice, Market Failure, and Government Failure in Principles Textbooks

    ERIC Educational Resources Information Center

    Fike, Rosemarie; Gwartney, James

    2015-01-01

    Public choice uses the tools of economics to analyze how the political process allocates resources and impacts economic activity. In this study, the authors examine twenty-three principles texts regarding coverage of public choice, market failure, and government failure. Approximately half the texts provide coverage of public choice and recognize…

  12. The influence of gouge defects on failure pressure of steel pipes

    NASA Astrophysics Data System (ADS)

    Alang, N. A.; Razak, N. A.; Zulfadli, M. R.

    2013-12-01

    Failure pressure of API X42 steel pipes with gouge defects was estimated through a nonlinear finite element (FE) analysis. The effect of gouge length on failure pressure of different pipe diameters was investigated. Stress modified critical strain (SMCS) model was applied as in predicting the failure of the pipe. The model uses strain based criteria to predict the failure. For validation of the model, the FE results were compared to experimental data in literature showing overall good agreement. The results show that the gouge length has significant influence on failure pressure. A smaller pipe diameter gives highest value of failure pressure.

  13. Failure to Replicate: Sound the Alarm.

    PubMed

    Ioannidis, John P A

    2015-01-01

    Science has always relied on reproducibility to build confidence in experimental results. Now, the most comprehensive investigation ever done about the rate and predictors of reproducibility in social and cognitive sciences has found that regardless of the analytic method or criteria used, fewer than half of the original findings were successfully replicated. While a failure to reproduce does not necessarily mean the original report was incorrect, the results suggest that more rigorous methods are long overdue. PMID:27420921

  14. Fulminant hepatic failure.

    PubMed

    Sass, David A; Shakil, A Obaid

    2003-12-01

    FHF is a devastating illness of varied causes, carrying considerable mortality and affecting patients with previously healthy livers. The clinical presentation varies widely but encephalopathy is the defining criterion. Management requires a multidisciplinary approach, including rapid triage, monitoring, and referral to a transplantation center for further evaluation. Early prognostication and timely availability of donor livers are essential for a successful outcome. A donor shortage, however, continues to pose problems for both hepatologists and surgeons. Effective liver support devices may greatly prolong the window of opportunity to provide a donor liver, or alternatively to allow the native liver to regenerate. Despite decades of great progress in the field of liver support systems, the ideal system is still a long-cherished goal in hepatology. Hybrid systems have garnered most of the recent attention, but the quest for improved synthetic function has not yet been realized. It is hoped that rapid conceptual and technologic developments with respect to hybrid systems, hepatocyte transplantation, and xenografting will yield a safe and accessible tool for managing these critically ill patients. Controlled, multicenter trials in well-defined patient groups and with standard outcome measures are essential to evaluate the clinical value of these devices. A better understanding of mechanisms responsible for liver cell death and multiorgan failure, and the development of strategies to enhance liver regeneration, may allow a more targeted approach to therapy.

  15. Biomarkers in acute heart failure.

    PubMed

    Mallick, Aditi; Januzzi, James L

    2015-06-01

    The care of patients with acutely decompensated heart failure is being reshaped by the availability and understanding of several novel and emerging heart failure biomarkers. The gold standard biomarkers in heart failure are B-type natriuretic peptide and N-terminal pro-B-type natriuretic peptide, which play an important role in the diagnosis, prognosis, and management of acute decompensated heart failure. Novel biomarkers that are increasingly involved in the processes of myocardial injury, neurohormonal activation, and ventricular remodeling are showing promise in improving diagnosis and prognosis among patients with acute decompensated heart failure. These include midregional proatrial natriuretic peptide, soluble ST2, galectin-3, highly-sensitive troponin, and midregional proadrenomedullin. There has also been an emergence of biomarkers for evaluation of acute decompensated heart failure that assist in the differential diagnosis of dyspnea, such as procalcitonin (for identification of acute pneumonia), as well as markers that predict complications of acute decompensated heart failure, such as renal injury markers. In this article, we will review the pathophysiology and usefulness of established and emerging biomarkers for the clinical diagnosis, prognosis, and management of acute decompensated heart failure.

  16. Compression failure of composite laminates

    NASA Technical Reports Server (NTRS)

    Pipes, R. B.

    1983-01-01

    This presentation attempts to characterize the compressive behavior of Hercules AS-1/3501-6 graphite-epoxy composite. The effect of varying specimen geometry on test results is examined. The transition region is determined between buckling and compressive failure. Failure modes are defined and analytical models to describe these modes are presented.

  17. Failure to Manage Constant Change

    ERIC Educational Resources Information Center

    McDonald, Ann

    2010-01-01

    This study examines patterns of system failure (communication, typographic, material, economic, maintenance) and the resulting workarounds in signs that are intended to communicate frequently changing information in the built environment. The observed failures and workarounds in the communication of ephemeral data and the accompanying narratives…

  18. A failure diagnosis and impact assessment prototype for Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Baker, Carolyn G.; Marsh, Christopher A.

    1991-01-01

    NASA is investigating the use of advanced automation to enhance crew productivity for Space Station Freedom in numerous areas, one being failure management. A prototype is described that diagnoses failure sources and assesses the future impacts of those failures on other Freedom entities.

  19. Failure detection system risk reduction assessment

    NASA Technical Reports Server (NTRS)

    Aguilar, Robert B. (Inventor); Huang, Zhaofeng (Inventor)

    2012-01-01

    A process includes determining a probability of a failure mode of a system being analyzed reaching a failure limit as a function of time to failure limit, determining a probability of a mitigation of the failure mode as a function of a time to failure limit, and quantifying a risk reduction based on the probability of the failure mode reaching the failure limit and the probability of the mitigation.

  20. Intelligent Design and Intelligent Failure

    NASA Technical Reports Server (NTRS)

    Jerman, Gregory

    2015-01-01

    Good Evening, my name is Greg Jerman and for nearly a quarter century I have been performing failure analysis on NASA's aerospace hardware. During that time I had the distinct privilege of keeping the Space Shuttle flying for two thirds of its history. I have analyzed a wide variety of failed hardware from simple electrical cables to cryogenic fuel tanks to high temperature turbine blades. During this time I have found that for all the time we spend intelligently designing things, we need to be equally intelligent about understanding why things fail. The NASA Flight Director for Apollo 13, Gene Kranz, is best known for the expression "Failure is not an option." However, NASA history is filled with failures both large and small, so it might be more accurate to say failure is inevitable. It is how we react and learn from our failures that makes the difference.

  1. Cascading failure analysis and restoration strategy in an interdependent network

    NASA Astrophysics Data System (ADS)

    Hong, Sheng; Lv, Chuan; Zhao, Tingdi; Wang, Baoqing; Wang, Jianghui; Zhu, Juxing

    2016-05-01

    In modern society, many infrastructures are interdependent owing to functional and logical relations among components in different systems. These networked infrastructures can be modeled as interdependent networks. In the real world, different networks carry different traffic loads whose values are dynamic and stem from the load redistribution in the same network and disturbance from the interdependent network. Interdependency makes interdependent networks so fragile that even a slight initial disturbance may lead to a cascading failure of the entire systems. In this paper, interdependencies among networks are modeled and a failure cascade process is studied considering their effects on failure propagation. Meanwhile, an in-process restoration strategy after the initial failure is investigated. The restoration effects depend strongly on the trigger timing, restoration probability and priority of the restoration actions along with the additional disturbances. Our findings highlight the necessity to decrease the large-scale cascading failure by structuring and managing an interdependent network reasonably.

  2. The role of rigidity in controlling material failure

    PubMed Central

    Driscoll, Michelle M.; Chen, Bryan Gin-ge; Beuman, Thomas H.; Ulrich, Stephan; Nagel, Sidney R.; Vitelli, Vincenzo

    2016-01-01

    We investigate how material rigidity acts as a key control parameter for the failure of solids under stress. In both experiments and simulations, we demonstrate that material failure can be continuously tuned by varying the underlying rigidity of the material while holding the amount of disorder constant. As the rigidity transition is approached, failure due to the application of uniaxial stress evolves from brittle cracking to system-spanning diffuse breaking. This evolution in failure behavior can be parameterized by the width of the crack. As a system becomes more and more floppy, this crack width increases until it saturates at the system size. Thus, the spatial extent of the failure zone can be used as a direct probe for material rigidity. PMID:27621463

  3. The Current and Potential Clinical Relevance of Heart Failure Biomarkers.

    PubMed

    Gandhi, Parul U; Testani, Jeffrey M; Ahmad, Tariq

    2015-10-01

    Heart failure is a growing epidemic, and our understanding of the intricacies of its pathophysiology continues to evolve. Over the last decade, biomarkers of heart failure have been extensively investigated, particularly for diagnosis and risk stratification. While the natriuretic peptides remain the gold standard heart failure biomarker, they are plagued by their non-specific nature; furthermore, the strategy of natriuretic peptide-guided care remains elusive. Multiple candidate markers indicative of other physiologic aspects of heart failure have been identified and studied, including soluble ST2, galectin-3, and high-sensitivity cardiac troponins. Each of these biomarkers has the potential to provide unique therapeutically relevant information. Ultimately, a multi-marker approach may be applied to improve care of patients with heart failure. Definitive clinical trials and the use of advanced statistical analytic techniques are needed to truly determine the optimal strategy of biomarker-assisted diagnosis, prognostication, and management of patients who suffer from this devastating condition.

  4. Heart failure in North America.

    PubMed

    Blair, John E A; Huffman, Mark; Shah, Sanjiv J

    2013-05-01

    Heart failure is a major health problem that affects patients and healthcare systems worldwide. Within the continent of North America, differences in economic development, genetic susceptibility, cultural practices, and trends in risk factors and treatment all contribute to both inter-continental and within-continent differences in heart failure. The United States and Canada represent industrialized countries with similar culture, geography, and advanced economies and infrastructure. During the epidemiologic transition from rural to industrial in countries such as the United States and Canada, nutritional deficiencies and infectious diseases made way for degenerative diseases such as cardiovascular diseases, cancer, overweight/obesity, and diabetes. This in turn has resulted in an increase in heart failure incidence in these countries, especially as overall life expectancy increases. Mexico, on the other hand, has a less developed economy and infrastructure, and has a wide distribution in the level of urbanization as it becomes more industrialized. Mexico is under a period of epidemiologic transition and the etiology and incidence of heart failure is rapidly changing. Ethnic differences within the populations of the United States and Canada highlight the changing demographics of each country as well as potential disparities in heart failure care. Heart failure with preserved ejection fraction makes up approximately half of all hospital admissions throughout North America; however, important differences in demographics and etiology exist between countries. Similarly, acute heart failure etiology, severity, and management differ between countries in North America. The overall economic burden of heart failure continues to be large and growing worldwide, with each country managing this burden differently. Understanding the inter-and within-continental differences may help improve understanding of the heart failure epidemic, and may aid healthcare systems in delivering

  5. Adaptive control of nonlinear systems with actuator failures and uncertainties

    NASA Astrophysics Data System (ADS)

    Tang, Xidong

    2005-11-01

    Actuator failures have damaging effect on the performance of control systems, leading to undesired system behavior or even instability. Actuator failures are unknown in terms of failure time instants, failure patterns, and failure parameters. For system safety and reliability, the compensation of actuator failures is of both theoretical and practical significance. This dissertation is to further the study of adaptive designs for actuator failure compensation to nonlinear systems. In this dissertation a theoretical framework for adaptive control of nonlinear systems with actuator failures and system uncertainties is established. The contributions are the development of new adaptive nonlinear control schemes to handle unknown actuator failures for convergent tracking performance, the specification of conditions as a guideline for applications and system designs, and the extension of the adaptive nonlinear control theory. In the dissertation, adaptive actuator failure compensation is studied for several classes of nonlinear systems. In particular, adaptive state feedback schemes are developed for feedback linearizable systems and parametric strict-feedback systems. Adaptive output feedback schemes are deigned for output-feedback systems and a class of systems with unknown state-dependent nonlinearities. Furthermore, adaptive designs are addressed for MIMO systems with actuator failures, based on two grouping techniques: fixed grouping and virtual grouping. Theoretical issues such as controller structures, actuation schemes, zero dynamics, observation, grouping conditions, closed-loop stability, and tracking performance are extensively investigated. For each scheme, design conditions are clarified, and detailed stability and performance analysis is presented. A variety of applications including a wing-rock model, twin otter aircraft, hypersonic aircraft, and cooperative multiple manipulators are addressed with simulation results showing the effectiveness of the

  6. Coupling Between Knickpoint Migration and Hillslope Failures: an Experimental Study

    NASA Astrophysics Data System (ADS)

    Bigi, A.; Hasbargen, L.; Paola, C.

    2002-12-01

    We designed a physical experiment to investigate the strength of coupling between stream incision and hillslope failures in a drainage basin at steady state, where erosion and uplift rates are balanced over the entire basin. The experimental basin is a circular tank roughly 1 m in diameter and 1 m deep. The substrate consists of silica silt mixed with kaolinite. Greenhouse misters generate rainfall over the surface, and runoff exits the tank at a motor controlled gate, which we drop continuously during an experiment. These conditions allow a 3-5 order drainage basin to develop and erode through several units of relief. Dominant erosive processes in the basin include surface runoff, hillslope failures, and knickpoints in streams. We mapped in detail knickpoint and hillslope failures over a length of time required to erode through half of the total instantaneous relief. In general, knickpoint migration rates decrease in upstream reaches. Hillslope failure size distributions exhibit large numbers of small events, with decreasing numbers of large events, similar to power law distributions observed for natural landscapes. The fraction of total erosion represented by hillslope failures is about 15%, implying that surface runoff on hillslopes accounts for a large portion of erosion in the experiment we present here. We also observed cycles of increased deposition in valleys followed by knickpoint generation and excavation. We hypothesized that knickpoint migration and hillslope failure activity would be strongly coupled, that is, hillslope failure activity would increase in the wake of a migrating knickpoint. Our results suggest that hillslope failures are not directly tied to knickpoint migration. As a measure of hillslope failure scatter, we compare hillslope failure locations to a Monte Carlo simulation of randomly scattered events across the basin. Initial results suggest that experimental failures exhibit little difference from randomly scattered events.

  7. Patterns of Locoregional Failure After Exclusive IMRT for Oropharyngeal Carcinoma

    SciTech Connect

    Sanguineti, Giuseppe Gunn, G. Brandon; Endres, Eugene J.; Chaljub, Gregory; Cheruvu, Praveena; Parker, Brent

    2008-11-01

    Purpose: To assess the patterns of failure after intensity-modulated radiotherapy (IMRT) for oropharyngeal squamous cell carcinoma (SCC). Methods and Materials: We analyzed patients treated at the University of Texas Medical Branch between May 2002 and February 2006 who met the following criteria: (1) definitive IMRT without chemotherapy for oropharyngeal SCC; (2) no pretreatment radical surgery; (3) minimal follow-up of 1 year. The location of each nodal/primary failure was co-registered to the pretreatment planning computed tomography scan and then expanded by 5 mm to a planning target volume (PTV) of the failure (PTV-f). We then investigated whether the prescription dose to the PTV-f had been appropriate for the amount of disease present before treatment and whether the PTV-f had been adequately covered. Results: A total of 50 patients were eligible. With a median follow-up of 32.6 months (range, 12.1-58.6), three local and six regional failures were observed in 8 patients. All but one failure, that had been neglected, were recorded within 14 months of the treatment end. Of the nine failures, four developed in the neck treated electively to the lowest dose level; in all of them, we could retrospectively identify initial positive lymph nodes that might have justified the subsequent failure. The remaining five failures developed in proximity of the high-dose volume. In all but one, the volume of region of interest receiving {>=}95% of the dose of the PTV-f was >95%, suggesting adequate coverage. In 1 patient, about 20% of PTV-f was outside the 95% isodose, so that marginal underdosing could not be ruled out. Conclusions: A potential cause could be identified in all the failures in the lowest dose level. The implications and possible remedies are discussed. Most failures around the high-dose region were 'true failures' with no apparent technical caus000.

  8. [Premature ovarian failures].

    PubMed

    Bricaire, Léopoldine; Laroche, Emmanuelle; Bourcigaux, Nathalie; Donadille, Bruno; Christin-Maitre, Sophie

    2013-11-01

    Premature ovarian failure (POF) is clinically suspected by amenorrhea and confirmed by an elevated FSH serum level above 40 mUI/L (even 20 mUI/L) twice, in a woman before the age of 40. Prevalence of POF is between 1 to 2% in women. In 90% of cases, no aetiology is identified. Obvious causes are chemotherapy, pelvic radiotherapy, ovarian surgery and diethylstilbestrol exposure in utero. A karyotype should be performed as Turner Syndrome is the most frequent genetic cause of POF. Some X abnormalities such as X deletion or X autosome translocation can be found. FMR1 pre-mutation (fragile X syndrome) should be searched for, even though no cases of mental retardation are known, in the family. Other genetic abnormalities can be suggested by associated symptoms (i.e.: FOXL2, SF1 mutations). Auto-immune aetiology can be suspected if other auto-immune features are present, however, there are no reliable auto-antibodies to confirm auto-immunity in POF. Treatment of POF is based on hormonal replacement therapy in order to avoid estrogen deficiency, suppress vasomotor symptoms and avoid bone loss as well as cardiovascular risk. Estrogens should be associated with progesterone or a progestin, at least up to the age of 51. Patients with POF should be informed that spontaneous pregnancies may occur (in 5% of cases). In case of desire of pregnancy, the patient should be oriented to a specialized unit for in vitro fertilization with oocyte donation. Psychological support is essential and should be part of the treatment. POF is associated with an increased risk of emotional distress and depression. No preventive treatment of POF is available so far. PMID:24157186

  9. Global Failure Modes in Composite Structures

    NASA Technical Reports Server (NTRS)

    Knauss, W. G.; Gonzalez, Luis

    2001-01-01

    . The question of "scaling" is an essential concern in any structural materials investigation. For example, experiments in the past have shown that the "strength" of a composite depends on hole size. As a consequence the validity of traditional fracture mechanics concepts applied to composite materials failure must be questioned. The size of the fibers, the dimensions of the laminae, etc. together with the fact that, because of the layered anisotropy, the stress field is no longer two-dimensional, prevent the otherwise obviously confident use of "similarity concepts". Therefore, the question needs to be raised of whether in composites "size matters or not", i.e., whether the results obtained in a laboratory using small coupons are truly representative of the situation involving a full scale component.

  10. Failure environment analysis tool applications

    NASA Technical Reports Server (NTRS)

    Pack, Ginger L.; Wadsworth, David B.

    1994-01-01

    Understanding risks and avoiding failure are daily concerns for the women and men of NASA. Although NASA's mission propels us to push the limits of technology, and though the risks are considerable, the NASA community has instilled within it, the determination to preserve the integrity of the systems upon which our mission and, our employees lives and well-being depend. One of the ways this is being done is by expanding and improving the tools used to perform risk assessment. The Failure Environment Analysis Tool (FEAT) was developed to help engineers and analysts more thoroughly and reliably conduct risk assessment and failure analysis. FEAT accomplishes this by providing answers to questions regarding what might have caused a particular failure; or, conversely, what effect the occurrence of a failure might have on an entire system. Additionally, FEAT can determine what common causes could have resulted in other combinations of failures. FEAT will even help determine the vulnerability of a system to failures, in light of reduced capability. FEAT also is useful in training personnel who must develop an understanding of particular systems. FEAT facilitates training on system behavior, by providing an automated environment in which to conduct 'what-if' evaluation. These types of analyses make FEAT a valuable tool for engineers and operations personnel in the design, analysis, and operation of NASA space systems.

  11. Failure environment analysis tool applications

    NASA Technical Reports Server (NTRS)

    Pack, Ginger L.; Wadsworth, David B.

    1993-01-01

    Understanding risks and avoiding failure are daily concerns for the women and men of NASA. Although NASA's mission propels us to push the limits of technology, and though the risks are considerable, the NASA community has instilled within, the determination to preserve the integrity of the systems upon which our mission and, our employees lives and well-being depend. One of the ways this is being done is by expanding and improving the tools used to perform risk assessment. The Failure Environment Analysis Tool (FEAT) was developed to help engineers and analysts more thoroughly and reliably conduct risk assessment and failure analysis. FEAT accomplishes this by providing answers to questions regarding what might have caused a particular failure; or, conversely, what effect the occurrence of a failure might have on an entire system. Additionally, FEAT can determine what common causes could have resulted in other combinations of failures. FEAT will even help determine the vulnerability of a system to failures, in light of reduced capability. FEAT also is useful in training personnel who must develop an understanding of particular systems. FEAT facilitates training on system behavior, by providing an automated environment in which to conduct 'what-if' evaluation. These types of analyses make FEAT a valuable tool for engineers and operations personnel in the design, analysis, and operation of NASA space systems.

  12. New medications for heart failure.

    PubMed

    Gordin, Jonathan S; Fonarow, Gregg C

    2016-08-01

    Heart failure is common and results in substantial morbidity and mortality. Current guideline-based therapies for heart failure with reduced ejection fraction, including beta blockers, angiotensin converting enzyme (ACE) inhibitors, and aldosterone antagonists aim to interrupt deleterious neurohormonal pathways and have shown significant success in reducing morbidity and mortality associated with heart failure. Continued efforts to further improve outcomes in patients with heart failure with reduced ejection fraction have led to the first new-in-class medications approved for heart failure since 2005, ivabradine and sacubitril/valsartan. Ivabradine targets the If channels in the sinoatrial node of the heart, decreasing heart rate. Sacubitril/valsartan combines a neprilysin inhibitor that increases levels of beneficial vasodilatory peptides with an angiotensin receptor antagonist. On a background of previously approved, guideline-directed medical therapies for heart failure, these medications have shown improved clinical outcomes ranging from decreased hospitalizations in a select group of patients to a reduction in all-cause mortality across all pre-specified subgroups. In this review, we will discuss the previously established guideline-directed medical therapies for heart failure with reduced ejection fraction, the translational research that led to the development of these new therapies, and the results from the major clinical trials of ivabradine and sacubitril/valsartan. PMID:27038558

  13. Failure Analysis and Mechanisms of Failure of Fibrous Composite Structures

    NASA Technical Reports Server (NTRS)

    Noor, A. K. (Compiler); Shuart, M. J. (Compiler); Starnes, J. H., Jr. (Compiler); Williams, J. G. (Compiler)

    1983-01-01

    The state of the art of failure analysis and current design practices, especially as applied to the use of fibrous composite materials in aircraft structures is discussed. Deficiencies in these technologies are identified, as are directions for future research.

  14. Composite failure prediction of π-joint structures under bending

    NASA Astrophysics Data System (ADS)

    Huang, Hong-mei; Yuan, Shen-fang

    2012-03-01

    In this article, the composite -joint is investigated under bending loads. The "L" preform is the critical component regarding composite -joint failure. The study is presented in the failure detection of a carbon fiber composite -joint structure under bending loads using fiber Bragg grating (FBG) sensor. Firstly, based on the general finite element method (FEM) software, the 3-D finite element (FE) model of composite -joint is established, and the failure process and every lamina failure load of composite -joint are investigated by maximum stress criteria. Then, strain distributions along the length of FBG are extracted, and the reflection spectra of FBG are calculated according to the strain distribution. Finally, to verify the numerical results, a test scheme is performed and the experimental spectra of FBG are recorded. The experimental results indicate that the failure sequence and the corresponding critical loads of failure are consistent with the numerical predictions, and the computational error of failure load is less than 6.4%. Furthermore, it also verifies the feasibility of the damage detection system.

  15. [Syndrome of multiple organ failure].

    PubMed

    Charbonneau, P; Suisse, A

    1990-11-01

    The multiple organ failure syndrome (MOF) is a relatively new entity defined as the successive occurrence of respiratory (ARDS), hepatic, renal, myocardial, gastro-intestinal or neurological failure in patients with hyperkinetic haemodynamic and hypermetabolic states. The etiologies are: infection, septic and non-septic shock, burns and multiple injuries. The MOF syndrome is considered to be a generalised "inflammatory reaction" to tissue aggression involving a cascade of mediatory factors (TNF, interleukines...) of macrophagic, lymphocytic origin, causing multiple organ failure. The treatment depends on early correction of cellular hypoxia related to circulatory disturbances, nutritional support, anti-infective therapy and, in the near future, "control of mediator activity" (immunotherapy).

  16. Offshore pipeline failures. Master's thesis

    SciTech Connect

    Woodson, R.D.

    1990-12-01

    An overview of current concerns in the regulation of offshore pipelines is presented along with tabulated summaries of pipeline failure causes, failure prevention techniques, and pipeline monitoring and early intervention techniques. A database of over 1000 offshore pipeline failures in the Gulf of Mexico Offshore waters has been compiled from combined records of the Department of Transportation Office of pipeline Safety, U.S. Coast Guard National Response Center, and the Department of Interior Minerals Management Service. The data has been analyzed to identify trends and initial recommendations for future data collection have been suggested.

  17. Acute liver failure in children.

    PubMed

    Devictor, Denis; Tissieres, Pierre; Afanetti, Mickael; Debray, Dominique

    2011-06-01

    The management of children with acute liver failure mandates a multidisciplinary approach and intense monitoring. In recent years, considerable progress has been made in developing specific and supportive medical measures, but clinical studies have mainly concerned adult patients. There are no specific medical therapies, except for a few metabolic diseases presenting with acute liver failure. Liver transplantation still remains the only definitive therapy in most instances. Recent clinical studies suggest that hepatocyte transplantation may be useful for bridging patients to liver transplantation, for providing metabolic support during liver failure and for replacing liver transplantation in certain metabolic liver diseases.

  18. Mars Exploration Rover potentiometer problems, failures and lessons learned

    NASA Technical Reports Server (NTRS)

    Balzer, Mark A.

    2006-01-01

    During qualification testing of three types of nonwire-wound precision potentiometers for the Mars Exploration Rover, a variety of problems and failures were encountered. This paper will describe some of the more interesting problems, detail their investigations and present their final solutions. The failures were found to be caused by design errors, manufacturing errors, improper handling, test errors, and carelessness. A trend of decreasing total resistance was noted, and a resistance histogram was used to identify an outlier. A gang fixture is described for simultaneously testing multiple pots, and real time X-ray imaging was used extensively to assist in the failure analyses. Lessons learned are provided.

  19. Mars Exploration Rover Potentiometer Problems, Failures and Lessons Learned

    NASA Technical Reports Server (NTRS)

    Balzer, Mark

    2006-01-01

    During qualification testing of three types of non-wire-wound precision potentiometers for the Mars Exploration Rover, a variety of problems and failures were encountered. This paper will describe some of the more interesting problems, detail their investigations and present their final solutions. The failures were found to be caused by design errors, manufacturing errors, improper handling, test errors, and carelessness. A trend of decreasing total resistance was noted, and a resistance histogram was used to identify an outlier. A gang fixture is described for simultaneously testing multiple pots, and real time X-ray imaging was used extensively to assist in the failure analyses. Lessons learned are provided.

  20. Acute renal failure in the "Comrades Marathon" runners.

    PubMed

    Seedat, Y K; Aboo, N; Naicker, S; Parsoo, I

    This study investigated the clinical and biochemical features of acute renal failure in marathon runners. Over a period of 18 years (1969-1986), 19 patients were admitted to the renal unit. The histories and biochemical data of 4 patients seen in 1986 are described. The pathophysiology of acute renal failure is multifactorial and is the combined effect of rhabdomyolysis, dehydration, hypotension, nonsteroidal anti-inflammatory drugs, and hyperuricaemia. Efforts to correct dehydration have resulted in a decrease in the incidence of acute renal failure. The use of nonsteroidal anti-inflammatory drugs is to be deprecated and efforts should be made to publicize this harmful effect. PMID:2485484

  1. Probabilistic analysis of cascade failure dynamics in complex network

    NASA Astrophysics Data System (ADS)

    Zhang, Ding-Xue; Zhao, Dan; Guan, Zhi-Hong; Wu, Yonghong; Chi, Ming; Zheng, Gui-Lin

    2016-11-01

    The impact of initial load and tolerance parameter distribution on cascade failure is investigated. By using mean field theory, a probabilistic cascade failure model is established. Based on the model, the damage caused by certain attack size can be predicted, and the critical attack size is derived by the condition of cascade failure end, which ensures no collapse. The critical attack size is larger than the case of constant tolerance parameter for network of random distribution. Comparing three typical distributions, simulation results indicate that the network whose initial load and tolerance parameter both follow Weibull distribution performs better than others.

  2. Mesoscale simulation of concrete spall failure

    NASA Astrophysics Data System (ADS)

    Knell, S.; Sauer, M.; Millon, O.; Riedel, W.

    2012-05-01

    Although intensively studied, it is still being debated which physical mechanisms are responsible for the increase of dynamic strength and fracture energy of concrete observed at high loading rates, and to what extent structural inertia forces on different scales contribute to the observation. We present a new approach for the three dimensional mesoscale modelling of dynamic damage and cracking in concrete. Concrete is approximated as a composite of spherical elastic aggregates of mm to cm size embedded in an elastic cement stone matrix. Cracking within the matrix and at aggregate interfaces in the μm range are modelled with adaptively inserted—initially rigid—cohesive interface elements. The model is applied to analyse the dynamic tensile failure observed in Hopkinson-Bar spallation experiments with strain rates up to 100/s. The influence of the key mesoscale failure parameters of strength, fracture energy and relative weakening of the ITZ on macromechanic strength, momentum and energy conservation is numerically investigated.

  3. Development of failure criterion for Kevlar-epoxy fabric laminates

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Elliott, W. G.

    1984-01-01

    The development of the tensor polynomial failure criterion for composite laminate analysis is discussed. In particular, emphasis is given to the fabrication and testing of Kevlar-49 fabric (Style 285)/Narmco 5208 Epoxy. The quadratic-failure criterion with F(12)=0 provides accurate estimates of failure stresses for the Kevlar/Epoxy investigated. The cubic failure criterion was re-cast into an operationally easier form, providing the engineer with design curves that can be applied to laminates fabricated from unidirectional prepregs. In the form presented no interaction strength tests are required, although recourse to the quadratic model and the principal strength parameters is necessary. However, insufficient test data exists at present to generalize this approach for all undirectional prepregs and its use must be restricted to the generic materials investigated to-date.

  4. Evaluation of failure criterion for graphite/epoxy fabric laminates

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Wharram, G. E.

    1985-01-01

    The development and application of the tensor polynomial failure criterion for composite laminate analysis is described. Emphasis is given to the fabrication and testing of Narmco Rigidite 5208-WT300, a plain weave fabric of Thornel 300 Graphite fibers impregnated with Narmco 5208 Resin. The quadratic-failure criterion with F sub 12=0 provides accurate estimates of failure stresses for the graphite/epoxy investigated. The cubic failure criterion was recast into an operationally easier form, providing design curves that can be applied to laminates fabricated from orthotropic woven fabric prepregs. In the form presented, no interaction strength tests are required, although recourse to the quadratic model and the principal strength parameters is necessary. However, insufficient test data exist at present to generalize this approach for all prepreg constructions, and its use must be restricted to the generic materials and configurations investigated to date.

  5. Urea distribution in renal failure

    PubMed Central

    Blackmore, D. J.; Elder, W. J.; Bowden, C. H.

    1963-01-01

    An assessment of intracellular urea removed during haemodialysis has been made from urea extraction and plasma urea estimations. An apparent wide variation in the movement of intracellular urea in patients with acute renal failure from obstetric and traumatic causes and with chronic renal failure is reported. A method for the estimation of red cell water urea is presented. In two patients with chronic renal failure the red cell urea level was much higher than would have been expected from the plasma urea level before dialysis. In two obstetric patients there was no such discrepancy. The conclusion is drawn that research should be directed to variations of intracellular metabolism in renal failure before a more rational approach can be made to its management. PMID:16811009

  6. Heart failure - fluids and diuretics

    MedlinePlus

    ... Clinical Cardiology; American Heart Association Council on Nutrition, Physical Activity, and Metabolism; American Heart Association Interdisciplinary Council on Quality of Care and Outcomes Research. State of the science: promoting self-care in persons with heart failure: ...

  7. Data and Statistics: Heart Failure

    MedlinePlus

    ... this? Submit What's this? Submit Button Related CDC Web Sites Heart Disease Stroke High Blood Pressure Salt ... to Prevent and Control Chronic Diseases Million Hearts® Web Sites with More Information About Heart Failure For ...

  8. How Is Respiratory Failure Treated?

    MedlinePlus

    ... Once your doctor figures out what's causing your respiratory failure, he or she will plan how to treat that disease or condition. Treatments may include medicines, procedures, and other therapies. Rate This Content: NEXT >> Updated: December 19, 2011 Twitter ...

  9. Ejection Fraction Heart Failure Measurement

    MedlinePlus

    ... 70. You can have a normal ejection fraction reading and still have heart failure (called HFpEF or ... to be made. Here we delve into the importance of shared decision making. HF Resources For Life ...

  10. Identifying Clients Predisposed To Failure

    ERIC Educational Resources Information Center

    Carnes, G. D.

    1973-01-01

    Studies are reviewed that report the prediction of rehabilitation failure from personality measures. Related research is discussed that suggest the dynamics underlying a key concept, the "hypochondriacally organized personality" which is identifiable from the Rorschach anatomy response percentage. (Author)

  11. Severe Obesity and Heart Failure

    MedlinePlus

    ... https://medlineplus.gov/news/fullstory_161011.html Severe Obesity and Heart Failure Study sees link even without ... 2016 FRIDAY, Sept. 16, 2016 (HealthDay News) -- Severe obesity appears to be an independent risk factor for ...

  12. Review of the NASA Voyager spacecraft polycarbonate capacitor failure incident

    NASA Technical Reports Server (NTRS)

    Ott, F. M.; Yen, S. P. S.; Somoano, R. B.

    1985-01-01

    The premission failure of a Voyager spacecraft capacitor has prompted an investigation into the use of polycarbonate capacitors in high impedance circuits, during which capacitor failures were induced by thermal cycling together with extended periods at high temperature. Measurement of leakage path temperature coefficients indicates that there are two distinct leakage types whose mechanisms are complicated by movement within the capacitor during temperature changes. A novel system for pulse detection during capacitor burn-in and ramp testing has proven to be beneficial.

  13. Analyses of Transistor Punchthrough Failures

    NASA Technical Reports Server (NTRS)

    Nicolas, David P.

    1999-01-01

    The failure of two transistors in the Altitude Switch Assembly for the Solid Rocket Booster followed by two additional failures a year later presented a challenge to failure analysts. These devices had successfully worked for many years on numerous missions. There was no history of failures with this type of device. Extensive checks of the test procedures gave no indication for a source of the cause. The devices were manufactured more than twenty years ago and failure information on this lot date code was not readily available. External visual exam, radiography, PEID, and leak testing were performed with nominal results Electrical testing indicated nearly identical base-emitter and base-collector characteristics (both forward and reverse) with a low resistance short emitter to collector. These characteristics are indicative of a classic failure mechanism called punchthrough. In failure analysis punchthrough refers to an condition where a relatively low voltage pulse causes the device to conduct very hard producing localized areas of thermal runaway or "hot spots". At one or more of these hot spots, the excessive currents melt the silicon. Heavily doped emitter material diffuses through the base region to the collector forming a diffusion pipe shorting the emitter to base to collector. Upon cooling, an alloy junction forms between the pipe and the base region. Generally, the hot spot (punch-through site) is under the bond and no surface artifact is visible. The devices were delidded and the internal structures were examined microscopically. The gold emitter lead was melted on one device, but others had anomalies in the metallization around the in-tact emitter bonds. The SEM examination confirmed some anomalies to be cosmetic defects while other anomalies were artifacts of the punchthrough site. Subsequent to these analyses, the contractor determined that some irregular testing procedures occurred at the time of the failures heretofore unreported. These testing

  14. Early failure of the famous.

    PubMed

    Illingworth, R

    1986-01-01

    This is a historical review of school failure, underachievement and underestimation of the ability of children destined for world fame. Many were refused admission to a college of higher education, many failed to secure a university degree, more than 30 were expelled from school or university and several were sent to prison. Some reasons are discussed for the failure of parents and teachers to recognize outstanding ability in children.

  15. Acute hepatic failure in children.

    PubMed Central

    Riely, C. A.

    1984-01-01

    Many diseases may present as acute hepatic failure in the pediatric age group, including viral hepatitis A and B, adverse drug reactions, both toxic and "hepatitic," and inherited metabolic disorders such as tyrosinemia, alpha 1 antitrypsin deficiency, and Wilson's disease. Management is primarily supportive, with care taken to anticipate the known complications of hepatic failure. Few "curative" therapies are known, although attempts at stimulating hepatic regeneration may be helpful. Images FIG. 1 FIG. 3 FIG. 4 PMID:6433587

  16. The failure-tolerant leader.

    PubMed

    Farson, Richard; Keyes, Ralph

    2002-08-01

    "The fastest way to succeed," IBM's Thomas Watson, Sr., once said, "is to double your failure rate." In recent years, more and more executives have embraced Watson's point of view, coming to understand what innovators have always known: Failure is a prerequisite to invention. But while companies may grasp the value of making mistakes at the level of corporate practices, they have a harder time accepting the idea at the personal level. People are afraid to fail, and corporate culture reinforces that fear. In this article, psychologist and former Harvard Business School professor Richard Farson and coauthor Ralph Keyes discuss how companies can reduce the fear of miscues. What's crucial is the presence of failure-tolerant leaders--executives who, through their words and actions, help employees overcome their anxieties about making mistakes and, in the process, create a culture of intelligent risk-taking that leads to sustained innovation. Such leaders don't just accept productive failure, they promote it. Drawing from their research in business, politics, sports, and science, the authors identify common practices among failure-tolerant leaders. These leaders break down the social and bureaucratic barriers that separate them from their followers. They engage at a personal level with the people they lead. They avoid giving either praise or criticism, preferring to take a nonjudgmental, analytical posture as they interact with staff. They openly admit their own mistakes rather than trying to cover them up or shifting the blame. And they try to root out the destructive competitiveness built into most organizations. Above all else, failure-tolerant leaders push people to see beyond traditional definitions of success and failure. They know that as long as a person views failure as the opposite of success, rather than its complement, he or she will never be able to take the risks necessary for innovation. PMID:12195921

  17. Peyronie's disease and erectile failure

    SciTech Connect

    Metz, P.; Ebbehoj, J.; Uhrenholdt, A.; Wagner, G.

    1983-12-01

    A total of 20 patients with Peyronie's disease, including 15 with erectile failure and 5 with normal potency, underwent evaluation with dynamic xenon washout and infusion cavernosography. Abnormal drainage from the cavernous body was found in 13 of the 15 patients with erectile failure and in none of the 5 potent patients, indicating that this condition seems to be the underlying pathological mechanism leading to erectile impotence in patients with Peyronie's disease.

  18. [Metabolic therapy for heart failure].

    PubMed

    Loiacono, Ferdinando; Alberti, Luca; Lauretta, Ludovica; Puccetti, Patrizia; Silipigni, Carmen; Margonato, Alberto; Fragasso, Gabriele

    2014-01-01

    Heart failure may promote metabolic changes such as insulin resistance, in part through neurohumoral activation, and determining an increased utilization of non-carbohydrate substrates for energy production. In fact, fasting blood ketone bodies as well as fat oxidation have been shown to be increased in patients with heart failure. The result is depletion of myocardial ATP, phosphocreatine and creatine kinase with decreased efficiency of mechanical work. A direct approach to manipulate cardiac energy metabolism consists in modifying substrate utilization by the failing heart. To date, the most effective metabolic treatments include several pharmacological agents that directly inhibit fatty acid oxidation. The results of current research are supporting the concept that shifting the energy substrate preference away from fatty acid metabolism and toward glucose metabolism could be an effective adjunctive treatment in patients with heart failure. Trimetazidine is the most studied drug in this context. Several small studies have evidenced the usefulness of such additional therapeutic tools for heart failure. More specifically, recent meta-analyses and a multicenter retrospective study have shown that additional use of trimetazidine in patients with heart failure, along with symptoms and cardiac function improvement, also provides a significant protective effect on all-cause mortality, cardiovascular events and hospitalization due to cardiac causes. Nevertheless, the exact role of metabolic therapy in heart failure is yet to be established, and a large multicenter randomized trial is necessary. PMID:25072544

  19. Epigenetic regulation and heart failure.

    PubMed

    Cao, Dian J

    2014-09-01

    Heart failure has become a huge public health problem. The treatment options for heart failure, however, are considerably limited. The significant disparity between the scope of a prominent health problem and the restricted means of therapy propagates heart failure epidemics. Delineating novel mechanisms of heart failure is imperative. Emerging evidence suggests that epigenetic regulation may take part in the pathogenesis of heart failure. Epigenetic regulation involves DNA and histone modifications that lead to changes in DNA-based transcriptional programs without altering the DNA sequence. Although more and more mechanisms are being discovered, the best understood epigenetic modifications are achieved through covalent biochemical reactions including histone acetylation, histone methylation and DNA methylation. Connecting environmental stimuli with genomic programs, epigenetic regulation remains important in maintaining homeostases and the pathogeneses of diseases. This review summarizes the most recent developments regarding individual epigenetic modifications and their implications in the pathogenesis of heart failure. Understanding this strategically important mechanism is potentially the key for developing powerful interventions in the future.

  20. Bond failure patterns in vivo.

    PubMed

    Linklater, Rognvald A; Gordon, Peter H

    2003-05-01

    The aim of this study was to identify the presence and pattern of differences in bond failure between tooth types in vivo when bonding orthodontic brackets with the no-mix orthodontic composite adhesive Right-On. In vivo bond failure for a single operator was recorded for 108 consecutive patients undergoing fixed-appliance orthodontic treatment. The bond failure data were analyzed by survival analysis. Time to first failure or censorship was recorded for each bonded attachment. Overall failure in the sample matched previous clinical studies but conflicted with previous ex vivo bond strength data. Mandibular and posterior teeth had significantly higher rates of failure than did maxillary and anterior teeth. The type of attachment used had a significant effect on bond survival. The results of this study confirm that in vivo bond survival is not uniform for all teeth. Comparisons between the findings of this study and those of a previous ex vivo study by the same authors failed to validate ex vivo bond strength testing as clinically relevant.

  1. [Competence Network Heart Failure (CNHF). Together against heart failure].

    PubMed

    Ertl, Georg; Störk, Stefan; Börste, Rita

    2016-04-01

    Heart failure is one of the most urgent medical and socio-economic challenges of the 21(st) century. Up to three million people are affected in Germany; this means one in ten people over the age of 65  live with heart failure. The current demographic changes will accentuate the importance of this grave health problem. The care of patients with heart failure, as well as the associated research mandates a comprehensive, multidisciplinary approach. The Competence Network Heart Failure (CNHF) pursues this objective. CNHF is a research alliance with 11 sites in Germany and was funded by the Federal Ministry of Research (BMBF) from 2003 through 2014. Since January 2015, the network has been an associate cooperating partner of the German Centre for Cardiovascular Research (DZHK). During the 12-year funding period by the BMBF, scientists in the field of heart failure from 30 university hospitals, 5 research institutes, 7 heart centers, 17 cardiovascular clinics, over 200 general practitioners, 4 rehabilitation clinics, as well as numerous organizations and associations were involved in cooperative CNHF research. In the context of 22 projects, the CNHF covered basic, clinical, and health care research, and generated numerous groundbreaking insights into disease mechanisms, as well as diagnosis and treatment of heart failure, which are documented in more than 350 publications. With its central study database and bank of biomaterials, the network has set up a Europe-wide unique research resource, which can be used in the future for national and international cooperations with the DZHK and other partners. Furthermore, the CNHF strongly promotes nation- and Europe-wide public relations and heart failure awareness activities. PMID:26979718

  2. Failure mechanisms of fibrin-based surgical tissue adhesives

    NASA Astrophysics Data System (ADS)

    Sierra, David Hugh

    A series of studies was performed to investigate the potential impact of heterogeneity in the matrix of multiple-component fibrin-based tissue adhesives upon their mechanical and biomechanical properties both in vivo and in vitro. Investigations into the failure mechanisms by stereological techniques demonstrated that heterogeneity could be measured quantitatively and that the variation in heterogeneity could be altered both by the means of component mixing and delivery and by the formulation of the sealant. Ex vivo tensile adhesive strength was found to be inversely proportional to the amount of heterogeneity. In contrast, in vivo tensile wound-closure strength was found to be relatively unaffected by the degree of heterogeneity, while in vivo parenchymal organ hemostasis in rabbits was found to be affected: greater heterogeneity appeared to correlate with an increase in hemostasis time and amount of sealant necessary to effect hemostasis. Tensile testing of the bulk sealant showed that mechanical parameters were proportional to fibrin concentration and that the physical characteristics of the failure supported a ductile mechanism. Strain hardening as a function of percentage of strain, and strain rate was observed for both concentrations, and syneresis was observed at low strain rates for the lower fibrin concentration. Blister testing demonstrated that burst pressure and failure energy were proportional to fibrin concentration and decreased with increasing flow rate. Higher fibrin concentration demonstrated predominately compact morphology debonds with cohesive failure loci, demonstrating shear or viscous failure in a viscoelastic rubbery adhesive. The lower fibrin concentration sealant exhibited predominately fractal morphology debonds with cohesive failure loci, supporting an elastoviscous material condition. The failure mechanism for these was hypothesized and shown to be flow-induced ductile fracture. Based on these findings, the failure mechanism was

  3. Experimental methods for identifying failure mechanisms

    NASA Technical Reports Server (NTRS)

    Daniel, I. M.

    1983-01-01

    Experimental methods for identifying failure mechanisms in fibrous composites are studied. Methods to identify failure in composite materials includes interferometry, holography, fractography and ultrasonics.

  4. Common Cause Failures and Ultra Reliability

    NASA Technical Reports Server (NTRS)

    Jones, Harry W.

    2012-01-01

    A common cause failure occurs when several failures have the same origin. Common cause failures are either common event failures, where the cause is a single external event, or common mode failures, where two systems fail in the same way for the same reason. Common mode failures can occur at different times because of a design defect or a repeated external event. Common event failures reduce the reliability of on-line redundant systems but not of systems using off-line spare parts. Common mode failures reduce the dependability of systems using off-line spare parts and on-line redundancy.

  5. Level of Automation and Failure Frequency Effects on Simulated Lunar Lander Performance

    NASA Technical Reports Server (NTRS)

    Marquez, Jessica J.; Ramirez, Margarita

    2014-01-01

    A human-in-the-loop experiment was conducted at the NASA Ames Research Center Vertical Motion Simulator, where instrument-rated pilots completed a simulated terminal descent phase of a lunar landing. Ten pilots participated in a 2 x 2 mixed design experiment, with level of automation as the within-subjects factor and failure frequency as the between subjects factor. The two evaluated levels of automation were high (fully automated landing) and low (manual controlled landing). During test trials, participants were exposed to either a high number of failures (75% failure frequency) or low number of failures (25% failure frequency). In order to investigate the pilots' sensitivity to changes in levels of automation and failure frequency, the dependent measure selected for this experiment was accuracy of failure diagnosis, from which D Prime and Decision Criterion were derived. For each of the dependent measures, no significant difference was found for level of automation and no significant interaction was detected between level of automation and failure frequency. A significant effect was identified for failure frequency suggesting failure frequency has a significant effect on pilots' sensitivity to failure detection and diagnosis. Participants were more likely to correctly identify and diagnose failures if they experienced the higher levels of failures, regardless of level of automation

  6. The role of shear and tensile failure in dynamically triggered landslides

    USGS Publications Warehouse

    Gipprich, T.L.; Snieder, R.K.; Jibson, R.W.; Kimman, W.

    2008-01-01

    Dynamic stresses generated by earthquakes can trigger landslides. Current methods of landslide analysis such as pseudo-static analysis and Newmark's method focus on the effects of earthquake accelerations on the landslide mass to characterize dynamic landslide behaviour. One limitation of these methods is their use Mohr-Coulomb failure criteria, which only accounts for shear failure, but the role of tensile failure is not accounted for. We develop a limit-equilibrium model to investigate the dynamic stresses generated by a given ground motion due to a plane wave and use this model to assess the role of shear and tensile failure in the initiation of slope instability. We do so by incorporating a modified Griffith failure envelope, which combines shear and tensile failure into a single criterion. Tests of dynamic stresses in both homogeneous and layered slopes demonstrate that two modes of failure exist, tensile failure in the uppermost meters of a slope and shear failure at greater depth. Further, we derive equations that express the dynamic stress in the near-surface in the acceleration measured at the surface. These equations are used to approximately define the depth range for each mechanism of failure. The depths at which these failure mechanisms occur suggest that shear and tensile failure might collaborate in generating slope failure. ?? 2007 The Authors Journal compilation ?? 2007 RAS.

  7. Progress in Predicting Rock-Slope Failures

    NASA Astrophysics Data System (ADS)

    Korup, O.

    2015-12-01

    Recent research on predicting landslides has seen a massive increase in statistical and computational methods that are largely adapted from the fields of machine learning and data mining. Judging from a sample of some 150 recent scientific papers, the gross majority of the reported success rates of these statistical methods are overwhelmingly high and promising at between 71% and 98%. Perhaps surprisingly, though, the death toll and damage from landslides has remained elevated in the early 21st century, so that reliably predicting the occurrence of rock-slope failures without overfitting our models remains challenging. Here I review some of the recent advances in this field, and show how novel results from landslide seismology and landslide sedimentology have promoted our ability of detecting large rock-slope failures in mountainous terrain. Several new detailed investigations of the internal nature of large rockslide deposits, for example, help to reduce the confusion potential with macroscopically similar moraine debris, or microscopically similar fault breccia. I further outline some of the limitations of empirical models that use rainfall intensity-duration thresholds for landslide early warning, and of multivariate methods concerned with mapping landslide susceptibility at the regional scale. I conclude by discussing the occurrence of 'black swans' such as long-runout rock-ice avalanches in size distributions of rock-slope failures, and their implications for quantitative hazard appraisals.

  8. Posterror speeding after threat-detection failure.

    PubMed

    Caudek, Corrado; Ceccarini, Francesco; Sica, Claudio

    2015-04-01

    Cognitive control enables individuals to rapidly adapt to changing task demands. To investigate error-driven adjustments in cognitive control, we considered performance changes in posterror trials, when participants performed a visual search task requiring detection of angry, happy, or neutral facial expressions in crowds of faces. We hypothesized that the failure to detect a potential threat (angry face) would prompt a different posterror adjustment than the failure to detect a nonthreatening target (happy or neutral face). Indeed, in 3 sets of experiments, we found evidence of posterror speeding, in the first case, and of posterror slowing, in the second case. Previous results indicate that a threatening stimulus can improve the efficiency of visual search. The results of the present study show that a similar effect can also be observed when participants fail to detect a threat. The impact of threat-detection failure on cognitive control, as revealed by the present study, suggests that posterror adjustments should be understood as the product of domain-specific mechanisms that are strongly influenced by affective information, rather than as the effect of a general-purpose error-monitoring system.

  9. Failure Modes during Low-Voltage Electrowetting.

    PubMed

    Mibus, Marcel; Hu, Xiaoyu; Knospe, Carl; Reed, Michael L; Zangari, Giovanni

    2016-06-22

    Low-voltage electrowetting devices allow significant contact angle changes below a 50 V bias; however, operation under prolonged cycling and failure modes have not yet been sufficiently elucidated. In this work, the failure modes and performance degradation of Cytop (23-210 nm)/aluminum oxide (15-44 nm) bilayers have been investigated. Contact angle and leakage current were measured during stepped voltage measurements up to failure, showing three electrowetting response regimes: ideal Young-Lippmann behavior, contact angle saturation, and dielectric breakdown. The onset of ionic conduction in aluminum oxide and the resulting breakdown control when the layer would ultimately fail, but the thickness of the Cytop layer determined the achievable contact angle versus voltage characteristics. Cyclic electrowetting measurements studied the repeatability of contact angle change using an applied voltage above or below the voltage drop needed for polymer breakdown (VT). Results show repeatable electrowetting below VT and a rapidly diminishing contact angle response above VT. The leakage current and injected charge cannot be used to comprehensively assess the stability of the system during operation. The contact potential difference measured with a Kelvin probe provides an alternative means of assessing the extent of the damage. PMID:27253515

  10. Abdominal contributions to cardiorenal dysfunction in congestive heart failure.

    PubMed

    Verbrugge, Frederik H; Dupont, Matthias; Steels, Paul; Grieten, Lars; Malbrain, Manu; Tang, W H Wilson; Mullens, Wilfried

    2013-08-01

    Current pathophysiological models of congestive heart failure unsatisfactorily explain the detrimental link between congestion and cardiorenal function. Abdominal congestion (i.e., splanchnic venous and interstitial congestion) manifests in a substantial number of patients with advanced congestive heart failure, yet is poorly defined. Compromised capacitance function of the splanchnic vasculature and deficient abdominal lymph flow resulting in interstitial edema might both be implied in the occurrence of increased cardiac filling pressures and renal dysfunction. Indeed, increased intra-abdominal pressure, as an extreme marker of abdominal congestion, is correlated with renal dysfunction in advanced congestive heart failure. Intriguing findings provide preliminary evidence that alterations in the liver and spleen contribute to systemic congestion in heart failure. Finally, gut-derived hormones might influence sodium homeostasis, whereas entrance of bowel toxins into the circulatory system, as a result of impaired intestinal barrier function secondary to congestion, might further depress cardiac as well as renal function. Those toxins are mainly produced by micro-organisms in the gut lumen, with presumably important alterations in advanced heart failure, especially when renal function is depressed. Therefore, in this state-of-the-art review, we explore the crosstalk between the abdomen, heart, and kidneys in congestive heart failure. This might offer new diagnostic opportunities as well as treatment strategies to achieve decongestion in heart failure, especially when abdominal congestion is present. Among those currently under investigation are paracentesis, ultrafiltration, peritoneal dialysis, oral sodium binders, vasodilator therapy, renal sympathetic denervation and agents targeting the gut microbiota. PMID:23747781

  11. Adrenal GRK2 upregulation mediates sympathetic overdrive in heart failure.

    PubMed

    Lymperopoulos, Anastasios; Rengo, Giuseppe; Funakoshi, Hajime; Eckhart, Andrea D; Koch, Walter J

    2007-03-01

    Cardiac overstimulation by the sympathetic nervous system (SNS) is a salient characteristic of heart failure, reflected by elevated circulating levels of catecholamines. The success of beta-adrenergic receptor (betaAR) antagonists in heart failure argues for SNS hyperactivity being pathogenic; however, sympatholytic agents targeting alpha2AR-mediated catecholamine inhibition have been unsuccessful. By investigating adrenal adrenergic receptor signaling in heart failure models, we found molecular mechanisms to explain the failure of sympatholytic agents and discovered a new strategy to lower SNS activity. During heart failure, there is substantial alpha2AR dysregulation in the adrenal gland, triggered by increased expression and activity of G protein-coupled receptor kinase 2 (GRK2). Adrenal gland-specific GRK2 inhibition reversed alpha2AR dysregulation in heart failure, resulting in lowered plasma catecholamine levels, improved cardiac betaAR signaling and function, and increased sympatholytic efficacy of a alpha2AR agonist. This is the first demonstration, to our knowledge, of a molecular mechanism for SNS hyperactivity in heart failure, and our study identifies adrenal GRK2 activity as a new sympatholytic target.

  12. High Fidelity Failure Analysis for a Composite Fuselage Section

    NASA Technical Reports Server (NTRS)

    Li, Jain; Davila, Carlos G.; Chen, Tzi-Kang

    2001-01-01

    A high fidelity delamination failure analysis was developed by combining a local failure analysis with a global full-scale finite element structural analysis to address strength and delamination failure in a single package. The methodology was demonstrated through a local three-dimensional pull-off failure analysis and a geometrically nonlinear structural analysis of a five-foot composite helicopter fuselage section. Pull-off specimens were used to identify potential debonding failure of co-cured skin-stringer/frame fuselage structures. An investigation of the failed pull-off specimens was performed to determine the location of the failure initiation. Three-dimensional strain energy release rate analysis indicates that the delamination initiation and growth is controlled by Mode 1 opening mode. The bending moment at the delamination tip was identified as the crucial factor controlling the failure. The geometrically nonlinear structural analysis of a five-foot composite fuselage section was performed using a detailed finite element model. Loads were applied along the periphery of the subcomponent using displacement fields generated from solutions of a full-vehicle model.

  13. An Investigation of Theories of Failure for Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Hemann, John H.

    1995-01-01

    In order to further advance the understanding of the mechanical behavior of ceramic matrix composites (CMCs), acoustic emission (AE) techniques were imple mented to monitor and identify damage mechanisms in CMCs under tensile loading. In addition to real-time AE monitoring techniques, a data acquisition system was developed and implemented in order to capture AE waveforms resulting from stress-induced damage. Waveforms were inspected for multiple events, separated in distinct events, and then analyzed to determine waveform characteristics in the time and frequency domains. Waveform characteristics included peak amplitude, event duration, MARSE, energy, and dominant and centroidal frequency. In addition to conventional methods for determining a damage discrimination criteria, a study of the distribution and correlation the waveform characteristics was performed to aid in the determination of a damage discrimination criteria. The damage discrimination criteria was tested for "uniqueness", i.e., the effectiveness of the criteria to identify and monitor damage independent of the stress-strain relationship. Insitu radiography was used to substantiate the damage accumulation.

  14. 29 CFR 501.21 - Failure to cooperate with investigations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... REGULATIONS ENFORCEMENT OF CONTRACTUAL OBLIGATIONS FOR TEMPORARY ALIEN AGRICULTURAL WORKERS ADMITTED UNDER... recommend that OFLC revoke the existing certification that is the basis for the employment of the...

  15. 29 CFR 501.21 - Failure to cooperate with investigations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... REGULATIONS ENFORCEMENT OF CONTRACTUAL OBLIGATIONS FOR TEMPORARY ALIEN AGRICULTURAL WORKERS ADMITTED UNDER... recommend that OFLC revoke the existing certification that is the basis for the employment of the...

  16. 29 CFR 502.21 - Failure to cooperate with investigations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... REGULATIONS ENFORCEMENT OF CONTRACTUAL OBLIGATIONS FOR TEMPORARY ALIEN AGRICULTURAL WORKERS ADMITTED UNDER.... The WHD may also recommend to ETA that an existing certification be revoked. The taking of any...

  17. Failure Investigation of WB-57 Aircraft Engine Cowling

    NASA Technical Reports Server (NTRS)

    Martinez, J. E.; Gafka, T.; Figert, J.

    2014-01-01

    The NASA Johnson Space Center (JSC) in Houston, Texas is the home of the NASA WB-57 High Altitude Research Program. Three fully operational WB-57 aircraft are based near JSC at Ellington Field. The aircraft have been flying research missions since the early 1960's, and continue to be an asset to the scientific community with professional, reliable, customer-oriented service designed to meet all scientific objectives. The NASA WB-57 Program provides unique, high-altitude airborne platforms to US Government agencies, academic institutions, and commercial customers in order to support scientific research and advanced technology development and testing at locations around the world. Mission examples include atmospheric and earth science, ground mapping, cosmic dust collection, rocket launch support, and test bed operations for future airborne or spaceborne systems. During the return from a 6 hour flight, at 30,000 feet, in the clean configuration, traveling at 175 knots indicated airspeed, in un-accelerated flight with the auto pilot engaged, in calm air, the 2-man crew heard a mechanical bang and felt a slight shudder followed by a few seconds of high frequency vibration. The crew did not notice any other abnormalities leading up to, or for the remaining 1 hour of flight and made an uneventful landing. Upon taxi into the chocks, the recovery ground crew noticed the high frequency long wire antenna had become disconnected from the vertical stabilizer and was trailing over the left inboard wing, and that the left engine upper center removable cowling panel was missing, with noticeable damage to the left engine inboard cowling fixed structure. The missing cowling panel was never recovered. Each engine cowling panel is attached to the engine nacelle using six bushings made of 17-4 PH steel. The cylinder portions of four of the six bushings were found still attached to the aircraft (Fig 1). The other two bushings were lost with the panel. The other four bushings exhibited ratchet marks (multiple fatigue origins) which initiated in the sharp radius of the flange/cylinder fillet and were observed 300 degrees around the flange perimeter (Fig 2-3). Low stress, high cycle fatigue (HCF) was observed on the fracture surfaces of all four bushings (Fig 4). To improve the cowling panel joint design and enable return to flight, new cowling bushings with thicker flanges and a larger machined flange/cylinder fillet radius were installed on all cowling panels. In addition, a spacer was added to the joint to achieve the proper stack tolerance. Finally, a time change requirement for all cowling bushings was instituted.

  18. High Energy Failure Containment for Spacecraft

    NASA Technical Reports Server (NTRS)

    Pektas, Pete; Baker, Christopher

    2011-01-01

    Objective: The objective of this paper will be to investigate advancements and any commonality between spacecraft debris containment and the improvements being made in ballistic protection. Scope: This paper will focus on cross application of protection devices and methods, and how they relate to protecting humans from failures in spacecraft. The potential gain is to reduce the risk associated with hardware failure, while decreasing the weight and size of energy containment methods currently being used by the government and commercial industry. Method of Approach: This paper will examine testing that has already been accomplished in regards to the failure of high energy rotating hardware and compare it to advancements in ballistic protection. Examples are: DOT research and testing of turbine containment as documented in DOT/FAA/AR-96/110, DOT/FAA/AR-97/82, DOT/FAA/AR-98/22. It will also look at work accomplished by companies such as ApNano and IBD Deisenroth in the development of nano ceramics and nanometric steels. Other forms of energy absorbent materials and composites will also be considered and discussed. New Advances in State of the Art: There have been numerous advances in technology in regards to high energy debris containment and in the similar field of ballistic protection. This paper will discuss methods such as using impregnated or dry Kevlar, ceramic, and nano-technology which have been successfully tested but are yet to be utilized in spacecraft. Reports on tungsten disulfide nanotubes claim that they are 4-5 times stronger than steel and reports vary about the magnitude increase over Kevlar, but it appears to be somewhere in the range of 2-6 times stronger. This technology could also have applications in the protection of pressure vessels, motor housings, and hydraulic component failures.

  19. Characterization of failure processes in tungsten copper composites under fatigue loading conditions

    NASA Technical Reports Server (NTRS)

    Kim, Yong-Suk; Verrilli, Michael J.; Gabb, Timothy P.

    1989-01-01

    A fractographic and metallographic investigation was performed on specimens of a tungsten fiber reinforced copper matrix composite (9 vol percent), which had experienced fatigue failures at elevated temperatures. Major failure modes and possible failure mechanisms, with an emphasis placed on characterizing fatigue damage accumulation, were determined. Metallography of specimens fatigued under isothermal cyclic loading suggested that fatigue damage initiates in the matrix. Cracks nucleated within the copper matrix at grain boundaries, and they propagated through cavity coalescence. The growing cracks subsequently interacted with the reinforcing tungsten fibers, producing a localized ductile fiber failure. Examinations of interrupted tests before final failure confirmed the suggested fatigue damage processes.

  20. Genomic variation and neurohormonal intervention in heart failure.

    PubMed

    McNamara, Dennis M

    2010-01-01

    Neurohormonal activation is an important driver of heart-failure progression, and all pharmacologic interventions that improve heart-failure survival inhibit this systemic response to myocardial injury. Adrenergic stimulation of beta(1) receptors in the kidney results in the release of plasma renin, the conversion of peptide precursors to angiotensin II (a2), and ultimately the production of aldosterone. beta(1)-blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and aldosterone receptor antagonists all act by inhibiting the activity of critical protein of this core pathway: the beta(1) receptor, ACE, the a2 receptor, and aldosterone synthase. Investigation of the pharmacogenetic interactions of the ACE D/I polymorphism and heart-failure therapy demonstrates the power of genomics to target therapeutics. This review explores how genetic variation in genes involved in neurohormonal activation influences heart-failure outcomes and the impact of pharmacotherapy.

  1. Gross trunnion failure after primary total hip arthroplasty.

    PubMed

    Banerjee, Samik; Cherian, Jeffrey J; Bono, James V; Kurtz, Steven M; Geesink, Rudolph; Meneghini, R Michael; Delanois, Ronald E; Mont, Michael A

    2015-04-01

    Unfavorable outcomes from trunnion fretting and corrosion damage have been reported in the literature, gross failures of tapers in primary total hip arthroplasties have been less frequently reported. We report on 5 patients, who presented with gross trunnion failures of modular metal-on-polyethylene or ceramic-on-polyethylene bearings from 5 implant manufacturers, all necessitating revision surgery. None of these patients had an antecedent history of trauma, and the majority presented with pain or instability. No common factor was identified that may be predictive of these type of failures. Since there were 5 different stem designs, this suggests that it may be a rare generic phenomenon occurring with multiple designs. Currently, further investigations are necessary, including retrieval analysis, to identify risk factors that may predispose to such failures.

  2. Performance of wireless sensor networks under random node failures

    SciTech Connect

    Bradonjic, Milan; Hagberg, Aric; Feng, Pan

    2011-01-28

    Networks are essential to the function of a modern society and the consequence of damages to a network can be large. Assessing network performance of a damaged network is an important step in network recovery and network design. Connectivity, distance between nodes, and alternative routes are some of the key indicators to network performance. In this paper, random geometric graph (RGG) is used with two types of node failure, uniform failure and localized failure. Since the network performance are multi-facet and assessment can be time constrained, we introduce four measures, which can be computed in polynomial time, to estimate performance of damaged RGG. Simulation experiments are conducted to investigate the deterioration of networks through a period of time. With the empirical results, the performance measures are analyzed and compared to provide understanding of different failure scenarios in a RGG.

  3. Failure Assessment of Stainless Steel and Titanium Brazed Joints

    NASA Technical Reports Server (NTRS)

    Flom, Yury A.

    2012-01-01

    Following successful application of Coulomb-Mohr and interaction equations for evaluation of safety margins in Albemet 162 brazed joints, two additional base metal/filler metal systems were investigated. Specimens consisting of stainless steel brazed with silver-base filler metal and titanium brazed with 1100 Al alloy were tested to failure under combined action of tensile, shear, bending and torsion loads. Finite Element Analysis (FEA), hand calculations and digital image comparison (DIC) techniques were used to estimate failure stresses and construct Failure Assessment Diagrams (FAD). This study confirms that interaction equation R(sub sigma) + R(sub tau) = 1, where R(sub sigma) and R(sub t u) are normal and shear stress ratios, can be used as conservative lower bound estimate of the failure criterion in stainless steel and titanium brazed joints.

  4. Frequency of low-risk hospital admissions for heart failure.

    PubMed

    Butler, J; Hanumanthu, S; Chomsky, D; Wilson, J R

    1998-01-01

    Heart failure is one of the most common reasons for admission to acute care hospitals. A proportion of these admissions are probably low risk and could be managed in subacute care facilities, resulting in substantial cost savings. To investigate the proportion of low-risk hospital admissions for heart failure, all admissions for heart failure to Vanderbilt University Medical Center between July 1993 and June 1995 were identified (n = 743). One hundred twenty of these admissions were randomly selected, reviewed, and classified into a high-risk versus low-risk group on admission based on the severity of heart failure and the presence of life-threatening complications. Of the 120 admissions, 57 (48%) were classified as high risk based on the presence of moderate to severe heart failure for the first time or recurrent heart failure with a major complicating factor. Sixteen admissions (28%) were associated with adverse outcomes, including myocardial infarction in 5 (9%), intubation in 6 (11%), and death in 4 (7%). Sixty-three admissions (52%) were classified as low risk based on the presence of new-onset mild heart failure or mild to moderate recurrent heart failure with no complicating factors. Most of these admissions were for dyspnea without any life-threatening complication; 57 (91%) had no evidence of interstitial or alveolar pulmonary edema, and arterial oxygen saturation averaged 95 +/- 3%. Only 3 of these low risk admissions (5%) were associated with an adverse cardiovascular event. None of the patients died. These data suggest that over half of the patients admitted for heart failure to an acute care facility are low risk and probably could be managed in a subacute care setting, resulting in large cost savings. PMID:9462604

  5. Time-dependent statistical failure of fiber networks

    NASA Astrophysics Data System (ADS)

    Mattsson, Amanda; Uesaka, Tetsu

    2015-10-01

    Numerical simulations of time-dependent stochastic failure of fiber network have been performed by using a central-force, triangular lattice model. This two-dimensional (2D) network can be seen as the next level of structural hierarchy to fiber bundles, which have been investigated for many years both theoretically and numerically. Unlike fiber bundle models, the load sharing of the fiber network is determined by the network mechanics rather than a preassigned rule, and its failure is defined as the point of avalanche rather than the total fiber failure. We have assumed that the fiber in the network follows Coleman's probabilistic failure law [B. D. Coleman, J. Appl. Phys. 29, 968 (1958), 10.1063/1.1723343] with the Weibull shape parameter β =1 (memory less fiber). Our interests are how the fiber-level probabilistic failure law is transformed into the one for the network and how the failure characteristics and disorders on the fiber level influence the network failure response. The simulation results showed that, with increasing the size of the network (N ), weakest-link scaling (WLS) appeared and each lifetime distribution at a given size approximately followed Weibull distribution. However, the scaling behavior of the mean and the Weibull shape parameter clearly deviate from what we can predict from the WLS of Weibull distribution. We have found that a characteristic distribution function has, in fact, a double exponential form, not Weibull form. Accordingly, for the 2D network system, Coleman's probabilistic failure law holds but only approximately. Comparing the fiber and network failure properties, we found that the network structure induces an increase of the load sensitivity factor ρ (more brittle than fiber) and Weibull shape parameter β (less uncertainty of lifetime). Superimposed disorders on the fiber level reduce all these properties for the network.

  6. Time-dependent statistical failure of fiber networks.

    PubMed

    Mattsson, Amanda; Uesaka, Tetsu

    2015-10-01

    Numerical simulations of time-dependent stochastic failure of fiber network have been performed by using a central-force, triangular lattice model. This two-dimensional (2D) network can be seen as the next level of structural hierarchy to fiber bundles, which have been investigated for many years both theoretically and numerically. Unlike fiber bundle models, the load sharing of the fiber network is determined by the network mechanics rather than a preassigned rule, and its failure is defined as the point of avalanche rather than the total fiber failure. We have assumed that the fiber in the network follows Coleman's probabilistic failure law [B. D. Coleman, J. Appl. Phys. 29, 968 (1958)] with the Weibull shape parameter β=1 (memory less fiber). Our interests are how the fiber-level probabilistic failure law is transformed into the one for the network and how the failure characteristics and disorders on the fiber level influence the network failure response. The simulation results showed that, with increasing the size of the network (N), weakest-link scaling (WLS) appeared and each lifetime distribution at a given size approximately followed Weibull distribution. However, the scaling behavior of the mean and the Weibull shape parameter clearly deviate from what we can predict from the WLS of Weibull distribution. We have found that a characteristic distribution function has, in fact, a double exponential form, not Weibull form. Accordingly, for the 2D network system, Coleman's probabilistic failure law holds but only approximately. Comparing the fiber and network failure properties, we found that the network structure induces an increase of the load sensitivity factor ρ (more brittle than fiber) and Weibull shape parameter β (less uncertainty of lifetime). Superimposed disorders on the fiber level reduce all these properties for the network. PMID:26565219

  7. Stop sucker rod failures to save money

    SciTech Connect

    Moore, K.H.

    1981-07-01

    This study presents examples of frequent and common sucker rod failures, explains how failures occur, presents methods to recognize these failures, and discusses changes in conditions that cause failure. From early identification, corrective measures can be taken to prevent their recurrence, reducing downtime and lost production.

  8. Understand Your Risk for Heart Failure

    MedlinePlus

    ... Tools & Resources Stroke More Causes and Risks for Heart Failure Updated:Jul 29,2016 Who Develops Heart Failure ( ... HF. This content was last reviewed April 2015. Heart Failure • Home • About Heart Failure • Causes and Risks for ...

  9. Integrated Circuit Failure Analysis Expert System

    1995-10-03

    The software assists a failure analyst performing failure anaysis on intergrated circuits. The software can also be used to train inexperienced failure analysts. The software also provides a method for storing information and making it easily available to experienced failure analysts.

  10. Integrated Circuit Failure Analysis Hypertext Help System

    1995-02-23

    This software assists a failure analyst performing failure analysis on integrated circuits. The software can also be used to train inexperienced failure analysts. The software also provides a method for storing information and making it easily available to experienced failure analysts.

  11. Acute Decompensated Heart Failure Update

    PubMed Central

    Teerlink, John R; Alburikan, Khalid; Metra, Marco; Rodgers, Jo E

    2015-01-01

    Acute decompensated heart failure (ADHF) continues to increase in prevalence and is associated with substantial mortality and morbidity including frequent hospitalizations. The American Heart Association is predicting that more than eight million Americans will have heart failure by 2030 and that the total direct costs associated with the disease will rise from $21 billion in 2012 to $70 billion in 2030. The increase in the prevalence and cost of HF is primarily the result of shifting demographics and a growing population. Although many large, randomized, controlled clinical trials have been conducted in patients with chronic heart failure, it was not until recently that a growing number of studies began to address the management of ADHF. It is the intent of this review to update the clinician regarding the evaluation and optimal management of ADHF. PMID:24251454

  12. [Inherited bone marrow failure syndromes].

    PubMed

    Okuno, Yusuke

    2016-02-01

    Inherited bone marrow failure syndromes comprise a series of disorders caused by various gene mutations. Genetic tests were formerly difficult to perform because of the large size and number of causative genes. However, recent advances in next-generation sequencing has enabled simultaneous testing of all causative genes to be performed at an acceptable cost. We collaboratively conducted a series of whole-exome sequencing studies of patients with inherited bone marrow failure syndromes and discovered RPS27/RPL27 and FANCT as causative genes of Diamond-Blackfan anemia and Fanconi anemia, respectively. Furthermore, we established a target gene sequencing system to cover 189 genes associated with pediatric blood diseases to assist genetic diagnoses in clinical practice. In this review, discovery of new causative genes and possible roles of next-generation sequencing in the genetic diagnosis of inherited bone marrow failure syndromes are discussed. PMID:26935625

  13. Heart failure: SGLT2 inhibitors and heart failure -- clinical implications.

    PubMed

    Raz, Itamar; Cahn, Avivit

    2016-04-01

    The latest findings from the EMPA-REG OUTCOME trial show a 34% reduction in hospitalization for heart failure or cardiovascular death in patients receiving empagliflozin, a sodium/glucose cotransporter 2 (SGLT2) inhibitor, compared with placebo. These outstanding results call for discussion of the clinical implications, and in-depth studies of the mechanisms of action of SGLT2 inhibitors.

  14. Heart failure in African Americans.

    PubMed

    Yancy, Clyde W

    2005-10-10

    The demographics of the United States are changing, and in the next few decades there will no longer be a racial/ethnic majority population. Increased awareness of cardiovascular disease (CVD) in special populations is warranted as these populations increase. Heart failure carries a substantial burden on those affected, particularly African Americans, who have a disproportionate burden of heart disease. Current treatments for heart failure include angiotensin-converting enzyme inhibitors, beta-blockers, angiotensin II-receptor antagonists, and vasodilating agents. This review discusses the unique characteristics of CVD in African Americans and addresses the need for targeted treatments to reduce the excess burden found in this population.

  15. Redesign overcomes electrode hammer failures

    SciTech Connect

    Roberts, R.; Necessary, J.; Spond, D. )

    1992-06-01

    This paper reports that growing numbers of collection electrode (CE) hammer failures challenged Arkansas Power and Light Co. (AP and L) engineers recently during their studies of electrostatic precipitator (ESP) incidents. Failed hammers eventually cause opacity compliance violations. Quick response was deemed necessary. During an August, 1989, inspection of the precipitator, plant engineers found pieces of CE hammers in the inlet field of A box. Findings showed that failures resulted form reverse bending fatigue, which was caused by repetitive impact loads on these low alloy steel castings.

  16. Diastolic Function in Heart Failure

    PubMed Central

    Kovács, Sándor J

    2015-01-01

    Heart failure has reached epidemic proportions, and diastolic heart failure or heart failure with preserved ejection fraction (HFpEF) constitutes about 50% of all heart failure admissions. Long-term prognosis of both reduced ejection fraction heart failure and HFpEF are similarly dismal. No pharmacologic agent has been developed that actually treats or repairs the physiologic deficit(s) responsible for HFpEF. Because the physiology of diastole is both subtle and counterintuitive, its role in heart failure has received insufficient attention. In this review, the focus is on the physiology of diastole in heart failure, the dominant physiologic laws that govern the process in all hearts, how all hearts work as a suction pump, and, therefore, the elucidation and characterization of what actually is meant by “diastolic function”. The intent is for the reader to understand what diastolic function actually is, what it is not, and how to measure it. Proper measurement of diastolic function requires one to go beyond the usual E/A, E/E′, etc. phenomenological metrics and employ more rigorous causality (mathematical modeling) based parameters of diastolic function. The method simultaneously provides new physiologic insight into the meaning of in vivo “equilibrium volume” of the left ventricle (LV), longitudinal versus transverse volume accommodation of the chamber, diastatic “ringing” of the mitral annulus, and the mechanism of L-wave generation, as well as availability of a load-independent index of diastolic function (LIIDF). One important consequence of understanding what diastolic function is, is the recognition that all that current therapies can do is basically alter the load, rather than actually “repair” the functional components (chamber stiffness, chamber relaxation). If beneficial (biological/structural/metabolic) remodeling due to therapy does manifest ultimately as improved diastolic function, it is due to resumption of normal physiology (as in

  17. Graphical Displays Assist In Analysis Of Failures

    NASA Technical Reports Server (NTRS)

    Pack, Ginger; Wadsworth, David; Razavipour, Reza

    1995-01-01

    Failure Environment Analysis Tool (FEAT) computer program enables people to see and better understand effects of failures in system. Uses digraph models to determine what will happen to system if set of failure events occurs and to identify possible causes of selected set of failures. Digraphs or engineering schematics used. Also used in operations to help identify causes of failures after they occur. Written in C language.

  18. A simple approach to modeling ductile failure.

    SciTech Connect

    Wellman, Gerald William

    2012-06-01

    Sandia National Laboratories has the need to predict the behavior of structures after the occurrence of an initial failure. In some cases determining the extent of failure, beyond initiation, is required, while in a few cases the initial failure is a design feature used to tailor the subsequent load paths. In either case, the ability to numerically simulate the initiation and propagation of failures is a highly desired capability. This document describes one approach to the simulation of failure initiation and propagation.

  19. [Failure effects and gender differences in perfectionism].

    PubMed

    Masson, A M; Cadot, M; Ansseau, M

    2003-01-01

    Perfectionism is a dimension which has been studied very little as a separate entity. It is not even considered as a nosological factor. No classification of the medical sciences underlines its importance other than to speak of a personality trait, of an aspect, or of a parameter. Nevertheless, perfectionism is related to multiple disorders such as depression (18, 20, 36), suicide (8, 16, 55), nutritional problems (11, 28), anxiety (3), obsessive-compulsive personality disorder (53), social phobia (2), as well as insomnia (46). Certain authors stress the possible role of perfectionism in the development or the persistence of a substantial number of these disorders (7, 22, 38). Given these facts, it is all the easier to understand the interest shown by clinicians and researchers in the subject. Better detection and evaluation of its impact on behaviour is important in putting therapies in place (6, 53). Relationships between perfectionism and fear of failure have been approached (21, 51, 54). Correlations between perfectionism and high levels of state and trait anxiety have been demonstrated (23). The evaluation of perfectionism has been dealt with very little. Some questionnaires devote a sub-category to it, such as the Eating Disorder Inventory and the Irrational Beliefs Test. However, recently, it has been recognized that perfectionism is a multidimensional construct. Two Multidimensional Perfectionism Scales have been developed and investigated in relative isolation. Frost, Marten, Lahart and Rosenblate defined perfectionism as the setting of excessively high standards for performance associated with critical self-evaluation. Six dimensions are described: concern over making mistakes, high personal standards, parental expectations, parental criticism, doubt about quality of performance and organization. Internal consistency and validity have been established (25, 26). Hewitt and Flett (30, 31, 33, 35) have developed another approach where three dimensions of

  20. [Failure effects and gender differences in perfectionism].

    PubMed

    Masson, A M; Cadot, M; Ansseau, M

    2003-01-01

    Perfectionism is a dimension which has been studied very little as a separate entity. It is not even considered as a nosological factor. No classification of the medical sciences underlines its importance other than to speak of a personality trait, of an aspect, or of a parameter. Nevertheless, perfectionism is related to multiple disorders such as depression (18, 20, 36), suicide (8, 16, 55), nutritional problems (11, 28), anxiety (3), obsessive-compulsive personality disorder (53), social phobia (2), as well as insomnia (46). Certain authors stress the possible role of perfectionism in the development or the persistence of a substantial number of these disorders (7, 22, 38). Given these facts, it is all the easier to understand the interest shown by clinicians and researchers in the subject. Better detection and evaluation of its impact on behaviour is important in putting therapies in place (6, 53). Relationships between perfectionism and fear of failure have been approached (21, 51, 54). Correlations between perfectionism and high levels of state and trait anxiety have been demonstrated (23). The evaluation of perfectionism has been dealt with very little. Some questionnaires devote a sub-category to it, such as the Eating Disorder Inventory and the Irrational Beliefs Test. However, recently, it has been recognized that perfectionism is a multidimensional construct. Two Multidimensional Perfectionism Scales have been developed and investigated in relative isolation. Frost, Marten, Lahart and Rosenblate defined perfectionism as the setting of excessively high standards for performance associated with critical self-evaluation. Six dimensions are described: concern over making mistakes, high personal standards, parental expectations, parental criticism, doubt about quality of performance and organization. Internal consistency and validity have been established (25, 26). Hewitt and Flett (30, 31, 33, 35) have developed another approach where three dimensions of

  1. Failure prediction of thin beryllium sheets used in spacecraft structures

    NASA Technical Reports Server (NTRS)

    Roschke, Paul N.; Mascorro, Edward; Papados, Photios; Serna, Oscar R.

    1991-01-01

    The primary objective of this study is to develop a method for prediction of failure of thin beryllium sheets that undergo complex states of stress. Major components of the research include experimental evaluation of strength parameters for cross-rolled beryllium sheet, application of the Tsai-Wu failure criterion to plate bending problems, development of a high order failure criterion, application of the new criterion to a variety of structures, and incorporation of both failure criteria into a finite element code. A Tsai-Wu failure model for SR-200 sheet material is developed from available tensile data, experiments carried out by NASA on two circular plates, and compression and off-axis experiments performed in this study. The failure surface obtained from the resulting criterion forms an ellipsoid. By supplementing experimental data used in the the two-dimensional criterion and modifying previously suggested failure criteria, a multi-dimensional failure surface is proposed for thin beryllium structures. The new criterion for orthotropic material is represented by a failure surface in six-dimensional stress space. In order to determine coefficients of the governing equation, a number of uniaxial, biaxial, and triaxial experiments are required. Details of these experiments and a complementary ultrasonic investigation are described in detail. Finally, validity of the criterion and newly determined mechanical properties is established through experiments on structures composed of SR200 sheet material. These experiments include a plate-plug arrangement under a complex state of stress and a series of plates with an out-of-plane central point load. Both criteria have been incorporated into a general purpose finite element analysis code. Numerical simulation incrementally applied loads to a structural component that is being designed and checks each nodal point in the model for exceedance of a failure criterion. If stresses at all locations do not exceed the failure

  2. Failure Analysis of Space Shuttle Orbiter Valve Poppet

    NASA Technical Reports Server (NTRS)

    Russell, Rick

    2010-01-01

    The poppet failed during STS-126 due to fatigue cracking that most likely was initiated during MDC ground-testing. This failure ultimately led to the discovery that the cracking problem was a generic issue effecting numerous poppets throughout the Shuttle program's history. This presentation has focused on the laboratory analysis of the failed hardware, but this analysis was only one aspect of a comprehensive failure investigation. One critical aspect of the overall investigation was modeling of the fluid flow through this valve to determine the possible sources of cyclic loading. This work has led to the conclusion that the poppets are failing due to flow-induced vibration.

  3. Understanding and Exploiting Spatial Properties of System Failures on Extreme-Scale HPC Systems

    SciTech Connect

    Rogers, James H; Maxwell, Don E

    2015-01-01

    As we approach exascale, the scientific simulations are expected to experience more interruptions due to increased system failures. Designing better HPC resilience techniques requires understanding the key characteristics of system failures on these systems. While temporal properties of system failures on HPC systems have been well-investigated, there is limited understanding about the spatial characteristics of system failures and its impact on the resilience mechanisms. Therefore, we examine the spatial characteristics and behavior of system failures. We investigate the interaction between spatial and temporal characteristics of failures and its implications for system operations and resilience mechanisms on large-scale HPC systems. We show that system failures have spatial locality at different granularity in the system; study impact of different failure-types; and investigate the correlation among different failure-types. Finally, we propose a novel scheme that exploits the spatial locality in failures to improve application and system performance. Our evaluation shows that the proposed scheme significantly improves the system performance in a dynamic and production-level HPC system.

  4. Polyhydramnios and acute renal failure

    PubMed Central

    Hamilton, D. V.; Kelly, Moira B.; Pryor, J. S.

    1980-01-01

    Acute renal failure secondary to ureteric obstruction is described in a primigravida with twin gestation and polyhydramnios. Relief of the obstruction occurred on drainage of the liquor and return to normal renal function following delivery. ImagesFig. 1 PMID:7022419

  5. Insulin Signaling and Heart Failure.

    PubMed

    Riehle, Christian; Abel, E Dale

    2016-04-01

    Heart failure is associated with generalized insulin resistance. Moreover, insulin-resistant states such as type 2 diabetes mellitus and obesity increases the risk of heart failure even after adjusting for traditional risk factors. Insulin resistance or type 2 diabetes mellitus alters the systemic and neurohumoral milieu, leading to changes in metabolism and signaling pathways in the heart that may contribute to myocardial dysfunction. In addition, changes in insulin signaling within cardiomyocytes develop in the failing heart. The changes range from activation of proximal insulin signaling pathways that may contribute to adverse left ventricular remodeling and mitochondrial dysfunction to repression of distal elements of insulin signaling pathways such as forkhead box O transcriptional signaling or glucose transport, which may also impair cardiac metabolism, structure, and function. This article will review the complexities of insulin signaling within the myocardium and ways in which these pathways are altered in heart failure or in conditions associated with generalized insulin resistance. The implications of these changes for therapeutic approaches to treating or preventing heart failure will be discussed. PMID:27034277

  6. Nonresident Fathering and School Failure

    ERIC Educational Resources Information Center

    Menning, Chadwick L.

    2006-01-01

    Does involvement by nonresident fathers affect adolescents' propensity to remain in school? If so, is some involvement necessarily better than none, and are changes in involvement with time associated with changes in the odds of school failure? What aspects of involvement matter the most? This study uses data from the National Longitudinal Study…

  7. Failure Is Always an Option

    ERIC Educational Resources Information Center

    Chudnov, Daniel

    2008-01-01

    Things are failing everywhere. A few years ago, several large companies disappeared almost overnight in a series of scandals. This year, the mortgage industry imploded. More recently, stalwart financial and insurance corporations have been dropping like flies. Failures happen on a smaller scale too. Recently, the all-caps word "FAIL" became a…

  8. Skin Failure: An Emerging Concept.

    PubMed

    Levine, Jeffrey M

    2016-07-01

    Skin failure is an emerging concept that clarifies trends in clinical practice. Its recognition provides common nomenclature, opens research directions, and questions assumptions regarding pressure ulcers as a quality measure. Adoption of the term is a step toward uniform terminology in compliance with a value based payment system.

  9. Insulin Signaling and Heart Failure.

    PubMed

    Riehle, Christian; Abel, E Dale

    2016-04-01

    Heart failure is associated with generalized insulin resistance. Moreover, insulin-resistant states such as type 2 diabetes mellitus and obesity increases the risk of heart failure even after adjusting for traditional risk factors. Insulin resistance or type 2 diabetes mellitus alters the systemic and neurohumoral milieu, leading to changes in metabolism and signaling pathways in the heart that may contribute to myocardial dysfunction. In addition, changes in insulin signaling within cardiomyocytes develop in the failing heart. The changes range from activation of proximal insulin signaling pathways that may contribute to adverse left ventricular remodeling and mitochondrial dysfunction to repression of distal elements of insulin signaling pathways such as forkhead box O transcriptional signaling or glucose transport, which may also impair cardiac metabolism, structure, and function. This article will review the complexities of insulin signaling within the myocardium and ways in which these pathways are altered in heart failure or in conditions associated with generalized insulin resistance. The implications of these changes for therapeutic approaches to treating or preventing heart failure will be discussed.

  10. Children's Coping with Academic Failure

    ERIC Educational Resources Information Center

    Raftery-Helmer, Jacquelyn N.; Grolnick, Wendy S.

    2016-01-01

    There is little consensus on how to conceptualize coping after perceived failure and less is known about the contextual resources that may support or undermine the use of specific coping strategies. This study examined parenting in relation to coping using the framework of self-determination theory and examined the motivational processes through…

  11. Failure rate analysis using GLIMMIX

    SciTech Connect

    Moore, L.M.; Hemphill, G.M.; Martz, H.F.

    1998-12-01

    This paper illustrates use of a recently developed SAS macro, GLIMMIX, for implementing an analysis suggested by Wolfinger and O`Connell (1993) in modeling failure count data with random as well as fixed factor effects. Interest in this software tool arose from consideration of modernizing the Failure Rate Analysis Code (FRAC), developed at Los Alamos National Laboratory in the early 1980`s by Martz, Beckman and McInteer (1982). FRAC is a FORTRAN program developed to analyze Poisson distributed failure count data as a log-linear model, possibly with random as well as fixed effects. These statistical modeling assumptions are a special case of generalized linear mixed models, identified as GLMM in the current statistics literature. In the nearly 15 years since FRAC was developed, there have been considerable advances in computing capability, statistical methodology and available statistical software tools allowing worthwhile consideration of the tasks of modernizing FRAC. In this paper, the approaches to GLMM estimation implemented in GLIMMIX and in FRAC are described and a comparison of results for the two approaches is made with data on catastrophic time-dependent pump failures from a report by Martz and Whiteman (1984). Additionally, statistical and graphical model diagnostics are suggested and illustrated with the GLIMMIX analysis results.

  12. Leveraging Failure in Design Research

    ERIC Educational Resources Information Center

    Lobato, Joanne; Walters, C. David; Hohensee, Charles; Gruver, John; Diamond, Jaime Marie

    2015-01-01

    Even in the resource-rich, more ideal conditions of many design-based classroom interventions, unexpected events can lead to disappointing results in student learning. However, if later iterations in a design research study are more successful, the previous failures can provide opportunities for comparisons to reveal subtle differences in…

  13. Slope failures in municipal solid waste dumps and landfills: a review.

    PubMed

    Blight, Geoffrey

    2008-10-01

    Between 1977 and 2005 six large-scale failures of municipal solid waste dumps and landfills have been recorded in the technical literature. The volumes of waste mobilized in the failures varied from 10-12 000 m(3) in a failure that killed nearly 300 people to 1.5 million m(3) in a failure that caused no deaths or injuries. Of the six failures, four occurred in dumps that, as far as is known, had not been subjected to any prior technical investigation of their shear stability. The remaining two failures occurred in engineer-designed landfills, one of which practised leachate recirculation, and the other co-disposed of liquid waste along with solid waste. The paper reviews, describes and analyses the failures and summarizes their causes.

  14. X-33 Tank Failure During Autoclave Fabrication

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.; Munafo, Paul (Technical Monitor)

    2001-01-01

    During a repair cure cycle on tank #1 of the X-33 liquid hydrogen tanks, a skin to core disbond occurred. Both the inner skin and outer skin of the lobe #1 sandwich panel was noted to have been disbonded and cracked- An investigation was undertaken to determine the cause of this failure. The investigation consisted of reviewing all of the processing data and performing testing on the failed lobe #1, as well as the other lobes, which did not fail during the cure cycle. The tests consisted of residual stress measurements in one of the intact lobes and "plug-pulls" to assess skin to core strength on all of the remaining lobes. Results showed an extremely low bondline strength due to lack of proper filleting of the adhesive, in addition, tests showed a very rapid decrease in strength with increasing temperature, as well as a further decrease in strength with a larger number of cycles. Also, the honeycomb used was not vented so pressure could build up within the cells. All of these factors appeared to be contributors to the failure.

  15. Ampoule failure sensor time response testing: Experiment 1

    NASA Technical Reports Server (NTRS)

    Johnson, M. L.; Watring, D. A.

    1994-01-01

    The response time of an ampoule failure sensor exposed to a liquid or vapor gallium-arsenide (GaAs) is investigated. The experimental configuration represents the sample/ampoule cartridge assembly used in NASA's Crystal Growth Furnace (CGF). The sensor is a chemical fuse made from a metal with which the semiconductor material reacts more rapidly than it does with the containing cartridge. For the III-IV compound of GaAs, a platinum metal was chosen based on the reaction of platinum and arsenic at elevated temperatures which forms a low melting eutectic. Ampoule failure is indicated by a step change in resistance of the failure sensor on the order of megohms. The sensors will increase the safety of crystal growth experiments by providing an indication that an ampoule has failed. Experimental results indicate that the response times (after a known ampoule failure) for the 0.003 and 0.010 inch ampoule failure sensors are 2.4 and 3.6 minutes, respectively. This ampoule failure sensor will be utilized in the CGF during the second United States Microgravity Laboratory Mission (USML-2) and is the subject of a NASA patent application.

  16. Genetics Home Reference: action myoclonus-renal failure syndrome

    MedlinePlus

    ... Action Myoclonus - Renal Failure Syndrome Genetic Testing Registry: Epilepsy, progressive myoclonic 4, with or without renal failure ... failure syndrome action myoclonus–renal failure syndrome AMRF epilepsy, progressive myoclonic 4, with or without renal failure ...

  17. Mechanisms of heart failure in obesity.

    PubMed

    Ebong, Imo A; Goff, David C; Rodriguez, Carlos J; Chen, Haiying; Bertoni, Alain G

    2014-01-01

    Heart failure is a leading cause of morbidity and mortality and its prevalence continues to rise. Because obesity has been linked with heart failure, the increasing prevalence of obesity may presage further rise in heart failure in the future. Obesity-related factors are estimated to cause 11% of heart failure cases in men and 14% in women. Obesity may result in heart failure by inducing haemodynamic and myocardial changes that lead to cardiac dysfunction, or due to an increased predisposition to other heart failure risk factors. Direct cardiac lipotoxicity has been described where lipid accumulation in the heart results in cardiac dysfunction inexplicable of other heart failure risk factors. In this overview, we discussed various pathophysiological mechanisms that could lead to heart failure in obesity, including the molecular mechanisms underlying cardiac lipotoxicity. We defined the obesity paradox and enumerated various premises for the paradoxical associations observed in the relationship between obesity and heart failure.

  18. Taming Test Anxiety: The Activation of Failure-Related Concepts Enhances Cognitive Test Performance of Test-Anxious Students

    ERIC Educational Resources Information Center

    Tempel, Tobias; Neumann, Roland

    2016-01-01

    We investigated processes underlying performance decrements of highly test-anxious persons. Three experiments contrasted conditions that differed in the degree of activation of concepts related to failure. Participants memorized a list of words either containing words related to failure or containing no words related to failure in Experiment 1. In…

  19. Limitations of global morphometry in predicting trabecular bone failure.

    PubMed

    Stauber, Martin; Nazarian, Ara; Müller, Ralph

    2014-01-01

    Efforts in finding independent measures for accurate and reliable prediction of trabecular bone failure have led to the development of a number of morphometric indices characterizing trabecular bone microstructure. Generally, these indices assume a high homogeneity within the bone specimen. However, in the present study we found that the variance in bone volume fraction (BV/TV) in a single bone specimen can be relatively large (CV = 9.07% to 28.23%). To assess the limitations of morphometric indices in the prediction of bone failure for specimens in which the assumption of homogeneity is not met, we harvested 13 cadaveric samples from a single human spine. We tested these cylindrical samples using image-guided failure assessment (IGFA), a technique combining stepwise microcompression and time-lapsed micro-computed tomography (µCT). Additionally, we computed morphometric indices for the entire sample as well as for 10 equal subregions along the anatomical axis. We found that ultimate strength was equally well predicted by BV/TV of the entire sample (R(2)  = 0.55) and BV/TV of the weakest subregion (R(2)  = 0.57). Investigating three-dimensional animations of structural bone failure, we showed that two main failure mechanisms determine the competence of trabecular bone samples; in homogeneous, isotropic trabecular bone samples, competence is determined by a whole set of trabecular elements, whereas in inhomogeneous, anisotropic bone samples a single or a missing trabeculae may induce catastrophic failure. The latter failure mechanism cannot be described by conventional morphometry, indicating the need for novel morphometric indices also applicable to the prediction of failure in inhomogeneous bone samples. PMID:23761214

  20. Orbiter post-tire failure and skid testing results

    NASA Technical Reports Server (NTRS)

    Daugherty, Robert H.; Stubbs, Sandy M.

    1989-01-01

    An investigation was conducted at the NASA Langley Research Center's Aircraft Landing Dynamics Facility (ALDF) to define the post-tire failure drag characteristics of the Space Shuttle Orbiter main tire and wheel assembly. Skid tests on various materials were also conducted to define their friction and wear rate characteristics under higher speed and bearing pressures than any previous tests. The skid tests were conducted to support a feasibility study of adding a skid to the orbiter strut between the main tires to protect an intact tire from failure due to overload should one of the tires fail. Roll-on-rim tests were conducted to define the ability of a standard and a modified orbiter main wheel to roll without a tire. Results of the investigation are combined into a generic model of strut drag versus time under failure conditions for inclusion into rollout simulators used to train the shuttle astronauts.

  1. Interventions for heart failure readmissions: successes and failures.

    PubMed

    Fleming, Lisa M; Kociol, Robb D

    2014-06-01

    Heart failure readmissions result in significant costs to the health care system and to patients' quality of life, but programs to reduce readmissions have met with mixed success. Successful strategies have included multidisciplinary hospital-based quality initiatives, disease management programs, and care transition interventions. Devices like telemonitors and indwelling catheters, however, have met with mixed success. Research is still needed to elucidate the most effective interventions for readmission reduction in the HF population.

  2. Determining the influence of calcification on the failure properties of abdominal aortic aneurysm (AAA) tissue.

    PubMed

    O'Leary, Siobhan A; Mulvihill, John J; Barrett, Hilary E; Kavanagh, Eamon G; Walsh, Michael T; McGloughlin, Tim M; Doyle, Barry J

    2015-02-01

    Varying degrees of calcification are present in most abdominal aortic aneurysms (AAAs). However, their impact on AAA failure properties and AAA rupture risk is unclear. The aim of this work is evaluate and compare the failure properties of partially calcified and predominantly fibrous AAA tissue and investigate the potential reasons for failure. Uniaxial mechanical testing was performed on AAA samples harvested from 31 patients undergoing open surgical repair. Individual tensile samples were divided into two groups: fibrous (n=31) and partially calcified (n=38). The presence of calcification was confirmed by fourier transform infrared spectroscopy (FTIR). A total of 69 mechanical tests were performed and the failure stretch (λf), failure stress (σf) and failure tension (Tf) were recorded for each test. Following mechanical testing, the failure sites of a subset of both tissue types were examined using scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) to investigate the potential reasons for failure. It has been shown that the failure properties of partially calcified tissue are significantly reduced compared to fibrous tissue and SEM and EDS results suggest that the junction between a calcification deposit and the fibrous matrix is highly susceptible to failure. This study implicates the presence of calcification as a key player in AAA rupture risk and provides further motivation for the development of non-invasive methods of measuring calcification.

  3. Determining the influence of calcification on the failure properties of abdominal aortic aneurysm (AAA) tissue.

    PubMed

    O'Leary, Siobhan A; Mulvihill, John J; Barrett, Hilary E; Kavanagh, Eamon G; Walsh, Michael T; McGloughlin, Tim M; Doyle, Barry J

    2015-02-01

    Varying degrees of calcification are present in most abdominal aortic aneurysms (AAAs). However, their impact on AAA failure properties and AAA rupture risk is unclear. The aim of this work is evaluate and compare the failure properties of partially calcified and predominantly fibrous AAA tissue and investigate the potential reasons for failure. Uniaxial mechanical testing was performed on AAA samples harvested from 31 patients undergoing open surgical repair. Individual tensile samples were divided into two groups: fibrous (n=31) and partially calcified (n=38). The presence of calcification was confirmed by fourier transform infrared spectroscopy (FTIR). A total of 69 mechanical tests were performed and the failure stretch (λf), failure stress (σf) and failure tension (Tf) were recorded for each test. Following mechanical testing, the failure sites of a subset of both tissue types were examined using scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) to investigate the potential reasons for failure. It has been shown that the failure properties of partially calcified tissue are significantly reduced compared to fibrous tissue and SEM and EDS results suggest that the junction between a calcification deposit and the fibrous matrix is highly susceptible to failure. This study implicates the presence of calcification as a key player in AAA rupture risk and provides further motivation for the development of non-invasive methods of measuring calcification. PMID:25482218

  4. On a common critical state in localized and diffuse failure modes

    NASA Astrophysics Data System (ADS)

    Zhu, Huaxiang; Nguyen, Hien N. G.; Nicot, François; Darve, Félix

    2016-10-01

    Accurately modeling the critical state mechanical behavior of granular material largely relies on a better understanding and characterizing the critical state fabric in different failure modes, i.e. localized and diffuse failure modes. In this paper, a mesoscopic scale is introduced, in which the organization of force-transmission paths (force-chains) and cells encompassed by contacts (meso-loops) can be taken into account. Numerical drained biaxial tests using a discrete element method are performed with different initial void ratios, in order to investigate the critical state fabric on the meso-scale in both localized and diffuse failure modes. According to the displacement and strain fields extracted from tests, the failure mode and failure area of each specimen are determined. Then convergent critical state void ratios are observed in failure area of specimens. Different mechanical features of two kinds of meso-structures (force-chains and meso-loops) are investigated, to clarify whether there exists a convergent meso-structure inside the failure area of granular material, as the signature of critical state. Numerical results support a positive answer. Failure area of both localized and diffuse failure modes therefore exhibits the same fabric in critical state. Hence, these two failure modes prove to be homological with respect to the concept of the critical state.

  5. Disastrous events and political failures.

    PubMed

    Levett, Jeffrey

    2015-06-01

    Response to the Ebola crisis (ongoing event) has been less than efficient. It has been monitored less than adequately by the international community and has been coordinated poorly in the USA. The event is used as a platform to examine deficiencies in public health infrastructure, the limits of its political and financial support, and how political outcomes can be affected. The need to tease out the political determinants implicit in policy failure and disaster management is argued in this Editorial. Failures mentioned include in the Balkans and in Greece with ongoing austerity. Comments on the real heroes of Ebola on the ground in Africa and the need for a charismatic role for political leaders in public health are also included. PMID:25882131

  6. Red eyes in renal failure.

    PubMed Central

    Klaassen-Broekema, N; van Bijsterveld, O P

    1992-01-01

    Of 57 patients with chronic renal failure who all had deposition of calcium salts in the conjunctival and corneal tissue two developed a brief episode of painful irritation and redness of the conjunctiva and subconjunctiva. This hyperaemia was adjacent to erosions of the corneal epithelium of the eye as a consequence of exfoliation of calcium concretions from the superficial corneal epithelium. Eight patients showed inflammatory reactions of the conjunctivae that were clinically identical to inflamed pingueculae. Three patients showed an inflammatory reaction of the eye that was characterised by a waxy red, more or less diffuse, episcleral and conjunctival hyperaemia extending beyond the palpebral fissure. The average value of the serum calcium concentration in these patients was particularly high and statistically significantly higher than in patients with calcification but without inflammatory signs and also higher than in patients who showed pingueculitis. We propose to reserve the term 'red eye of renal failure' for the latter group of patients. Images PMID:1390507

  7. Disastrous events and political failures.

    PubMed

    Levett, Jeffrey

    2015-06-01

    Response to the Ebola crisis (ongoing event) has been less than efficient. It has been monitored less than adequately by the international community and has been coordinated poorly in the USA. The event is used as a platform to examine deficiencies in public health infrastructure, the limits of its political and financial support, and how political outcomes can be affected. The need to tease out the political determinants implicit in policy failure and disaster management is argued in this Editorial. Failures mentioned include in the Balkans and in Greece with ongoing austerity. Comments on the real heroes of Ebola on the ground in Africa and the need for a charismatic role for political leaders in public health are also included.

  8. SYNTHETIC SLING FAILURE - EVALUATIONS & RECOMMENDATIONS

    SciTech Connect

    MACKEY TC; HENDERSON CS

    2009-10-26

    The information and evaluations provided in this report were compiled to address the recurring problem of synthetic sling failure. As safety is the number one priority in all work aspects, a solution must be devised to prevent accidents from occurring. A total of thirteen cases regarding synthetic sling failure were evaluated in order to determine their causes, effects, and preventative measures. From the collected data, it was found that all cases in which the synthetic sling contacted the edge of its load resulted in sling failure. It is required that adequate synthetic sling protection devices be used to protect slings in any lift where the sling comes in direct contact with the edge or corner of its load. However, there are no consensus codes or standards stating the type, material, or purpose of the type of protective device used to protect the sling from being cut. Numerous industry standards and codes provide vague descriptions on how to protect synthetic slings. Without a clear, concise statement of how to protect synthetic slings, it is common for inadequate materials and sling protection devices to be used in an attempt to meet the intent of these requirements. The use of an inadequate sling protection device is the main cause of synthetic sling failure in all researched cases. Commercial sling protection devices come in many shapes and sizes, and have a variety of names, as well as advertised uses. 'Abrasion pads' and 'wear protectors' are two different names for products with the same intended purpose. There is no distinguishable way to determine the extent of sling protection which these devices will provide, or what specific scenarios they are made for. This creates room for error in a field where error is unacceptable. This report provides a recommended action for hoisting and rigging activities which require synthetic slings to contact a load, as well as recommended changes to industry standards which will benefit overall industry safety.

  9. [Reactor safety and human failure].

    PubMed

    Smidt, D

    1979-12-01

    Reactor safety is given by the reliable solution of 3 tasks: on-time shutdown, continuous decay-heat removal, safe containment. After describing the general strategy of their solution even under upset conditions the most important engineered safeguards of pressurized water reactors are summarized. The important problem of human failure is discussed in some more detail. For the example Harrisburg some difficulties, but also some technical countermeasures are illustrated. PMID:537639

  10. Multiaxial failure characterization of composites

    SciTech Connect

    Groves, S.E.; Sanchez, R.J.; Feng, W.W.

    1991-02-01

    The primary objective of this research has been to develop a multiaxial testing capability for continuous fiber composites using the axial/torsion/internal pressurization of tubes. This capability enables one to generate the two-dimensional (in-plane) failure surface for these materials. The multiaxial test specimen consists of a 5.08 cm (2.0 in.) diameter composite tube with 15{degrees} cast epoxy end cones for gripping. The unique advancement with this new technique is the simple, but very efficient, gripping mechanism that provides a very smooth transition in load from the grip into the specimen. This has eliminated grip related stress risers in the composite tube. Consequently, most of the failures occur in the gage section of the tube. This system is coupled into a biaxial MTS servo hydraulic test machine capable of simultaneously applying axial load, torque, and internal pressure, providing one complete control of the axial, transverse, and shear stresses that develop in the wall of the composite tube. This paper will present the failure results obtained to date for various laminate configurations of Toray 1000/DER332-T403 filament wound carbon/epoxy tubes along with T300/F263 prepreg carbon/epoxy tubes. The goal of our efforts is to develop a more fully characterized three-dimensional failure criterion for these materials. This model will then be incorporated into a large three-dimensional orthotropic finite element model for structural analysis as well as a specialized three-dimensional orthotropic finite element model capable of detailed sub-ply level analysis on sub-structural components. 19 refs., 10 figs.

  11. Accountability for network backup failures

    SciTech Connect

    Benson, W.H.

    1994-02-01

    Regular hard disk backups for workstations are widely recommended. The necessity of backups -- akin to one`s own mortality -- is something most people would rather not think about. This attitude has two consequences. When people do subscribe to automated network backups, they expect the system to perform at a high level of reliability and that their files will be there for them when they need them. Second, they usually fail to appreciate that reliability is a shared responsibility. Although ostensibly their only responsibility is to keep the computer powered on overnight, there are actually many more opportunities for failure within the user`s jurisdiction than in other parts of the infrastructure. High reliability is almost a sine qua non for backups. We describe a strategy for enhancing reliability based on the principle of accountability. This strategy involves monitoring the system, gathering statistics, detecting problems, anticipating problems, troubleshooting, and finally determining where failure occurred within the infrastructure and who should be accountable. We describe a specific backup system in a specific network environment to illustrate the value of accountability. This system, macdumps, backs up Macintosh disks over an AppleTalk network. The original software was written by Dan Tappan of BBN in the early years of the Mac and is available by ftp for noncommercial use. It has proven reliable and robust. Despite the high quality of the fundamental software, there are still many opportunities for failure within the infrastructure. We first discuss accountability in the context of network backups, then briefly describe how the backup system operates, the components of the infrastructure, types of failures experienced, and then summarize our experience.

  12. Outpatient treatment of heart failure.

    PubMed

    McConaghy, John R; Smith, Steven R

    2002-06-01

    Heart failure (HF) affects more than 2 million adults in the United States. This common, costly, and disabling disorder mainly affects the elderly, with prevalence rates up to 10% in patients older than 65 years. The management of HF is responsible for millions of outpatient visits per year, is the most common discharge diagnosis for Medicare beneficiaries, and accounts for more than 5% of total health care dollars spent.

  13. Detecting failure of climate predictions

    USGS Publications Warehouse

    Runge, Michael C.; Stroeve, Julienne C.; Barrett, Andrew P.; McDonald-Madden, Eve

    2016-01-01

    The practical consequences of climate change challenge society to formulate responses that are more suited to achieving long-term objectives, even if those responses have to be made in the face of uncertainty1, 2. Such a decision-analytic focus uses the products of climate science as probabilistic predictions about the effects of management policies3. Here we present methods to detect when climate predictions are failing to capture the system dynamics. For a single model, we measure goodness of fit based on the empirical distribution function, and define failure when the distribution of observed values significantly diverges from the modelled distribution. For a set of models, the same statistic can be used to provide relative weights for the individual models, and we define failure when there is no linear weighting of the ensemble models that produces a satisfactory match to the observations. Early detection of failure of a set of predictions is important for improving model predictions and the decisions based on them. We show that these methods would have detected a range shift in northern pintail 20 years before it was actually discovered, and are increasingly giving more weight to those climate models that forecast a September ice-free Arctic by 2055.

  14. Detecting failure of climate predictions

    NASA Astrophysics Data System (ADS)

    Runge, Michael C.; Stroeve, Julienne C.; Barrett, Andrew P.; McDonald-Madden, Eve

    2016-09-01

    The practical consequences of climate change challenge society to formulate responses that are more suited to achieving long-term objectives, even if those responses have to be made in the face of uncertainty. Such a decision-analytic focus uses the products of climate science as probabilistic predictions about the effects of management policies. Here we present methods to detect when climate predictions are failing to capture the system dynamics. For a single model, we measure goodness of fit based on the empirical distribution function, and define failure when the distribution of observed values significantly diverges from the modelled distribution. For a set of models, the same statistic can be used to provide relative weights for the individual models, and we define failure when there is no linear weighting of the ensemble models that produces a satisfactory match to the observations. Early detection of failure of a set of predictions is important for improving model predictions and the decisions based on them. We show that these methods would have detected a range shift in northern pintail 20 years before it was actually discovered, and are increasingly giving more weight to those climate models that forecast a September ice-free Arctic by 2055.

  15. Predicting Electronic Failure from Smoke

    SciTech Connect

    Tanaka, T.J.

    1999-01-15

    Smoke can cause electronic equipment to fail through increased leakage currents and shorts. Sandia National Laboratories is studying the increased leakage currents caused by smoke with varying characteristics. The objective is to develop models to predict the failure of electronic equipment exposed to smoke. This requires the collection of data on the conductivity of smoke and knowledge of critical electrical systems that control high-consequence operations. We have found that conductivity is a function of the type of fuel, how it is burned, and smoke density. Video recordings of highly biased dc circuits exposed in a test chamber show that during a fire, smoke is attracted to high voltages and can build fragile carbon bridges that conduct leakage currents. The movement of air breaks the bridges, so the conductivity decreases after the fire is extinguished and the test chamber is vented. During the fire, however, electronic equipment may not operate correctly, leading to problems for critical operations dependent on electronic control. The potential for electronic failure is highly dependent on the type of electrical circuit, and Sandia National Laboratories plans to include electrical circuit modeling in the failure models.

  16. Model for heart failure education.

    PubMed

    Baldonado, Analiza; Dutra, Danette; Abriam-Yago, Katherine

    2014-01-01

    Heart failure (HF) is the heart's inability to meet the body's need for blood and oxygen. According to the American Heart Association 2013 update, approximately 5.1 million people are diagnosed with HF in the United States in 2006. Heart failure is the most common diagnosis for hospitalization. In the United States, the HF direct and indirect costs are estimated to be US $39.2 billion in 2010. To address this issue, nursing educators designed innovative teaching frameworks on HF management both in academia and in clinical settings. The model was based on 2 resources: the American Association of Heart Failure Nurses (2012) national nursing certification and the award-winning Pierce County Responsive Care Coordination Program. The HF educational program is divided into 4 modules. The initial modules offer foundational levels of Bloom's Taxonomy then progress to incorporate higher-levels of learning when modules 3 and 4 are reached. The applicability of the key components within each module allows formatting to enhance learning in all areas of nursing, from the emergency department to intensive care units to the medical-surgical step-down units. Also applicable would be to provide specific aspects of the modules to nurses who care for HF patients in skilled nursing facility, rehabilitation centers, and in the home-health care setting. PMID:25140745

  17. Decreased Self-Reported Cognitive Failures after Memory Training

    ERIC Educational Resources Information Center

    Preiss, Marek; Lukavsky, Jiri; Steinova, Dana

    2010-01-01

    In recent years, attention has been focused on investigating the effectiveness of composite memory intervention programs with different age and diagnostics groups. The goal of this study was to measure changes in cognitive lapses by Cognitive Failure Questionnaire (CFQ) in a large trained, dementia free group (Mini-Mental State Examination [MMSE]…

  18. Neurotic Fear of Success, Fear of Failure and Need Achievement.

    ERIC Educational Resources Information Center

    Boardman, Susan K.; And Others

    Neurotic fear of success is conceptually connected to achievement motivation and achievement related conflicts. To investigate the relationship between individuals identified as success-fearers, or failure-fearers, and those high in achievement motivation, 426 college students completed Cohen's Fear of Success Scale, Mandler-Sarason's Test Anxiety…

  19. CSM RCS Design Considerations and Failure Modes

    NASA Technical Reports Server (NTRS)

    Interbartolo, Michael

    2009-01-01

    Objectives include: a) Define major Command and Service Module (CSM) design considerations; b) List Command Module (CM) RCS failures and lessons learned; and c) List Service Module (SM) RCS failures and lessons learned.

  20. Program Helps In Analysis Of Failures

    NASA Technical Reports Server (NTRS)

    Stevenson, R. W.; Austin, M. E.; Miller, J. G.

    1993-01-01

    Failure Environment Analysis Tool (FEAT) computer program developed to enable people to see and better understand effects of failures in system. User selects failures from either engineering schematic diagrams or digraph-model graphics, and effects or potential causes of failures highlighted in color on same schematic-diagram or digraph representation. Uses digraph models to answer two questions: What will happen to system if set of failure events occurs? and What are possible causes of set of selected failures? Helps design reviewers understand exactly what redundancies built into system and where there is need to protect weak parts of system or remove them by redesign. Program also useful in operations, where it helps identify causes of failure after they occur. FEAT reduces costs of evaluation of designs, training, and learning how failures propagate through system. Written using Macintosh Programmers Workshop C v3.1. Can be linked with CLIPS 5.0 (MSC-21927, available from COSMIC).

  1. Heart failure - what to ask your doctor

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000224.htm Heart failure - what to ask your doctor To use the ... a pump that moves blood through your body. Heart failure occurs when blood does not move well and ...

  2. Limitations and Failures of the Layzer Model

    SciTech Connect

    Mikaelian, K O

    2007-12-21

    We report several limitations and failure modes of the recently expanded Layzer model for hydrodynamic instabilities. The failures occur for large initial amplitudes, for stable accelerations, and for spikes in two-fluid systems.

  3. Make Program Failures Work for You.

    ERIC Educational Resources Information Center

    Keller, M. Jean; Mills, Helen H.

    1984-01-01

    Recreation program planners can learn from program failures. Failures should not be viewed as negative statements about personnel. Examining feelings in a supportive staff environment is suggested as a technique for developing competence. (DF)

  4. Prognostic modeling in pediatric acute liver failure.

    PubMed

    Jain, Vandana; Dhawan, Anil

    2016-10-01

    Liver transplantation (LT) is the only proven treatment for pediatric acute liver failure (PALF). However, over a period of time, spontaneous native liver survival is increasingly reported, making us wonder if we are overtransplanting children with acute liver failure (ALF). An effective prognostic model for PALF would help direct appropriate organ allocation. Only patients who would die would undergo LT, and those who would spontaneously recover would avoid unnecessary LT. Deriving and validating such a model for PALF, however, encompasses numerous challenges. In particular, the heterogeneity of age and etiology in PALF, as well as a lack of understanding of the natural history of the disease, contributed by the availability of LT has led to difficulties in prognostic model development. Several prognostic laboratory variables have been identified, and the incorporation of these variables into scoring systems has been attempted. A reliable targeted prognostic model for ALF in Wilson's disease has been established and externally validated. The roles of physiological, immunological, and metabolomic parameters in prognosis are being investigated. This review discusses the challenges with prognostic modeling in PALF and describes predictive methods that are currently available and in development for the future. Liver Transplantation 22 1418-1430 2016 AASLD. PMID:27343006

  5. Impact failure mechanisms of layered structures

    NASA Astrophysics Data System (ADS)

    Choi, Seung-Woo

    The response of layered materials to impact is extensively investigated. This study provides a demonstration of failure mechanisms of structures that undergo elastic and plastic deformation and sustain damage ranging in severity from surface plastic deformation and cracks at low velocity, variously developed conical, lateral and radial cracking at intermediate speeds, to catastrophic fragmentation and erosion that cause penetration at sufficiently high velocity. In order to demonstrate cracking fragmentation and penetration during impact in a structure, the cohesive element modeling and element erosion scheme are used, which is based on nonlinear dynamics using corotational scheme that is particularly effective method for handling relatively large deflection and rotations. It will provide a means of design of structure to moderate in impact loading from foreign object to protect safety zone by identifying the failure modes of structures for a wide range of impact. The assessment of the protection efficiency to impact is presented by computer simulation. Extensive results from a parametric study of the effects of confinement on residual strength and effects of interactions between phenomena that are essentially accompanied by impact, are also provided to supplement the statement.

  6. Gene therapy for heart failure.

    PubMed

    Greenberg, Barry

    2015-09-01

    Heart failure is a major public health problem throughout the world and it is likely that its prevalence will continue to grow over the next several decades. Despite advances in the treatment of heart failure, morbidity and mortality remain unacceptably high. Gene transfer therapy provides a novel strategy for targeting abnormalities in cardiac cells that adversely affect cardiac function. New vectors for gene delivery, mainly adeno-associated viruses (AAVs) that are preferentially taken up by cardiomyocytes, can result in sustained transgene expression. The cardiac isoform of sarco(endo)plasmic reticulum Ca(2+)ATPase (SERCA2a) plays a major role in regulating calcium levels in cardiomyocytes. Abnormal calcium handling by the failing heart caused by a reduction in SERCA2a activity adversely affects both systolic and diastolic function. The Calcium Upregulation by Percutaneous Administration of Gene Therapy in Cardiac Disease (CUPID) study was a Phase 2a double-blind, randomized, placebo-controlled, dose-finding study that was performed in patients with advanced heart failure due to systolic dysfunction. Eligible patients received AAV/SERCA2a or placebo by direct antegrade infusion into the coronary circulation. At the end of 12 months, patients receiving high-dose therapy (i.e. 1×10(13) DNase Resistant Particles) had evidence of favorable changes in several clinically relevant domains compared to patients treated with placebo. There were no safety concerns at any dose of AAV/SERCA2a. Patients treated with AAV/SERCA2a exhibited a striking reduction in cardiovascular events that persisted through 36 months of follow-up compared to patients who received placebo. Transgene expression was detected in the myocardium of patients receiving AAV/SERCA2a gene therapy as long as 31 months after delivery. A second Phase 2b study, CUPID 2, designed to confirm this favorable effect on heart failure events, is currently underway with the results expected to be presented later in

  7. Failure analysis: Status and future trends

    SciTech Connect

    Anderson, R.E.; Soden, J.M.; Henderson, C.L.

    1995-02-01

    Failure analysis is a critical element in the integrated circuit manufacturing industry. This paper reviews the changing role of failure analysis and describes major techniques employed in the industry today. Several advanced failure analysis techniques that meet the challenges imposed by advancements in integrated circuit technology are described and their applications are discussed. Future trends in failure analysis needed to keep pace with the continuing advancements in integrated circuit technology are anticipated.

  8. Treatment failure in humanistic and experiential psychotherapy.

    PubMed

    Watson, Jeanne C

    2011-11-01

    In this article, treatment failure in humanistic experiential psychotherapy is defined and explored. I outline several markers that indicate when treatment is not going well. Factors that contribute to failure include client factors, for example, emotional processing capacities, shame, and impoverished narratives, as well as therapist factors including lack of empathic attunement and inflexibility. Treatment failure is illuminated with a case example drawn from humanistic/experiential psychotherapy, and clinical strategies for dealing with failures are recommended.

  9. Drug Treatment of Heart Failure in Children: Focus on Recent Recommendations from the ISHLT Guidelines for the Management of Pediatric Heart Failure.

    PubMed

    Hussey, Alexander D; Weintraub, Robert G

    2016-04-01

    The International Society of Heart and Lung Transplantation (ISHLT) recently updated consensus pediatric heart failure guidelines from those published in 2004 with an aim to provide a practical evidence-based resource whilst recognizing the influence of adult heart failure practice. The new guidelines were formed from published evidence for heart failure management and used parallels with adult literature where pediatric evidence was lacking. This is a summary of the pharmacological therapies discussed in the new 2014 guidelines, emphasizing changes from the previous recommendations with regards to treatment of chronic heart failure with reduced ejection fraction, chronic heart failure with preserved ejection fraction, and acute decompensated heart failure. Each recommendation is classified according to strength and level of evidence. We also discuss future perspectives in the pharmacological treatment of heart failure. The 2014 ISHLT guidelines have evolved considerably from those published in 2004 with extensive information surrounding the underlying pathophysiology, investigations and recommended treatment. The new guidelines contain a modest amount of new pediatric data on pharmacological therapies and extrapolate adult data when appropriate. It is likely that most new recommendations for pediatric heart failure will continue to be based on therapies of proven benefit in adult heart failure studies. PMID:26939781

  10. 30 CFR 57.7010 - Power failures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Power failures. 57.7010 Section 57.7010 Mineral... Drilling-Surface Only § 57.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  11. 30 CFR 56.7010 - Power failures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Power failures. 56.7010 Section 56.7010 Mineral... Drilling § 56.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  12. The advent of failure analysis software technology

    SciTech Connect

    Henderson, C.L.; Barnard, R.D.

    1994-02-01

    The increasing complexity of integrated circuits demands that software tools, in addition to hardware tools, be used for successful diagnosis of failure. A series of customizable software tools have been developed that organize failure analysis information and provide expert level help to failure analysts to increase their productivity and success.

  13. 30 CFR 56.7010 - Power failures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Power failures. 56.7010 Section 56.7010 Mineral... Drilling § 56.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  14. 30 CFR 57.7010 - Power failures.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Power failures. 57.7010 Section 57.7010 Mineral... Drilling-Surface Only § 57.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  15. 30 CFR 57.7010 - Power failures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Power failures. 57.7010 Section 57.7010 Mineral... Drilling-Surface Only § 57.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  16. 30 CFR 57.7010 - Power failures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Power failures. 57.7010 Section 57.7010 Mineral... Drilling-Surface Only § 57.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  17. 30 CFR 57.7010 - Power failures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Power failures. 57.7010 Section 57.7010 Mineral... Drilling-Surface Only § 57.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  18. 30 CFR 56.7010 - Power failures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Power failures. 56.7010 Section 56.7010 Mineral... Drilling § 56.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  19. 30 CFR 56.7010 - Power failures.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Power failures. 56.7010 Section 56.7010 Mineral... Drilling § 56.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  20. 30 CFR 56.7010 - Power failures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Power failures. 56.7010 Section 56.7010 Mineral... Drilling § 56.7010 Power failures. In the event of power failure, drill controls shall be placed in the neutral position until power is restored....

  1. Acute Renal Failure after Uterine Artery Embolization

    SciTech Connect

    Rastogi, Sachin; Wu, Yu-Hsin; Shlansky-Goldberg, Richard D.; Stavropoulos, S. William

    2004-09-15

    Renal failure is a potential complication of any endovascular procedure using iodinated contrast, including uterine artery embolization (UAE). In this report we present a case of acute renal failure (ARF) following UAE performed as a treatment for uterine fibroids. The likely causes of ARF in this patient are explored and the possible etiologies of renal failure in patients undergoing UAE are reviewed.

  2. Learning from Failures: Archiving and Designing with Failure and Risk

    NASA Technical Reports Server (NTRS)

    VanWie, Michael; Bohm, Matt; Barrientos, Francesca; Turner, Irem; Stone, Robert

    2005-01-01

    Identifying and mitigating risks during conceptual design remains an ongoing challenge. This work presents the results of collaborative efforts between The University of Missouri-Rolla and NASA Ames Research Center to examine how an early stage mission design team at NASA addresses risk, and, how a computational support tool can assist these designers in their tasks. Results of our observations are given in addition to a brief example of our implementation of a repository based computational tool that allows users to browse and search through archived failure and risk data as related to either physical artifacts or functionality.

  3. Structural Failure Condition for Bifurcated Rubble Pile Asteroids

    NASA Astrophysics Data System (ADS)

    Hirabayashi, M.; Scheeres, D. J.

    2014-12-01

    The present study investigates the structural failure conditions of uniformly rotating bifurcated asteroids with cohesion due to a static spin-up. We apply a newly derived technique (Hirabayashi and Scheeres, submitted) that probes the failure state of an asteroid. The technique determines an upper bound condition for structural failure of a slice normal to the minimum moment of inertia axis. The detailed study of these failure modes for cohesive, rotating rubble pile asteroid is motivated by recent observations of 'active asteroids,' bodies which are seemingly disintegrating and fissioning due to their rapid spin rates (Jewitt et al. 2013, 2014; Hirabayashi et al. 2014). Figure 1 shows the shape of 4486 Mithra. We compare 3 slices, slices 1 and 3 including the knobs and slice 2 being the neck (Fig. 1), to determine a more precise condition for structural failure. Figures 2 and 3 describe the limit of friction angle with cohesion of 0 Pa and 500 Pa, respectively. The narrow solid, dashed, and dotted lines give the limits of slices 1, 2, and 3, respectively. The bold solid lines indicate the limit of the total volume, i.e., the whole volume reaching the failure point, and that of the partial volume, i.e., the most sensitive condition among the slices. The shadowed areas show the structurally stable regions. The results show that Mithra's failure locations change as a function of its spin periods and cohesion. For the cohesionless case, the knobs are more sensitive to structural failure than the neck at a spin period ranging from 3.8 hr to 4.8 hr, while the neck fails first at other spin periods. For the 500 Pa cohesion case, the limits of friction angle shift to higher spin periods. Also, at higher spin periods, we find that a lower friction angle is sometimes stronger than a higher friction angle. This comes from the fact that under constant cohesion a lower friction angle can give wider stable regions below the yield envelope. Our study reveals that there exits a

  4. Effects of Treatment Integrity Failures during Differential Reinforcement of Alternative Behavior: A Translational Model

    ERIC Educational Resources Information Center

    Pipkin, Claire St. Peter; Vollmer, Timothy R.; Sloman, Kimberly N.

    2010-01-01

    Differential reinforcement of alternative behavior (DRA) is used frequently as a treatment for problem behavior. Previous studies on treatment integrity failures during DRA suggest that the intervention is robust, but research has not yet investigated the effects of different types of integrity failures. We examined the effects of two types of…

  5. Use of dialysis in the treatment of renal failure in liver disease

    PubMed Central

    Parsons, Victor; Wilkinson, S. P.; Weston, M. J.

    1975-01-01

    Early and thorough peritoneal and haemodialysis has a part to play in the management of selected patients with hepato-renal failure. Patients with advanced irreversible hepatic damage due to cirrhosis, however, may have their prognosis shortened by dialysis, but there are many problems in these techniques in patients with multiple organ failure which still require investigation and solution. PMID:1234334

  6. A Perceptuomotor and Oral Language Program for Children Identified as Potential Failures.

    ERIC Educational Resources Information Center

    Weimer, Wayne Robert

    This study sought to determine whether the de Hirsch Predictive Index Tests would accurately identify children who were potential failures in school. The study also investigated whether a perceptual-motor and oral language program would aid those children identified as potential failures. The Predictive Index Tests were administered to 645 first…

  7. 19 CFR 210.17 - Failures to act other than the statutory forms of default.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 3 2011-04-01 2011-04-01 false Failures to act other than the statutory forms of default. 210.17 Section 210.17 Customs Duties UNITED STATES INTERNATIONAL TRADE COMMISSION INVESTIGATIONS OF UNFAIR PRACTICES IN IMPORT TRADE ADJUDICATION AND ENFORCEMENT Motions § 210.17 Failures to...

  8. 19 CFR 210.17 - Failures to act other than the statutory forms of default.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 3 2010-04-01 2010-04-01 false Failures to act other than the statutory forms of default. 210.17 Section 210.17 Customs Duties UNITED STATES INTERNATIONAL TRADE COMMISSION INVESTIGATIONS OF UNFAIR PRACTICES IN IMPORT TRADE ADJUDICATION AND ENFORCEMENT Motions § 210.17 Failures to...

  9. P513 A RAPID APPROACH FOR DIAGNOSING CERIODAPHNIA DUBIA REPRODUCTIVE FAILURE

    EPA Science Inventory

    Sources of failure in C. dubia culture and testing can be difficult to determine without outside assistance. Investigation of these failures can be time consuming. In the current study, USEPA Region 7 laboratory suffered a drop in reproduction in the C. dubia cultures, with wee...

  10. Non-pharmacological modulation of the autonomic tone to treat heart failure.

    PubMed

    Singh, Jagmeet P; Kandala, Jagdesh; Camm, A John

    2014-01-01

    The autonomic nervous system has a significant role in the pathophysiology and progression of heart failure. The absence of any recent breakthrough advances in the medical therapy of heart failure has led to the evolution of innovative non-pharmacological interventions that can favourably modulate the cardiac autonomic tone. Several new therapeutic modalities that may act at different levels of the autonomic nervous system are being investigated for their role in the treatment of heart failure. The current review examines the role of renal denervation, vagal nerve stimulators, carotid baroreceptors, and spinal cord stimulators in the treatment of heart failure.

  11. Abruptness of Cascade Failures in Power Grids

    NASA Astrophysics Data System (ADS)

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into ``super-grids''.

  12. Abruptness of Cascade Failures in Power Grids

    PubMed Central

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into “super-grids”. PMID:24424239

  13. Abruptness of cascade failures in power grids.

    PubMed

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into "super-grids". PMID:24424239

  14. LDEF electronic systems: Successes, failures, and lessons

    NASA Technical Reports Server (NTRS)

    Miller, Emmett; Porter, Dave; Smith, Dave; Brooks, Larry; Levorsen, Joe; Mulkey, Owen

    1991-01-01

    Following the Long Duration Exposure Facility (LDEF) retrieval, the Systems Special Investigation Group (SIG) participated in an extensive series of tests of various electronic systems, including the NASA provided data and initiate systems, and some experiment systems. Overall, these were found to have performed remarkably well, even though most were designed and tested under limited budgets and used at least some nonspace qualified components. However, several anomalies were observed, including a few which resulted in some loss of data. The postflight test program objectives, observations, and lessons learned from these examinations are discussed. All analyses are not yet complete, but observations to date will be summarized, including the Boeing experiment component studies and failure analysis results related to the Interstellar Gas Experiment. Based upon these observations, suggestions for avoiding similar problems on future programs are presented.

  15. Abruptness of cascade failures in power grids.

    PubMed

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-15

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into "super-grids".

  16. Design, Fabrication and Failure Analysis of Stretchable Electrical Routings

    PubMed Central

    Hocheng, Hong; Chen, Chao-Ming

    2014-01-01

    Stretchable microelectromechanical systems (MEMS) possess higher mechanical deformability and adaptability than devices based on conventional solid and flexible substrates, hence they are particularly desirable for biomedical, optoelectronic, textile and other innovative applications. The stretchability performance can be evaluated by the failure strain of the embedded routing and the strain applied to the elastomeric substrate. The routings are divided into five forms according to their geometry: straight; wavy; wrinkly; island-bridge; and conductive-elastomeric. These designs are reviewed and their resistance-to-failure performance is investigated. The failure modeling, numerical analysis, and fabrication of routings are presented. The current review concludes with the essential factors of the stretchable electrical routing for achieving high performance, including routing angle, width and thickness. The future challenges of device integration and reliability assessment of the stretchable routings are addressed. PMID:24999718

  17. Shuttle Gaseous Hydrogen Venting Risk from Flow Control Valve Failure

    NASA Technical Reports Server (NTRS)

    Drummond, J. Philip; Baurle, Robert A.; Gafney, Richard L.; Norris, Andrew T.; Pellett, Gerald L.; Rock, Kenneth E.

    2009-01-01

    This paper describes a series of studies to assess the potential risk associated with the failure of one of three gaseous hydrogen flow control valves in the orbiter's main propulsion system during the launch of Shuttle Endeavour (STS-126) in November 2008. The studies focused on critical issues associated with the possibility of combustion resulting from release of gaseous hydrogen from the external tank into the atmosphere during assent. The Shuttle Program currently assumes hydrogen venting from the external tank will result in a critical failure. The current effort was conducted to increase understanding of the risk associated with venting hydrogen given the flow control valve failure scenarios being considered in the Integrated In-Flight Anomaly Investigation being conducted by NASA.

  18. A Comparative Study of Failure with Incremental Forming

    NASA Astrophysics Data System (ADS)

    Wu, S. H.; Song, N. N.; Pires, F. M. Andrade

    2016-08-01

    Incremental forming (ISF) is an innovative flexible sheet metal forming process which can be used to manufacture complex shapes from various materials. Due to its flexibility, it has attracted more and more attention over recent decades. Localized deformation and shear through the thickness are essential characteristics of ISF. These lead to specific failure modes and formability of ISF that are different from the conventional stamping process. In this contribution, three continuum damage models (Lemaitre, Gurson, extended GTN models) are formulated and fully coupled with the finite element simulation in a commercial software ABAQUS to predict failure in incremental forming. A comparative investigation of these three damage models has been carried out to analyze both the deformation behavior and failure mechanisms.

  19. The opportunities for the Internet to assist with failure analysis

    SciTech Connect

    Graham-Jones, P.J.; Mellor, B.G.

    1997-12-01

    One of the major reasons for the failure of components is the lack of information readily available to engineers. An engineer cannot be expected to known everything and thus must rely on information that is both accurate and relevant. Within the paper the opportunities for the Internet to assist the engineer by supplying accurate and relevant information are investigated. It is foreseen that rapid development in this field will produce many opportunities for companies to exploit, but a careful evaluation of the requirements and a commonality in the structure and computer protocols used is paramount to the success of such developments. Two techniques are extensively discussed: data mining and the World Wide Web (WWW). Data mining can show the relative occurrence of failure modes and this can help develop Expert and knowledge based systems. Using the WWW, a knowledge-based system for failure analysis has been developed.

  20. Failure Mechanisms of Hollow Fiber Supported Ionic Liquid Membranes

    PubMed Central

    Zeh, Matthew; Wickramanayake, Shan; Hopkinson, David

    2016-01-01

    Hollow fiber supported ionic liquid membranes (SILMs) were tested using the bubble point method to investigate potential failure modes, including the maximum transmembrane pressure before loss of the ionic liquid from the support. Porous hollow fiber supports were fabricated with different pore morphologies using Matrimid® and Torlon® as the polymeric material and 1-hexyl-3-methylimidalzolium bis(trifluoromethylsulfonyl)imide ([C6mim][Tf2N]) as the ionic liquid (IL) component. Hollow fiber SILMs were tested for their maximum pressure before failure, with pressure applied either from the bore side or shell side. It was found that the membranes exhibited one or more of three different modes of failure when pressurized: liquid loss (occurring at the bubble point), rupture, and collapse. PMID:27023620

  1. Cell cycle regulation: repair and regeneration in acute renal failure.

    PubMed

    Price, Peter M; Megyesi, Judit; Safirstein, Robert L

    2003-09-01

    Research into mechanisms of acute renal failure has begun to reveal molecular targets for possible therapeutic intervention. Much useful knowledge into the causes and prevention of this syndrome has been gained by the study of animal models. Most recently, investigation of the effects on acute renal failure of selected gene knock-outs in mice has contributed to our recognition of many previously unappreciated molecular pathways. Particularly, experiments have revealed the protective nature of 2 highly induced genes whose functions are to inhibit and control the cell cycle after acute renal failure. By use of these models we have started to understand the role of increased cell cycle activity after renal stress and the role of proteins induced by these stresses that limit this proliferation.

  2. Cell cycle regulation: repair and regeneration in acute renal failure.

    PubMed

    Price, Peter M; Megyesi, Judit; Saf Irstein, Robert L

    2004-08-01

    Research into mechanisms of acute renal failure has begun to reveal molecular targets for possible therapeutic intervention. Much useful knowledge into the causes and prevention of this syndrome has been gained by the study of animal models. Most recently, investigation of the effects on acute renal failure of selected gene knock-outs in mice has contributed to our recognition of many previously unappreciated molecular pathways. Particularly, experiments have revealed the protective nature of two highly induced genes whose functions are to inhibit and control the cell cycle after acute renal failure. By use of these models we have started to understand the role of increased cell cycle activity after renal stress, and the role of proteins induced by these stresses that limit this proliferation.

  3. Real-time failure control (SAFD)

    NASA Technical Reports Server (NTRS)

    Panossian, Hagop V.; Kemp, Victoria R.; Eckerling, Sherry J.

    1990-01-01

    The Real Time Failure Control program involves development of a failure detection algorithm, referred as System for Failure and Anomaly Detection (SAFD), for the Space Shuttle Main Engine (SSME). This failure detection approach is signal-based and it entails monitoring SSME measurement signals based on predetermined and computed mean values and standard deviations. Twenty four engine measurements are included in the algorithm and provisions are made to add more parameters if needed. Six major sections of research are presented: (1) SAFD algorithm development; (2) SAFD simulations; (3) Digital Transient Model failure simulation; (4) closed-loop simulation; (5) SAFD current limitations; and (6) enhancements planned for.

  4. Malignant vagotonia due to selective baroreflex failure

    NASA Technical Reports Server (NTRS)

    Jordan, J.; Shannon, J. R.; Black, B. K.; Costa, F.; Ertl, A. C.; Furlan, R.; Biaggioni, I.; Robertson, D.

    1997-01-01

    Baroreflex failure is characterized by dramatic fluctuations of sympathetic activity and paroxysms of hypertension and tachycardia. In contrast, unopposed parasympathetic activity has not been described in patients with baroreflex failure because of concurrent parasympathetic denervation of the heart. We describe the unusual case of a patient with baroreflex failure in a setting of preserved parasympathetic control of HR manifesting episodes of severe bradycardia and asystole. Thus, parasympathetic control of the HR may be intact in occasional patients with baroreflex failure. Patients with this selective baroreflex failure require a unique therapeutic strategy for the control of disease manifestations.

  5. Systemic sarcoidosis complicated of acute renal failure: about 12 cases.

    PubMed

    Mahfoudhi, Madiha; Mamlouk, Habiba; Turki, Sami; Kheder, Adel

    2015-01-01

    The sarcoidosis is a systemic granulomatosis affecting most frequently the lungs and the mediastinum. An acute renal failure reveals exceptionally this disease. It's a retrospective study implicating 12 cases of sarcoidosis complicated of acute renal failure. The aim of this study is to determine epidemiological, clinical, biological and histological profile in these cases and then to indicate the interest to consider the diagnosis of sarcoidosis in cases of unexplained renal failure. Extra-renal complications, therapeutic modalities and the outcome were determined in all patients. Our series involved 12 women with an average age of 40 years. Biological investigations showed an abnormal normocalcemia in 7 cases, a hypercalcemia in 5 cases, a hypercalciuria in 10 cases and polyclonal hypergammaglobulinemia in 7 cases. An acute renal failure was found in all patients with a median creatinin of 520 umol/L. For all patients, the renal echography was normal however, the kidney biopsy showed tubulo-interstitial nephritis. The extra-renal signs highlighting pulmonary interstitial syndrome in 5 cases, a sicca syndrome in 4 cases, mediastinal lymph nodes in 2 cases, a lymphocytic alveolitis in 3 cases, an anterior granulomatous uveitis in 2 cases and a polyarthritis in 5 cases. Five patients benefited of hemodialysis. The treatment consisted of corticosteroid in all cases. The follow up was marked by complete resolution of clinical and biological signs. The diagnosis of renal sarcoidosis must be done quickly to prevent renal failure.

  6. Failure mechanisms of ventricular tissue due to deep penetration.

    PubMed

    Gasser, T Christian; Gudmundson, Peter; Dohr, Gottfried

    2009-03-26

    Lead perforation is a rare but serious complication of pacemaker implantations, and in the present study the associated tissue failure was investigated by means of in-vitro penetration of porcine and bovine ventricular tissue. Rectangular patches from the right ventricular free wall and the interventricular septum were separated, bi-axially stretched and immersed in physiological salt solution at 37( composite function)C before load displacement curves of in total 891 penetrations were recorded. To this end flat-bottomed cylindrical punches of different diameters were used, and following mechanical testing the penetration sites were histological analyzed using light and electron microscopes. Penetration pressure, i.e. penetration force divided by punch cross-sectional area decreased slightly from 2.27(SD 0.66) to 1.76(SD0.46)N/mm(2) for punches of 1.32 to 2.30 mm in diameter, respectively. Deep penetration formed cleavages aligned with the local fiber orientation of the tissue, and hence, a mode-I crack developed, where the crack faces were wedged open by the advancing punch. The performed study derived novel failure data from ventricular tissue due to deep penetration and uncovered associated failure mechanisms. This provides information to derive mechanical failure models, which are essential to enrich our current understanding of failure of soft biological tissues and to guide medical device development.

  7. Failure mechanism of single crystal alumina (sapphire) in conventional machining

    SciTech Connect

    Liang, H.

    1995-12-31

    This work is to investigate the types of common failure of sapphire during machining. The various features of failure indicated and types of failure characteristics will be discussed, and where appropriate, several of the fundamental mechanisms involved will be explained. The objective of this work is to show how sapphire is removed during machining. Based on a good understanding of the failure mechanism, the machining conditions can be optimized. Machining methods discussed in this work are all conventional methods. They include grinding, diamond saw cutting, diamond core drilling, abrasive and chemomechanical polishing. The machining conditions used for each different orientation of crystal planes were consistent. The machining surfaces were observed by using optical microscope and scanning electron microscope. The surface roughness and subsurface damage were also measured and compared. Under a consistent machining condition, sapphire is machined based on its different crystal orientations. Before machining, these crystals were annealed in order to get rid of the preexisting defects. After machining, these samples were etched, and observed under optical and scanning electronic microscope. A series of observations was compared. The machining induced failures, as observed, for example, are cleavage, twinning, chipping, and pitting, etc. The effect of crystal orientation on machining is also discussed. Results show the effect of crystal orientation on material removal rate, surface and subsurface damage and thereafter surface finish. It suggests a certain orientation of crystal for a certain type of machining method.

  8. The distinct element analysis of toppling failure mechanisms

    NASA Astrophysics Data System (ADS)

    Özge Dinç, Şaziye; Sinan Işık, Nihat; Karaca, Zeki

    2016-04-01

    This project investigates the toppling failure mechanisms of rock masses having different rock materials and discontinuity properties in slopes that are designed in different heights. For this purpose, PFC2D as a distinct element code was used to anticipate the post failure behaviors of rock masses. After the simulation of laboratory tests on the samples in 2 (width) *4 (height) m, macro mechanical properties of rock masses were determined to be assigned the slopes. The properties of discontinuities were set up based on the smooth-joint method in PFC. The movements in the slopes -equipped with persistent and non-persistent discontinuities- were analyzed by using gravity increase method. The results show that the post failure behaviors of all rock samples have been controlled primarily by joint location and joint length. In addition to this, an increase on the slope height has an influence on the failure mechanism such that triggers the materials to transit from the toppling to circular yielding manner in some models. It has been also worth note that all models begin to fail as soon as the wing cracks develop by tension stresses, thus the tensile strength of the relevant rock material is the most critical mechanic parameter on the failure.

  9. Development of GENOA Progressive Failure Parallel Processing Software Systems

    NASA Technical Reports Server (NTRS)

    Abdi, Frank; Minnetyan, Levon

    1999-01-01

    A capability consisting of software development and experimental techniques has been developed and is described. The capability is integrated into GENOA-PFA to model polymer matrix composite (PMC) structures. The capability considers the physics and mechanics of composite materials and structure by integration of a hierarchical multilevel macro-scale (lamina, laminate, and structure) and micro scale (fiber, matrix, and interface) simulation analyses. The modeling involves (1) ply layering methodology utilizing FEM elements with through-the-thickness representation, (2) simulation of effects of material defects and conditions (e.g., voids, fiber waviness, and residual stress) on global static and cyclic fatigue strengths, (3) including material nonlinearities (by updating properties periodically) and geometrical nonlinearities (by Lagrangian updating), (4) simulating crack initiation. and growth to failure under static, cyclic, creep, and impact loads. (5) progressive fracture analysis to determine durability and damage tolerance. (6) identifying the percent contribution of various possible composite failure modes involved in critical damage events. and (7) determining sensitivities of failure modes to design parameters (e.g., fiber volume fraction, ply thickness, fiber orientation. and adhesive-bond thickness). GENOA-PFA progressive failure analysis is now ready for use to investigate the effects on structural responses to PMC material degradation from damage induced by static, cyclic (fatigue). creep, and impact loading in 2D/3D PMC structures subjected to hygrothermal environments. Its use will significantly facilitate targeting design parameter changes that will be most effective in reducing the probability of a given failure mode occurring.

  10. Telehealth on heart failure: results of the Recap project.

    PubMed

    Varon, Carolina; Alao, Morenikeji; Minter, Jan; Stapleton, Michelle; Thomson, Stuart; Jaecques, Siegfried; Rocca, Hans-Peter Bl; Huffel, Sabine V

    2015-09-01

    Telehealth has become a very important tool that allows the monitoring of heart failure patients in a home environment. However, little is known about the effect that such monitoring systems have on patients' compliance, evolution and self-care behaviour. In particular, the effect that the selected user interface has on these factors is unknown. This study aims to investigate this, and to determine some practicalities that must be considered when designing and implementing a telehealth programme for heart failure. To achieve this, daily measurements of blood pressure, pulse, SpO2 and weight were collected from 534 patients suffering from heart failure. In addition, they were asked to fill in the European heart failure self-care behaviour scale questionnaire and the EQ-5D quality of life questionnaire, before and after the monitoring period. Two telehealth systems were used, the Motiva platform provided by Philips and the standalone unit provided by Docobo, the Doc@Home system. Significant differences were found between both systems concerning the compliance and adherence of patients. Moreover, a general, positive effect of telehealth was identified due to the fact that patients showed an increased self-awareness when managing their condition. These findings are supported by behavioural changes and a better understanding of heart failure from the patients' perspective.

  11. Colloquium: Failure of molecules, bones, and the Earth itself

    NASA Astrophysics Data System (ADS)

    Buehler, Markus J.; Keten, Sinan

    2010-04-01

    Materials fail by recurring rupture and shearing of interatomic bonds at microscopic, molecular scales, leading to disintegration of matter at macroscale and a loss of function. In this Colloquium, the state-of-the-art of investigations on failure mechanisms in materials are reviewed, in particular focusing on atomistic origin of deformation and fracture and relationships between molecular mechanics and macroscale behavior. Simple examples of fracture phenomena are used to illustrate the significance and impact of material failure on our daily lives. Based on case studies, mechanisms of failure of a wide range of materials are discussed, ranging from tectonic plates to rupture of single molecules, and an explanation on how atomistic simulation can be used to complement experimental studies and theory to provide a novel viewpoint in the analysis of complex systems is provided. Biological protein materials are used to illustrate how extraordinary properties are achieved through the utilization of intricate structures where the interplay of weak and strong chemical bonds, size and confinement effects, and hierarchical features play a fundamental role. This leads to a discussion of how even the most robust biological material systems fail, leading to diseases that arise from structural and mechanical alterations at molecular, cellular, and tissue levels. New research directions in the field of materials failure and materials science are discussed and the impact of improving the current understanding of materials failure for applications in nanotechnology, biotechnology, medicine as well as the built environment.

  12. Failure of molecules, bones, and the Earth itself

    NASA Astrophysics Data System (ADS)

    Keten, Sinan

    2012-02-01

    Materials fail by recurring rupture and shearing of interatomic bonds at microscopic, molecular scales, leading to disintegration of matter at macroscale, and a loss of function. In this talk, the state-of-the-art of investigations on failure mechanisms in materials will be presented, in particular focusing on atomistic origin of deformation and fracture, and the relationships between molecular mechanics and macroscale behavior. Simple examples of fracture phenomena are used to illustrate the significance and impact of material failure on our daily lives. Based on case studies, mechanisms of failure of a wide range of materials are discussed, ranging from tectonic plates to rupture of single molecules, and an explanation on how atomistic simulation can be used to complement experimental studies and theory to provide a novel viewpoint in the analysis of complex systems is provided. Biological protein materials are used to illustrate how extraordinary properties are achieved through the utilization of intricate structures where the interplay of weak and strong chemical bonds, size and confinement effects, and hierarchical features play a fundamental role. This leads to a discussion of how even the most robust biological material systems fail, leading to diseases that arise from structural and mechanical alterations at molecular, cellular, and tissue levels. New research directions in the field of materials failure and materials science are discussed and the impact of improving the current understanding of materials failure for applications in nanotechnology, biotechnology, medicine as well as the built environment.

  13. Systemic sarcoidosis complicated of acute renal failure: about 12 cases

    PubMed Central

    Mahfoudhi, Madiha; Mamlouk, Habiba; Turki, Sami; Kheder, Adel

    2015-01-01

    The sarcoidosis is a systemic granulomatosis affecting most frequently the lungs and the mediastinum. An acute renal failure reveals exceptionally this disease. It's a retrospective study implicating 12 cases of sarcoidosis complicated of acute renal failure. The aim of this study is to determine epidemiological, clinical, biological and histological profile in these cases and then to indicate the interest to consider the diagnosis of sarcoidosis in cases of unexplained renal failure. Extra-renal complications, therapeutic modalities and the outcome were determined in all patients. Our series involved 12 women with an average age of 40 years. Biological investigations showed an abnormal normocalcemia in 7 cases, a hypercalcemia in 5 cases, a hypercalciuria in 10 cases and polyclonal hypergammaglobulinemia in 7 cases. An acute renal failure was found in all patients with a median creatinin of 520 umol/L. For all patients, the renal echography was normaln however, the kidney biopsy showed tubulo-interstitial nephritis. The extra-renal signs highlighting pulmonary interstitial syndrome in 5 cases, a sicca syndrome in 4 cases, mediastinal lymph nodes in 2 cases, a lymphocytic alveolitis in 3 cases, an anterior granulomatous uveitis in 2 cases and a polyarthritis in 5 cases. Five patients benefited of hemodialysis. The treatment consisted of corticosteroid in all cases. The follow up was marked by complete resolution of clinical and biological signs. The diagnosis of renal sarcoidosis must be done quickly to prevent renal failure. PMID:26834928

  14. Heart Failure in Rural Communities.

    PubMed

    Verdejo, Hugo E; Ferreccio, Catterina; Castro, Pablo F

    2015-10-01

    Patients with chronic heart failure (CHF) living in rural areas face an increased risk of adverse cardiovascular events. Even in countries with universal access to health care, rural areas are characteristically underserved, with reduced health care providers supply, greater distance to health care centers, decreased physician density with higher reliance on generalists, and high health care staff turnover. On the other hand, patient-related characteristics vary widely among published data. This review describes the epidemiology of CHF in rural or remote settings, organizational and patient-related factors involved in cardiovascular outcomes, and the role of interventions to improve rural health care.

  15. Nutritional support during liver failure.

    PubMed

    Gecelter, G R; Comer, G M

    1995-07-01

    Critically ill patients in varying degrees of liver failure are catabolic and consequently require expeditious caloric support. Unique problems in this group of patients essentially revolve around the diagnosis and management of hepatic encephalopathy. From the overview provided in this text, it can be concluded that, only in overt hepatic coma, should all nitrogen products be withheld while precipitating causes are evaluated. Protein should be reintroduced as rapidly as possible to avoid the consequences of protein deprivation. Once the acute intercurrent illness has resolved, the cirrhotic patient returns to baseline energy and protein requirements indistinguishable from the population at large. PMID:7552976

  16. [Diuretic therapy in heart failure].

    PubMed

    Trullàs, Joan Carles; Morales-Rull, José Luís; Formiga, Francesc

    2014-02-20

    Many of the primary clinical manifestations of heart failure (HF) are due to fluid retention, and treatments targeting congestion play a central role in HF management. Diuretic therapy remains the cornerstone of congestion treatment, and diuretics are prescribed to the majority of HF patients. Despite this ubiquitous use, there is limited evidence from prospective randomized studies to guide the use of diuretics. With the chronic use of diuretic and usually in advanced stages of HF, diuretics may fail to control salt and water retention. This review describes the mechanism of action of available diuretic classes, reviews their clinical use based on scientific evidence and discusses strategies to overcome diuretic resistance.

  17. Failure Assessment of Brazed Structures

    NASA Technical Reports Server (NTRS)

    Flom, Yuri

    2012-01-01

    Despite the great advances in analytical methods available to structural engineers, designers of brazed structures have great difficulties in addressing fundamental questions related to the loadcarrying capabilities of brazed assemblies. In this chapter we will review why such common engineering tools as Finite Element Analysis (FEA) as well as many well-established theories (Tresca, von Mises, Highest Principal Stress, etc) don't work well for the brazed joints. This chapter will show how the classic approach of using interaction equations and the less known Coulomb-Mohr failure criterion can be employed to estimate Margins of Safety (MS) in brazed joints.

  18. Common Variants for Heart Failure

    PubMed Central

    Shen, Shutong; Tao, Lichan; Wang, Xiuzhi; Kong, Xiangqing; Li, Xinli

    2015-01-01

    Heart failure (HF) is a common disease with high morbidity and mortality; however, none of the drugs available are now entirely optimal for the treatment of HF. In addition to various clinical diseases and environment influences, genetic factors also contribute to the development and progression of HF. Identifying the common variants for HF by genome-wide association studies will facilitate the understanding of pathophysiological mechanisms underlying HF. This review summarizes the recently identified common variants for HF risk and outcome and discusses their implications for the clinic therapy. PMID:26085806

  19. Mineralcorticoid antagonists in heart failure.

    PubMed

    D'Elia, Emilia; Krum, Henry

    2014-10-01

    Mineralocorticoid receptor antagonists (MRAs) have become mandated therapy in patients with reduced ejection fraction (systolic) heart failure (HF) across all symptom classes. These agents should also be prescribed in the early post-myocardial infarction setting in those with reduced ejection fraction and either HF symptoms or diabetes. This article explores the pathophysiological role of aldosterone, an endogenous ligand for the mineralcorticoid receptor (MR), and summarizes the clinical data supporting guideline recommendations for these agents in systolic HF. The use of MRAs in novel areas beyond systolic HF ejection is also explored. Finally, the current status of newer agents will be examined. PMID:25217431

  20. Socioeconomic Inequalities in Heart Failure.

    PubMed

    Díaz-Toro, Felipe; Verdejo, Hugo E; Castro, Pablo F

    2015-10-01

    Prevalence and incidence of chronic heart failure (CHF) has increased during the past decades. Beyond its impact on mortality rates, CHF severely impairs quality of life, particularly with the elderly and vulnerable population. Several studies have shown that CHF takes its toll mostly on the uneducated, low-income population, who exhibit impaired access to health care systems, less knowledge regarding its pathology and poorer self-care behaviors. This review summarizes the available evidence linking socioeconomic inequalities and CHF, focusing on the modifiable factors that may explain the impaired health outcomes in socioeconomically deprived populations. PMID:26462090

  1. Post-hepatectomy liver failure

    PubMed Central

    Kauffmann, Rondi

    2014-01-01

    Hepatectomies are among some of the most complex operative interventions performed. Mortality rates after major hepatectomy are as high as 30%, with post-hepatic liver failure (PHLF) representing the major source of morbidity and mortality. We present a review of PHLF, including the current definition, predictive factors, pre-operative risk assessment, techniques to prevent PHLF, identification and management. Despite great improvements in morbidity and mortality, liver surgery continues to demand excellent clinical judgement in selecting patients for surgery. Appropriate choice of pre-operative techniques to improve the functional liver remnant (FLR), fastidious surgical technique, and excellent post-operative management are essential to optimize patient outcomes. PMID:25392835

  2. [Bone-based anchorage failure].

    PubMed

    Mer, Grégoria; Brezulier, Damien; Sorel, Olivier

    2016-03-01

    The aim of this article is to list the circumstances likely to give rise to failure of orthodontic temporary bone-supported anchorage and, hence, to attempt to define criteria for correct miniscrew usage. Our study was based on a review of the literature and analyses of clinical cases. Our findings show that, with a sound knowledge of the indications for screw selection and positioning and of the insertion protocols combined with a clear understanding of orthodontic mechanics, bone-based anchorage can henceforth provide orthodontists with an essential tool to enable formerly unachievable dental movements and to stabilize unwanted movements, thus making treatment both more reliable and more effective. PMID:27083224

  3. Organic Evaporator steam valve failure

    SciTech Connect

    Jacobs, R. A.

    1992-09-29

    DWPF Technical has requested an analysis of the capacity of the organic Evaporator (OE) condenser (OEC) be performed to determine its capability in the case where the OE steam flow control valve fails open. Calculations of the OE boilup and the OEC heat transfer coefficient indicate the OEC will have more than enough capacity to remove the heat at maximum OE boilup. In fact, the Salt Cell Vent Condenser (SCVC) should also have sufficient capacity to handle the maximum OE boilup. Therefore it would require simultaneous loss of OEC and/or SCVC condensing capacity for the steam valve failure to cause high benzene in the Process Vessel Vent System (PVVS).

  4. Fracture - An Unforgiving Failure Mode

    NASA Technical Reports Server (NTRS)

    Goodin, James Ronald

    2006-01-01

    During the 2005 Conference for the Advancement for Space Safety, after a typical presentation of safety tools, a Russian in the audience simply asked, "How does that affect the hardware?" Having participated in several International System Safety Conferences, I recalled that most attention is dedicated to safety tools and little, if any, to hardware. The intent of this paper on the hazard of fracture and failure modes associated with fracture is my attempt to draw attention to the grass roots of system safety - improving hardware robustness and resilience.

  5. Predicting Failure Progression and Failure Loads in Composite Open-Hole Tension Coupons

    NASA Technical Reports Server (NTRS)

    Arunkumar, Satyanarayana; Przekop, Adam

    2010-01-01

    Failure types and failure loads in carbon-epoxy [45n/90n/-45n/0n]ms laminate coupons with central circular holes subjected to tensile load are simulated using progressive failure analysis (PFA) methodology. The progressive failure methodology is implemented using VUMAT subroutine within the ABAQUS(TradeMark)/Explicit nonlinear finite element code. The degradation model adopted in the present PFA methodology uses an instantaneous complete stress reduction (COSTR) approach to simulate damage at a material point when failure occurs. In-plane modeling parameters such as element size and shape are held constant in the finite element models, irrespective of laminate thickness and hole size, to predict failure loads and failure progression. Comparison to published test data indicates that this methodology accurately simulates brittle, pull-out and delamination failure types. The sensitivity of the failure progression and the failure load to analytical loading rates and solvers precision is demonstrated.

  6. Renal failure in patients with multiple myeloma.

    PubMed

    Almueilo, Samir H

    2015-01-01

    Renal dysfunction is encountered in 20-25% of patients with multiple myeloma (MM) at the time of diagnosis. There is often a precipitating event. Several biochemical and clinical correlations with renal failure in MM have been reported. Renal failure in MM is associated with worse outcome of the disease. We retrospectively analyzed the medical records of 64 patients with MM admitted to our institution during the period January 1992 to December 2012. Abnormal renal function was observed in 24 (37.5%) patients and 17 (26.6%) of them had renal failure; 14 of the 17 (82.4%) of patients with renal failure had Stage III MM. Urine Bence- Jones protein was positive in ten (58.8%) patients with renal failure versus ten (21.3%) patients without renal failure (P = 0.004). Potential precipitating factors of renal failure were determined in nine patients. Renal function normalized in 11 patients with simple measures, while six patients required hemodialysis; one remained dialysis dependent till time of death. Early mortality occurred in five (29.4%) patients with renal failure as compared with two (4.3%) patients in the group without renal failure (P = 0.005). In conclusion, renal failure is associated with a higher tumor burden and Bence-Jones proteinuria in patients with MM. It is reversible in the majority of patients; however, early mortality tends to be higher in patients with persistent renal failure.

  7. Hypogonadism and renal failure: An update.

    PubMed

    Thirumavalavan, Nannan; Wilken, Nathan A; Ramasamy, Ranjith

    2015-01-01

    The prevalence of both hypogonadism and renal failure is increasing. Hypogonadism in men with renal failure carries with it significant morbidity, including anemia and premature cardiovascular disease. It remains unclear whether testosterone therapy can affect the morbidity and mortality associated with renal failure. As such, in this review, we sought to evaluate the current literature addressing hypogonadism and testosterone replacement, specifically in men with renal failure. The articles chosen for this review were selected by performing a broad search using Pubmed, Embase and Scopus including the terms hypogonadism and renal failure from 1990 to the present. This review is based on both primary sources as well as review articles. Hypogonadism in renal failure has a multifactorial etiology, including co-morbid conditions such as diabetes, hypertension, old age and obesity. Renal failure can lead to decreased luteinizing hormone production and decreased prolactin clearance that could impair testosterone production. Given the increasing prevalence of hypogonadism and the potential morbidity associated with hypogonadism in men with renal failure, careful evaluation of serum testosterone would be valuable. Testosterone replacement therapy should be considered in men with symptomatic hypogonadism and renal failure, and may ameliorate some of the morbidity associated with renal failure. Patients with all stages of renal disease are at an increased risk of hypogonadism that could be associated with significant morbidity. Testosterone replacement therapy may reduce some of the morbidity of renal failure, although it carries risk.

  8. The intergenerational transmission of fear of failure.

    PubMed

    Elliot, Andrew J; Thrash, Todd M

    2004-08-01

    The intergenerational transmission of fear of failure was examined in two studies with undergraduates and their parents. Parent-undergraduate concordance in fear of failure was documented for mothers and fathers, controlling for parents' and undergraduate's impression management and self-deceptive enhancement response tendencies. Love withdrawal was validated as a mediator of parent-undergraduate concordance in fear of failure for mothers but not for fathers. Mothers' and fathers' fear of failure was also a positive predictor of undergraduate's adoption of performance-avoidance goals in the classroom, and undergraduate's fear of failure was shown to mediate this relationship. Fathers' fear of failure was also a negative predictor of undergraduate's mastery goal adoption, and this relationship was likewise mediated by undergraduate's fear of failure. The results are discussed in terms of the reorienting of positive, appetitive achievement motivation toward negative, aversive achievement motivation. PMID:15257781

  9. Interfibre Failure Characterisation of Unidirectional and Triax Glass Fibre Non-Crimp Fabric Reinforced Epoxy Laminates

    NASA Astrophysics Data System (ADS)

    Laustsen, S.; Lund, E.; Kühlmeier, L.; Thomsen, O. T.

    2015-02-01

    The in-plane failure envelopes of unidirectional (UD) laminae in a UD and a Triax (0°, ±45°) laminate configuration have been investigated. The two laminate configurations have been characterised by testing off-axis specimens in uniaxial tension and compression at different angles relative to the fibre direction and further by Iosipescu shear tests. Strain gauge and Digital Image Correlation (DIC) measurements were used to measure the deformation states during loading, and to record the stress-strain responses to identify the initiation of failure and investigate the heterogeneity of the material and possible parasitic effects. A novel analysis methodology to determine the so-called `failure initiation strength' based on the second derivative of the stresses with respect to the strains has been adopted. The experimentally determined `failure initiation stresses' were compared with predictions from the commonly applied Maximum Stress, Tsai-Wu, and Puck failure criteria. From this work, a thorough comparison of the UD and Triax failure envelopes has been facilitated. It is shown that failure prediction for the Triax laminate based on the failure envelope derived from UD lamina tests may be too conservative in comparison with fitting a failure criterion directly to the Triax laminate test data. The latter approach implies that the Triax laminate is considered as a single lamina with homogenised properties, which in principle violates the theoretical background of the considered failure criteria, since these are established to predict failure for a UD lamina. However, the simple homogenisation is shown to be a useful design oriented approach for providing a simple estimation of the onset of failure in laminate configurations composed of e.g., multiple layers of Triax. Thus, a reliable and efficient approach is offered for the structural integrity assessment, which takes the non-crimp fabric configurations directly or `as delivered' into account.

  10. Floods from tailings dam failures.

    PubMed

    Rico, M; Benito, G; Díez-Herrero, A

    2008-06-15

    This paper compiles the available information on historic tailings dam failures with the purpose to establish simple correlations between tailings ponds geometric parameters (e.g., dam height, tailings volume) and the hydraulic characteristics of floods resulting from released tailings. Following the collapse of a mining waste dam, only a part of tailings and polluted water stored at the dam is released, and this outflow volume is difficult to estimate prior the incident. In this study, tailings' volume stored at the time of failure was shown to have a good correlation (r2=0.86) with the tailings outflow volume, and the volume of spilled tailings was correlated with its run-out distance (r2=0.57). An envelope curve was drawn encompassing the majority of data points indicating the potential maximum downstream distance affected by a tailings' spill. The application of the described regression equations for prediction purposes needs to be treated with caution and with support of on-site measurement and observations. However, they may provide a universal baseline approximation on tailing outflow characteristics (even if detailed dam information is unavailable), which is of a great importance for risk analysis purposes.

  11. [Nutrition and chronic renal failure].

    PubMed

    Ayúcar Ruiz de Galarreta, A; Cordero Lorenzana, M L; Martínez-Puga y López, E; Gómez Seijo, A; Escudero Alvarez, E

    2000-01-01

    The causes of malnutrition in chronic terminal kidney failure are reviewed in the situation both before and after dialysis, as are the malnutrition rates in both circumstances and their treatment. Malnutrition has a high prevalence in terminal kidney patients, partly as a result of the therapeutic restriction on calories and proteins, but also due to the metabolic reactions typical of the disease and to anorexia. In patients subjected to dialytical methods, certain other mechanisms are added. In addition to malnutrition, there are alterations in the metabolism of calcium, phosphorus and potassium, as well as lipids, thus limiting nutritional therapy's ability to restore the nutritional status to normal. An awareness of energy expenditure in chronic terminal kidney failure and the consequences of malnutrition have led to new challenges in nutritional therapy, both in the dose and quality of the proteins, with a debate raging over the advantages of ketoanalogues, and also in the methods for providing nutrients. The ideal nutritional method for repletion is oral administration, but this can be enhanced with artificial support such as oral supplements, parenteral nutrition during dialysis or such alternatives as enteral nutrition at home in the case of chronic kidney problems in children, using percutaneous endoscopic gastrostomy (PEG), in order to nourish the patients and minimize growth disorders.

  12. The failure of cancer chemoprevention.

    PubMed

    Potter, John D

    2014-05-01

    Chemoprevention is proposed as a clinical analogue of population prevention, aimed at reducing likelihood of disease progression, not across the population, but in identified high-risk individuals and not by behavioral or lifestyle modification, but by the use of pharmaceutical agents. Cardiovascular chemoprevention is successful via control of hyperlipidemias and hypertension. However, chemoprevention of cancer is an almost universal failure: not only are some results null; even more frequently, there is an excess of disease, including disease that the agents were chosen specifically to reduce. A brief introduction is followed by the evidence for a wide variety of agents and their largely deleterious, sometimes null, and in one case, largely beneficial, consequences as possible chemopreventives. The agents include (i) those that are food derived and their synthetic analogues: β-carotene, folic acid, retinol and retinoids, vitamin E, multivitamin supplements, vitamin C, calcium and selenium and (ii) agents targeted at metabolic and hormonal pathways: statins, estrogen and antagonists, 5α-reductase inhibitors. There are two agents for which there is good evidence of benefit when the strategy is focused on those at defined high risk but where wider application is much more problematic: aspirin and tamoxifen. The major problems with cancer chemoprevention are presented. This is followed by a hypothesis to explain the failure of cancer chemoprevention as an enterprise, arguing that the central tenets that underpin it are flawed and showing why, far from doing good, cancer chemoprevention causes harm.

  13. Heart failure and sleep disorders.

    PubMed

    Parati, Gianfranco; Lombardi, Carolina; Castagna, Francesco; Mattaliano, Paola; Filardi, Pasquale Perrone; Agostoni, Piergiuseppe

    2016-07-01

    Awareness of the importance of sleep-related disorders in patients with cardiovascular diseases is growing. In particular, sleep-disordered breathing, short sleep time, and low sleep quality are frequently reported by patients with heart failure (HF). Sleep-disordered breathing, which includes obstructive sleep apnoea (OSA) and central sleep apnoea (CSA), is common in patients with HF and has been suggested to increase the morbidity and mortality in these patients. Both OSA and CSA are associated with increased sympathetic activation, vagal withdrawal, altered haemodynamic loading conditions, and hypoxaemia. Moreover, OSA is strongly associated with arterial hypertension, the most common risk factor for cardiac hypertrophy and failure. Intrathoracic pressure changes are also associated with OSA, contributing to haemodynamic alterations and potentially affecting overexpression of genes involved in ventricular remodelling. HF treatment can decrease the severity of both OSA and CSA. Indeed, furosemide and spironolactone administration, exercise training, cardiac resynchronization therapy, and eventually heart transplantation have shown a positive effect on OSA and CSA in patients with HF. At present, whether CSA should be treated and, if so, which is the optimal therapy is still debated. By contrast, more evidence is available on the beneficial effects of OSA treatment in patients with HF.

  14. Analysis of sucker rod and sinkerbar failures

    SciTech Connect

    Waggoner, J.R.; Buchheit, R.G.

    1992-12-31

    This paper presents results from a study to analyze the performance and failures of the sucker rod/sinkerbar string used in beam-pumping operations through metallography, structural finite element analysis, and detailed failure data collection. Metallography demonstrated that microstructure of steel bar stock needs to be considered. Current specification based on tensile strength, or yield strength, may not be appropriate since failure occurs because of fatigue and not yielding. Finite element analysis of the threaded connection identifies stress and fatigue concentrations and quantitatively assesses the performance and failure of coupling designs under a variety of loading conditions. Subcritical fractures observed in the metallography are also suggested by the calculated stress distribution in the threaded coupling. Failure data illustrates both magnitude and frequency of the failures, as well as categorizing the suspected cause of failure. This failure information alone can reduce failures by indicating specific problem areas. These results are expected to yield improved choice of metal bar stock, thread design, and make-up practices which can reduce sucker rod failures.

  15. Analysis of sucker rod and sinkerbar failures

    SciTech Connect

    Waggoner, J.R.; Buchheit, R.G.

    1992-01-01

    This paper presents results from a study to analyze the performance and failures of the sucker rod/sinkerbar string used in beam-pumping operations through metallography, structural finite element analysis, and detailed failure data collection. Metallography demonstrated that microstructure of steel bar stock needs to be considered. Current specification based on tensile strength, or yield strength, may not be appropriate since failure occurs because of fatigue and not yielding. Finite element analysis of the threaded connection identifies stress and fatigue concentrations and quantitatively assesses the performance and failure of coupling designs under a variety of loading conditions. Subcritical fractures observed in the metallography are also suggested by the calculated stress distribution in the threaded coupling. Failure data illustrates both magnitude and frequency of the failures, as well as categorizing the suspected cause of failure. This failure information alone can reduce failures by indicating specific problem areas. These results are expected to yield improved choice of metal bar stock, thread design, and make-up practices which can reduce sucker rod failures.

  16. Postbuckling failure of composite plates with holes

    NASA Technical Reports Server (NTRS)

    Lee, H. H.; Hyer, M. W.

    1992-01-01

    This paper summarizes a study focused on understanding the failure mechanisms present in a plate with a centrally located circular hole loaded inplane into the postbuckling range of deflections. The study was numerical and experimental in nature and had as a goal the a priori prediction of failure using existing failure data from several sources, together with a stress analysis. The maximum stress failure criterion was used to predict failure and both intra- and interlaminar stresses were considered. Four laminates were considered. The phenomenon of modal interaction, or the jumping from one deformed configuration to another, is discussed. With this jumping, the plate configuration may change from one half-wave in the loading direction to two half-waves in the loading direction. The study concludes that the failure in (+/-45/0/90)2s and (+/-45/2(2))2s laminates is due to fiber compression failure and is predictable. The failure load is, for the most part, independent of response configuration. The (+/-45/0/(6))s laminate fails due to interlaminar shear along the simple support, while the response and failure of the (+/-45)4s laminate is governed to a large degree by material nonlinearities and progressive failure.

  17. Plasma Glutamine Concentrations in Liver Failure

    PubMed Central

    Helling, Gunnel; Wahlin, Staffan; Smedberg, Marie; Pettersson, Linn; Tjäder, Inga; Norberg, Åke; Rooyackers, Olav; Wernerman, Jan

    2016-01-01

    Background Higher than normal plasma glutamine concentration at admission to an intensive care unit is associated with an unfavorable outcome. Very high plasma glutamine levels are sometimes seen in both acute and chronic liver failure. We aimed to systematically explore the relation between different types of liver failure and plasma glutamine concentrations. Methods Four different groups of patients were studies; chronic liver failure (n = 40), acute on chronic liver failure (n = 20), acute fulminant liver failure (n = 20), and post-hepatectomy liver failure (n = 20). Child-Pugh and Model for End-stage Liver Disease (MELD) scores were assessed as indices of liver function. All groups except the chronic liver failure group were followed longitudinally during hospitalisation. Outcomes were recorded up to 48 months after study inclusion. Results All groups had individuals with very high plasma glutamine concentrations. In the total group of patients (n = 100), severity of liver failure correlated significantly with plasma glutamine concentration, but the correlation was not strong. Conclusion Liver failure, regardless of severity and course of illness, may be associated with a high plasma glutamine concentration. Further studies are needed to understand whether high glutamine levels should be regarded as a biomarker or as a contributor to symptomatology in liver failure. PMID:26938452

  18. Space Shuttle Solid Rocket Booster Decelerator Subsystem Drop Test 3 - Anatomy of a failure

    NASA Technical Reports Server (NTRS)

    Runkle, R. E.; Woodis, W. R.

    1979-01-01

    A test failure dramatically points out a design weakness or the limits of the material in the test article. In a low budget test program, with a very limited number of tests, a test failure sparks supreme efforts to investigate, analyze, and/or explain the anomaly and to improve the design such that the failure will not recur. The third air drop of the Space Shuttle Solid Rocket Booster Recovery System experienced such a dramatic failure. On air drop 3, the 54-ft drogue parachute was totally destroyed 0.7 sec after deployment. The parachute failure investigation, based on analysis of drop test data and supporting ground element test results is presented. Drogue design modifications are also discussed.

  19. The Displacement Perspective During Ultimate Failure of Composite Laminates

    NASA Astrophysics Data System (ADS)

    Pal, P.; Bhar, A.

    2013-04-01

    This paper deals with the studies on the state of displacement of symmetric and anti-symmetric angle-ply and cross-ply laminated composite plates during its ultimate failure, subjected to transverse static load. First-order shear deformation theory (FSDT) is employed in conjunction with the finite element approach using eight-noded quadratic isoparametric element. The free vibration analyses of isotropic and laminated composite plates are carried out to ensure the overall validity of the present finite element formulation. The mid surface of the laminate is considered as the reference plane. The principal material directions in different laminae are oriented to produce a laminated structural element capable of resisting loads in several directions. The stiffness of a composite laminate is obtained from the properties of the constituent laminae. The affected stiffness of the failed lamina is discarded completely after the failure of weakest ply. The rigidity matrix of the laminate with remaining laminae is re-established. The re-evaluation process continues until the laminate fails completely. To investigate the displacement behaviour of laminates during the ultimate failure, parametric studies are carried out for different cases by varying the stacking sequences, fiber orientations, layer thicknesses, aspect ratios and the number of layers in the laminate. The comparison of results in terms of non-dimensional natural frequencies and ply-by-ply failure analyses obtained from the present investigation are made with those available in the reported literature.

  20. Exhausting Multiple Hemodialysis Access Failures

    PubMed Central

    Bolleke, Erjola; Seferi, Saimir; Rroji, Merita; Idrizi, Alma; Barbullushi, Myftar; Thereska, Nestor

    2014-01-01

    ABSTRACT Introduction: Vascular access is often considered the Achilles heel the of hemodialysis because of its impact on morbidity, all cause mortality and finally costs of these patients. The most common complication of permanent hemodialysis (HD) vascular access is thrombosis, with some cases being related to hypercoagulability states. Antiphospholipid antibody syndrome (APAS) is a cause of increased thrombotic tendency, and this may complicate the management of such patients on HD. Case report: We describe a 41-year-old woman with end stage renal disease (ESRD) from Adult Polycystic Kidney Disease who was referred to our tertiary care center for treatment and selection of renal replacement therapy form. It was thought to initiate with peritoneal dialysis considering her actual conditions. She was putted on hemodialysis for several sessions, and a subclavian cathether was her first vascular access. The surgeon created an arterio-venous fistula which did not mature. After the implantation of the peritoneal cathether she started peritoneal dialysis and continued living with that for 2 years. She felt exhausted and because of a grave peritonitis episode accompanied with procedure failure and a long hospitalization she was transferred to hemodialysis. Renal transplantation was not possible because she didn’t have a kidney donation. She was maintained on regular HD, but her dialysis care was complicated by recurrent vascular access failures. She had multiple interventions for arterio-venous fistulas and grafts but almost all of them failed due to thrombosis to the extent that only one access site was available for her routine renal replacement treatment. A thorough thrombophilia screen confirmed the presence of antiphospholipid antibodies. A diagnosis of APAS was made and she was anticoagulated with warfarin. The AVG made in this last available site is still working from 18 months. If it fails we have no answers and solutions for her. Conclusion: The presence of