Science.gov

Sample records for accelerated thermal cycling

  1. Mir Cooperative Solar Array Project Accelerated Life Thermal Cycling Test

    NASA Technical Reports Server (NTRS)

    Hoffman, David J.; Scheiman, David A.

    1996-01-01

    The Mir Cooperative Solar Array (MCSA) project was a joint U.S./Russian effort to build a photovoltaic (PV) solar array and deliver it to the Russian space station Mir. The MCSA will be used to increase the electrical power on Mir and provide PV array performance data in support of Phase 1 of the International Space Station. The MCSA was brought to Mir by space shuttle Atlantis in November 1995. This report describes an accelerated thermal life cycle test which was performed on two samples of the MCSA. In eight months time, two MCSA solar array 'mini' panel test articles were simultaneously put through 24,000 thermal cycles. There was no significant degradation in the structural integrity of the test articles and no electrical degradation, not including one cell damaged early and removed from consideration. The nature of the performance degradation caused by this one cell is briefly discussed. As a result of this test, changes were made to improve some aspects of the solar cell coupon-to-support frame interface on the flight unit. It was concluded from the results that the integration of the U.S. solar cell modules with the Russian support structure would be able to withstand at least 24,000 thermal cycles (4 years on-orbit). This was considered a successful development test.

  2. Accelerated Thermal Cycling and Failure Mechanisms for BGA and CSP Assemblies

    NASA Technical Reports Server (NTRS)

    Ghaffarian, Reza

    2000-01-01

    This paper reviews the accelerated thermal cycling test methods that are currently used by industry to characterize the interconnect reliability of commercial-off-the-shelf (COTS) ball grid array (BGA) and chip scale package (CSP) assemblies. Acceleration induced failure mechanisms varied from conventional surface mount (SM) failures for CSPs. Examples of unrealistic life projections for other CSPs are also presented. The cumulative cycles to failure for ceramic BGA assemblies performed under different conditions, including plots of their two Weibull parameters, are presented. The results are for cycles in the range of -30 C to 100 C, -55 C to 100 C, and -55 C to 125 C. Failure mechanisms as well as cycles to failure for thermal shock and thermal cycling conditions in the range of -55 C to 125 C were compared. Projection to other temperature cycling ranges using a modified Coffin-Manson relationship is also presented.

  3. Microstructural Evolution of SAC305 Solder Joints in Wafer Level Chip-Scale Packaging (WLCSP) with Continuous and Interrupted Accelerated Thermal Cycling

    NASA Astrophysics Data System (ADS)

    Zhou, Quan; Zhou, Bite; Lee, Tae-Kyu; Bieler, Thomas

    2016-06-01

    Four high-strain design wafer level chip scale packages were given accelerated thermal cycling with a 10°C/min ramp rate and 10 min hold times between 0°C and 100°C to examine the effects of continuous and interrupted thermal cycling on the number of cycles to failure. The interruptions given two of the samples were the result of periodic examinations using electron backscattered pattern mapping, leading to room temperature aging of 30 days-2.5 years after increments of about 100 cycles at several stages of the cycling history. The continuous thermal cycling resulted in solder joints with a much larger degree of recrystallization, whereas the interrupted thermal cycling tests led to much less recrystallization, which was more localized near the package side, and the crack was more localized near the interface and had less branching. The failure mode for both conditions was still the same, with cracks nucleating along the high angle grain boundaries formed during recrystallization. In conditions where there were few recrystallized grains, recovery led to formation of subgrains that strengthened the solder, and the higher strength led to a larger driving force for crack growth through the solder, leading to failure after less than half of the cycles in the continuous accelerated thermal cycling condition. This work shows that there is a critical point where sufficient strain energy accumulation will trigger recrystallization, but this point depends on the rate of strain accumulation in each cycle and various recovery processes, which further depends on local crystal orientations, stress state evolution, and specific activated slip and twinning systems.

  4. Effect of Thermal Cycling

    DTIC Science & Technology

    1988-05-01

    MEASUREMENT METHOD To characterize the surfaces, a real time Twyman -Green phase shifting interferometer was mounted on an air-suspended 8000 lb granite... interferometer and mirror mounts were augmented to decrease their natural resonance frequency. To minimize thermal effects, a thermal insulation... INTERFEROMETER INTERFACE HP COMPUTER Fig. 8. RTI test arrangement. 22 1𔃺a wa M VIl. SURFACE FIGURE RESULTS 1. Uniform heating - 60 K/hr (Figs. 9a

  5. Low-cycle thermal fatigue

    NASA Technical Reports Server (NTRS)

    Halford, G. R.

    1986-01-01

    A state-of-the-art review is presented of the field of thermal fatigue. Following a brief historical review, the concept is developed that thermal fatigue can be viewed as processes of unbalanced deformation and cracking. The unbalances refer to dissimilar mechanisms occurring in opposing halves of thermal fatigue loading and unloading cycles. Extensive data summaries are presented and results are interpreted in terms of the unbalanced processes involved. Both crack initiation and crack propagation results are summarized. Testing techniques are reviewed, and considerable discussion is given to a technique for thermal fatigue simulation, known as the bithermal fatigue test. Attention is given to the use of isothermal life prediction methods for the prediction of thermal fatigue lives. Shortcomings of isothermally-based life prediction methods are pointed out. Several examples of analyses and thermal fatigue life predictions of high technology structural components are presented. Finally, numerous dos and don'ts relative to design against thermal fatigue are presented.

  6. Thermal cycling graphite-polyimide

    NASA Technical Reports Server (NTRS)

    Hyer, M. W.; Hagaman, J. A.

    1979-01-01

    The effects of repetitive thermal cycling on the temperature-thermal deformation relation of graphite-polyimide were determined. The bending and axial strains, measured with strain gages, of unsymmetric 0 deg sub 2/90 deg sub 2 and 0 deg sub 4/90 deg sub 4 laminates were used as an indication of thermal deformation. The strains were measured as a function of temperature and two temperature ranges were used, room temperature to 180 C and room temperature to 315 C. Five cycles were run in each temperature range and the cycling was done in quasistatic fashion. The response of a flat 0 deg sub 8 laminate was measured as were the effects of repetitive cycling on the strain gages themselves. A piece-wise linear theory, based on classical lamination theory and using the variation of mechanical and thermal expansion properties with temperature, was compared with the experimental results. The correlation between theoretical predictions and experimental results for the thinner laminate was poor.

  7. Experiments on hypersonic ramjet propulsion cycles using a ram accelerator

    NASA Technical Reports Server (NTRS)

    Chew, G.; Knowlen, C.; Burnham, E. A.; Hertzberg, A.; Bruckner, A. P.

    1991-01-01

    Work on hypersonic propulsion research using a ram accelerator is presented. Several different ram accelerator propulsive cycles have been experimentally demonstrated over the Mach number range of 3 to 8.5. The subsonic, thermally choked combustion mode has accelerated projectiles to near the Chapman-Jouguet (C-J) detonation velocity within many different propellant mixtures. In the transdetonative velocity regime (85 to 115 percent of C-J speed), projectiles have established a propulsive cycle which allows them to transition smoothly from subdetonative to superdetonative velocities. Luminosity data indicate that the combustion process moves forward onto the projectile body as it approaches the C-J speed. In the superdetonative velocity range, the projectiles accelerate while always traveling faster than the C-J velocity. Ram accelerator projectiles operating continuously through these velocity regimes generate distinctive hypersonic phenomena which can be studied very effectively in the laboratory. These results would be very useful for validating sophisticated CFD computer codes and in collecting engineering data for potential airbreathing hypersonic propulsive systems.

  8. Investigation of Thermal High Cycle and Low Cycle Fatigue Mechanisms of Thick Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1998-01-01

    Thick thermal barrier coating systems in a diesel engine experience severe thermal low cycle fatigue (LCF) and high cycle fatigue (HCF) during engine operation. In this paper, the mechanisms of fatigue crack initiation and propagation in a ZrO2-8wt% Y2O3 thermal barrier coating, under simulated engine thermal LCF and HCF conditions, are investigated using a high power CO2 laser. Experiments showed that the combined LCF-HCF tests induced more severe coating surface cracking, microspallation and accelerated crack growth, as compared to the pure LCF test. Lateral crack branching and the ceramic/bond coat interface delaminations were also facilitated by HCF thermal loads, even in the absence of severe interfacial oxidation. Fatigue damage at crack wake surfaces, due to such phenomena as asperity/debris contact induced cracking and splat pull-out bending during cycling, was observed especially for the combined LCF-HCF tests. It is found that the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. The failure associated with HCF process, however, is mainly associated with a surface wedging mechanism. The interaction between the LCF, HCF and ceramic coating creep, and the relative importance of LCF and HCF in crack propagation are also discussed based on the experimental evidence.

  9. Investigation of Thermal High Cycle and Low Cycle Fatigue Mechanisms of Thick Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1998-01-01

    Thick thermal barrier coating systems in a diesel engine experience severe thermal low cycle fatigue (LCF) and high cycle fatigue (HCF) during engine operation. In this paper, the mechanisms of fatigue crack initiation and propagation in a ZrO2-8wt.% Y2O3 thermal barrier coating, under simulated engine thermal LCF and HCF conditions, are investigated using a high power CO2 laser. Experiments showed that the combined LCF/HCF tests induced more severe coating surface cracking, microspallation and accelerated crack growth, as compared to the pure LCF test. Lateral crack branching and the ceramic/bond coat interface delaminations were also facilitated by HCF thermal loads, even in the absence of severe interfacial oxidation. Fatigue damages at crack wake surfaces, due to such phenomena as asperity/debris contact induced cracking and splat pull-out bending during cycling, were observed especially for the combined LCF/HCF tests. It is found that the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. The failure associated with HCF process, however, is mainly associated with a surface wedging mechanism. The interaction between the LCF, HCF and ceramic coating creep, and the relative importance of LCF and HCF in crack propagation are also discussed based on the experimental evidence.

  10. Thermal Cycle Lifetest of Swaged Cathode Heaters

    NASA Technical Reports Server (NTRS)

    Polk, Jay; Ramesham, Rajeshuni

    2007-01-01

    This viewgraph presentation reviews the thermal cycling test for the Dawn mission. The flight system, the mission requirements, and the Ion Propulsion System (IPS) are shown. The Dawn mission requires periodic thruster shutdown for data transmission and coast periods. The thermal cycling test is designed to simulate approximately three complete mission profiles. The results of the tests are reviewed.

  11. Influence of High Cycle Thermal Loads on Thermal Fatigue Behavior of Thick Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Miller, Robert A.

    1997-01-01

    Thick thermal barrier coating systems in a diesel engine experience severe thermal Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF) during engine operation. In the present study, the mechanisms of fatigue crack initiation and propagation, as well as of coating failure, under thermal loads which simulate engine conditions, are investigated using a high power CO2 laser. In general, surface vertical cracks initiate early and grow continuously under LCF and HCF cyclic stresses. It is found that in the absence of interfacial oxidation, the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. Experiments show that the HCF cycles are very damaging to the coating systems. The combined LCF and HCF tests produced more severe coating surface cracking, microspallation and accelerated crack growth, as compared to the pure LCF test. It is suggested that the HCF component cannot only accelerate the surface crack initiation, but also interact with the LCF by contributing to the crack growth at high temperatures. The increased LCF stress intensity at the crack tip due to the HCF component enhances the subsequent LCF crack growth. Conversely, since a faster HCF crack growth rate will be expected with lower effective compressive stresses in the coating, the LCF cycles also facilitate the HCF crack growth at high temperatures by stress relaxation process. A surface wedging model has been proposed to account for the HCF crack growth in the coating system. This mechanism predicts that HCF damage effect increases with increasing temperature swing, the thermal expansion coefficient and the elastic modulus of the ceramic coating, as well as the HCF interacting depth. A good agreement has been found between the analysis and experimental evidence.

  12. Non-thermal Electron Acceleration in Low Mach Number Collisionless Shocks. I. Particle Energy Spectra and Acceleration Mechanism

    NASA Astrophysics Data System (ADS)

    Guo, Xinyi; Sironi, Lorenzo; Narayan, Ramesh

    2014-10-01

    Electron acceleration to non-thermal energies in low Mach number (Ms <~ 5) shocks is revealed by radio and X-ray observations of galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Diffusive shock acceleration, also known as first-order Fermi acceleration, cannot be directly invoked to explain the acceleration of electrons. Rather, an additional mechanism is required to pre-accelerate the electrons from thermal to supra-thermal energies, so they can then participate in the Fermi process. In this work, we use two- and three-dimensional particle-in-cell plasma simulations to study electron acceleration in low Mach number shocks. We focus on the particle energy spectra and the acceleration mechanism in a reference run with Ms = 3 and a quasi-perpendicular pre-shock magnetic field. We find that about 15% of the electrons can be efficiently accelerated, forming a non-thermal power-law tail in the energy spectrum with a slope of p ~= 2.4. Initially, thermal electrons are energized at the shock front via shock drift acceleration (SDA). The accelerated electrons are then reflected back upstream where their interaction with the incoming flow generates magnetic waves. In turn, the waves scatter the electrons propagating upstream back toward the shock for further energization via SDA. In summary, the self-generated waves allow for repeated cycles of SDA, similarly to a sustained Fermi-like process. This mechanism offers a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  13. Non-thermal electron acceleration in low Mach number collisionless shocks. I. Particle energy spectra and acceleration mechanism

    SciTech Connect

    Guo, Xinyi; Narayan, Ramesh; Sironi, Lorenzo

    2014-10-20

    Electron acceleration to non-thermal energies in low Mach number (M{sub s} ≲ 5) shocks is revealed by radio and X-ray observations of galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Diffusive shock acceleration, also known as first-order Fermi acceleration, cannot be directly invoked to explain the acceleration of electrons. Rather, an additional mechanism is required to pre-accelerate the electrons from thermal to supra-thermal energies, so they can then participate in the Fermi process. In this work, we use two- and three-dimensional particle-in-cell plasma simulations to study electron acceleration in low Mach number shocks. We focus on the particle energy spectra and the acceleration mechanism in a reference run with M{sub s} = 3 and a quasi-perpendicular pre-shock magnetic field. We find that about 15% of the electrons can be efficiently accelerated, forming a non-thermal power-law tail in the energy spectrum with a slope of p ≅ 2.4. Initially, thermal electrons are energized at the shock front via shock drift acceleration (SDA). The accelerated electrons are then reflected back upstream where their interaction with the incoming flow generates magnetic waves. In turn, the waves scatter the electrons propagating upstream back toward the shock for further energization via SDA. In summary, the self-generated waves allow for repeated cycles of SDA, similarly to a sustained Fermi-like process. This mechanism offers a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  14. Generating clock signals for a cycle accurate, cycle reproducible FPGA based hardware accelerator

    SciTech Connect

    Asaad, Sameth W.; Kapur, Mohit

    2016-01-05

    A method, system and computer program product are disclosed for generating clock signals for a cycle accurate FPGA based hardware accelerator used to simulate operations of a device-under-test (DUT). In one embodiment, the DUT includes multiple device clocks generating multiple device clock signals at multiple frequencies and at a defined frequency ratio; and the FPG hardware accelerator includes multiple accelerator clocks generating multiple accelerator clock signals to operate the FPGA hardware accelerator to simulate the operations of the DUT. In one embodiment, operations of the DUT are mapped to the FPGA hardware accelerator, and the accelerator clock signals are generated at multiple frequencies and at the defined frequency ratio of the frequencies of the multiple device clocks, to maintain cycle accuracy between the DUT and the FPGA hardware accelerator. In an embodiment, the FPGA hardware accelerator may be used to control the frequencies of the multiple device clocks.

  15. Methods and compositions for rapid thermal cycling

    DOEpatents

    Beer, Neil Reginald; Benett, William J.; Frank, James M.; Deotte, Joshua R.; Spadaccini, Christopher

    2015-10-27

    The rapid thermal cycling of a material is targeted. A microfluidic heat exchanger with an internal porous medium is coupled to tanks containing cold fluid and hot fluid. Fluid flows alternately from the cold tank and the hot tank into the porous medium, cooling and heating samples contained in the microfluidic heat exchanger's sample wells. A valve may be coupled to the tanks and a pump, and switching the position of the valve may switch the source and direction of fluid flowing through the porous medium. A controller may control the switching of valve positions based on the temperature of the samples and determined temperature thresholds. A sample tray for containing samples to be thermally cycled may be used in conjunction with the thermal cycling system. A surface or internal electrical heater may aid in heating the samples, or may replace the necessity for the hot tank.

  16. Enhanced IPMC actuation by thermal cycling

    NASA Astrophysics Data System (ADS)

    Rossiter, Jonathan; Takashima, Kazuto; Mukai, Toshiharu

    2012-04-01

    IPMCs are bi-polar actuators capable of large, rapid actuation in flexural configurations. The limit of actuation is defined by the maximal voltage that can be applied to the IPMC, above which electrolysis of the electrolyte and damage to the IPMC may occur. In this paper we present preliminary results that indicate how this actuation limit could be tuned and even exceeded through controlled thermal cycling of gold-plated Nafion IPMCs. Thermal cycling is used to move the centre point of the actuation stroke. Subsequent voltage stimulation actuates the structure around this new centre point. It is shown that by further thermal cycling this centre point naturally returns to its initial position. By exploiting this shape memory characteristic as part of a control system it is expected that more sophisticated IPMC actuation will be achievable.

  17. Cycle life estimation of lithium secondary battery by extrapolation method and accelerated aging test

    NASA Astrophysics Data System (ADS)

    Takei, K.; Kumai, K.; Kobayashi, Y.; Miyashiro, H.; Terada, N.; Iwahori, T.; Tanaka, T.

    The testing methods to estimate the life cycles of lithium ion batteries for a short period, have been developed using a commercialized cell with LiCoO 2/hard carbon cell system. The degradation reactions with increasing cycles were suggested to occur predominantly above 4 V from the results of operating voltage range divided tests. In the case of the extrapolation method using limited cycle data, the straight line approximation was useful as the cycle performance has the linearity, but the error is at most 40% in using the initial short cycle data. In the case of the accelerated aging tests using the following stress factors, the charge and/or discharge rate, large accelerated coefficients were obtained in the high charge rate and the high temperature thermal stress.

  18. idaho Accelerator Center Advanced Fuel Cycle Research

    SciTech Connect

    Wells, Douglas; Dale, Dan

    2011-10-20

    The technical effort has been in two parts called; Materials Science and Instrumentation Development. The Materials Science technical program has been based on a series of research and development achievements in Positron-Annihilation Spectroscopy (PAS) for defect detection in structural materials. This work is of particular importance in nuclear power and its supporting systems as the work included detection of defects introduced by mechanical and thermal phenomena as well as those caused by irradiation damage. The second part of the program has focused on instrumentation development using active interrogation techniques supporting proliferation resistant recycling methodologies and nuclear material safeguards. This effort has also lead to basic physics studies of various phenomena relating to photo-fission. Highlights of accomplishments and facility improvement legacies in these areas over the program period include

  19. Prediction of thermal cycling induced matrix cracking

    NASA Technical Reports Server (NTRS)

    Mcmanus, Hugh L.

    1992-01-01

    Thermal fatigue has been observed to cause matrix cracking in laminated composite materials. A method is presented to predict transverse matrix cracks in composite laminates subjected to cyclic thermal load. Shear lag stress approximations and a simple energy-based fracture criteria are used to predict crack densities as a function of temperature. Prediction of crack densities as a function of thermal cycling is accomplished by assuming that fatigue degrades the material's inherent resistance to cracking. The method is implemented as a computer program. A simple experiment provides data on progressive cracking of a laminate with decreasing temperature. Existing data on thermal fatigue is also used. Correlations of the analytical predictions to the data are very good. A parametric study using the analytical method is presented which provides insight into material behavior under cyclical thermal loads.

  20. Convectively driven PCR thermal-cycling

    DOEpatents

    Benett, William J.; Richards, James B.; Milanovich, Fred P.

    2003-07-01

    A polymerase chain reaction system provides an upper temperature zone and a lower temperature zone in a fluid sample. Channels set up convection cells in the fluid sample and move the fluid sample repeatedly through the upper and lower temperature zone creating thermal cycling.

  1. Hubble Space Telescope solar cell module thermal cycle test

    NASA Technical Reports Server (NTRS)

    Douglas, Alexander; Edge, Ted; Willowby, Douglas; Gerlach, Lothar

    1992-01-01

    The Hubble Space Telescope (HST) solar array consists of two identical double roll-out wings designed after the Hughes flexible roll-up solar array (FRUSA) and was developed by the European Space Agency (ESA) to meet specified HST power output requirements at the end of 2 years, with a functional lifetime of 5 years. The requirement that the HST solar array remain functional both mechanically and electrically during its 5-year lifetime meant that the array must withstand 30,000 low Earth orbit (LEO) thermal cycles between approximately +100 and -100 C. In order to evaluate the ability of the array to meet this requirement, an accelerated thermal cycle test in vacuum was conducted at NASA's Marshall Space Flight Center (MSFC), using two 128-cell solar array modules which duplicated the flight HST solar array. Several other tests were performed on the modules. The thermal cycle test was interrupted after 2,577 cycles, and a 'cold-roll' test was performed on one of the modules in order to evaluate the ability of the flight array to survive an emergency deployment during the dark (cold) portion of an orbit. A posttest static shadow test was performed on one of the modules in order to analyze temperature gradients across the module. Finally, current in-flight electrical performance data from the actual HST flight solar array will be tested.

  2. Space Launch System Accelerated Booster Development Cycle

    NASA Technical Reports Server (NTRS)

    Arockiam, Nicole; Whittecar, William; Edwards, Stephen

    2012-01-01

    , affordability is defined as lifecycle cost, which includes design, development, test, and engineering (DDT&E), production and operational costs (P&O). For this study, the system objectives include reducing DDT&E schedule by a factor of three, showing 99.9% reliability, flying up to four times per year, serving both crew and cargo missions, and evolving to a lift capability of 130 metric tons.3 After identifying gaps in the current system s capabilities, this study seeks to identify non-traditional and innovative technologies and processes that may improve performance in these areas and assess their impacts on booster system development. The DDT&E phase may be improved by incorporating incremental development testing and integrated demonstrations to mitigate risk. To further reduce DDT&E, this study will also consider how aspects of the booster system may have commonality with other users, such as the Department of Defense, commercial applications, or international partners; by sharing some of the risk and investment, the overall development cost may be reduced. Consideration is not limited to solid and liquid rocket boosters. A set of functional performance characteristics, such as engine thrust, specific impulse (Isp), mixture ratio, and throttle range are identified and their impacts on the system are evaluated. This study also identifies how such characteristics affect overall life cycle cost, including DDT&E and fixed and variable P&O.

  3. Thermal High- and Low-Cycle Fatigue Behavior of Thick Thermal Barrier Coating Systems

    NASA Technical Reports Server (NTRS)

    Miller, Robert A.

    1998-01-01

    Ceramic thermal barrier coatings have received increasing attention for advanced gas turbine and diesel engine applications because of their ability to provide thermal insulation to engine components. However, the durability of these coatings under the severe thermal cycling conditions encountered in a diesel engine (ref. 1) still remains a major issue. In this research at the NASA Lewis Research Center, a high-power laser was used to investigate the thermal fatigue behavior of a yttria-stabilized zirconia coating system under simulated diesel engine conditions. The mechanisms of fatigue crack initiation and propagation, and of coating failure under complex thermal low-cycle fatigue (LCF, representing stop/start cycles) and thermal high-cycle fatigue (HCF, representing operation at 1300 rpm) are described. Continuous wave and pulse laser modes were used to simulate pure LCF and combined LCF/HCF, respectively (ref. 2). The LCF mechanism was found to be closely related to the coating sintering and creep at high temperatures. These creep strains in the ceramic coating led to a tensile stress state during cooling, thus providing the major driving force for crack growth under LCF conditions. The combined LCF/HCF tests induced more severe coating surface cracking, microspallation, and accelerated crack growth than did the pure LCF test. HCF thermal loads also facilitated lateral crack branching and ceramic/bond coat interface delaminations. HCF is associated with the cyclic stresses originating from the high-frequency temperature fluctuation at the ceramic coating surface. The HCF thermal loads act on the crack by a wedging mechanism (ref. 1), resulting in continuous crack growth at temperature. The HCF stress intensity factor amplitude increases with the interaction depth and temperature swing, and decreases with the crack depth. HCF damage also increases with the thermal expansion coefficient and the Young's modulus of the ceramic coating (refs. 1 and 3).

  4. Ceramic thermal barrier coating for rapid thermal cycling applications

    DOEpatents

    Scharman, Alan J.; Yonushonis, Thomas M.

    1994-01-01

    A thermal barrier coating for metal articles subjected to rapid thermal cycling includes a metallic bond coat deposited on the metal article, at least one MCrAlY/ceramic layer deposited on the bond coat, and a ceramic top layer deposited on the MCrAlY/ceramic layer. The M in the MCrAlY material is Fe, Ni, Co, or a mixture of Ni and Co. The ceramic in the MCrAlY/ceramic layer is mullite or Al.sub.2 O.sub.3. The ceramic top layer includes a ceramic with a coefficient of thermal expansion less than about 5.4.times.10.sup.-6 .degree.C.sup.-1 and a thermal conductivity between about 1 J sec.sup.-1 m.sup.-1 .degree.C.sup.-1 and about 1.7 J sec.sup.-1 m.sup.-1 .degree.C.sup.-1.

  5. Thermal Properties, Thermal Shock, and Thermal Cycling Behavior of Lanthanum Zirconate-Based Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Guo, Xingye; Lu, Zhe; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing

    2016-06-01

    Lanthanum zirconate (La2Zr2O7) coatings are newly proposed thermal barrier coating (TBC) systems which exhibit lower thermal conductivity and potentially higher thermal stability compared to other traditional thermal barrier systems. In this work, La2Zr2O7 and 8 wt pct yttria stabilized zirconia (8YSZ) single-layer and double-layer TBC systems were deposited using the air plasma spray technique. Thermal properties of the coatings were measured. Furnace heat treatment and jet engine thermal shock tests were implemented to evaluate coating performance during thermal cycling. The measured average thermal conductivity of porous La2Zr2O7 coating ranged from 0.59 to 0.68 W/m/K in the temperature range of 297 K to 1172 K (24 °C to 899 °C), which was approximately 25 pct lower than that of porous 8YSZ (0.84 to 0.87 W/m/K) in the same temperature range. The coefficients of thermal expansion values of La2Zr2O7 were approximately 9 to 10 × 10-6/K from 400 K to 1600 K (127 °C to 1327 °C), which were about 10 pct lower than those of porous 8YSZ. The double-layer coating system consisting of the porous 8YSZ and La2Zr2O7 layers had better thermal shock resistance and thermal cycling performance than those of single-layer La2Zr2O7 coating and double-layer coating with dense 8YSZ and La2Zr2O7 coatings. This study suggests that porous 8YSZ coating can be employed as a buffer layer in La2Zr2O7-based TBC systems to improve the overall coating durability during service.

  6. Accelerator Generation and Thermal Separation (AGATS) of Technetium-99m

    SciTech Connect

    2010-01-01

    Accelerator Generation and Thermal Separation (AGATS) of Technetium-99m is a linear electron accelerator-based technology for producing medical imaging radioisotopes from a separation process that heats, vaporizes and condenses the desired radioisotope. You can learn more about INL's education programs at http://www.facebook.com/idahonationallaboratory.

  7. Accelerator Generation and Thermal Separation (AGATS) of Technetium-99m

    ScienceCinema

    None

    2016-07-12

    Accelerator Generation and Thermal Separation (AGATS) of Technetium-99m is a linear electron accelerator-based technology for producing medical imaging radioisotopes from a separation process that heats, vaporizes and condenses the desired radioisotope. You can learn more about INL's education programs at http://www.facebook.com/idahonationallaboratory.

  8. Prolonging thermal barrier coated specimen life by thermal cycle management

    NASA Technical Reports Server (NTRS)

    Hendricks, R. C.; Mcdonald, G.; Poolos, N. P.

    1981-01-01

    Thermal barrier coatings applied to the heated side of engine components such as seals, combustor, and blades of a gas turbine offer a potential increase in efficiency through the use of higher gas temperatures or less cooling air or benefits arising from extended component life by reducing component metal temperatures. The considered investigation has the objective to show that while a thermal barrier coated (TBC) specimen can be brought to a fixed temperature using various fuel-air ratio (F/A) values, lower calculated stresses are associated with lower (F/A) values. This implies that control of (F/A) values (i.e., rates of heat input) during the starting transient and to a lesser extent during shutdown and operation, offers a potential method of improving TBC lifetime through thermal cycle management.

  9. Crystal structure and texture changes during thermal cycling of TATB

    SciTech Connect

    Vogel, Sven C.; Yeager, John David

    2015-02-20

    Goals: Understand crystal structure and micro-structure changes during thermal cycling, understand reasons for ratcheting of TATB during thermal cycling, and Support of B61 LEP. Deliverables achieved: Completed in situ thermal cycling of loose powder and pressed pellet TATB on HIPPO, Quantified preferred orientation of pressed pellet, and quantified relative change of each of the six lattic parameters.

  10. The role of accelerators in the nuclear fuel cycle

    SciTech Connect

    Takahashi, Hiroshi.

    1990-01-01

    The use of neutrons produced by the medium energy proton accelerator (1 GeV--3 GeV) has considerable potential in reconstructing the nuclear fuel cycle. About 1.5 {approximately} 2.5 ton of fissile material can be produced annually by injecting a 450 MW proton beam directly into fertile materials. A source of neutrons, produced by a proton beam, to supply subcritical reactors could alleviate many of the safety problems associated with critical assemblies, such as positive reactivity coefficients due to coolant voiding. The transient power of the target can be swiftly controlled by controlling the power of the proton beam. Also, the use of a proton beam would allow more flexibility in the choice of fuel and structural materials which otherwise might reduce the reactivity of reactors. This paper discusses the rate of accelerators in the transmutation of radioactive wastes of the nuclear fuel cycles. 34 refs., 17 figs., 9 tabs.

  11. Nonlinear Particle Acceleration and Thermal Particles in GRB Afterglows

    NASA Astrophysics Data System (ADS)

    Warren, Donald C.; Ellison, Donald C.; Barkov, Maxim V.; Nagataki, Shigehiro

    2017-02-01

    The standard model for GRB afterglow emission treats the accelerated electron population as a simple power law, N(E)\\propto {E}-p for p≳ 2. However, in standard Fermi shock acceleration, a substantial fraction of the swept-up particles do not enter the acceleration process at all. Additionally, if acceleration is efficient, then the nonlinear back-reaction of accelerated particles on the shock structure modifies the shape of the nonthermal tail of the particle spectra. Both of these modifications to the standard synchrotron afterglow impact the luminosity, spectra, and temporal variation of the afterglow. To examine the effects of including thermal particles and nonlinear particle acceleration on afterglow emission, we follow a hydrodynamical model for an afterglow jet and simulate acceleration at numerous points during the evolution. When thermal particles are included, we find that the electron population is at no time well fitted by a single power law, though the highest-energy electrons are; if the acceleration is efficient, then the power-law region is even smaller. Our model predicts hard–soft–hard spectral evolution at X-ray energies, as well as an uncoupled X-ray and optical light curve. Additionally, we show that including emission from thermal particles has drastic effects (increases by factors of 100 and 30, respectively) on the observed flux at optical and GeV energies. This enhancement of GeV emission makes afterglow detections by future γ-ray observatories, such as CTA, very likely.

  12. Initiation of combustion in the thermally choked ram accelerator

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Burnham, E. A.; Knowlen, C.; Hertzberg, A.; Bogdanoff, D. W.

    1992-01-01

    The methodology for initiating stable combustion in a ram accelerator operating in the thermally choked mode is presented in this paper. The ram accelerator is a high velocity ramjet-in-tube projectile launcher whose principle of operation is similar to that of an airbreathing ramjet. The subcaliber projectile travels supersonically through a stationary tube filled with a premixed combustible gas mixture. In the thermally choked propulsion mode subsonic combustion takes place behind the base of the projectile and leads to thermal choking, which stabilizes a normal shock system on the projectile, thus producing forward thrust. Projectiles with masses in the 45-90 g range have been accelerated to velocities up to 2650 m/sec in a 38 mm bore, 16 m long accelerator tube. Operation of the ram accelerator is started by injecting the projectile into the accelerator tube at velocities in the 700 - 1300 m/sec range by means of a conventional gas gun. A specially designed obturator, which seals the bore of the gun during this initial acceleration, enters the ram accelerator together with the projectile. The interaction of the obturator with the propellant gas ignites the gas mixture and establishes stable combustion behind the projectile.

  13. Induced natural convection thermal cycling device

    DOEpatents

    Heung, Leung Kit

    2002-08-13

    A device for separating gases, especially isotopes, by thermal cycling of a separation column using a pressure vessel mounted vertically and having baffled sources for cold and heat. Coils at the top are cooled with a fluid such as liquid nitrogen. Coils at the bottom are either electrical resistance coils or a tubular heat exchange. The sources are shrouded with an insulated "top hat" and simultaneously opened and closed at the outlets to cool or heat the separation column. Alternatively, the sources for cold and heat are mounted separately outside the vessel and an external loop is provided for each circuit.

  14. SRF Performance of CEBAF After Thermal Cycle to Ambient Temperature

    SciTech Connect

    Robert Rimmer; Jay Benesch; Joseph Preble; Charles Reece

    2005-05-01

    In September 2003, in the wake of Hurricane Isabel, JLab was without power for four days after a tree fell on the main power lines feeding the site. This was long enough to lose insulating vacuum in the cryomodules and cryogenic systems resulting in the whole accelerator warming up and the total loss of the liquid helium inventory. This thermal cycle stressed many of the cryomodule components causing several cavities to become inoperable due to helium to vacuum leaks. At the same time the thermal cycle released years of adsorbed gas from the cold surfaces. Over the next days and weeks this gas was pumped away, the insulating vacuum was restored and the machine was cooled back down and re-commissioned. In a testament to the robustness of SRF technology, only a small loss in energy capability was apparent, although individual cavities had quite different field-emission characteristics compared to before the event. In Summer 2004 a section of the machine was again cycled to room temperature during the long maintenance shutdown. We report on the overall SRF performance of the machine after these major disturbances and on efforts to characterize and optimize the new behavior for high-energy running.

  15. High Cycle Thermal Fatigue in French PWR

    SciTech Connect

    Blondet, Eric; Faidy, Claude

    2002-07-01

    Different fatigue-related incidents which occurred in the world on the auxiliary lines of the reactor coolant system (SIS, RHR, CVC) have led EDF to search solutions in order to avoid or to limit consequences of thermodynamic phenomenal (Farley-Tihange, free convection loop and stratification, independent thermal cycling). Studies are performed on mock-up and compared with instrumentation on nuclear power stations. At the present time, studies allow EDF to carry out pipe modifications and to prepare specifications and recommendations for next generation of nuclear power plants. In 1998, a new phenomenal appeared on RHR system in Civaux. A crack was discovered in an area where hot and cold fluids (temperature difference of 140 deg. C) were mixed. Metallurgic studies concluded that this crack was caused by high cycle thermal fatigue. Since 1998, EDF is making an inventory of all mixing areas in French PWR on basis of criteria. For all identified areas, a method was developed to improve the first classifying and to keep back only potential damage pipes. Presently, studies are performing on the charging line nozzle connected to the reactor pressure vessel. In order to evaluate the load history, a mock-up has been developed and mechanical calculations are realised on this nozzle. The paper will make an overview of EDF conclusions on these different points: - dead legs and vortex in a no flow connected line; - stratification; - mixing tees with high {delta}T. (authors)

  16. Thermal Cycling of Mir Cooperative Solar Array (MCSA) Test Panels

    NASA Technical Reports Server (NTRS)

    Hoffman, David J.; Scheiman, David A.

    1997-01-01

    The Mir Cooperative Solar Array (MCSA) project was a joint US/Russian effort to build a photovoltaic (PV) solar array and deliver it to the Russian space station Mir. The MCSA is currently being used to increase the electrical power on Mir and provide PV array performance data in support of Phase 1 of the International Space Station (ISS), which will use arrays based on the same solar cells used in the MCSA. The US supplied the photovoltaic power modules (PPMs) and provided technical and programmatic oversight while Russia provided the array support structures and deployment mechanism and built and tested the array. In order to ensure that there would be no problems with the interface between US and Russian hardware, an accelerated thermal life cycle test was performed at NASA Lewis Research Center on two representative samples of the MCSA. Over an eight-month period (August 1994 - March 1995), two 15-cell MCSA solar array 'mini' panel test articles were simultaneously put through 24,000 thermal cycles (+80 C to -100 C), equivalent to four years on-orbit. The test objectives, facility, procedure and results are described in this paper. Post-test inspection and evaluation revealed no significant degradation in the structural integrity of the test articles and no electrical degradation, not including one cell damaged early as an artifact of the test and removed from consideration. The interesting nature of the performance degradation caused by this one cell, which only occurred at elevated temperatures, is discussed. As a result of this test, changes were made to improve some aspects of the solar cell coupon-to-support frame interface on the flight unit. It was concluded from the results that the integration of the US solar cell modules with the Russian support structure would be able to withstand at least 24,000 thermal cycles (4 years on-orbit).

  17. Thermal cycling of Mir Cooperative Solar Array (MCSA) test panels

    SciTech Connect

    Hoffman, D.J.; Scheiman, D.A.

    1997-12-31

    The Mir Cooperative Solar Array (MCSA) project was a joint US/Russian effort to build a photovoltaic (PV) solar array and deliver it to the Russian space station Mir. The MCSA is currently being used to increase the electrical power on Mir and provide PV array performance data in support of Phase 1 of the International Space Station (ISS), which will use arrays based on the same solar cells used in the MCSA. The US supplied the photovoltaic power modules (PPMs) and provided technical and programmatic oversight while Russia provided the array support structures and deployment mechanism and built and tested the array. In order to ensure that there would be no problems with the interface between US and Russian hardware, an accelerated thermal life cycle test was performed at NASA Lewis Research Center on two representative samples of the MCSA. Over an eight-month period (August 1994--March 1995), two 15-cell MCSA solar array mini panel test articles were simultaneously put through 24000 thermal cycles (+80 C to {minus}100 C), equivalent to four years on-orbit. The test objectives, facility, procedure and results are described in this paper. Post-test inspection and evaluation revealed no significant degradation in the structural integrity of the test articles and no electrical degradation, not including one cell damaged early as an artifact of the test and removed from consideration. The interesting nature of the performance degradation caused by this one cell, which only occurred at elevated temperatures, is discussed. As a result of this test, changes were made to improve some aspects of the solar cell coupon-to-support frame interface on the flight unit. It was concluded from the results that the integration of the US solar cell modules with the Russian support structure would be able to withstand at least 24000 thermal cycles (4 years on-orbit).

  18. Cycle Trades for Nuclear Thermal Rocket Propulsion Systems

    NASA Technical Reports Server (NTRS)

    White, C.; Guidos, M.; Greene, W.

    2003-01-01

    Nuclear fission has been used as a reliable source for utility power in the United States for decades. Even in the 1940's, long before the United States had a viable space program, the theoretical benefits of nuclear power as applied to space travel were being explored. These benefits include long-life operation and high performance, particularly in the form of vehicle power density, enabling longer-lasting space missions. The configurations for nuclear rocket systems and chemical rocket systems are similar except that a nuclear rocket utilizes a fission reactor as its heat source. This thermal energy can be utilized directly to heat propellants that are then accelerated through a nozzle to generate thrust or it can be used as part of an electricity generation system. The former approach is Nuclear Thermal Propulsion (NTP) and the latter is Nuclear Electric Propulsion (NEP), which is then used to power thruster technologies such as ion thrusters. This paper will explore a number of indirect-NTP engine cycle configurations using assumed performance constraints and requirements, discuss the advantages and disadvantages of each cycle configuration, and present preliminary performance and size results. This paper is intended to lay the groundwork for future efforts in the development of a practical NTP system or a combined NTP/NEP hybrid system.

  19. Parallel Computation of Integrated Electromagnetic, Thermal and Structural Effects for Accelerator Cavities

    SciTech Connect

    Akcelik, V.; Candel, A.E.; Kabel, A.C.; Ko, K.; Lee, L.; Li, Z.; Ng, C.K.; Xiao, L.; /SLAC

    2011-11-02

    The successful operation of accelerator cavities has to satisfy both rf and mechanical requirements. It is highly desirable that electromagnetic, thermal and structural effects such as cavity wall heating and Lorentz force detuning in superconducting rf cavities can be addressed in an integrated analysis. Based on the SLAC parallel finite-element code infrastructure for electromagnetic modeling, a novel multi-physics analysis tool has been developed to include additional thermal and mechanical effects. The parallel computation enables virtual prototyping of accelerator cavities on computers, which would substantially reduce the cost and time of a design cycle. The multi-physics tool is applied to the LCLS rf gun for electromagnetic, thermal and structural analyses.

  20. Investigation of thermal fatigue in fiber composite materials. [(thermal cycling tests)

    NASA Technical Reports Server (NTRS)

    Fahmy, A. A.; Cunningham, T. G.

    1976-01-01

    Graphite-epoxy laminates were thermally cycled to determine the effects of thermal cycles on tensile properties and thermal expansion coefficients of the laminates. Three 12-ply laminate configurations were subjected to up to 5,000 thermal cycles. The cumulative effect of the thermal cycles was determined by destructive inspection (electron micrographs and tensile tests) of samples after progressively larger numbers of cycles. After thermal cycling, the materials' tensile strengths, moduli, and thermal expansion coefficients were significantly lower than for the materials as fabricated. Most of the degradation of properties occurred after only a few cycles. The property degradation was attributed primarily to the progressive development of matrix cracks whose locations depended upon the layup orientation of the laminate.

  1. Acceleration of Thermal Protons by Generic Phenomenological Mechanisms

    NASA Astrophysics Data System (ADS)

    Petrosian, Vahé; Kang, Byungwoo

    2015-11-01

    We investigate heating and acceleration of protons from a thermal gas with a generic diffusion and acceleration model, and subject to Coulomb scattering and energy loss, as was done by Petrosian & East for electrons. As protons gain energy their loss to electrons becomes important. Thus, we need to solve the coupled proton-electron kinetic equation. We numerically solve the coupled Fokker-Planck equations and compute the time evolution of the spectra of both particles. We show that this can lead to a quasi-thermal component plus a high-energy nonthermal tail. We determine the evolution of the nonthermal tail and the quasi-thermal component. The results may be used to explore the possibility of inverse bremsstrahlung radiation as a source of hard X-ray emissions from hot sources such as solar flares, accretion disk coronas, and the intracluster medium of galaxy clusters. We find that the emergence of nonthermal protons is accompanied by excessive heating of the entire plasma, unless the turbulence needed for scattering and acceleration is steeper than Kolmogorov and the acceleration parameters, the duration of the acceleration, and/or the initial distributions are significantly fine-tuned. These results severely constrain the feasibility of the nonthermal inverse bremsstrahlung process producing hard X-ray emissions. However, the nonthermal tail may be the seed particles for further re-acceleration to relativistic energies, say by a shock. In the Appendix we present some tests of the integrity of the algorithm used and present a new formula for the energy loss rate due to inelastic proton-proton interactions.

  2. ACCELERATION OF THERMAL PROTONS BY GENERIC PHENOMENOLOGICAL MECHANISMS

    SciTech Connect

    Petrosian, Vahé; Kang, Byungwoo E-mail: redcrux8@stanford.edu

    2015-11-01

    We investigate heating and acceleration of protons from a thermal gas with a generic diffusion and acceleration model, and subject to Coulomb scattering and energy loss, as was done by Petrosian and East for electrons. As protons gain energy their loss to electrons becomes important. Thus, we need to solve the coupled proton–electron kinetic equation. We numerically solve the coupled Fokker–Planck equations and compute the time evolution of the spectra of both particles. We show that this can lead to a quasi-thermal component plus a high-energy nonthermal tail. We determine the evolution of the nonthermal tail and the quasi-thermal component. The results may be used to explore the possibility of inverse bremsstrahlung radiation as a source of hard X-ray emissions from hot sources such as solar flares, accretion disk coronas, and the intracluster medium of galaxy clusters. We find that the emergence of nonthermal protons is accompanied by excessive heating of the entire plasma, unless the turbulence needed for scattering and acceleration is steeper than Kolmogorov and the acceleration parameters, the duration of the acceleration, and/or the initial distributions are significantly fine-tuned. These results severely constrain the feasibility of the nonthermal inverse bremsstrahlung process producing hard X-ray emissions. However, the nonthermal tail may be the seed particles for further re-acceleration to relativistic energies, say by a shock. In the Appendix we present some tests of the integrity of the algorithm used and present a new formula for the energy loss rate due to inelastic proton–proton interactions.

  3. Diagnosis of MEA degradation under accelerated relative humidity cycling

    NASA Astrophysics Data System (ADS)

    Vengatesan, S.; Fowler, Michael W.; Yuan, Xiao-Zi; Wang, Haijiang

    The objective of this work is to identify the failure mode diagnosis protocols for polymer electrolyte membrane (PEM) fuel cells with the use of accelerated testing conditions. The single cells used in this work were constructed using commercial Ion Power ® membrane electrode assemblies (MEAs) and the performance degradation was studied under accelerated dynamic reactant relative humidity (RH) conditions. The influence of RH on cell performance was investigated, and a strong dependence of degradation with respect to relative humidity was found. RH cycling was seen to not only cause the gradual decrease in performance at the beginning of cell operation, but it was also related to the rapid decline in performance observed after 330 h operation. This change in degradation rate is seen a change in the material degradation failure mechanism at this point in the operational history of the cell. The increase in cell resistance, membrane crossover, fluoride release rate and decrease in electrochemical surface area (ESA) were also observed with time, and these results were correlated to change in degradation rate. Infra-Red (IR) imaging of an aged MEA was utilized to show varying temperature profiles and outline the possibility of cracks, tears or pinholes in the membrane.

  4. Open cycle ocean thermal energy conversion system

    DOEpatents

    Wittig, J. Michael

    1980-01-01

    An improved open cycle ocean thermal energy conversion system including a flash evaporator for vaporizing relatively warm ocean surface water and an axial flow, elastic fluid turbine having a vertical shaft and axis of rotation. The warm ocean water is transmitted to the evaporator through a first prestressed concrete skirt-conduit structure circumferentially situated about the axis of rotation. The unflashed warm ocean water exits the evaporator through a second prestressed concrete skirt-conduit structure located circumferentially about and radially within the first skirt-conduit structure. The radially inner surface of the second skirt conduit structure constitutes a cylinder which functions as the turbine's outer casing and obviates the need for a conventional outer housing. The turbine includes a radially enlarged disc element attached to the shaft for supporting at least one axial row of radially directed blades through which the steam is expanded. A prestressed concrete inner casing structure of the turbine has upstream and downstream portions respectively situated upstream and downstream from the disc element. The radially outer surfaces of the inner casing portions and radially outer periphery of the axially interposed disc cooperatively form a downwardly radially inwardly tapered surface. An annular steam flowpath of increasing flow area in the downward axial direction is radially bounded by the inner and outer prestressed concrete casing structures. The inner casing portions each include a transversely situated prestressed concrete circular wall for rotatably supporting the turbine shaft and associated structure. The turbine blades are substantially radially coextensive with the steam flowpath and receive steam from the evaporator through an annular array of prestressed concrete stationary vanes which extend between the inner and outer casings to provide structural support therefor and impart a desired flow direction to the steam.

  5. Damage Assessment of Stress-Thermal Cycled High Temperature

    NASA Technical Reports Server (NTRS)

    Ju, Jach-Yung; Prochazka, Michael; Ronke, Ben; Morgan, Roger; Shin, Eugene

    2003-01-01

    We report on the characterization of bismaleimide and polyimide carbon fiber composite, microcrack development under stress thermal cycling loading. Such cycle range from cryogenic temperatures associated with cryogenic fuel (LN, LOX) containment to high temperatures of 300 degrees associated with future hypervelocity aeropropulsion systems. Microcrack development thresholds as a function of temperature range of the thermal cycle, the number of cycles, and the applied stress level imposed on the composite are reported. We have conducted stress-thermal cycles on thin bismaleimide-woven carbon fiber foils for three temperature range cycles. The principle findings are that the full cycles from -196 degree celsius up to 250 degree celsius cause the most significant microcrack development. These observations indicate that the high temperature portion of the cycle under load causes fiber-matrix interface failure and subsequent exposure to higher stresses at the cryogenic, low temperature region results in composite matrix microcracking as a result of the additional stresses associated with the fiber-matrix thermal expansion mismatch. Our initial studies for 12 ply PMR-II-50 polyimide/M6OJB carbon fabric [0f, 90f, 90f, 0f, 0f, 90f] composites will be presented. The stress-thermal cycle test procedure for these will be described. Moisture absorption characteristics between cycles will be used to monitor interconnected microcrack development. The applied stress level will be 75 percent of the composite cryogenic -196 degree celsius ultimate strength.

  6. Thermal cycling can extend tool life in orthopaedic operating rooms.

    PubMed

    Katchky, Ryan N; McLachlin, Stewart D; Wong, Edwin K Y; Finkelstein, Joel; Kreder, Hans J; Whyne, Cari M

    2016-03-01

    Thermal cycling is a temperature modulation process developed to improve the performance, durability and longevity of materials. This process has been successfully utilized in the automotive, aeronautic and manufacturing industries. Surgical cutting tools undergo cyclical loading and generally fail by dulling, suggesting that thermal cycling may improve their performance and longevity. Ten 2.5 mm orthopaedic drill bits were randomized, with five undergoing thermal cycling within their sterile packaging and five serving as untreated controls. Using a servohydraulic testing machine, 100 drilling cycles were performed with each drill bit into the diaphyseal region of bovine femurs. After every 25 cycles, data was collected by performing identical drilling cycles into simulated human cortical bone material. Maximum force, maximum normalized torque and drilling work were measured, and a scanning electron microscope was used to measure outer corner wear. After 100 drilling cycles, the maximum drilling force, maximum normalized torque, drilling work and microscopic outer corner wear were all significantly lower for the treated drill bits (p < 0.05). Thermal cycling has the potential to decrease operating room costs and thermal necrosis associated with dull cutting tools. Application of this technology may also be relevant to surgical cutting tools such as saw blades, burrs and reamers.

  7. Induction acceleration of heavy ions in the KEK digital accelerator: Demonstration of a fast-cycling induction synchrotron

    NASA Astrophysics Data System (ADS)

    Takayama, K.; Yoshimoto, T.; Barata, M.; Wah, Leo Kwee; Xingguang, Liu; Iwashita, T.; Harada, S.; Adachi, T.; Arai, T.; Arakawa, D.; Asao, H.; Kadokura, E.; Kawakubo, T.; Nakanishi, H.; Okada, Y.; Okamura, K.; Okazaki, K.; Takagi, A.; Takano, S.; Wake, M.

    2014-01-01

    A fast-cycling induction synchrotron was demonstrated. Ions with extremely low energies and mass-to-charge ratios (A /Q) in the range from 2 to 10 were injected, captured by barrier voltages, and accelerated to the end of the acceleration cycle of 50 ms by flat pulse voltages generated by pulse transformers referred to as induction cells. Induction acceleration in a wide dynamic frequency range of 56 kHz to 1 MHz was also demonstrated. This accelerator is expected as the next generation of a heavy ion driver for cancer therapy, where a large scale injector is not required. A wide variety of ions for ion energy implantation experiments needing novel materials will be delivered from this compact circular accelerator.

  8. Electronic assembly thermal testing - Dwell/duration/cycling

    NASA Technical Reports Server (NTRS)

    Gibbel, Mark; Clawson, James F.

    1990-01-01

    Testing of electronic assemblies varies throughout industry, NASA, and the military. Differences include test levels, atmospheric versus vacuum testing of assemblies, dwell durations at temperature extremes (especially high temperature), and thermal cycling versus dwell testing. Of particular interest are the different philosophies of thermal cycling versus single-cycle thermal dwell. An examination of the various failure physics for electronic assemblies has been initiated at JPL. The intent is to determine which failure modes are best revealed by thermal cycling testing and which are susceptible to high-temperature dwell physics. Preliminary results of this study are presented, along with discussions of testing goals, flight environments, reliability models, and the differences between industry and JPL design/test approaches.

  9. Thermal cycling fatigue of organic thermal interface materials using a thermal-displacement measurement technique

    NASA Astrophysics Data System (ADS)

    Steill, Jason Scott

    The long term reliability of polymer-based thermal interface materials (TIM) is essential for modern electronic packages which require robust thermal management. The challenge for today's materials scientists and engineers is to maximize the heat flow from integrated circuits through a TIM and out the heat sink. Thermal cycling of the electronic package and non-uniformity in the heat flux with respect to the plan area can lead to void formation and delamination which re-introduces inefficient heat transfer. Measurement and understanding at the nano-scale is essential for TIM development. Finding and documenting the evolution of the defects is dependent upon a full understanding of the thermal probes response to changing environmental conditions and the effects of probe usage. The response of the thermal-displacement measurement technique was dominated by changes to the environment. Accurate measurement of the thermal performance was hindered by the inability to create a model system and control the operating conditions. This research highlights the need for continued study into the probe's thermal and mechanical response using tightly controlled test conditions.

  10. Investigation of starting transients in the thermally choked ram accelerator

    NASA Technical Reports Server (NTRS)

    Burnham, E. A.; Hinkey, J. B.; Bruckner, A. P.

    1992-01-01

    An experimental investigation of the starting transients of the thermally choked ram accelerator is presented in this paper. Construction of a highly instrumented tube section and instrumentation inserts provide high resolution experimental pressure, luminosity, and electromagnetic data of the starting transients. Data obtained prior to and following the entrance diaphragm show detailed development of shock systems in both combustible and inert mixtures. With an evacuated launch tube, starting the diffuser is possible at any Mach number above the Kantrowitz Mach number. The detrimental effects and possible solutions of higher launch tube pressures and excessive obturator leakage (blow-by) are discussed. Ignition of a combustible mixture is demonstrated with both perforated and solid obturators. The relative advantages and disadvantages of each are discussed. Data obtained from these starting experiments enhance the understanding of the ram accelerator, as well as assist in the validation of unsteady, chemically reacting CFD codes.

  11. Thermal cycling of tungsten-fibre-reinforced superalloy composites

    NASA Technical Reports Server (NTRS)

    Wetherhold, Robert C.; Westfall, Leonard J.

    1988-01-01

    The thermal cycling of a tungsten-fiber-reinforced superalloy (TFRS) composite is typical of its application in high-temperature engine environments. The mismatch in thermal expansion coefficients between fiber and matrix causes substantial longitudinal (0 deg) stresses in the composite, which can produce inelastic damage-producing matrix strains. The case of thermal fatigue is explored as a "worst case" of the possible matrix damage, in comparison with specimens which are also mechanically loaded in tension. The thermally generated cyclic stresses and the attendant matrix plasticity may be estimated using a nonlinear finite-element program, by proposing a physical analog to the micromechanics equations. A damage metric for the matrix is proposed using the Coffin-Manson criterion, which metric can facilitate comparisons of damage among different candidate materials, and also comparisons for a given material subjected to different temperature cycles. An experimental program was carried out for thermal cycling of a 37 vol pct TFRS composite to different maximum temperatures. The results confirm the prediction that thermal cycling produces matrix degradation and composite strength reduction, which become more pronounced with increasing maximum cyclic temperature. The strength of the fiber is shown to be identical for the as-fabricated and thermally cycled specimens, suggesting that the reduction in composite strength is due to the loss of matrix contribution and also to notching effects of the matrix voids on the fiber.

  12. Solar thermal organic rankine cycle for micro-generation

    NASA Astrophysics Data System (ADS)

    Alkahli, N. A.; Abdullah, H.; Darus, A. N.; Jalaludin, A. F.

    2012-06-01

    The conceptual design of an Organic Rankine Cycle (ORC) driven by solar thermal energy is developed for the decentralized production of electricity of up to 50 kW. Conventional Rankine Cycle uses water as the working fluid whereas ORC uses organic compound as the working fluid and it is particularly suitable for low temperature applications. The ORC and the solar collector will be sized according to the solar flux distribution in the Republic of Yemen for the required power output of 50 kW. This will be a micro power generation system that consists of two cycles, the solar thermal cycle that harness solar energy and the power cycle, which is the ORC that generates electricity. As for the solar thermal cycle, heat transfer fluid (HTF) circulates the cycle while absorbing thermal energy from the sun through a parabolic trough collector and then storing it in a thermal storage to increase system efficiency and maintains system operation during low radiation. The heat is then transferred to the organic fluid in the ORC via a heat exchanger. The organic fluids to be used and analyzed in the ORC are hydrocarbons R600a and R290.

  13. Damage Assessment of Stress-Thermal Cycled high temperature

    NASA Technical Reports Server (NTRS)

    Ju, Jae-Hyung; Prochazka, Michael; Ronke, Ben; Morgan, Roger; Shin, Eugence

    2004-01-01

    We report on the characterization of bismaleimide and polyimide carbon fiber composite, microcrack development under stress thermal cycling loading. Such cycles range from cryogenic temperatures associated with cryogenic fuel (LN, LOX) containment to high temperatures of 300 degrees Celsius associated with future hypervelocity aeropropulsion systems. Microcrack development thresholds as a function of temperature range of the thermal cycle; the number of cycles; the applied stress level imposed on the composite are reported. We have conducted stress-thermal cycles on thin bismaleimide-woven carbon fiber foils for three temperature range cycles: 1. Ambient temperature - -196 degrees celsius. 2. Ambient temperature - 150 degrees Celsius; 200 degrees Celsius; 250 degrees Celsius. 3. -196 degrees Celsius - 250 degrees Celsius. The Principle findings are that the full cycles from -196 degrees Celsius to to 250 degrees Celsius cause the most significant microcrack of development. These observations indicate that the high temperature portion of the cycle under load causes fiber-matrix interface failure and subsequent exposure to higher stresses at the cryogenic, low temperature region results in composite matrix microcracking as a result of the additional stresses associate with the fiber-matrix thermal expansion mismatch. Our initial studies for 12 ply PMR-II-50 polyimide/M60JB carbon fabric [0f,90f,90f,0f,0f,90f]ls composites will be presented. The stress-thermal cycle test procedure for these will be described. Moisture absorption characteristics between cycles will be used to monitor interconnected microcrack development. The applied stress level will be 75% of the composite cryogenic (-196 degrees Celsius) ultimate strength.

  14. ELECTRON AND PROTON ACCELERATION DURING THE FIRST GROUND LEVEL ENHANCEMENT EVENT OF SOLAR CYCLE 24

    SciTech Connect

    Li, C.; Sun, L. P.; Firoz, Kazi A.; Miroshnichenko, L. I.

    2013-06-10

    High-energy particles were recorded by near-Earth spacecraft and ground-based neutron monitors (NMs) on 2012 May 17. This event was the first ground level enhancement (GLE) of solar cycle 24. In this study, we try to identify the acceleration source(s) of solar energetic particles by combining in situ particle measurements from the WIND/3DP, GOES 13, and solar cosmic rays registered by several NMs, as well as remote-sensing solar observations from SDO/AIA, SOHO/LASCO, and RHESSI. We derive the interplanetary magnetic field (IMF) path length (1.25 {+-} 0.05 AU) and solar particle release time (01:29 {+-} 00:01 UT) of the first arriving electrons by using their velocity dispersion and taking into account contamination effects. We found that the electron impulsive injection phase, indicated by the dramatic change in the spectral index, is consistent with flare non-thermal emission and type III radio bursts. Based on the potential field source surface concept, modeling of the open-field lines rooted in the active region has been performed to provide escape channels for flare-accelerated electrons. Meanwhile, relativistic protons are found to be released {approx}10 minutes later than the electrons, assuming their scatter-free travel along the same IMF path length. Combining multi-wavelength imaging data of the prominence eruption and coronal mass ejection (CME), we obtain evidence that GLE protons, with an estimated kinetic energy of {approx}1.12 GeV, are probably accelerated by the CME-driven shock when it travels to {approx}3.07 solar radii. The time-of-maximum spectrum of protons is typical for shock wave acceleration.

  15. Study on durability for thermal cycle of planar SOFC

    SciTech Connect

    Ando, Motoo; Nakata, Kei-ichi; Wakayama, Sin-ichi

    1996-12-31

    TONEN CORPORATION has developed planar type SOFC since 1986. We demonstrated the output of 1.3 kW in 1991 and 5.1 kW in 1995. Simultaneously we have studied how to raise electric efficiency and reliability utilizing hydrogen and propane as fuel. Durability for thermal cycle is one of the most important problems of planar SOFC to make it more practical. The planar type SOFC is made up of separator, zirconia electrolyte and glass sealant. The thermal expansion of these components are expected to be the same value, however, they still possess small differences. In this situation, a thermal cycle causes a thermal stress due to the difference of the cell components and is often followed by a rupture in cell components, therefore, the analysis of the thermal stress should give us much useful information. The thermal cycle process consists of a heating up and cooling down procedure. Zirconia electrolyte is not bonded to the separator under the condition of the initial heating up procedure, and glass sealant becomes soft or melts and glass seals spaces between the zirconia and separator. The glass sealant becomes harder with the cooling down procedure. Moreover, zirconia is tightly bonded with separator below a temperature which is defined as a constraint temperature and thermal stress also occurs. This indicates that the heating up process relaxes the thermal stress and the cooling down increases it. In this paper, we simulated dependence of the stress on the sealing configuration, thermal expansion of sealant and constraint temperature of sealant glass. Furthermore, we presented SOFC electrical properties after a thermal cycle.

  16. Degradation of a two-layer thermal barrier coating under thermal cycling. [for superalloys of aircraft turbine engine blades

    NASA Technical Reports Server (NTRS)

    Maier, R. D.; Scheuermann, C. M.; Andrews, C. W.

    1981-01-01

    A two-layer plasma-sprayed thermal barrier coating on a directionally solidified nickel-base eutectic alloy substrate was characterized prior to and after thermal cycling to 1095 C in an accelerated furnace test. The coating was comprised of an inner layer of Ni-16.4Cr-5.1Al-0.15Y (wt%) bond coat and an outer layer of ZrO2-7.9Y2O3 (wt%) thermal barrier. Characterization of the bond coat revealed that substantial amounts of yttrium and aluminum were oxidized during plasma-spraying in air. The oxidation of these elements reduced the protective capacity of the bond coat so that, on thermal exposure, severe degradation of the bond coat resulted and large amounts of nickel oxide formed. This nickel oxide was demonstrated to grow outward into the thermal barrier, which appears to have increased the stresses in the thermal barrier and contributed to its failure near the thermal barrier-bond coat interface.

  17. Electrons and protons acceleration during the first GLE event of solar cycle 24

    NASA Astrophysics Data System (ADS)

    Li, Chuan; Firoz, Kazi, A.; Sun, Lingpeng; Miroshnichenko, Leonty, I.

    2013-04-01

    High-energy particles were recorded by the near-Earth spacecraft particle detectors and ground-based neutron monitors (NMs) on 2012 May 17. This event was the first Ground Level Enhancement (GLE) of solar cycle 24. In present study, we try to identify the acceleration source of solar energetic particles (SEPs) by combining in-situ particle measurements from WIND/3DP, ACE/EPAM, GOES, and solar cosmic rays (SCRs) registered by several NMs, as well as the remote-sensing solar observations from SDO/AIA, SOHO/LASCO, and RHESSI. We derive the path length (1.25 ± 0.05 AU) of SEPs in the interplanetary magnetic field (IMF) and solar particle release (SPR) time (01:29 ± 1 UT) of the first arriving electrons by using their velocity dispersion and taking into account the contamination effects. It is found that the electrons impulsive injection phase, indicated by the dramatic change of spectral index, is consistent with the flare non-thermal emission and type III radio bursts. The potential field source surface (PFSS) modeled open-field lines rooted in the active region (AR) provide escaping channels for flare accelerated electrons. Meanwhile, relativistic protons are found to be released ~10 min later than the electrons, assuming their scatter-free travel along the same IMF path length. Combing multi-wavelength imaging data on the prominence eruption and coronal mass ejection (CME), we obtain some evidence of that GLE protons, with estimated kinetic energy of ~1.12 GeV, are probably accelerated by the CME-driven shock when it travels to ~3.07 solar radii.

  18. Thermal energy dissipation and xanthophyll cycles beyond the Arabidopsis model.

    PubMed

    García-Plazaola, José Ignacio; Esteban, Raquel; Fernández-Marín, Beatriz; Kranner, Ilse; Porcar-Castell, Albert

    2012-09-01

    Thermal dissipation of excitation energy is a fundamental photoprotection mechanism in plants. Thermal energy dissipation is frequently estimated using the quenching of the chlorophyll fluorescence signal, termed non-photochemical quenching. Over the last two decades, great progress has been made in the understanding of the mechanism of thermal energy dissipation through the use of a few model plants, mainly Arabidopsis. Nonetheless, an emerging number of studies suggest that this model represents only one strategy among several different solutions for the environmental adjustment of thermal energy dissipation that have evolved among photosynthetic organisms in the course of evolution. In this review, a detailed analysis of three examples highlights the need to use models other than Arabidopsis: first, overwintering evergreens that develop a sustained form of thermal energy dissipation; second, desiccation tolerant plants that induce rapid thermal energy dissipation; and third, understorey plants in which a complementary lutein epoxide cycle modulates thermal energy dissipation. The three examples have in common a shift from a photosynthetically efficient state to a dissipative conformation, a strategy widely distributed among stress-tolerant evergreen perennials. Likewise, they show a distinct operation of the xanthophyll cycle. Expanding the list of model species beyond Arabidopsis will enhance our knowledge of these mechanisms and increase the synergy of the current studies now dispersed over a wide number of species.

  19. Effects of thermal cycling on composite materials for space structures

    NASA Technical Reports Server (NTRS)

    Tompkins, Stephen S.

    1989-01-01

    The effects of thermal cycling on the thermal and mechanical properties of composite materials that are candidates for space structures are briefly described. The results from a thermal analysis of the orbiting Space Station Freedom is used to define a typical thermal environment and the parameters that cause changes in the thermal history. The interactions of this environment with composite materials are shown and described. The effects of this interaction on the integrity as well as the properties of GR/thermoset, Gr/thermoplastic, Gr/metal and Gr/glass composite materials are discussed. Emphasis is placed on the effects of the interaction that are critical to precision spacecraft. Finally, ground test methodology are briefly discussed.

  20. N2-fixing red alder indirectly accelerates ecosystem nitrogen cycling

    USGS Publications Warehouse

    Perakis, Steven S.; Matkins, Joselin J.; Hibbs, David E.

    2012-01-01

    Symbiotic N2-fixing tree species can accelerate ecosystem N dynamics through decomposition via direct pathways by producing readily decomposed leaf litter and increasing N supply to decomposers, as well as via indirect pathways by increasing tissue and detrital N in non-fixing vegetation. To evaluate the relative importance of these pathways, we compared three-year decomposition and N dynamics of N2-fixing red alder leaf litter (2.34 %N) to both low-N (0.68 %N) and high-N (1.21 %N) litter of non-fixing Douglas-fir, and decomposed each litter source in four forests dominated by either red alder or Douglas-fir. We also used experimental N fertilization of decomposition plots to assess elevated N availability as a potential mechanism of N2-fixer effects on litter mass loss and N dynamics. Direct effects of N2-fixing red alder on decomposition occurred primarily as faster N release from red alder than Douglas-fir litter, but direct increases in N supply to decomposers via fertilization did not stimulate decomposition of any litter. Fixed N indirectly influenced detrital dynamics by increasing Douglas-fir tissue and litter N concentrations, which accelerated litter N release without accelerating mass loss. By increasing soil N, tissue N, and the rate of N release from litter of non-fixers, we conclude that N2-fixing vegetation can indirectly foster plant-soil feedbacks that contribute to the persistence of elevated N availability in terrestrial ecosystems.

  1. Shortening tobacco life cycle accelerates functional gene identification in genomic research.

    PubMed

    Ning, G; Xiao, X; Lv, H; Li, X; Zuo, Y; Bao, M

    2012-11-01

    Definitive allocation of function requires the introduction of genetic mutations and analysis of their phenotypic consequences. Novel, rapid and convenient techniques or materials are very important and useful to accelerate gene identification in functional genomics research. Here, over-expression of PmFT (Prunus mume), a novel FT orthologue, and PtFT (Populus tremula) lead to shortening of the tobacco life cycle. A series of novel short life cycle stable tobacco lines (30-50 days) were developed through repeated self-crossing selection breeding. Based on the second transformation via a gusA reporter gene, the promoter from BpFULL1 in silver birch (Betula pendula) and the gene (CPC) from Arabidopsis thaliana were effectively tested using short life cycle tobacco lines. Comparative analysis among wild type, short life cycle tobacco and Arabidopsis transformation system verified that it is optional to accelerate functional gene studies by shortening host plant material life cycle, at least in these short life cycle tobacco lines. The results verified that the novel short life cycle transgenic tobacco lines not only combine the advantages of economic nursery requirements and a simple transformation system, but also provide a robust, effective and stable host system to accelerate gene analysis. Thus, shortening tobacco life cycle strategy is feasible to accelerate heterologous or homologous functional gene identification in genomic research.

  2. Thermal Cycling on Fatigue Failure of the Plutonium Vitrification Melter

    SciTech Connect

    Jordan, Jeffrey; Gorczyca, Jennifer

    2009-02-11

    One method for disposition of excess plutonium is vitrification into cylindrical wasteforms. Due to the hazards of working with plutonium, the vitrification process must be carried out remotely in a shielded environment. Thus, the equipment must be easily maintained. With their simple design, induction melters satisfy this criterion, making them ideal candidates for plutonium vitrification. However, due to repeated heating and cooling cycles and differences in coefficients of thermal expansion of contacting materials fatigue failure of the induction melter is of concern. Due to the cost of the melter, the number of cycles to failure is critical. This paper presents a method for determining the cycles to failure for an induction melter by using the results from thermal and structural analyses as input to a fatigue failure model.

  3. Thermal Energy Storage in a Confined Aquifer: Second Cycle

    NASA Astrophysics Data System (ADS)

    Molz, F. J.; Parr, A. D.; Andersen, P. F.

    1981-06-01

    During the first 6-month injection-storage-recovery cycle of the Auburn University Aquifer Thermal Energy Storage Project, water pumped from an upper supply aquifer was heated to an average temperature of 55°C with an oil-fired boiler and then injected into a lower storage aquifer. Injection and recovery temperatures, flow rates, and temperatures at six depths in 10 observation wells and hydraulic heads in seven wells were recorded twice daily. The second-cycle injection, which was performed in a manner similar to the first, began on September 23, 1978, and continued until November 25, 1978, when 58,010 m3 of water had been pumped into the storage aquifer. The major problem experienced during the first cycle, a clogging injection well, was reduced by regular backwashing. This was done 8 times during injection and resulted in a 24% average injection rate increase compared to the first cycle. A 63-day storage period ended on January 27, 1979, and production of hot water began with an initial temperature of 54°C. By March 23 this temperature had dropped to 33°C, with 66,400 m3 of water and 76% of the injected thermal energy recovered. This compares to 66% recovery during the first cycle over the same drop in production temperature. Production of hot water continued until April 20, at which time 100,100 m3 of water and 89% of the injected thermal energy was recovered at a final production temperature of 27.5°C. During the second cycle, measurements were made of relative land subsidence and rebound to a precision approaching 0.1 mm. The surface elevation near the injection well rose 4 mm during injection, fell during storage, and fell more rapidly toward its original elevation during production. This movement was due to thermal expansion and contraction rather than to effects caused by head changes in the storage aquifer.

  4. High-speed thermal cycling system and method of use

    DOEpatents

    Hansen, Anthony D. A.; Jaklevic, Joseph M.

    1996-01-01

    A thermal cycling system and method of use are described. The thermal cycling system is based on the-circulation of temperature-controlled water directly to the underside of thin-walled polycarbonate microtiter plates. The water flow is selected from a manifold fed by pumps from heated reservoirs. The plate wells are loaded with typically 15-20 .mu.l of reagent mix for the PCR process. Heat transfer through the thin polycarbonate is sufficiently rapid that the contents reach thermal equilibrium with the water in less than 15 seconds. Complete PCR amplification runs of 40 three-step cycles have been performed in as little as 14.5 minutes, with the results showing substantially enhanced specificity compared to conventional technology requiring run times in excess of 100 minutes. The plate clamping station is designed to be amenable to robotic loading and unloading of the system. It includes a heated lid, thus eliminating the need for mineral oil overlay of the reactants. The present system includes three or more plate holder stations, fed from common reservoirs but operating with independent switching cycles. The system can be modularly expanded.

  5. High-speed thermal cycling system and method of use

    DOEpatents

    Hansen, A.D.A.; Jaklevic, J.M.

    1996-04-16

    A thermal cycling system and method of use are described. The thermal cycling system is based on the circulation of temperature-controlled water directly to the underside of thin-walled polycarbonate plates. The water flow is selected from a manifold fed by pumps from heated reservoirs. The plate wells are loaded with typically 15-20 microliters of reagent mix for the PCR process. Heat transfer through the thin polycarbonate is sufficiently rapid that the contents reach thermal equilibrium with the water in less than 15 seconds. Complete PCR amplification runs of 40 three-step cycles have been performed in as little as 14.5 minutes, with the results showing substantially enhanced specificity compared to conventional technology requiring run times in excess of 100 minutes. The plate clamping station is designed to be amenable to robotic loading and unloading of the system. It includes a heated lid, thus eliminating the need for mineral oil overlay of the reactants. The present system includes three or more plate holder stations, fed from common reservoirs but operating with independent switching cycles. The system can be modularly expanded. 13 figs.

  6. Thermal cycling tests on surface-mount assemblies

    SciTech Connect

    Jennings, C.W.

    1988-03-01

    The capability of surface-mount (SM) solder joints to withstand various thermal cycle stresses was evaluated through electrical circuit resistance changes of a test pattern and by visual examination for cracks in the solder after exposure to thermal cycling. The joints connected different electrical components, primarily leadless-chip carriers (LCCs), and printed wiring-board (PWB) pads on different laminate substrates. Laminate compositions were epoxy-glass and polyimide-glass with and without copper/Invar/copper (CIC) inner layers, polyimide-quartz, epoxy-Kevlar, and polyimide-Kevlar. The most resistant joints were between small LCCs (24 and 48 pins) and polyimide-glass laminate with CIC inner layers. Processing in joint formation was found to be an important part of joint resistant. Thermal cycling was varied with respect to both time and temperature. A few resistors, capacitors, and inductors showed opens after 500 30-min cycles between -65/degree/C and 125/degree/C. Appreciable moisture contents were measured for laminate materials, especially those of polyimide-Kevlar after equilibration in 100/percent/ relative humidity at room temperature. If not removed or reduced, moisture can cause delamination in vapor-phase soldering. 17 refs, 12 figs.,10 tabs.

  7. Accelerator Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

    SciTech Connect

    Brown, Nicholas R.; Heidet, Florent; Haj Tahar, Malek

    2016-01-01

    This article is a review of several accelerator–reactor interface issues and nuclear fuel cycle applications of acceleratordriven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systems on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.

  8. Accelerator Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

    DOE PAGES

    Brown, Nicholas R.; Heidet, Florent; Haj Tahar, Malek

    2016-01-01

    This article is a review of several accelerator–reactor interface issues and nuclear fuel cycle applications of acceleratordriven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systemsmore » on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.« less

  9. Thermal modelling of Li-ion polymer battery for electric vehicle drive cycles

    NASA Astrophysics Data System (ADS)

    Chacko, Salvio; Chung, Yongmann M.

    2012-09-01

    Time-dependent, thermal behaviour of a lithium-ion (Li-ion) polymer cell has been modelled for electric vehicle (EV) drive cycles with a view to developing an effective battery thermal management system. The fully coupled, three-dimensional transient electro-thermal model has been implemented based on a finite volume method. To support the numerical study, a high energy density Li-ion polymer pouch cell was tested in a climatic chamber for electric load cycles consisting of various charge and discharge rates, and a good agreement was found between the model predictions and the experimental data. The cell-level thermal behaviour under stressful conditions such as high power draw and high ambient temperature was predicted with the model. A significant temperature increase was observed in the stressful condition, corresponding to a repeated acceleration and deceleration, indicating that an effective battery thermal management system would be required to maintain the optimal cell performance and also to achieve a full battery lifesapn.

  10. FTIR characterization of thermally cycled PMR-15 composites

    NASA Technical Reports Server (NTRS)

    Young, Philip R.; Chang, A. C.

    1988-01-01

    Chemical characterization results are presented for a variety of PMR-15/graphite composites, differentiated according to prepreg types and cure cycles, which were subjected to 1000 thermal cycles between 0 and 450 F. Fourier transform IR spectroscopy was used in conjunction with diffuse reflectance sampling to examine whether changes in the matrix resin chemistry due to environmental exposure may have contributed to microcracking. Analysis based on compound spectra revealed behavior associated with the oxidation of methylene groups to carbonyl groups on the composite surface; evidence of crosslinking also emerged, although the two phenomena do not appear to be related.

  11. Carbon dioxide release from ocean thermal energy conversion (OTEC) cycles

    SciTech Connect

    Green, H.J. ); Guenther, P.R. )

    1990-09-01

    This paper presents the results of recent measurements of CO{sub 2} release from an open-cycle ocean thermal energy conversion (OTEC) experiment. Based on these data, the rate of short-term CO{sub 2} release from future open-cycle OTEC plants is projected to be 15 to 25 times smaller than that from fossil-fueled electric power plants. OTEC system that incorporate subsurface mixed discharge are expected to result in no long-term release. OTEC plants can significantly reduce CO{sub 2} emissions when substituted for fossil-fueled power generation. 12 refs., 4 figs., 3 tabs.

  12. Accelerator-driven thorium-cycle fission power

    NASA Astrophysics Data System (ADS)

    Sattarov, Akhdiyor

    2009-10-01

    A flux-coupled stack of superconducting isochronous cyclotrons could be used to drive thorium-cycle fission power. The 800 MeV proton beams produce fast neutrons through spallation, then the fast neutrons transmute the thorium into uranium and drive fission. The thorium reactor would provide GW electric power, eat its own long-lived waste, run for 7 years between core accesses, operate below criticality, and be stable against melt-down. Reserves of thorium are sufficient to provide the world's energy needs for a thousand years.

  13. Phosphorus constrains accelerated nitrogen cycling in limed acidic forests

    NASA Astrophysics Data System (ADS)

    Deforest, J. L.; Shaw, A. N.; Kluber, L. A.; Burke, D. J.; Carrino-Kyker, S. R.; Smemo, K. A.

    2011-12-01

    Anthropogenic deposition can increase phosphorus (P) limitation by abiotic and biotic means. Soil acidification can remove P from available pools and nitrogen (N) deposition can increase the demand for P. We reason that chronic acidic deposition is promoting P limitation in acidic hardwood forests and thereby altering N cycling. The objectives of this study were to investigate the interactive influence of P availability and soil pH on N and P cycling and availability to determine if the response varies between two physiographic regions experiencing similar chronic acidic deposition. We addressed these objectives by experimentally manipulating soil pH, P, or both in strongly acidic glaciated and unglaciated hardwood forests in eastern Ohio, USA. Our results suggest complex interactions between P, soil pH, and the N cycle. Glaciated soils were found to be more N-saturated with nitrification rates 18 times greater than in unglaciated soils. Elevating pH, with or without added P, doubled nitrification rates in glaciated soils. For unglaciated soils, raising pH increased nitrification 10-fold, but increased nitrification only 5-fold in combination with P. This result suggests raising soil pH lowered the demand of soil N, or directly stimulated nitrifying activity, and that increasing P availability could limit N availability. To various degrees, readily available P was geochemically or biologically immobilized in all treatments, suggesting chronic P deficiency in these ecosystems. Phosphorus immobilization decreased as soil pH was elevated, but elevated P either had no effect (glaciated) or doubled P immobilization rates (unglaciated). These results suggest that raising soil pH reduces microbial P limitation for phosphate, whereas adding P appears to make phosphate scarcer. We suggest that P plays an important role in N transformations and cycling, but appears more important in unglaciated soils than in glaciated soils. Chronic soil acidification may have a greater

  14. Accelerated cycle-life testing of small sealed lead/acid batteries

    NASA Astrophysics Data System (ADS)

    Kim, I.; Oh, S. H.; Kang, H. Y.

    An attempt has been made to devise methods for reducing the cycle-testing time of long-life sealed lead/acid batteries. In order for the accelerated test results to equate to the actual field operations, it is assumed that the failure modes under both normal and accelerated conditions must be the same. As a first step in the search for a reliable accelerated test, observations of the battery ageing process have been made under different daily duty cycles, viz., 1 (normal), 8 and 16 cycles/day at ambient temperature and 80% depth-of-discharge. It has been found that the main cause of failure is different for a given duty cycle. This complicates the task of applying accelerated test results to field operations. For the 8 cycles/day schedule, the main cause of failure is degradation of the positive active material. Positive grid corrosion is the main factor in the 16 cycles/day case. Under normal conditions, both grid corrosion and PbO 2 degradation appear to be equally significant.

  15. Materials constitutive models for nonlinear analysis of thermally cycled structures

    NASA Technical Reports Server (NTRS)

    Kaufman, A.; Hunt, L. E.

    1982-01-01

    Effects of inelastic materials models on computed stress-strain solutions for thermally loaded structures were studied by performing nonlinear (elastoplastic creep) and elastic structural analyses on a prismatic, double edge wedge specimen of IN 100 alloy that was subjected to thermal cycling in fluidized beds. Four incremental plasticity creep models (isotropic, kinematic, combined isotropic kinematic, and combined plus transient creep) were exercised for the problem by using the MARC nonlinear, finite element computer program. Maximum total strain ranges computed from the elastic and nonlinear analyses agreed within 5 percent. Mean cyclic stresses, inelastic strain ranges, and inelastic work were significantly affected by the choice of inelastic constitutive model. The computing time per cycle for the nonlinear analyses was more than five times that required for the elastic analysis.

  16. Thermal analysis of wildfires and effects on global ecosystem cycling

    NASA Technical Reports Server (NTRS)

    Ambrosia, Vincent G.; Brass, James A.

    1988-01-01

    Biomass combustion plays an important role in the earth's biogeochemical cycling. The monitoring of wildfires and their associated variables at global scales is feasible and can lead to predictions of the influence of combustion on biogeochemical cycling and tropospheric chemistry. Remote sensing data collected during the 1985 California wildfire season indicate that the information content of key thermal and infrared/thermal wave band channels centered at 11.5 microns, 3.8 microns, and 2.25 microns are invaluable for discriminating and calculating fire related variables. These variables include fire intensity, rate-of-spread, soil cooling recovery behind the fire front, and plume structure. Coinciding Advanced Very High Resolution Radiometer (AVHRR) data provided information regarding temperature estimations and the movement of the smoke plume from one wildfire into the Los Angeles basin.

  17. Prediction of thermal cycling induced cracking in polmer matrix composites

    NASA Technical Reports Server (NTRS)

    Mcmanus, Hugh L.

    1994-01-01

    The work done in the period August 1993 through February 1994 on the 'Prediction of Thermal Cycling Induced Cracking In Polymer Matrix Composites' program is summarized. Most of the work performed in this period, as well as the previous one, is described in detail in the attached Master's thesis, 'Analysis of Thermally Induced Damage in Composite Space Structures,' by Cecelia Hyun Seon Park. Work on a small thermal cycling and aging chamber was concluded in this period. The chamber was extensively tested and calibrated. Temperatures can be controlled very precisely, and are very uniform in the test chamber. Based on results obtained in the previous period of this program, further experimental progressive cracking studies were carried out. The laminates tested were selected to clarify the differences between the behaviors of thick and thin ply layers, and to explore other variables such as stacking sequence and scaling effects. Most specimens tested were made available from existing stock at Langley Research Center. One laminate type had to be constructed from available prepreg material at Langley Research Center. Specimens from this laminate were cut and prepared at MIT. Thermal conditioning was carried out at Langley Research Center, and at the newly constructed MIT facility. Specimens were examined by edge inspection and by crack configuration studies, in which specimens were sanded down in order to examine the distribution of cracks within the specimens. A method for predicting matrix cracking due to decreasing temperatures and/or thermal cycling in all plies of an arbitrary laminate was implemented as a computer code. The code also predicts changes in properties due to the cracking. Extensive correlations between test results and code predictions were carried out. The computer code was documented and is ready for distribution.

  18. Thermal stress cycling of GaAs solar cells

    NASA Astrophysics Data System (ADS)

    Janousek, B. K.; Francis, R. W.; Wendt, J. P.

    A thermal cycling experiment was performed on GaAs solar cells to establish the electrical and structural integrity of these cells under the temperature conditions of a simulated low-Earth orbit of 3-year duration. Thirty single junction GaAs cells were obtained and tests were performed to establish the beginning-of-life characteristics of these cells. The tests consisted of cell I-V power output curves, from which were obtained short-circuit current, open circuit voltage, fill factor, and cell efficiency, and optical micrographs, spectral response, and ion microprobe mass analysis (IMMA) depth profiles on both the front surfaces and the front metallic contacts of the cells. Following 5,000 thermal cycles, the performance of the cells was reexamined in addition to any factors which might contribute to performance degradation. It is established that, after 5,000 thermal cycles, the cells retain their power output with no loss of structural integrity or change in physical appearance.

  19. Parametric Studies Of Failure Mechanisms In Thermal Barrier Coatings During Thermal Cycling Using FEM

    NASA Astrophysics Data System (ADS)

    Srivathsa, B.; Das, D. K.

    2015-12-01

    Thermal barrier coatings (TBCs) are widely used on different hot components of gas turbine engines such as blades and vanes. Although, several mechanisms for the failure of the TBCs have been suggested, it is largely accepted that the durability of these coatings is primarily determined by the residual stresses that are developed during the thermal cycling. In the present study, the residual stress build-up in an electron beam physical vapour deposition (EB-PVD) based TBCs on a coupon during thermal cycling has been studied by varying three parameters such as the cooling rate, TBC thickness and substrate thickness. A two-dimensional thermomechanical generalized plane strain finite element simulations have been performed for thousand cycles. It was observed that these variations change the stress profile significantly and the stress severity factor increases non-linearly. Overall, the predictions of the model agree with reported experimental results and help in predicting the failure mechanisms.

  20. Signal of Acceleration and Physical Mechanism of Water Cycle in Xinjiang, China

    PubMed Central

    Feng, Guo-Lin; Wu, Yong-Ping

    2016-01-01

    Global warming accelerates water cycle with features of regional difference. However, little is known about the physical mechanism behind the phenomenon. To reveal the links between water cycle and climatic environment, we analyzed the changes of water cycle elements and their relationships with climatic and environmental factors. We found that when global warming was significant during the period of 1986-2003, the precipitation in Tarim mountains as well as Xinjiang increased rapidly except for Tarim plains, which indicated that there existed a signal of acceleration for water cycle in Xinjiang. The speed of water cycle is mainly affected by altitude, latitude, longitude, slope direction, and the most fundamental element is temperature. Moreover, according to Clausius-Kela Bai Lung relation, we found that the climate change induced the increase of temperature and accelerated the local water cycle only for the wet places. Our results provide a possible physical mechanisms of water cycle and thus well link the climate change to water circulation. PMID:27907078

  1. Neutron Production from Feedback Controlled Thermal Cycling of a Pyroelectric Crystal Stack

    SciTech Connect

    Tang, V; Meyer, G; Schmid, G; Spadaccini, C; Kerr, P; Rusnak, B; Sampayan, S; Naranjo, B; Putterman, S

    2007-08-09

    The LLNL Crystal Driven Neutron Source is operational and has produced record ion currents of {approx}10 nA and neutron output of 1.9 ({+-}0.3) x 10{sup 5} per thermal cycle using a crystal heating rate of 0.2 C/s from 10 C to 110 C. A 3 cm diameter by 1 cm thick LiTaO{sub 3} crystal with a socket secured field emitter tip is thermally cycled with feedback control for ionization and acceleration of deuterons onto a deuterated target to produce D-D fusion neutrons. The entire crystal and temperature system is mounted on a bellows which allows movement of the crystal along the beam axis and is completely contained on a single small vacuum flange. The modular crystal assembly permitted experimental flexibility. Operationally, flashover breakdowns along the side of the crystal and poor emitter tip characteristics can limit the neutron source. The experimental neutron results extend earlier published work by increasing the ion current and pulse length significantly to achieve a factor-of-two higher neutron output per thermal cycle. These findings are reviewed along with details of the instrument.

  2. Proton acceleration by single-cycle laser pulses offers a novel monoenergetic and stable operating regime

    NASA Astrophysics Data System (ADS)

    Zhou, M. L.; Yan, X. Q.; Mourou, G.; Wheeler, J. A.; Bin, J. H.; Schreiber, J.; Tajima, T.

    2016-04-01

    Prompted by the possibility to produce high energy, single-cycle laser pulses with tens of Petawatt (PW) power, we have investigated laser-matter interactions in the few optical cycle and ultra relativistic intensity regimes. A particularly interesting instability-free regime for ion production was revealed leading to the efficient coherent generation of short (femtosecond; 10 - 15 s ) monoenergetic ion bunches with a peak energy greater than GeV. Of paramount importance, the interaction is absent of the Rayleigh Taylor Instabilities and hole boring that plague techniques such as target normal sheath acceleration and radiation pressure acceleration.

  3. X-class Solar Flare Energy Partition into Radiative, Non-Thermal Acceleration of Electrons and Peak Thermal Plasma Components - Methodology and Results

    NASA Astrophysics Data System (ADS)

    Moore, Christopher S.; Chamberlin, Phillip; Dennis, Brian R.; Hock, Rachel

    2015-08-01

    Solar flares are among the most energetic processes in the solar system. X-class flares are the largest and can convert up to 1033 ergs of magnetic energy into the acceleration of charged particles and the heating of plasma. They are often accompanied by coronal mass ejections (CMEs). We discuss the methodology and results of the energy partition into three main components: (1) radiative energy, (2) non-thermal acceleration of electrons, and (3) the peak thermal energy content, for a subset of the largest eruptive events from Solar Cycle 23, as derived from satellite observations and empirical models. The bolometric energy content is on the order of 1031 - 1032 ergs and is extracted from Total Solar Irradiance (TSI) measurements by the Total Irradiance Monitor (TIM) onboard the SOlar Radiation and Climate Experiment (SORCE). The Vacuum Ultraviolet (VUV) contribution of the total radiative output is obtained by implementing the Flare Irradiance Spectral Model (FISM). Furthermore, we partition the radiative release into impulsive and gradual phases. X-ray spectra from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) are used to deduce the energy in the non-thermal accelerated electrons, generally found to be 1031 -1032 ergs, and the peak thermal energy content of around 1030 - 1031 ergs. Aside from the CME kinetic energy, these three components contain a substantial amount of the initial available magnetic energy.

  4. Influence of Thermal Cycle Frequency on the TGO Growth and Cracking Behaviors of an APS-TBC

    NASA Astrophysics Data System (ADS)

    Chen, W. R.; Wu, X.; Dudzinski, D.

    2012-12-01

    The durability of thermal barrier coatings (TBCs) is controlled by fracture near the interface between the ceramic topcoat and the metallic bond coat, where a layer of thermally grown oxide (TGO) forms during service exposure. In the present work, the influence of thermal cycle frequency on the oxidation performance, in terms of TGO growth and cracking behavior, of an air-plasma-sprayed (APS) Co-32Ni-21Cr-8Al-0.5Y (wt.%) bond coat was studied. The results show that while TGO growth exhibited an initial parabolic growth behavior followed by an accelerated growth stage, higher cycle frequency resulted in a faster TGO growth and a higher crack propagation rate. It is found that a power-law relationship exists between the maximum crack length and the TGO thickness, which is independent of the cycle frequency. This relationship may warrant a TBC life prediction methodology based on the maximum crack length criterion.

  5. RELATION BETWEEN THE CORONAL MASS EJECTION ACCELERATION AND THE NON-THERMAL FLARE CHARACTERISTICS

    SciTech Connect

    Berkebile-Stoiser, S.; Veronig, A. M.; Bein, B. M.; Temmer, M.

    2012-07-01

    We investigate the relationship between the main acceleration phase of coronal mass ejections (CMEs) and the particle acceleration in the associated flares as evidenced in Reuven Ramaty High Energy Solar Spectroscopic Imager non-thermal X-rays for a set of 37 impulsive flare-CME events. Both the CME peak velocity and peak acceleration yield distinct correlations with various parameters characterizing the flare-accelerated electron spectra. The highest correlation coefficient is obtained for the relation of the CME peak velocity and the total energy in accelerated electrons (c = 0.85), supporting the idea that the acceleration of the CME and the particle acceleration in the associated flare draw their energy from a common source, probably magnetic reconnection in the current sheet behind the erupting structure. In general, the CME peak velocity shows somewhat higher correlations with the non-thermal flare parameters than the CME peak acceleration, except for the spectral index of the accelerated electron spectrum, which yields a higher correlation with the CME peak acceleration (c Almost-Equal-To -0.6), indicating that the hardness of the flare-accelerated electron spectrum is tightly coupled to the impulsive acceleration process of the rising CME structure. We also obtained high correlations between the CME initiation height h{sub 0} and the non-thermal flare parameters, with the highest correlation of h{sub 0} to the spectral index {delta} of flare-accelerated electrons (c Almost-Equal-To 0.8). This means that CMEs erupting at low coronal heights, i.e., in regions of stronger magnetic fields, are accompanied by flares that are more efficient at accelerating electrons to high energies. In the majority of events ({approx}80%), the non-thermal flare emission starts after the CME acceleration, on average delayed by Almost-Equal-To 6 minutes, in line with the standard flare model where the rising flux rope stretches the field lines underneath until magnetic

  6. SOFIA-EXES: Probing the Thermal Structure of M Supergiant Wind Acceleration Zones

    NASA Astrophysics Data System (ADS)

    Harper, Graham M.; O'Gorman, Eamon; Guinan, Edward F.; EXES Instrument Team, EXES Science Team

    2016-01-01

    There is no standard model for mass loss from cool evolved stars, particularly for non-pulsating giants and supergiants. For the early-M supergiants, radiation pressure, convective ejections, magnetic fields, and Alfven waves have all been put forward as potential mass loss mechanisms. A potential discriminator between these ideas is the thermal structure resulting from the heating-cooling balance in the acceleration zone - the most important region to study mass loss physics.We present mid-IR [Fe II] emission line profiles of Betelgeuse and Antares obtained with NASA-DLR SOFIA-EXES and NASA IRTF-TEXES that were obtained as part of a GO program (Harper: Cycle 2-0004) and EXES instrument commissioning observations. The intra-term transitions sample a range of excitation conditions, Texc=540K, 3,400K, and 11,700K, i.e., from the warm chromospheric plasma, that also emits in the cm-radio and ultraviolet, to the cold inner circumstellar envelope. The spectrally-resolved profiles, when combined with VLA cm-radio observations, provide new constraints on the temperature and flow velocity in the outflow accelerating region. The semi-empirical energy balance can be used to test theoretical predictions of wind heating.

  7. Fuel Cycle Performance of Thermal Spectrum Small Modular Reactors

    SciTech Connect

    Worrall, Andrew; Todosow, Michael

    2016-01-01

    Small modular reactors may offer potential benefits, such as enhanced operational flexibility. However, it is vital to understand the holistic impact of small modular reactors on the nuclear fuel cycle and fuel cycle performance. The focus of this paper is on the fuel cycle impacts of light water small modular reactors in a once-through fuel cycle with low-enriched uranium fuel. A key objective of this paper is to describe preliminary reactor core physics and fuel cycle analyses conducted in support of the U.S. Department of Energy Office of Nuclear Energy Fuel Cycle Options Campaign. Challenges with small modular reactors include: increased neutron leakage, fewer assemblies in the core (and therefore fewer degrees of freedom in the core design), complex enrichment and burnable absorber loadings, full power operation with inserted control rods, the potential for frequent load-following operation, and shortened core height. Each of these will impact the achievable discharge burn-up in the reactor and the fuel cycle performance. This paper summarizes the results of an expert elicitation focused on developing a list of the factors relevant to small modular reactor fuel, core, and operation that will impact fuel cycle performance. Preliminary scoping analyses were performed using a regulatory-grade reactor core simulator. The hypothetical light water small modular reactor considered in these preliminary scoping studies is a cartridge type one-batch core with 4.9% enrichment. Some core parameters, such as the size of the reactor and general assembly layout, are similar to an example small modular reactor concept from industry. The high-level issues identified and preliminary scoping calculations in this paper are intended to inform on potential fuel cycle impacts of one-batch thermal spectrum SMRs. In particular, this paper highlights the impact of increased neutron leakage and reduced number of batches on the achievable burn-up of the reactor. Fuel cycle performance

  8. Thermal Cycling Assessment of Steel-Based Thermal Barrier Coatings for Al Protection

    NASA Astrophysics Data System (ADS)

    Poirier, Dominique; Lamarre, Jean-Michel; Legoux, Jean-Gabriel

    2015-01-01

    There is a strong interest from the transportation industry to achieve vehicle weight reduction through the replacement of steel components by aluminum parts. For some applications, aluminum requires protective coatings due to its limited wear and lower temperature resistance compared to steel. The objective of this study was to assess the potential of amorphous-type plasma-sprayed steel coatings and conventional arc-sprayed steel coatings as thermal barrier coatings, mainly through the evaluation of their spalling resistance under thermal cycling. The microstructures of the different coatings were first compared via SEM. The amorphicity of the coatings produced via plasma spraying of specialized alloyed steel and the crystalline phases of the conventional arc-sprayed steel coatings were confirmed through x-ray diffraction. The thermal diffusivity of all coatings produced was measured to be about a third of that of bulk stainless steel. Conventional arc-sprayed steel coatings typically offered better spalling resistance under thermal cycling than steel-based amorphous coatings due probably to their higher initial bond strength. However, the presence of vertical cracks in the steel-based amorphous coatings was found to have a beneficial effect on their thermal cycling resistance. The amorphous plasma-sprayed steel coatings presented indications of recrystallization after their exposure to high temperature.

  9. Assessment of variations in thermal cycle life data of thermal barrier coated rods

    NASA Astrophysics Data System (ADS)

    Hendricks, R. C.; McDonald, G.

    An analysis of thermal cycle life data for 22 thermal barrier coated (TBC) specimens was conducted. The Zr02-8Y203/NiCrAlY plasma spray coated Rene 41 rods were tested in a Mach 0.3 Jet A/air burner flame. All specimens were subjected to the same coating and subsequent test procedures in an effort to control three parametric groups; material properties, geometry and heat flux. Statistically, the data sample space had a mean of 1330 cycles with a standard deviation of 520 cycles. The data were described by normal or log-normal distributions, but other models could also apply; the sample size must be increased to clearly delineate a statistical failure model. The statistical methods were also applied to adhesive/cohesive strength data for 20 TBC discs of the same composition, with similar results. The sample space had a mean of 9 MPa with a standard deviation of 4.2 MPa.

  10. Thermal Cycling of Thermal Control Paints on Carbon-Carbon and Carbon-Polyimide Composites

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.

    2006-01-01

    Carbon-carbon composites and carbon-polyimide composites are being considered for space radiator applications owing to their light weight and high thermal conductivity. For those radiator applications where sunlight will impinge on the surface, it will be necessary to apply a white thermal control paint to minimize solar absorptance and enhance infrared emittance. Several currently available white thermal control paints were applied to candidate carbon-carbon and carbon-polyimide composites and were subjected to vacuum thermal cycling in the range of -100 C to +277 C. The optical properties of solar absorptance and infrared emittance were evaluated before and after thermal cycling. In addition, adhesion of the paints was evaluated utilizing a tape test. The test matrix included three composites: resin-derived carbon-carbon and vapor infiltrated carbon-carbon, both reinforced with pitch-based P-120 graphite fibers, and a polyimide composite reinforced with T-650 carbon fibers, and three commercially available white thermal control paints: AZ-93, Z-93-C55, and YB-71P.

  11. Cycle accurate and cycle reproducible memory for an FPGA based hardware accelerator

    DOEpatents

    Asaad, Sameh W.; Kapur, Mohit

    2016-03-15

    A method, system and computer program product are disclosed for using a Field Programmable Gate Array (FPGA) to simulate operations of a device under test (DUT). The DUT includes a device memory having a number of input ports, and the FPGA is associated with a target memory having a second number of input ports, the second number being less than the first number. In one embodiment, a given set of inputs is applied to the device memory at a frequency Fd and in a defined cycle of time, and the given set of inputs is applied to the target memory at a frequency Ft. Ft is greater than Fd and cycle accuracy is maintained between the device memory and the target memory. In an embodiment, a cycle accurate model of the DUT memory is created by separating the DUT memory interface protocol from the target memory storage array.

  12. Thermal analysis of SC quadrupoles in accelerator interaction regions

    SciTech Connect

    Novitski, Igor; Zlobin, Alexander V.; /Fermilab

    2006-09-01

    This paper presents results of a thermal analysis and operation margin calculation performed for NbTi and Nb{sub 3}Sn low-beta quadrupoles in collider interaction regions. Results of the thermal analysis for NbTi quadrupoles are compared with the relevant experimental data. An approach to quench limit measurements for Nb{sub 3}Sn quadrupoles is discussed.

  13. Thermal cycling characteristics of plasma synthesized mullite films

    SciTech Connect

    Monteiro, O.R.; Hou, P.Y.; Brown, I.G.

    1997-12-01

    The authors have developed a plasma-based technique for the synthesis of mullite and mullite-like films on silicon carbide substrate material. The method, which they refer to as MePIIID (for Metal Plasma Immersion Ion Implantation and Deposition), uses two vacuum arc plasma sources and simultaneous pulse biasing of the substrate in a low pressure oxygen atmosphere. The Al:Si ratio can be controlled via the separate plasma guns, and the film adhesion, structure and morphology can be controlled via the ion energy which in turn is controlled by the pulse bias voltage. The films are amorphous as-deposited, and crystalline mullite is formed by subsequent annealing at 1000 C for 2 hours in air. Adhesion between the aluminum-silicon oxide film and the substrate increases after this first annealing. They have tested the behavior of films when subjected to repetitive thermal cycling between room temperature and 1100 C, and found that the films retain their adhesion and quality. Here they review the plasma synthesis technique and the characteristics of the mullite films prepared in this way, and summarize the status of the thermal cycling experiments.

  14. [Acceleration of Embryonic Development of Pinus sibirica Trees with a One-Year Reproductive Cycle].

    PubMed

    Tret'yakova, I N; Lukina, N V

    2016-01-01

    The study of the formation of embryonic structures in Pinus sibirica forms with a one-year reproductive cycle showed that the acceleration of the embryonic process manifested itself as a reduction of the coenocytic stage of the female gametophyte development (1.5 months instead of 1 year). The egg was not fertilized because of the asynchronous maturation of male and female gametophytes. Seeds without embryos were formed. We assumed that the acceleration of the reproductive process in Pinus sibirica was caused by a mutation in the female generative organs.

  15. Residual stress within nanoscale metallic multilayer systems during thermal cycling

    SciTech Connect

    Economy, David Ross; Cordill, Megan Jo; Payzant, E. Andrew; Kennedy, Marian S.

    2015-09-21

    Projected applications for nanoscale metallic multilayers will include wide temperature ranges. Since film residual stress has been known to alter system reliability, stress development within new film structures with high interfacial densities should be characterized to identify potential long-term performance barriers. To understand factors contributing to thermal stress evolution within nanoscale metallic multilayers, stress in Cu/Nb systems adhered to Si substrates was calculated from curvature measurements collected during cycling between 25 °C and 400 °C. Additionally, stress within each type of component layers was calculated from shifts in the primary peak position from in-situ heated X-ray diffraction. The effects of both film architecture (layer thickness) and layer order in metallic multilayers were tracked and compared with monolithic Cu and Nb films. Analysis indicated that the thermoelastic slope of nanoscale metallic multilayer films depends on thermal expansion mismatch, elastic modulus of the components, and also interfacial density. The layer thickness (i.e. interfacial density) affected thermoelastic slope magnitude while layer order had minimal impact on stress responses after the initial thermal cycle. When comparing stress responses of monolithic Cu and Nb films to those of the Cu/Nb systems, the nanoscale metallic multilayers show a similar increase in stress above 200 °C to the Nb monolithic films, indicating that Nb components play a larger role in stress development than Cu. Local stress calculations from X-ray diffraction peak shifts collected during heating reveal that the component layers within a multilayer film respond similarly to their monolithic counterparts.

  16. Residual stress within nanoscale metallic multilayer systems during thermal cycling

    DOE PAGES

    Economy, David Ross; Cordill, Megan Jo; Payzant, E. Andrew; ...

    2015-09-21

    Projected applications for nanoscale metallic multilayers will include wide temperature ranges. Since film residual stress has been known to alter system reliability, stress development within new film structures with high interfacial densities should be characterized to identify potential long-term performance barriers. To understand factors contributing to thermal stress evolution within nanoscale metallic multilayers, stress in Cu/Nb systems adhered to Si substrates was calculated from curvature measurements collected during cycling between 25 °C and 400 °C. Additionally, stress within each type of component layers was calculated from shifts in the primary peak position from in-situ heated X-ray diffraction. The effects ofmore » both film architecture (layer thickness) and layer order in metallic multilayers were tracked and compared with monolithic Cu and Nb films. Analysis indicated that the thermoelastic slope of nanoscale metallic multilayer films depends on thermal expansion mismatch, elastic modulus of the components, and also interfacial density. The layer thickness (i.e. interfacial density) affected thermoelastic slope magnitude while layer order had minimal impact on stress responses after the initial thermal cycle. When comparing stress responses of monolithic Cu and Nb films to those of the Cu/Nb systems, the nanoscale metallic multilayers show a similar increase in stress above 200 °C to the Nb monolithic films, indicating that Nb components play a larger role in stress development than Cu. Local stress calculations from X-ray diffraction peak shifts collected during heating reveal that the component layers within a multilayer film respond similarly to their monolithic counterparts.« less

  17. Thermochemical cycles for energy storage: Thermal decomposition of ZnCO sub 4 systems

    SciTech Connect

    Wentworth, W.E. )

    1992-04-01

    The overall objective of our research has been to develop thermochemical cycles that can be used for energy storage. A specific cycle involving ammonium hydrogen sulfate (NH{sub 4}HSO{sub 4}) has been proposed. Each reaction in the proposed cycle has been examined experimentally. Emphasis has been placed on the basic chemistry of these reactions. In the concluding phase of this research, reported herein, we have shown that when NH{sub 4}HSO{sub 4} is mixed with ZnO and decomposed, the resulting products can be released stepwise (H{sub 2}A{sub (g)} at {approximately}163{degrees}C, NH{sub 3(g)} at 365--418{degrees}C, and a mixture of SO{sub 2(g)} and SO{sub 3(g)} at {approximately}900{degrees}C) and separated by controlling the reaction temperature. Side reactions do not appear to be significant and the respective yields are high as would be required for the successful use of this energy storage reaction in the proposed cycle. Thermodynamic, kinetic, and other reaction parameters have been measured for the various steps of the reaction. Finally we have completed a detailed investigation of one particular reaction: the thermal decomposition of zinc sulfate (ZnSO{sub 4}). We have demonstrated that this reaction can be accelerated and the temperature required reduced by the addition of excess ZnO, V{sub 2}A{sub 5} and possibly other metal oxides.

  18. Thermochemical cycles for energy storage: Thermal decomposition of ZnSO4 systems

    NASA Astrophysics Data System (ADS)

    Wentworth, W. E.

    1992-04-01

    The overall objective of our research has been to develop thermochemical cycles that can be used for energy storage. A specific cycle involving ammonium hydrogen sulfate (NH4HSO4) has been proposed. Each reaction in the proposed cycle has been examined experimentally. Emphasis has been placed on the basic chemistry of these reactions. In the concluding phase of this research, we have shown that when NH4HSO4 is mixed with ZnO and decomposed, the resulting products can be released stepwise (H2O (gaseous) at approximately 163 C, NH3 (gaseous) at 365-418 C, and a mixture of SO2 (gaseous) and SO3 (gaseous) at approximately 900 C) and separated by controlling the reaction temperature. Side reactions do not appear to be significant and the respective yields are high, as would be required for the successful use of this energy storage reaction in the proposed cycle. Thermodynamic, kinetic, and other reaction parameters have been measured for the various steps of the reaction. Finally, we have completed a detailed investigation of one particular reaction: the thermal decomposition of zinc sulfate (ZnSO4). We have demonstrated that this reaction can be accelerated and the temperature required reduced by the addition of excess ZnO, V2A5, and possibly other metal oxides.

  19. Vacuum thermal cycle life testing of high temperature thermal energy storage

    NASA Astrophysics Data System (ADS)

    Ponnappan, Rengasamy; Beam, Jerry E.

    1991-01-01

    An experimental program to investigate the corrosion compatibility of the high temperature thermal energy storage (TES) salts with Inconel-617 container was initiated at the Thermal Laboratory of the Wright Research and Development Center (WRDC) in 1985. Three fluoride eutectic mixtures: LiF-MgF2-KF, LiF-MgF2-NaF, and LiF-MgF2 having melting points in the neighborhood of 1000 K and heats of fusion above 750 kJ/kg were chosen. High purity analytical grade component salts were processed in oxygen and moisture-free inert atmosphere, and melted in situ in the Inconel-617 containers. The containers were sealed by electron beam-welding of the end caps thereby evacuating the void volume. The TES capsules thus formed were placed in a tubular vacuum furnace for continuous thermal cycle life testing by cycling them ±100 K from the eutectic temperature every 2 hours. The capsules have successfully undergone 40,000 hours and 10,000 cycles of testing as of April 1990 and continuing on the test. This is believed to be the longest record available on the TES corrosion compatibility data. The present results clearly indicate that careful processing and proper welding are key factors in obtaining a longlife TES salt-containment system.

  20. Investigations of thermal conductivity of metals in the field of centrifugal and vibration accelerations

    NASA Astrophysics Data System (ADS)

    Lepeshkin, A. R.; Vaganov, P. A.

    2016-11-01

    The methods of investigations of a thermal conductivity of materials in the field of centrifugal radial and circumferential and vibration accelerations have been developed. The setup for investigation of thermophysical characteristics properties of materials on a spin rig, using a vacuum chamber, under the influence of centrifugal radial and circumferential accelerations and on a vibration rig under the influence of vibration accelerations have been proposed. The results of the investigations of an unsteady thermal state of heat-conductors (metal samples) in the field of centrifugal and vibration accelerations are given. From the analysis of the results of experimental investigations one can conclude that the thermal conductivity of the heat-conductors increases significantly by increasing the rotation frequency or amplitude of oscillations in comparison with a steady state. Thus, this increase of the thermal conductivity is associated with an increase of the electron drift velocity under the influence of centrifugal and vibration accelerations according to Wiedemann-Franz law. The results obtained are of practical importance for the calculations of the thermal state of the rotating parts of aircraft engines and other energy turbomachines.

  1. Thermal Cycle Testing of the Powersphere Engineering Development Unit

    NASA Technical Reports Server (NTRS)

    Curtis, Henry; Piszczor, Mike; Kerslake, Thomas W.; Peterson, Todd T.; Scheiman, David A.; Simburger, Edward J.; Giants, Thomas W.; Matsumoto, James H.; Garcia, Alexander; Liu, Simon H.; Lin, John K.; Scarborough, Stephen E.; Gleeson, Daniel J.; Rawal, Suraj P.; Perry, Alan R.; Marshall, Craig H.

    2007-01-01

    During the past three years the team of The Aerospace Corporation, Lockheed Martin Space Systems, NASA Glenn Research Center, and ILC Dover LP have been developing a multifunctional inflatable structure for the PowerSphere concept under contract with NASA (NAS3-01115). The PowerSphere attitude insensitive solar power-generating microsatellite, which could be used for many different space and Earth science purposes, is ready for further refinement and flight demonstration. The development of micro- and nanosatellites requires the energy collection system, namely the solar array, to be of lightweight and small size. The limited surface area of these satellites precludes the possibility of body mounting the solar array system for required power generation. The use of large traditional solar arrays requires the support of large satellite volumes and weight and also requires a pointing apparatus. The current PowerSphere concept (geodetic sphere), which was envisioned in the late 1990 s by Mr. Simburger of The Aerospace Corporation, has been systematically developed in the past several years.1-7 The PowerSphere system is a low mass and low volume system suited for micro and nanosatellites. It is a lightweight solar array that is spherical in shape and does not require a pointing apparatus. The recently completed project culminated during the third year with the manufacturing of the PowerSphere Engineering Development Unit (EDU). One hemisphere of the EDU system was tested for packing and deployment and was subsequently rigidized. The other hemisphere was packed and stored for future testing in an uncured state. Both cured and uncured hemisphere components were delivered to NASA Glenn Research Center for thermal cycle testing and long-term storage respectively. This paper will discuss the design, thermal cycle testing of the PowerSphere EDU.

  2. Prediction of thermal cycling induced cracking in polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Mcmanus, Hugh L.

    1993-01-01

    This report summarizes the work done in the period February 1993 through July 1993 on the 'Prediction of Thermal Cycling Induced Cracking In Polymer Matrix Composites' program. An oral presentation of this work was given to Langley personnel in September of 1993. This document was prepared for archival purposes. Progress studies have been performed on the effects of spatial variations in material strength. Qualitative agreement was found with observed patterns of crack distribution. These results were presented to NASA Langley personnel in November 1992. The analytical methodology developed by Prof. McManus in the summer of 1992 (under an ASEE fellowship) has been generalized. A method for predicting matrix cracking due to decreasing temperatures and/or thermal cycling in all plies of an arbitrary laminate has been implemented as a computer code. The code also predicts changes in properties due to the cracking. Experimental progressive cracking studies on a variety of laminates were carried out at Langley Research Center. Results were correlated to predictions using the new methods. Results were initially mixed. This motivated an exploration of the configuration of cracks within laminates. A crack configuration study was carried out by cutting and/or sanding specimens in order to examine the distribution of cracks within the specimens. These investigations were supplemented by dye-penetrant enhanced X-ray photographs. The behavior of thin plies was found to be different from the behavior of thicker plies (or ply groups) on which existing theories are based. Significant edge effects were also noted, which caused the traditional metric of microcracking (count of cracks on a polished edge) to be very inaccurate in some cases. With edge and configuration taken into account, rough agreement with predictions was achieved. All results to date were reviewed with NASA Langley personnel in September 1993.

  3. Experimental and numerical life prediction of thermally cycled thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Persson, C.; Wigren, J.

    2004-09-01

    This article addresses the predominant degradation modes and life prediction of a plasma-sprayed thermal barrier coating (TBC). The studied TBC system consists of an air-plasma-sprayed bond coat and an air-plasma-sprayed, yttria partially stabilized zirconia top layer on a conventional Hastelloy X substrate. Thermal shock tests of as-sprayed TBC and pre-oxidized TBC specimens were conducted under different burner flame conditions at Volvo Aero Corporation (Trollhättan, Sweden). Finite element models were used to simulate the thermal shock tests. Transient temperature distributions and thermal mismatch stresses in different layers of the coatings during thermal cycling were calculated. The roughness of the interface between the ceramic top coat and the bond coat was modeled through an ideally sinusoidal wavy surface. Bond coat oxidation was simulated through adding an aluminum oxide layer between the ceramic top coat and the bond coat. The calculated stresses indicated that interfacial delamination cracks, initiated in the ceramic top coat at the peak of the asperity of the interface, together with surface cracking, are the main reasons for coating failure. A phenomenological life prediction model for the coating was proposed. This model is accurate within a factor of 3.

  4. Volatile cycling and the thermal evolution of planetary mantle

    NASA Astrophysics Data System (ADS)

    Sandu, Constantin

    The thermal histories of terrestrial planets are investigated using two parameterized mantle convection models for either Earth like planets and planets with no active plate tectonics. Using parameterized models of mantle convection, we performed computer simulations of planetary cooling and volatile cycling. The models estimate the amount of volatile in mantle reservoir, and calculate the outgassing and regassing rates. A linear model of volatile concentration-dependent is assumed for the activation energy of the solid-state creep in the mantle. The kinematic viscosity of the mantle is thus dynamically affected by the activation energy through a variable concentration in volatile. Mantle temperature and heat flux is calculated using a model derived from classic thermal boundary layer theory of a single layered mantle with temperature dependent viscosity. The rate of volatile exchanged between mantle and surface is calculated by balancing the amount of volatiles degassed in the atmosphere by volcanic and spreading related processes and the amount of volatiles recycled back in the mantle by the subduction process. In the cases that lack plate tectonics, the degassing efficiency is dramatically reduced and the regassing process is absent. The degassing effect is dependent on average spreading rate of tectonic plates and on the amount of volatile in the melt extract in the transition zone between mantle and upper boundary laver. The regassing effect is dependent on the subduction rate and on the amount of volatile present on a hydrated layer on top of the subducting slab. The degassing and regassing parameters are all related to the intensity of the convection in the mantle and to the surface temperature of the planet, and they are regulated by the amount of volatiles in reservoir. Comparative study with the previous models display significant differences and improve the versatility of the model. The optimum efficiency factors found are in the range of 0.01--0.06 for

  5. Generic Repository Concepts and Thermal Analysis for Advanced Fuel Cycles

    SciTech Connect

    Hardin, Ernest; Blink, James; Carter, Joe; Massimiliano, Fratoni; Greenberg, Harris; Howard, Rob L

    2011-01-01

    The current posture of the used nuclear fuel management program in the U.S. following termination of the Yucca Mountain Project, is to pursue research and development (R&D) of generic (i.e., non-site specific) technologies for storage, transportation and disposal. Disposal R&D is directed toward understanding and demonstrating the performance of reference geologic disposal concepts selected to represent the current state-of-the-art in geologic disposal. One of the principal constraints on waste packaging and emplacement in a geologic repository is management of the waste-generated heat. This paper describes the selection of reference disposal concepts, and thermal management strategies for waste from advanced fuel cycles. A geologic disposal concept for spent nuclear fuel (SNF) or high-level waste (HLW) consists of three components: waste inventory, geologic setting, and concept of operations. A set of reference geologic disposal concepts has been developed by the U.S. Department of Energy (DOE) Used Fuel Disposition Campaign, for crystalline rock, clay/shale, bedded salt, and deep borehole (crystalline basement) geologic settings. We performed thermal analysis of these concepts using waste inventory cases representing a range of advanced fuel cycles. Concepts of operation consisting of emplacement mode, repository layout, and engineered barrier descriptions, were selected based on international progress and previous experience in the U.S. repository program. All of the disposal concepts selected for this study use enclosed emplacement modes, whereby waste packages are in direct contact with encapsulating engineered or natural materials. The encapsulating materials (typically clay-based or rock salt) have low intrinsic permeability and plastic rheology that closes voids so that low permeability is maintained. Uniformly low permeability also contributes to chemically reducing conditions common in soft clay, shale, and salt formations. Enclosed modes are associated

  6. Estimation of thermal neutron fluences in the concrete of proton accelerator facilities from 36Cl production

    NASA Astrophysics Data System (ADS)

    Bessho, K.; Matsumura, H.; Miura, T.; Wang, Q.; Masumoto, K.; Hagura, H.; Nagashima, Y.; Seki, R.; Takahashi, T.; Sasa, K.; Sueki, K.; Matsuhiro, T.; Tosaki, Y.

    2007-06-01

    The thermal neutron fluence that poured into the shielding concrete of proton accelerator facilities was estimated from the in situ production of 36Cl. The thermal neutron fluences at concrete surfaces during 10-30 years of operation were in the range of 1012-1014 n/cm2. The maxima in thermal neutron fluences were observed at ≈5-15 cm in the depths analyzed for 36Cl/35Cl by AMS. These characteristics imply that thermalization of neutrons occurred inside the concrete. Compared to the several tens of MeV cyclotrons, secondary neutrons penetrate deeper into the concrete at the high-energy accelerators possessing acceleration energies of 400 MeV and 12 GeV. The attenuation length of neutrons reflects the energy spectra of secondary neutrons emitted by the nuclear reaction at the beam-loss points. Increasing the energy of secondary neutrons shifts the maximum in the thermal neutron fluences to deeper positions. The data obtained in this study will be useful for the radioactive waste management at accelerator facilities.

  7. Ultraviolet irradiation at elevated temperatures and thermal cycling in vacuum of FEP-A covered silicon solar cells

    NASA Technical Reports Server (NTRS)

    Broder, J. D.; Marsik, S. J.

    1978-01-01

    Silicon solar cells covered with FEP-A were irradiated in vacuum with ultraviolet light and then subjected to thermal cycling. These accelerated laboratory conditions are believed to be equivalent to those experienced by FEP-A covered cells on the ATS-6 spacecraft and the results indicate a probable mechanism for the faster degradation of the FEP-A covered cells. Heat-bonded FEP-A covers apparently embrittle when exposed to four months of space UV radiation at elevated temperatures, and crack when subjected to thermal cycling during the eclipse period. Low energy proton radiation can then penetrate to the junction of the cell causing degradation of the open circuit voltage and maximum power to occur. An alternate method of application of FEP-A, such as with adhesives, may prevent such cracking.

  8. Effects of thermal cycling on graphie-fiber-reinforced 6061 aluminum

    NASA Technical Reports Server (NTRS)

    Dries, G. A.; Tompkins, S. S.

    1986-01-01

    Graphite-reinforced aluminum alloy metal-matrix composites are among materials being considered for structural components in dimensionally stable space structures. This application requires materials with low values of thermal expansions and high specific stiffnesses. They must remain stable during exposures to the space environment for periods extending to 20 years. The effects of thermal cycling on the thermal expansion behavior and mechanical properties of Thornel P100 graphite 6061 aluminum composites, as fabricated and after thermal processing to eliminate thermal strain hysteresis, have been investigated. Two groups of composites were studied: one was fabricated by hot roll bonding and the other by diffusion bonding. Processing significantly reduced strain hysteresis during thermal cycling in both groups and improved the ultimate tensile strength and modulus in the diffusion-bonded composites. Thermal cycling stabilized the as-fabricated composites by reducing the residual fabrication stress and increased the matrix strength by metallurgical aging. Thermal expansion behavior of both groups after processing was insensitive to thermal cycling. Data scatter was too large to determine effects of thermal cycling on the mechanical properties. The primary effects of processing and thermal cycling can be attributed to changes in the metallurgical condition and stress state of the matrix.

  9. A Thorium/Uranium fuel cycle for an advanced accelerator transmutation of nuclear waste concept

    SciTech Connect

    Truebenbach, M.T.; Henderson, D.L.; Venneri, F.

    1993-12-31

    Utilizing the high thermal neutron flux of an accelerator driven transmuter to drive a Thorium-Uranium fuel production scheme, it is possible to produce enough energy in the transmuter not only to power the accelerator, but to have enough excess power available for commercial use. A parametric study has been initiated to determine the ``optimum`` equilibrium operation point in terms of the minimization of the equilibrium actinide inventory and the fuel {alpha} for various residence times in the High Flux Region (HFR) and in the Low Flux Region (LFR). For the cases considered, the ``optimum`` equilibrium operation point was achieved for a HFR residence time of 45 days and a LFR residence time of 60 days. For this case, the total actinide inventory in the system is about 20 tonnes and the fuel {alpha} approximately 1.46.

  10. Accelerating thermal deposition modeling at terahertz frequencies using GPUs

    NASA Astrophysics Data System (ADS)

    Doroski, Michael; Knight, Michael; Payne, Jason; Grundt, Jessica E.; Ibey, Bennett L.; Thomas, Robert; Roach, William P.; Wilmink, Gerald J.

    2011-03-01

    Finite-difference time-domain (FDTD) methods are widely used to model the propagation of electromagnetic radiation in biological tissues. High-performance central processing units (CPUs) can execute FDTD simulations for complex problems using 3-D geometries and heterogeneous tissue material properties. However, when FDTD simulations are employed at terahertz (THz) frequencies excessively long processing times are required to account for finer resolution voxels and larger computational modeling domains. In this study, we developed and tested the performance of 2-D and 3-D FDTD thermal propagation code executed on a graphics processing unit (GPU) device, which was coded using an extension of the C language referred to as CUDA. In order to examine the speedup provided by GPUs, we compared the performance (speed, accuracy) for simulations executed on a GPU (Tesla C2050), a high-performance CPU (Intel Xeon 5504), and supercomputer. Simulations were conducted to model the propagation and thermal deposition of THz radiation in biological materials for several in vitro and in vivo THz exposure scenarios. For both the 2-D and 3-D in vitro simulations, we found that the GPU performed 100 times faster than runs executed on a CPU, and maintained comparable accuracy to that provided by the supercomputer. For the in vivo tissue damage studies, we found that the GPU executed simulations 87x times faster than the CPU. Interestingly, for all exposure duration tested, the CPU, GPU, and supercomputer provided comparable predictions for tissue damage thresholds (ED50). Overall, these results suggest that GPUs can provide performance comparable to a supercomputer and at speeds significantly faster than those possible with a CPU. Therefore, GPUs are an affordable tool for conducting accurate and fast simulations for computationally intensive modeling problems.

  11. Rotating single cycle two-phase thermally activated heat pump

    SciTech Connect

    Fabris, G.

    1993-06-08

    A thermally activated heat pump is described which utilizes single working fluid which as a whole passes consecutively through all parts of the apparatus in a closed loop series; the working fluid in low temperature saturated liquid state at condensation is pumped to higher pressure with a pump; subsequently heat is added to the liquid of increased pressure, the liquid via the heating is brought to a high temperature saturated liquid state; the high temperature liquid passes and flashes subsequently in form of two-phase flow through a rotating two-phase flow turbine; in such a way the working fluid performs work on the two-phase turbine which in turn powers the liquid pump and a lower compressor; two-phase flow exiting the two-phase turbine separated by impinging tangentially on housing of the turbine; low temperature heat is added to the housing in such a way evaporating the separated liquid on the housing; in such a way the liquid is fully vaporized the vapor then enters a compressor, the compressor compresses the vapor to a higher condensation pressure and corresponding increased temperature, the vapor at the condensation pressure enters a condenser whereby heat is rejected and the vapor is fully condensed into state of saturated liquid, mid saturated liquid enters the pump and repeats the cycle.

  12. On-line DNA analysis system with rapid thermal cycling

    DOEpatents

    Swerdlow, Harold P.; Wittwer, Carl T.

    1999-01-01

    An apparatus particularly suited for subjecting biological samples to any necessary sample preparation tasks, subjecting the sample to rapid thermal cycling, and then subjecting the sample to subsequent on-line analysis using one or more of a number of analytical techniques. The apparatus includes a chromatography device including an injection means, a chromatography pump, and a chromatography column. In addition, the apparatus also contains a capillary electrophoresis device consisting of a capillary electrophoresis column with an inlet and outlet end, a means of injection, and means of applying a high voltage to cause the differential migration of species of interest through the capillary column. Effluent from the liquid chromatography column passes over the inlet end of the capillary electrophoresis column through a tee structure and when the loading of the capillary electrophoresis column is desired, a voltage supply is activated at a precise voltage and polarity over a specific duration to cause sample species to be diverted from the flowing stream to the capillary electrophoresis column. A laser induced fluorescence detector preferably is used to analyze the products separated while in the electrophoresis column.

  13. On-line DNA analysis system with rapid thermal cycling

    DOEpatents

    Swerdlow, H.P.; Wittwer, C.T.

    1999-08-10

    This application describes an apparatus particularly suited for subjecting biological samples to any necessary sample preparation tasks, subjecting the sample to rapid thermal cycling, and then subjecting the sample to subsequent on-line analysis using one or more of a number of analytical techniques. The apparatus includes a chromatography device including an injection means, a chromatography pump, and a chromatography column. In addition, the apparatus also contains a capillary electrophoresis device consisting of a capillary electrophoresis column with an inlet and outlet end, a means of injection, and means of applying a high voltage to cause the differential migration of species of interest through the capillary column. Effluent from the liquid chromatography column passes over the inlet end of the capillary electrophoresis column through a tee structure and when the loading of the capillary electrophoresis column is desired, a voltage supply is activated at a precise voltage and polarity over a specific duration to cause sample species to be diverted from the flowing stream to the capillary electrophoresis column. A laser induced fluorescence detector preferably is used to analyze the products separated while in the electrophoresis column. 6 figs.

  14. Geosynthetic clay liners shrinkage under simulated daily thermal cycles.

    PubMed

    Sarabadani, Hamid; Rayhani, Mohammad T

    2014-06-01

    Geosynthetic clay liners are used as part of composite liner systems in municipal solid waste landfills and other applications to restrict the escape of contaminants into the surrounding environment. This is attainable provided that the geosynthetic clay liner panels continuously cover the subsoil. Previous case histories, however, have shown that some geosynthetic clay liner panels are prone to significant shrinkage and separation when an overlying geomembrane is exposed to solar radiation. Experimental models were initiated to evaluate the potential shrinkage of different geosynthetic clay liner products placed over sand and clay subsoils, subjected to simulated daily thermal cycles (60°C for 8 hours and 22°C for 16 hours) modelling field conditions in which the liner is exposed to solar radiation. The variation of geosynthetic clay liner shrinkage was evaluated at specified times by a photogrammetry technique. The manufacturing techniques, the initial moisture content, and the aspect ratio (ratio of length to width) of the geosynthetic clay liner were found to considerably affect the shrinkage of geosynthetic clay liners. The particle size distribution of the subsoil and the associated suction at the geosynthetic clay liner-subsoil interface was also found to have significant effects on the shrinkage of the geosynthetic clay liner.

  15. Accelerated cycle life performance for ovonic nickel-metal hydride cells

    NASA Technical Reports Server (NTRS)

    Otzinger, Burton M.

    1991-01-01

    Nickel-Metal Hydride (Ni-MH) rechargeable batteries have emerged as the leading candidate for commercial replacement of nickel-cadmium (Ni-Cd) batteries. An important incentive is that the Ni-MH cell provides approximately twice the capacity of a Ni-Cd cell for a given size. A six-cell battery was committed to an accelerated cycle life test to determine the effect of separation type on performance. Results of the test may also show the Ni-MH battery to be a replacement candidate for the aerospace Ni-Cd battery.

  16. ELECTROMAGNETIC AND THERMAL SIMULATIONS FOR THE SWITCH REGION OF A COMPACT PROTON ACCELERATOR

    SciTech Connect

    Wang, L; Caporaso, G J; Sullivan, J S

    2007-06-15

    A compact proton accelerator for medical applications is being developed at Lawrence Livermore National Laboratory. The accelerator architecture is based on the dielectric wall accelerator (DWA) concept. One critical area to consider is the switch region. Electric field simulations and thermal calculations of the switch area were performed to help determine the operating limits of rmed SiC switches. Different geometries were considered for the field simulation including the shape of the thin Indium solder meniscus between the electrodes and SiC. Electric field simulations were also utilized to demonstrate how the field stress could be reduced. Both transient and steady steady-state thermal simulations were analyzed to find the average power capability of the switches.

  17. Turbulent thermal boundary layers subjected to severe acceleration

    NASA Astrophysics Data System (ADS)

    Araya, Guillermo; Castillo, Luciano

    2013-11-01

    Favorable turbulent boundary layers are flows of great importance in industry. Particularly, understanding the mechanisms of quasi-laminarization by means of a very strong favorable streamwise pressure gradient is indeed crucial in drag reduction and energy management applications. Furthermore, due to the low Reynolds numbers involved in the quasi-laminarization process, abundant experimental investigation can be found in the literature for the past few decades. However, several grey zones still remain unsolved, principally associated with the difficulties that experiments encounter as the boundary layer becomes smaller. In addition, little attention has been paid to the heat transfer in a quasi-laminarization process. In this investigation, DNS of spatially-developing turbulent thermal boundary layers with prescribed very strong favorable pressure gradients (K = 4 × 10-6) are performed. Realistic inflow conditions are prescribed based on the Dynamic Multi-scale Approach (DMA) [Araya et al. JFM, Vol. 670, pp. 581-605, 2011]. In this sense the flow carries the footprint of turbulence, particularly in the streamwise component of the Reynolds stresses.

  18. Ion acceleration by intense, few-cycle laser pulses with nanodroplets

    SciTech Connect

    Di Lucchio, Laura; Andreev, Alexander A.; Gibbon, Paul

    2015-05-15

    The energy distribution of electrons and ions emerging from the interaction of a few-cycle Gaussian laser pulse with spherical nanoclusters is investigated with the aim of determining prospects for accelerating ions in this regime. It is found that the direct conversion of laser energy into dense attosecond electron nanobunches results in rapid charge separation and early onset of Coulomb-explosion-dominated ion dynamics. The ion core of the cluster starts to expand soon after the laser has crossed the droplet, the fastest ions attaining 10 s of MeV at relativistic intensities. The current investigation should serve as a guide for contemporary experiments, i.e., using state-of-the-art few-cycle ultraintense lasers and nanoclusters of solid density.

  19. Rapid thermal cycling of metal-supported solid oxide fuel cellmembranes

    SciTech Connect

    Matus, Yuriy B.; De Jonghe, Lutgard C.; Jacobson, Craig P.; Visco, Steven J.

    2004-01-02

    Solid oxide fuel cell (SOFC) membranes were developed in which zirconia-based electrolyte thin films were supported by a composite metal/ceramic electrode, and were subjected to rapid thermal cycling between 200 and 800 C. The effects of this cycling on membrane performance were evaluated. The membranes, not yet optimized for performance, showed a peak power density of 350mW/cm2at 900 C in laboratory-sized SOFCs that was not affected by the thermal cycling. This resistance to cycling degradation is attributed to the close matching of thermal expansion coefficient of the cermet support electrode with that of the zirconia electrolyte.

  20. Accelerated multiscale space-time finite element simulation and application to high cycle fatigue life prediction

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Wen, Lihua; Naboulsi, Sam; Eason, Thomas; Vasudevan, Vijay K.; Qian, Dong

    2016-08-01

    A multiscale space-time finite element method based on time-discontinuous Galerkin and enrichment approach is presented in this work with a focus on improving the computational efficiencies for high cycle fatigue simulations. While the robustness of the TDG-based space-time method has been extensively demonstrated, a critical barrier for the extensive application is the large computational cost due to the additional temporal dimension and enrichment that are introduced. The present implementation focuses on two aspects: firstly, a preconditioned iterative solver is developed along with techniques for optimizing the matrix storage and operations. Secondly, parallel algorithms based on multi-core graphics processing unit are established to accelerate the progressive damage model implementation. It is shown that the computing time and memory from the accelerated space-time implementation scale with the number of degree of freedom N through ˜ O(N^{1.6}) and ˜ O(N), respectively. Finally, we demonstrate the accelerated space-time FEM simulation through benchmark problems.

  1. Flexible thermal cycle test equipment for concentrator solar cells

    DOEpatents

    Hebert, Peter H [Glendale, CA; Brandt, Randolph J [Palmdale, CA

    2012-06-19

    A system and method for performing thermal stress testing of photovoltaic solar cells is presented. The system and method allows rapid testing of photovoltaic solar cells under controllable thermal conditions. The system and method presents a means of rapidly applying thermal stresses to one or more photovoltaic solar cells in a consistent and repeatable manner.

  2. Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux

    DOEpatents

    Bowman, Charles D.

    1992-01-01

    Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility. In all applications, the accelerator power may be generated internally from fission and the waste produced thereby is transmuted internally so that waste management might not be required beyond the human lifespan.

  3. Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux

    DOEpatents

    Bowman, C.D.

    1992-11-03

    Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility. In all applications, the accelerator power may be generated internally from fission and the waste produced thereby is transmuted internally so that waste management might not be required beyond the human lifespan.

  4. Thermal performance analysis and measurements of the prototype cryomodules of European XFEL accelerator - part I

    NASA Astrophysics Data System (ADS)

    Wang, X. L.; Barbanotti, S.; Eschke, J.; Jensch, K.; Klos, R.; Maschmann, W.; Petersen, B.; Sawlanski, O.

    2014-11-01

    The European X-Ray Free Electron Laser (XFEL), the research facility currently under construction in the Hamburg area, Germany, is based on a superconducting linear accelerator that brings electrons to almost the speed of light. The linear accelerator consists of 100 accelerating cryomodules (CMs) operating at the temperature of 2 K. The thermal performances of the accelerator CMs are a key element to determine the heat load budget, the required capacity and the cost of the XFEL refrigerating system and to guarantee its efficient operation. The measurement of the thermal performances of the CMs is also an important step in the qualification of the CMs during the series production. This paper describes the thermal performance analysis of the European XFEL prototype cryomodules. The analysis takes into account all the main contributors (multilayer insulation, current leads, power couplers, support posts, and cavities) to the static and dynamic heat loads at various cryogenic temperature levels. Existing empirical databases are reviewed and used to evaluate the heat transfer through the multilayer insulation and numerical simulations are developed to investigate the heat loads generated from the different CM components.

  5. Effect of thermal cycling on whisker-reinforced dental resin composites.

    PubMed

    Xu, Hockin H K; Eichmiller, Frederick C; Smith, Douglas T; Schumacher, Gary E; Giuseppetti, Anthony A; Antonucci, Joseph M

    2002-09-01

    The mechanical properties of dental resin composites need to be improved in order to extend their use to high stress-bearing applications such as crown and bridge restorations. Recent studies used single crystal ceramic whiskers to reinforce dental composites. The aim of this study was to investigate the effects of thermal cycling on whisker-reinforced composites. It was hypothesized that the whisker composites would not show a reduction in mechanical properties or the breakdown of whisker-resin interface after thermal cycling. Silicon carbide whiskers were mixed with silica particles, thermally fused, then silanized and incorporated into resin to make flexural specimens. The filler mass fraction ranged from 0% to 70%. The specimens were thermal cycled in 5 degrees C and 60 degrees C water baths, and then fractured in three-point bending to measure strength. Nano-indentation was used to measure modulus and hardness. No significant loss in composite strength, modulus and hardness was found after 10(5) thermal cycles (family confidence coefficient=0.95; Tukey's multiple comparison test). The strength of whisker composite increased with filler level up to 60%, then plateaued when filler level was further increased to 70%; the modulus and hardness increased monotonically with filler level. The strength and modulus of whisker composite at 70% filler level were significantly higher than the non-whisker controls both before and after thermal cycling. SEM revealed no separation at the whisker-matrix interfaces, and observed resin remnants on the pulled-out whiskers, indicating strong whisker-resin bonding even after 10(5) thermal cycles. In conclusion, novel dental resin composites containing silica-fused whiskers possessed superior strength and modulus compared to non-whisker composites both before and after thermal cycling. The whisker-resin bonding appeared to be resistant to thermal cycling in water, so that no loss in composite strength or stiffness occurred after

  6. Degradation of Teflon(trademark) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline; Powers, Charles; Viens, Michael; Ayres-Treusdell, Mary; Munoz, Bruno

    1999-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon(trademark) FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon(trademark) FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon(trademark) FEP.

  7. Degradation of Teflon(tm) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Powers, Charles E.; Viens, Michael J.; Ayres-Treusdell, Mary T.; Munoz, Bruno F.

    1998-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon' FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon(registered trademark) FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon(registered trademark) FEP.

  8. Degradation of Teflon(tm) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Townsend, Jacqueline A.; Powers, Charles E.; Viens, Michael J.; Ayres-Treusdell, Mary T.; Munoz, Bruno

    1998-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon' FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon FEP.

  9. The effect of a thermal renal denervation cycle on the mechanical properties of the arterial wall.

    PubMed

    Hopkins, Alan A; Sheridan, William S; Sharif, Faisal; Murphy, Bruce P

    2014-11-28

    The aim of this study was to determine the effect that a thermal renal denervation cycle has on the mechanical properties of the arterial wall. Porcine arterial tissue specimens were tested in three groups: native tissue, decellularized tissue, decellularized with collagen digestion (e.g. elastin only). One arterial specimen was used as an unheated control specimen while another paired specimen was subjected to a thermal cycle of 70°C for 120s (n=10). The specimens were subjected to tensile loading and a shrinkage analysis. We observed two key results: The mechanical properties associated with the elastin extracellular matrix (ECM) were not affected by the thermal cycle. The effect of the thermal cycle on the collagen (ECM) was significant, in both the native and decellularized groups the thermal cycle caused a statistically significant decrease in stiffness, and failure strength, moreover the native tissue demonstrated a 27% reduction in lumen area post exposure to the thermal cycle. We have demonstrated that a renal denervation thermal cycle can significantly affect the mechanical properties of an arterial wall, and these changes in stiffness and failure strength were associated with alterations to the collagen rather than the elastin extracellular matrix component.

  10. Accelerator-Driven Thorium-Cycle Fission:. Green Nuclear Power for the New Millennium

    NASA Astrophysics Data System (ADS)

    McIntyre, Peter; Sattarov, Akhdiyor

    2011-03-01

    In thorium-cycle fission, fast neutrons are used to transmute thorium to fissionable 233U and then stimulate fission. In accelerator-driven thorium-cycle fission (ADTC) the fast neutrons are produced by injecting a symmetric pattern of 7 energetic proton beams into a Pb spallation zone in the core. The fast neutrons are adiabatically moderated by the Pb so that they capture efficiently on 232Th, and fission heat is transferred via a convective Pb column above the core. The 7 proton beams are generated by a flux-coupled stack of isochronous cyclotrons. ADTC offers a green solution to the Earth's energy needs: the core operates as a sub-critical pile and cannot melt down; it eats its own long-lived fission products; a GW ADTC core can operate with uniform power density for a 7-year fuel cycle without shuffling fuel pins, and there are sufficient thorium reserves to run man's energy needs for the next 2000 years.

  11. Suppression of Martensitic Transformation in Co2Cr(Ga,Si) Heusler Alloys by Thermal Cycling

    NASA Astrophysics Data System (ADS)

    Liang, Xiao; Xiao, Fei; Jin, Xuejun; Fukuda, Takashi; Kakeshita, Tomoyuki

    2017-03-01

    We have investigated the influence of thermal cycles on martensitic transformation of a Co2Cr(Ga,Si) ferromagnetic Heusler alloy. The as-quenched specimen exhibits successive L21(L)-D022-L21(H) martensitic transformation in the cooling process, which is known as reentrant martensitic transformation. However, heating to 800 K (527 °C) for reverse D022-L21 transformation with a rate of 10 K/min (10 °C/min) stabilizes the parent phase, meaning that the martensitic transformation is suppressed by the thermal cycles. We found precipitate after thermal cycles, and it will be the reason for the stabilization of parent phase.

  12. The logarithmic and power law behaviors of the accelerating, turbulent thermal boundary layer

    NASA Astrophysics Data System (ADS)

    Castillo, Luciano; Hussain, Fazle

    2017-02-01

    Direct numerical simulation of spatially evolving thermal turbulent boundary layers with strong favorable pressure gradient (FPG) shows that the thermal fluctuation intensity, θ' + and the Reynolds shear stress, u'v'¯+ exhibit a logarithmic behavior spanning the meso-layer (e.g., 50 ≤y+≤170 ). However, the mean thermal profile is not logarithmic even in the zero pressure gradient (ZPG) region; instead, it follows a power law. The maxima of u' 2 ¯+ and v'θ'¯+ change little with the strength of acceleration, while v'+, w'+, and u'v'¯+ continue to decay in the flow direction. Furthermore, θ'+ and u'θ'¯+ surprisingly experience changes from constants in ZPG to sharp rises in the FPG region. Such behavior appears to be due to squashing of the streaks which decreases the streak flank angle below the critical value for "transient growth" generation of streamwise vortices, shutting down production [W. Schoppa and F. Hussain, "Coherent structure generation near-wall turbulence," J. Fluid Mech. 453, 57-108 (2002)]. The streamwise vortices near the wall, although shrink because of stretching, simultaneously, also become weaker as the structures are progressively pushed farther down to the more viscous region near the wall. While the vortical structures decay rapidly in accelerating flows, the thermal field does not—nullifying the myth that both the thermal and velocity fields are similar.

  13. Coupled Mechanical-Electrochemical-Thermal Modeling for Accelerated Design of EV Batteries

    SciTech Connect

    Santhanagopalan, Shriram; Zhang, Chao; Kim, Gi-Heon; Pesaran, Ahmad A.

    2015-05-03

    This presentation provides an overview of the mechanical electrochemical-thermal (M-ECT) modeling efforts. The physical phenomena occurring in a battery are many and complex and operate at different scales (particle, electrodes, cell, and pack). A better understanding of the interplay between different physics occurring at different scales through modeling could provide insight to design improved batteries for electric vehicles. Work funded by the U.S. DOE has resulted in development of computer-aided engineering (CAE) tools to accelerate electrochemical and thermal design of batteries; mechanical modeling is under way. Three competitive CAE tools are now commercially available.

  14. Using a Tandem Pelletron accelerator to produce a thermal neutron beam for detector testing purposes.

    PubMed

    Irazola, L; Praena, J; Fernández, B; Macías, M; Bedogni, R; Terrón, J A; Sánchez-Nieto, B; Arias de Saavedra, F; Porras, I; Sánchez-Doblado, F

    2016-01-01

    Active thermal neutron detectors are used in a wide range of measuring devices in medicine, industry and research. For many applications, the long-term stability of these devices is crucial, so that very well controlled neutron fields are needed to perform calibrations and repeatability tests. A way to achieve such reference neutron fields, relying on a 3 MV Tandem Pelletron accelerator available at the CNA (Seville, Spain), is reported here. This paper shows thermal neutron field production and reproducibility characteristics over few days.

  15. [The surface degradation of various light-cured composite resins by thermal cycling].

    PubMed

    Hirabayashi, S; Nomoto, R; Harashima, I; Hirasawa, T

    1990-01-01

    The durability of four commercially available light-cured composite resins was investigated by thermal cycling, GR containing inorganic fillers treated with the graft polymerization of acryl ester, LF inorganic fillers treated with a silane coupling agent, PC silanized inorganic fillers and organic composite fillers, and the MFR-type SI containing the organic composite fillers. These materials were given 10,000, 30,000 and 50,000 thermal cycles (4 degrees C-60 degrees C) and the deterioration of materials by thermal cycling was evaluated by the measurement of the mechanical properties and the SEM observations of the surface of the thermocycled materials. Compressive strength and bending elastic moduli for all materials did not change greatly by thermal cycling. However, bending strength, toothbrush abrasion resistance and surface hardness decreased with increasing number of thermal cycles between 0 and 30,000, and changed little after 30,000 cycles. The percentage of bending strength after 50,000 thermal cycles to that of the non-thermocycled sample was 75% for GR, 60% for LF, 50% for PC and 65% for SI, respectively. Deterioration of materials was observed as cracks on the surface, which generated at the interface of the filler and matrix. The cracks generated relatively earlier during thermal cycling for SI and PC which contained the organic composite filler, later for LF which contained the silanized inorganic fillers, and the number of cracks on LF were fewer than SI and PC. On the other hand, for GR, no cracks were observed even after 50,000 thermal cycles. From these results, it can be presumed that the pre-treatment of filler by the graft polymerization is more effective to improve the durability of composite resin.

  16. Quantum Performance of Thermal Machines over Many Cycles

    NASA Astrophysics Data System (ADS)

    Watanabe, Gentaro; Venkatesh, B. Prasanna; Talkner, Peter; del Campo, Adolfo

    2017-02-01

    The performance of quantum heat engines is generally based on the analysis of a single cycle. We challenge this approach by showing that the total work performed by a quantum engine need not be proportional to the number of cycles. Furthermore, optimizing the engine over multiple cycles leads to the identification of scenarios with a quantum enhancement. We demonstrate our findings with a quantum Otto engine based on a two-level system as the working substance that supplies power to an external oscillator.

  17. Quantum Performance of Thermal Machines over Many Cycles.

    PubMed

    Watanabe, Gentaro; Venkatesh, B Prasanna; Talkner, Peter; Del Campo, Adolfo

    2017-02-03

    The performance of quantum heat engines is generally based on the analysis of a single cycle. We challenge this approach by showing that the total work performed by a quantum engine need not be proportional to the number of cycles. Furthermore, optimizing the engine over multiple cycles leads to the identification of scenarios with a quantum enhancement. We demonstrate our findings with a quantum Otto engine based on a two-level system as the working substance that supplies power to an external oscillator.

  18. Direct observation of prompt pre-thermal laser ion sheath acceleration

    NASA Astrophysics Data System (ADS)

    Zeil, K.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Kraft, S. D.; Sauerbrey, R.; Schramm, U.

    2012-06-01

    High-intensity laser plasma-based ion accelerators provide unsurpassed field gradients in the megavolt-per-micrometer range. They represent promising candidates for next-generation applications such as ion beam cancer therapy in compact facilities. The weak scaling of maximum ion energies with the square-root of the laser intensity, established for large sub-picosecond class laser systems, motivates the search for more efficient acceleration processes. Here we demonstrate that for ultrashort (pulse duration ~30 fs) highly relativistic (intensity ~1021 W cm-2) laser pulses, the intra-pulse phase of the proton acceleration process becomes relevant, yielding maximum energies of around 20 MeV. Prominent non-target-normal emission of energetic protons, reflecting an engineered asymmetry in the field distribution of promptly accelerated electrons, is used to identify this pre-thermal phase of the acceleration. The relevant timescale reveals the underlying physics leading to the near-linear intensity scaling observed for 100 TW class table-top laser systems.

  19. The Effects of Thermal Cycling on Gallium Nitride and Silicon Carbide Semiconductor Devices for Aerospace Use

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Hammoud, Ahmad

    2012-01-01

    Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These Include radiation, extreme temperatures, thermal cycling, to name a few. Preliminary data obtained on new Gallium Nitride and Silicon Carbide power devices under exposure to radiation followed by long term thermal cycling are presented. This work was done in collaboration with GSFC and JPL in support of the NASA Electronic Parts and Packaging (NEPP) Program

  20. Compressive Seal Development: Combined Ageing and Thermal Cycling Compressive

    SciTech Connect

    Chou, M.Y-S.; Stevenson, J.W.; Singh, P.

    2005-01-27

    The objective of this project was to evaluate the combined aging and cycling effect on hybrid Phlogopite mica seals with respect to materials and interfacial degradations in a simulated SOFC environment.

  1. Nonidentical and outlier duty cycles as factors accelerating UHMWPE wear in THA: a finite element exploration.

    PubMed

    Lundberg, Hannah J; Stewart, Kristofer J; Pedersen, Douglas R; Callaghan, John J; Brown, Thomas D

    2007-01-01

    Wear rate and wear direction vary considerably within total hip arthroplasty (THA) patient cohorts. Third body effects and wide-ranging differences in patient activity levels are two factors suspected of contributing to wear variability. A sliding-distance-coupled contact finite element formulation was used to test the hypothesis that nonidentical duty cycles (differing activities, or change of third body challenge) produce accelerations in polyethylene wear. Effects of nonidentical duty cycles, time-variant femoral head roughening, and outlier gait inputs were investigated. Without femoral head roughening, combination walk/stair-climb wear simulations did not result in appreciably higher volumetric wear than a walk-only simulation, but when a roughened zone was included, walk/stair-climb volumetric wear increased by approximately 57% above that of a similarly roughened walk-only simulation. To investigate time-variant femoral head roughening, wear simulations were begun with femoral head roughening at one location on the femoral head, switching to another location halfway through the simulation. Results varied depending on roughening sites, but cases of substantial increase in wear involved a transient jump in wear rate shortly after the change of head roughening location. Outlier duty cycles were simulated by increasing or decreasing the joint contact force and range of motion inputs, to levels at the 97.5th and 2.5th percentiles of a population of normal subjects. The resulting wear showed an increase or decrease closely proportional to the percentage by which each input (force or range of motion) was changed.

  2. Simulating Thermal Cycling and Isothermal Deformation Response of Polycrystalline NiTi

    NASA Technical Reports Server (NTRS)

    Manchiraju, Sivom; Gaydosh, Darrell J.; Noebe, Ronald D.; Anderson, Peter M.

    2011-01-01

    A microstructure-based FEM model that couples crystal plasticity, crystallographic descriptions of the B2-B19' martensitic phase transformation, and anisotropic elasticity is used to simulate thermal cycling and isothermal deformation in polycrystalline NiTi (49.9at% Ni). The model inputs include anisotropic elastic properties, polycrystalline texture, DSC data, and a subset of isothermal deformation and load-biased thermal cycling data. A key experimental trend is captured.namely, the transformation strain during thermal cycling is predicted to reach a peak with increasing bias stress, due to the onset of plasticity at larger bias stress. Plasticity induces internal stress that affects both thermal cycling and isothermal deformation responses. Affected thermal cycling features include hysteretic width, two-way shape memory effect, and evolution of texture with increasing bias stress. Affected isothermal deformation features include increased hardening during loading and retained martensite after unloading. These trends are not captured by microstructural models that lack plasticity, nor are they all captured in a robust manner by phenomenological approaches. Despite this advance in microstructural modeling, quantitative differences exist, such as underprediction of open loop strain during thermal cycling.

  3. Thermal performance of a flat polymer heat pipe heat spreader under high acceleration

    NASA Astrophysics Data System (ADS)

    Oshman, Christopher; Li, Qian; Liew, Li-Anne; Yang, Ronggui; Lee, Y. C.; Bright, Victor M.; Sharar, Darin J.; Jankowski, Nicholas R.; Morgan, Brian C.

    2012-04-01

    This paper presents the fabrication and application of a micro-scale hybrid wicking structure in a flat polymer-based heat pipe heat spreader, which improves the heat transfer performance under high adverse acceleration. The hybrid wicking structure which enhances evaporation and condensation heat transfer under adverse acceleration consists of 100 µm high, 200 µm wide square electroplated copper micro-pillars with 31 µm wide grooves for liquid flow and a woven copper mesh with 51 µm diameter wires and 76 µm spacing. The interior vapor chamber of the heat pipe heat spreader was 30×30×1.0 mm3. The casing of the heat spreader is a 100 µm thick liquid crystal polymer which contains a two-dimensional array of copper-filled vias to reduce the overall thermal resistance. The device performance was assessed under 0-10 g acceleration with 20, 30 and 40 W power input on an evaporator area of 8×8 mm2. The effective thermal conductivity of the device was determined to range from 1653 W (m K)-1 at 0 g to 541 W (m K)-1 at 10 g using finite element analysis in conjunction with a copper reference sample. In all cases, the effective thermal conductivity remained higher than that of the copper reference sample. This work illustrates the possibility of fabricating flexible, polymer-based heat pipe heat spreaders compatible with standardized printed circuit board technologies that are capable of efficiently extracting heat at relatively high dynamic acceleration levels.

  4. A quasimechanism of melt acceleration in the thermal decomposition of crystalline organic solids

    SciTech Connect

    Henson, Bryan F

    2009-01-01

    It has been know for half a century that many crystalline organic solids undergo an acceleration in the rate of thermal decomposition as the melting temperature is approached. This acceleration terminates at the melting point, exhibiting an Arrhenius-like temperature dependence in the faster decomposition rate from the liquid phase. This observation has been modeled previously using various premelting behaviors based on e.g. freezing point depression induced by decomposition products or solvent impurities. These models do not, however, indicate a mechanism for liquid formation and acceleration which is an inherent function of the bulk thermodynamics of the molecule. Here we show that such an inherent thermodynamic mechanism for liquid formation exists in the form of the so-called quasi-liquid layer at the solid surface. We explore a kinetic mechanism which describes the acceleration of rate and is a function of the free energies of sublimation and vaporization. We construct a differential rate law from these thermodynamic free energies and a normalized progress variable. We further construct a reduced variable formulation of the model which is a simple function of the metastable liquid activity below the melting point, and show that it is applicable to the observed melt acceleration in several common organic crystalline solids. A component of the differential rate law, zero order in the progress variable, is shown to be proportional to the thickness of the quasiliquid layer predicted by a recent thermodynamic theory for this phenomenon. This work therefore serves not only to provide new insight into thermal decomposition in a broad class or organic crystalline solids, but also further validates the underlying thermodynamic nature of the phenomenon of liquid formation on the molecular surface at temperatures below the melting point.

  5. A Peltier thermal cycling unit for radiopharmaceutical synthesis.

    PubMed

    McKinney, C J; Nader, M W

    2001-01-01

    We have investigated the use of Peltier devices to rapidly cycle the temperature of reaction vessels in a radiopharmaceutical synthesis system. Peltier devices have the advantage that they can be actively cooled as well as heated, allowing precise and rapid control of vessel temperatures. Reaction vessel temperatures of between -6 degrees C and 110 degrees C have been obtained with commercially available devices with reasonable cycle times. Two devices have been used as the basis for a general purpose, two-pot synthesis system for production of [11C] compounds such as raclopride.

  6. Influence of creep damage on the low cycle thermal-mechanical fatigue behavior of two tantalum base alloys

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.; Doble, G. S.

    1972-01-01

    Low cycle fatigue tests have been performed on the tantalum base alloys T-111 and ASTAR 811C with synchronized, independently programmed temperature and strain cycling. The thermal-mechanical cycles applied fell into three basic categories: these were isothermal cycling, in-phase thermal cycling, and out-of-phase thermal cycling. In-phase cycling was defined as tensile deformation associated with high temperature and compressive deformation with low temperature, while out-of-phase thermal cycling was defined as the reverse case. The in-phase thermal cycling had a pronounced detrimental influence on the fatigue life of both alloys, with the life reduction being greater in the solid solution strengthened T-111 alloy than in the carbide strengthened ASTAR 811C alloy. The out-of-phase tests also showed pronounced effects on the fatigue life of both alloys, although not as dramatic.

  7. Vapor cycle compressors for aerospace vehicle thermal management

    NASA Astrophysics Data System (ADS)

    Dexter, Peter F.; Watts, Roland J.; Haskin, William L.

    1990-10-01

    An overview is given of approaches to achieving high reliability and long life in vapor cycle compressor design for aerospace vehicles. The requirements peculiar to aircraft and spacecraft cooling systems are described. Piston, rotary vane, rolling piston, helical screw, scroll, and centrifugal compressors being developed for aerospace applications are discussed.

  8. Thermal cycling effect of dicalcium phosphate-reinforced composites on auto-mineralized dental resin.

    PubMed

    Chen, Wen-Cheng; Chang, Kai-Chi; Wu, Hui-Yu; Ko, Chia-Ling; Huang, Chien-Lin

    2014-12-01

    The mineralizing capabilities of surface-modified dicalcium phosphate anhydrous (DCPA), reinforced and treated with nanocrystals and capped with silane, in composite resins were analyzed via thermal cycling. We compared two light-curable composites that were mixed at filler-to-resin mass ratios of 30/70 and 50/50. The strengths, elastic moduli, and topographical structures of the samples were determined after thermal cycling between 5 and 55°C in deionized water for 600 and 2400 cycles. Silane-capped particles decreased the strength but enhanced the mineralizing capability of the composites. Nanocrystal-treated filler surfaces significantly increased the strength and moduli of the composites after 600 thermal cycles. However, these values declined after 2400 thermal cycles. The nanocrystal-treated filler surfaces prevented the reduction in strength before and after 2400 thermal cycles. Prior to silane capping, the nanocrystal-treated DCPA filler surfaces exhibited good mineralization capability without compromising strength. The potential for barrier generation through mineralization yielded positive effects and prevented micro-leakages.

  9. Hydraulic performance of compacted clay liners under simulated daily thermal cycles.

    PubMed

    Aldaeef, A A; Rayhani, M T

    2015-10-01

    Compacted clay liners (CCLs) are commonly used as hydraulic barriers in several landfill applications to isolate contaminants from the surrounding environment and minimize the escape of leachate from the landfill. Prior to waste placement in landfills, CCLs are often exposed to temperature fluctuations which can affect the hydraulic performance of the liner. Experimental research was carried out to evaluate the effects of daily thermal cycles on the hydraulic performance of CCLs under simulated landfill conditions. Hydraulic conductivity tests were conducted on different soil specimens after being exposed to various thermal and dehydration cycles. An increase in the CCL hydraulic conductivity of up to one order of magnitude was recorded after 30 thermal cycles for soils with low plasticity index (PI = 9.5%). However, medium (PI = 25%) and high (PI = 37.2%) plasticity soils did not show significant hydraulic deviation due to their self-healing potential. Overlaying the CCL with a cover layer minimized the effects of daily thermal cycles, and maintained stable hydraulic performance in the CCLs even after exposure to 60 thermal cycles. Wet-dry cycles had a significant impact on the hydraulic aspect of low plasticity CCLs. However, medium and high plasticity CCLs maintained constant hydraulic performance throughout the test intervals. The study underscores the importance of protecting the CCL from exposure to atmosphere through covering it by a layer of geomembrane or an interim soil layer.

  10. Thermal cycling for restorative materials: does a standardized protocol exist in laboratory testing? A literature review.

    PubMed

    Morresi, Anna Lucia; D'Amario, Maurizio; Capogreco, Mario; Gatto, Roberto; Marzo, Giuseppe; D'Arcangelo, Camillo; Monaco, Annalisa

    2014-01-01

    In vitro tests continue to be an indispensable method for the initial screening of dental materials. Thermal cycling is one of the most widely used procedures to simulate the physiological aging experienced by biomaterials in clinical practice. Consequently it is routinely employed in experimental studies to evaluate materials' performance. A literature review aimed to elucidate test parameters for in vitro aging of adhesive restorations was performed. This study aims to assess whether or not a standardized protocol of thermal cycling has been acknowledged from a review of the literature. An exhaustive literature search, examining the effect of thermal cycling on restorative dental materials, was performed with electronic database and by hand. The search was restricted to studies published from 1998 to August 2013. No language restrictions were applied. The search identified 193 relevant experimental studies. Only twenty-three studies had faithfully applied ISO standard. The majority of studies used their own procedures, showing only a certain consistency within the temperature parameter (5-55°C) and a great variability in the number of cycles and dwell time chosen. A wide variation in thermal cycling parameters applied in experimental studies has been identified. The parameters selected amongst these studies seem to be done on the basis of convenience for the authors in most cases. A comparison of results between studies would appear to be impossible. The available data suggest that further investigations will be required to ultimately develop a standardized thermal cycling protocol.

  11. Gravitational effects of process-induced dislocations in silicon. [during thermal cycling

    NASA Technical Reports Server (NTRS)

    Porter, W. A.; Parker, D. L.

    1974-01-01

    Matters pertaining to semiconductor device fabrication were studied in terms of the influence of gravity on the production of dislocations in silicon wafers during thermal cycling in a controlled ambient where no impurities are present and oxidation is minimal. Both n-type and p-type silicon wafers having a diameter of 1.25 in to 1.5 in, with fixed orientation and resistivity values, were used. The surface dislocation densities were measured quantitatively by the Sirtl etch technique. The results show two significant features of the plastic flow phenomenon as it is related to gravitational stress: (1) the density of dislocations generated during a given thermal cycle is directly related to the duration of the cycle; and (2) the duration of the thermal cycle required to produce a given dislocation density is inversely related to the equilibrium temperature. Analysis of the results indicates that gravitational stress is instrumental in process-induced defect generation.

  12. Climate-change effects on soils: Accelerated weathering, soil carbon and elemental cycling

    SciTech Connect

    Qafoku, Nikolla

    2015-04-01

    Climate change [i.e., high atmospheric carbon dioxide (CO2) concentrations (≥400 ppm); increasing air temperatures (2-4°C or greater); significant and/or abrupt changes in daily, seasonal, and inter-annual temperature; changes in the wet/dry cycles; intensive rainfall and/or heavy storms; extended periods of drought; extreme frost; heat waves and increased fire frequency] is and will significantly affect soil properties and fertility, water resources, food quantity and quality, and environmental quality. Biotic processes that consume atmospheric CO2, and create organic carbon (C) that is either reprocessed to CO2 or stored in soils are the subject of active current investigations, with great concern over the influence of climate change. In addition, abiotic C cycling and its influence on the inorganic C pool in soils is a fundamental global process in which acidic atmospheric CO2 participates in the weathering of carbonate and silicate minerals, ultimately delivering bicarbonate and Ca2+ or other cations that precipitate in the form of carbonates in soils or are transported to the rivers, lakes, and oceans. Soil responses to climate change will be complex, and there are many uncertainties and unresolved issues. The objective of the review is to initiate and further stimulate a discussion about some important and challenging aspects of climate-change effects on soils, such as accelerated weathering of soil minerals and resulting C and elemental fluxes in and out of soils, soil/geo-engineering methods used to increase C sequestration in soils, soil organic matter (SOM) protection, transformation and mineralization, and SOM temperature sensitivity. This review reports recent discoveries, identifies key research needs, and highlights opportunities offered by the climate-change effects on soils.

  13. Suppression of magnetostructural transition on GdSiGe thin film after thermal cyclings

    SciTech Connect

    Pires, A. L.; Belo, J. H.; Gomes, I. T.; Hadimani, R. L.; Schlagel, D. L.; Lograsso, T. A.; Jiles, D. C.; Lopes, A. M. L.; Araújo, J. P.; Pereira, A. M.

    2016-09-08

    The influence of thermal cycling on the microstructure, magnetic phase transition and magnetic entropy change of a Gd5Si1.3Ge2.7 thin film up to 1000 cycles is investigated. The authors found that after 1000 cycles a strong reduction of the crystallographic phase responsible for the magnetostructural transition (Orthorhombic II phase) occurs. We attribute this to the chemical disorder, caused by the large number of expansion/compression cycles that the Orthorhombic II phase undergoes across the magnetostructural transition. The suppression of the magnetostructural transition corresponds to a drastic decrease of the thin film magnetic entropy change. Our results reveal the importance of studying the thermal/magnetic cycles influence on magnetostructural transitions as they can damage a real-life device.

  14. Suppression of magnetostructural transition on GdSiGe thin film after thermal cyclings

    DOE PAGES

    Pires, A. L.; Belo, J. H.; Gomes, I. T.; ...

    2016-09-08

    The influence of thermal cycling on the microstructure, magnetic phase transition and magnetic entropy change of a Gd5Si1.3Ge2.7 thin film up to 1000 cycles is investigated. The authors found that after 1000 cycles a strong reduction of the crystallographic phase responsible for the magnetostructural transition (Orthorhombic II phase) occurs. We attribute this to the chemical disorder, caused by the large number of expansion/compression cycles that the Orthorhombic II phase undergoes across the magnetostructural transition. The suppression of the magnetostructural transition corresponds to a drastic decrease of the thin film magnetic entropy change. Our results reveal the importance of studying themore » thermal/magnetic cycles influence on magnetostructural transitions as they can damage a real-life device.« less

  15. Compatibility and accelerated aging study for Li(Si)/FeS2 thermally activated batteries

    NASA Astrophysics Data System (ADS)

    Mead, J. W.; Searcy, J. Q.; Neiswander, P. A.; Poole, R. L.

    Thermally activated batteries using Li(Si)/FeS2 for use in systems which require a storage life of 25 years and high reliability are examined. All of the materials in the system, both organic and inorganic are incorporated except the heat paper and electric match are studied. No compatibility or aging problems are indicated. The following results are reported: oxygen vanishes from the overgas in containers that were accelerated aged; hydrogen increases sharply in the overgas initially but generally decreases as aging progresses. No unexpected or significant changes were observed in the volume resistivity, glass transition temperature, or shear modulus or organic materials.

  16. On the Thermal Property of Arbitrarily Accelerating Charged Black Hole with a New Tortoise Coordinate Transformation

    NASA Astrophysics Data System (ADS)

    Zhenfeng, Niu; Wenbiao, Liu

    2006-07-01

    After a new tortoise coordinate transformation is adopted, the entropy and non-thermal radiation of an arbitrarily accelerating charged black hole are discussed as an example of non-stationary black holes. The same cut-off relation is chosen as static case, which is independent of space-time, and then the entropy of the non-stationary black hole is also proportional to the area of its event horizon. Meanwhile, the crossing of the particle energy levels near the event horizon is studied, the representative of the maximum value of the crossing energy levels is the same as the usual tortoise coordinate transformation.

  17. On a thermal analysis of a second stripper for rare isotope accelerator.

    SciTech Connect

    Momozaki, Y.; Nolen, J.; Nuclear Engineering Division

    2008-08-04

    This memo summarizes simple calculations and results of the thermal analysis on the second stripper to be used in the driver linac of Rare Isotope Accelerator (RIA). Both liquid (Sodium) and solid (Titanium and Vanadium) stripper concepts were considered. These calculations were intended to provide basic information to evaluate the feasibility of liquid (thick film) and solid (rotating wheel) second strippers. Nuclear physics calculations to estimate the volumetric heat generation in the stripper material were performed by 'LISE for Excel'. In the thermal calculations, the strippers were modeled as a thin 2D plate with uniform heat generation within the beam spot. Then, temperature distributions were computed by assuming that the heat spreads conductively in the plate in radial direction without radiative heat losses to surroundings.

  18. Carbon and nitrogen cycling in thermally heated sediments

    NASA Astrophysics Data System (ADS)

    Meyer-Dombard, D. R.; Burton, M.; Vennelakanti, S.; Havig, J. R.; Shock, E.

    2009-12-01

    Hydrothermally heated sediment environments, such as are found in abundance throughout Yellowstone National Park, host fully functional microbial ecosystems. As with any ecosystem, both sources and sinks of carbon, nitrogen, and a myriad of other nutrients and energy-driving factors must be supplied. While we know microbial communities in hydrothermal environments can be surprisingly diverse, we know little about basic ecological functions such as carbon and nitrogen cycling. Previous work has shown that carbon cycling in one hot spring in Yellowstone National Park [“Bison Pool”] and its associated runoff channel functions as a complex system. Analysis of carbon and nitrogen isotopes in sediments and biofilms across a temperature and chemical gradient at this location revealed that the four best studied carbon fixation pathways [Calvin, reverse tricarboxylic acid, acetyl-CoA, 3-hydroxypropionate cycles] may all be functioning in this system, and nitrogen fixation varies across the chemosynthetic/photosynthetic ecotone [1]. Microcosm experiments using biofilms from this hot spring as inoculae with 13C labeled carbon substrates indicate heterotrophic growth [2]. In addition, metagenomic analysis of environmental DNA has indicated the presence of genes involved in carbon fixation [both phototrophic and autotrophic], and heterotrophy, as well as nitrogen fixation [3]. Studies from other Yellowstone locations have also found genetic evidence for carbon and nitrogen fixation [4, 5]. Of particular interest is the role of individuals in carbon and nitrogen cycling as environmental conditions suitable for chemosynthetic and photosynthetic growth vary. This study explores the diversity of cbbM/cbbL [Calvin cycle], aclB/oor/porA [rTCA cycle], nifH [nitrogen fixation], nirK [nitrite reduction] and amoA [ammonia oxidation] genes across a variety of Yellowstone environments. The transition of genetic diversity within sediments and biofilms is focused on the chemosynthetic

  19. Kilovision: thermal modeling of a kilovoltage x-ray source integrated into a medical linear accelerator.

    PubMed

    Cho, Youngbin; Munro, P

    2002-09-01

    The thermal and thermo-mechanical (fatigue) properties of a stationary-anode kilovoltage x-ray source that can be integrated into the head of a medical linear accelerator have been modeled. A finite element program has been used to model two new target designs. The first design makes minor modifications to the existing target assembly of a Varian medical linear accelerator, while the second design adds an additional cooling tube, changes the target angle, and uses a tungsten-rhenium alloy rather than tungsten as the kilovoltage target material. The thermal calculations have been used to generate cyclic stress/strain values from which estimates of fatigue in the target designs have been made. Both kilovoltage and megavoltage operation have been studied. Analysis of the megavoltage operation shows that there are only small differences in the thermal and fatigue characteristics after the target assembly is modified to include a kilovoltage target. Thus, megavoltage operation should not be compromised. The first kilovoltage target design can handle a 900 W heat load (e.g., 120 kVp, 7.5 mA, 2 x 2 mm2 source size); the heat load being limited by the temperature at the surface of the cooling tubes and mechanical fatigue at the surface of the target. The second design can handle a 1250 W heat load (e.g., 120 kVp, approximately 10.4 mA, 2 x 2 mm2 source size). Our calculations show that installation of a kilovoltage x-ray target is practical from thermal and thermo-mechanical perspectives.

  20. Quasi-steady state thermal resistance of a flexible copper-water heat pipe subjected to transient acceleration loading

    SciTech Connect

    Thomas, S.K.; Yerkes, K.L.

    1996-12-31

    The thermal performance of a flexible copper-water heat pipe is investigated to determine its quasi-steady state characteristics under varying acceleration loadings. This was accomplished by attaching the heat pipe to a centrifuge table, where the imposed angular velocity was sinusoidal in nature. It was found that the thermal resistance of the heat pipe is a function of the acceleration frequency, heat input, condenser temperature, and dryout condition prior to changing the frequency. The objective of the present experimental study is to determine the potential performance characteristics of heat pipes used as heat sinks in transient acceleration environments typical of those seen in high-performance aircraft. In addition, this research will enable heat pipe designers to re-examine the effects of accelerations loading with respect to heat pipe wick and containment structures, so that new wicks and heat pipe shells can be developed and designed specifically for exploitation of the phenomena which occur in transient acceleration fields.

  1. High-frequency thermal-electrical cycles for pyroelectric energy conversion

    SciTech Connect

    Bhatia, Bikram; Damodaran, Anoop R.; Cho, Hanna; Martin, Lane W.; King, William P.

    2014-11-21

    We report thermal to electrical energy conversion from a 150 nm thick BaTiO{sub 3} film using pyroelectric cycles at 1 kHz. A microfabricated platform enables temperature and electric field control with temporal resolution near 1 μs. The rapid electric field changes as high as 11 × 10{sup 5 }kV/cm-s, and temperature change rates as high as 6 × 10{sup 5 }K/s allow exploration of pyroelectric cycles in a previously unexplored operating regime. We investigated the effect of phase difference between electric field and temperature cycles, and electric field and temperature change rates on the electrical energy generated from thermal-electrical cycles based on the pyroelectric Ericsson cycle. Complete thermodynamic cycles are possible up to the highest cycle rates tested here, and the energy density varies significantly with phase shifts between temperature and electric field waveforms. This work could facilitate the design and operation of pyroelectric cycles at high cycle rates, and aid in the design of new pyroelectric systems.

  2. Compressibility effects of unreacted propellant on thermally choked ram accelerator performance

    NASA Astrophysics Data System (ADS)

    Bauer, P.; Knowlen, C.

    2003-03-01

    Thrust calculations of the thermally choked ram accelerator propulsive mode based on quasi-steady, one-dimensional modeling of the flow process have been quite successful in predicting the experimental velocity-distance profile when real gas corrections are applied to the combustion products of propellants at initial fill pressures up to 8 MPa. A further refinement of the modeling takes into account real gas corrections for the initial state at higher fill pressures. It turns out that the Redlich-Kwong equation of state accurately determines the thermodynamic properties of the unreacted propellant for fill pressures up to at least 20 MPa. Using this equation of state for the calculation of the sound speed for a typical CH_4/O_2/N_2 propellant provides a 15% higher value at 20 MPa than that predicted for an ideal gas; this increase significantly affects the operating characteristics of the ram accelerator at a given velocity. The corresponding thrust maximum increases by 30%. This corrected theory is most appropriate under conditions of high pressure operation at relatively low acceleration levels; i.e., less than 10 000 g. The corrections to the aerothermodynamic equations that are discussed in this paper are fully generalized and can be applied using any equation of state.

  3. A thermal model for the seasonal nitrogen cycle on Triton

    NASA Technical Reports Server (NTRS)

    Hansen, Candice J.; Paige, David A.

    1992-01-01

    The seasonal N2-cycle model presently used to characterize such observed phenomena on Triton as atmospheric pressure and surface albedo features at the time of the Voyager encounter incorporates diurnal and seasonal subsurface heat conduction, and can account for the heat capacity of N2 frost deposits. The results obtained by this model differ from those of previous studies in that they do not predict the seasonal freezing-out of the Triton atmosphere; even for a wide range of input parameters, the bright southern polar cap is seen as rather unlikely to be N2. The results support the microphysical arguments for the presence of either dark or smooth translucent N2 frosts on the Triton surface.

  4. Preliminary consideration of a double, 480 GeV, fast cycling proton accelerator for production of neutrino beams at Fermilab

    SciTech Connect

    Piekarz, Henryk; Hays, Steven; /Fermilab

    2007-03-01

    We propose to build the DSF-MR (Double Super-Ferric Main Ring), 480 GeV, fast-cycling (2 second repetition rate) two-beam proton accelerator in the Main Ring tunnel of Fermilab. This accelerator design is based on the super-ferric magnet technology developed for the VLHC, and extended recently to the proposed LER injector for the LHC and fast cycling SF-SPS at CERN. The DSF-MR accelerator system will constitute the final stage of the proton source enabling production of two neutrino beams separated by 2 second time period. These beams will be sent alternately to two detectors located at {approx} 3000 km and {approx} 7500 km away from Fermilab. It is expected that combination of the results from these experiments will offer more than 3 order of magnitudes increased sensitivity for detection and measurement of neutrino oscillations with respect to expectations in any current experiment, and thus may truly enable opening the window into the physics beyond the Standard Model. We examine potential sites for the long baseline neutrino detectors accepting beams from Fermilab. The current injection system consisting of 400 MeV Linac, 8 GeV Booster and the Main Injector can be used to accelerate protons to 45 GeV before transferring them to the DSF-MR. The implementation of the DSF-MR will allow for an 8-fold increase in beam power on the neutrino production target. In this note we outline the proposed new arrangement of the Fermilab accelerator complex. We also briefly describe the DSF-MR magnet design and its power supply, and discuss necessary upgrade of the Tevatron RF system for the use with the DSF-MR accelerator. Finally, we outline the required R&D, cost estimate and possible timeline for the implementation of the DSF-MR accelerator.

  5. Thermal analysis of a simple-cycle gas turbine in biogas power generation

    SciTech Connect

    Yomogida, D.E.; Thinh, Ngo Dinh

    1995-09-01

    This paper investigates the technical feasibility of utilizing small simple-cycle gas turbines (25 kW to 125 kW) for biogas power generation through thermal analysis. A computer code, GTPower, was developed to evaluate the performance of small simple-cycle gas turbines specifically for biogas combustion. The 125 KW Solar Gas Turbine (Tital series) has been selected as the base case gas turbine for biogas combustion. After its design parameters and typical operating conditions were entered into GTPower for analysis, GTPower outputted expected values for the thermal efficiency and specific work. For a sensitivity analysis, the GTPower Model outputted the thermal efficiency and specific work. For a sensitivity analysis, the GTPower Model outputted the thermal efficiency and specific work profiles for various operating conditions encountered in biogas combustion. These results will assist future research projects in determining the type of combustion device most suitable for biogas power generation.

  6. Acceleration of the Arctic Water Cycle: evidence from the Lena Basin, Siberia

    NASA Astrophysics Data System (ADS)

    Cherry, J. E.; Alexeev, V.; Liepert, B.; Groisman, P.; Romanovsky, V.

    2006-12-01

    Strong positive climate feedbacks cause much of the Arctic to warm faster than the global average (IPCC, 2001; ACIA, 2004). The global hydrologic cycle is expected to accelerate in a warmer world because a warmer atmosphere can hold more water vapor. However, an important question that has not been adequately addressed is whether thawing of permafrost and deepening of the soil's active layer, which pulls moisture away from the surface into deeper reservoirs, will lead to a wetter or dryer Arctic climate (Vörösmarty et al., 2001). There is an apparent paradox in the Arctic between increasing annual precipitation trends (ACIA, 2004), increasing occurrence of forest fires (Kasischke et al., 1999; Korovin and Zukkert 2003), and the drying of surface lakes (Smith et al., 2005). Our investigation of hydroclimatological change in the Lena basin (Russia) points to an increasingly wet Arctic. Though much of the near-surface air temperature (SAT) warming is occurring when the ground is covered by snow, increases in frozen precipitation are also contributing to warmer soil temperatures by increasing soil insulation. A deeper active layer caused by spring and summer warming holds more soil moisture and is leading to increasing potential evapotranspiration (shown in the model), increasing hydrologic baseflow (modeled and observed), and increasing summer nighttime cloudiness (observed). Changes in summer cloud types are suppressing warming during the days, but warming the nights significantly even during the polar day (Groisman et al. 1996). Earlier onset of snow cover in autumn traps the spring and summer warming, a trend that leads to further deepening of the active layer. These observed and modeled feedbacks describe an Arctic hydroclimatological regime in which water storage and flow has increased and moved from the surface to the subsurface.

  7. Study of a Liquid Plug-Flow Thermal Cycling Technique Using a Temperature Gradient-Based Actuator

    PubMed Central

    Fuchiwaki, Yusuke; Nagai, Hidenori

    2014-01-01

    Easy-to-use thermal cycling for performing rapid and small-volume DNA amplification on a single chip has attracted great interest in the area of rapid field detection of biological agents. For this purpose, as a more practical alternative to conventional continuous flow thermal cycling, liquid plug-flow thermal cycling utilizes a thermal gradient generated in a serpentine rectangular flow microchannel as an actuator. The transit time and flow speed of the plug flow varied drastically in each temperature zone due to the difference in the tension at the interface between temperature gradients. According to thermal distribution analyses in microfluidics, the plug flow allowed for a slow heating process, but a fast cooling process. The thermal cycle of the microfluid was consistent with the recommended temperature gradient for PCR. Indeed, amplification efficiency of the plug flow was superior to continuous flow PCR, and provided an impressive improvement over previously-reported flow microchannel thermal cycling techniques. PMID:25350508

  8. Study of a liquid plug-flow thermal cycling technique using a temperature gradient-based actuator.

    PubMed

    Fuchiwaki, Yusuke; Nagai, Hidenori

    2014-10-27

    Easy-to-use thermal cycling for performing rapid and small-volume DNA amplification on a single chip has attracted great interest in the area of rapid field detection of biological agents. For this purpose, as a more practical alternative to conventional continuous flow thermal cycling, liquid plug-flow thermal cycling utilizes a thermal gradient generated in a serpentine rectangular flow microchannel as an actuator. The transit time and flow speed of the plug flow varied drastically in each temperature zone due to the difference in the tension at the interface between temperature gradients. According to thermal distribution analyses in microfluidics, the plug flow allowed for a slow heating process, but a fast cooling process. The thermal cycle of the microfluid was consistent with the recommended temperature gradient for PCR. Indeed, amplification efficiency of the plug flow was superior to continuous flow PCR, and provided an impressive improvement over previously-reported flow microchannel thermal cycling techniques.

  9. Ex Situ Thermal Cycle Annealing of Molecular Beam Epitaxy Grown HgCdTe/Si Layers

    DTIC Science & Technology

    2010-01-01

    during the growth process itself, is an effective means to reduce etch pit den- sity (EPD) and improve overall crystal quality. Subjecting CdTe /Si...results of ex situ thermal cycle annealing (TCA) of molecular beam epitaxy grown mercury cadmium telluride (HgCdTe) on Cd (Se)Te/ Si(211) composite...present the results of ex situ thermal cycle annealing (TCA) of molecular beam epitaxy grown mercury cadmium telluride (HgCdTe) on Cd (Se)Te/ Si(211

  10. Thermal Cycling and High Temperature Reverse Bias Testing of Control and Irradiated Gallium Nitride Power Transistors

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Boomer, Kristen T.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

    2014-01-01

    The power systems for use in NASA space missions must work reliably under harsh conditions including radiation, thermal cycling, and exposure to extreme temperatures. Gallium nitride semiconductors show great promise, but information pertaining to their performance is scarce. Gallium nitride N-channel enhancement-mode field effect transistors made by EPC Corporation in a 2nd generation of manufacturing were exposed to radiation followed by long-term thermal cycling and testing under high temperature reverse bias conditions in order to address their reliability for use in space missions. Result of the experimental work are presented and discussed.

  11. Effects of Radiation and Long-Term Thermal Cycling on EPC 1001 Gallium Nitride Transistors

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

    2012-01-01

    Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These include radiation, extreme temperatures, and thermal cycling, to name a few. Data obtained on long-term thermal cycling of new un-irradiated and irradiated samples of EPC1001 gallium nitride enhancement-mode transistors are presented. This work was done by a collaborative effort including GRC, GSFC, and support the NASA www.nasa.gov 1 JPL in of Electronic Parts and Packaging (NEPP) Program

  12. Effects of Thermal Cycling on Control and Irradiated EPC 2nd Generation GaN FETs

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

    2013-01-01

    The power systems for use in NASA space missions must work reliably under harsh conditions including radiation, thermal cycling, and exposure to extreme temperatures. Gallium nitride semiconductors show great promise, but information pertaining to their performance is scarce. Gallium nitride N-channel enhancement-mode field effect transistors made by EPC Corporation in a 2nd generation of manufacturing were exposed to radiation followed by long-term thermal cycling in order to address their reliability for use in space missions. Results of the experimental work are presented and discussed.

  13. Thermal cycling effect in U-10Mo/Zry-4 monolithic nuclear fuel

    NASA Astrophysics Data System (ADS)

    Lopes, Denise A.; Zimmermann, Angelo J. O.; Silva, Selma L.; Piqueira, J. R. C.

    2016-05-01

    Uranium alloys in a monolithic form have been considered attractive candidates for high density nuclear fuel. However, this high-density fissile material configuration keeps the volume permitted for the retention of fission products at a minimum. Additionally, the monolithic nuclear fuel has a peculiar configuration, whereby the fuel is in direct contact with the cladding. How this fuel configuration will retain fission products and how this will affect its integrity under various physical conditions - such as thermal cycling - are some of the technological problems for this new fuel. In this paper, the effect of out-of-pile thermal cycling is studied for a monolithic fuel plate produced by a hot co-rolling method using U-10Mo (wt %) as the fuel alloy and Zircaloy-4 as the cladding material. After performing 10 thermal cycles from 25 to 400 °C at a rate of 1 °C/min (∼125 h), the fuel alloy presented several fractures that were observed to occur in the last three cycles. These cracks nucleated approximately in the center of the fuel alloy and crossed the interdiffusion zone initiating an internal crack in the cladding. The results suggest that the origin of these fractures is the thermal fatigue of the U-10Mo alloy caused due to the combination of two factors: (i) the high difference in the thermal expansion coefficient of the fuel and of the cladding material, and (ii) the bound condition of fuel/cladding materials in this fuel element configuration.

  14. Residual thermal effects in macro fiber composite actuators exposed to persistent temperature cycling

    NASA Astrophysics Data System (ADS)

    Hobeck, J. D.; Owen, R. B.; Inman, D. J.

    2016-03-01

    In this letter, the authors present results of an experimental investigation demonstrating how extreme persistent thermal cycling influences the performance of piezoelectric macro fiber composite (MFC) actuators. More specifically, this research shows how repeated temperature cycling ranging from -60 °C to 90 °C and from -50 °C to 150 °C affects an MFCs ability to actuate while being driven at frequencies of 60 Hz to 90 Hz with a voltage of 20 Vpp. Experimental results show that thermal cycling causes MFC actuation characteristics to drift and eventually stabilize after approximately 20 cycles. In two cases presented here, thermal cycling alone caused a residual increase in actuation amplitude that exceeded the initial amplitude by 70%. This apparent thermal memory effect of MFCs may significantly impact the design and analysis of active structures where MFCs are used for vibration or displacement control in transient extreme temperature environments such as those encountered by aerospace structures, industrial equipment, automobiles, and civil infrastructure.

  15. Evaluation of thermal cycling creep-fatigue damage for a molten salt receiver

    NASA Astrophysics Data System (ADS)

    Grossman, James W.; Jones, Wendell B.; Veers, Paul S.

    1990-01-01

    A molten salt cavity receiver was solar tested at Sandia National Laboratories during a year-long test program. Upon completion of testing, an analysis was performed to determine the effect of thermal cycling on the receiver. The results indicate a substantial fatigue damage accumulation for the receiver when the relatively short test time is considered. This paper describes the methodology used to analyze the cycling, the results as they pertain to this receiver, and how they affect future receiver design.

  16. An active thermal compensator for closed-cycle helium refrigerators

    NASA Technical Reports Server (NTRS)

    Jennings, D. E.; Hillman, J. J.

    1977-01-01

    A technique was developed for reducing the amplitude of the temperature oscillation in He closed-cyle refrigerators. The device uses a semiconductor diode as a heating element to actively supply a small oscillating input of heat at a point between the laser and the cold-tip to cancel the heat oscillations due to the refrigerator. It was found that the heater diode could drive the temperature of the heat sink more effectively, i.e., with lower current and therefore less heat, if the heat sink was insulated slightly from the rest of the mount. A sine-wave generator was used to drive the programmable supply which provided the offset current to the heater diode. By matching the frequency and phase of the oscillator to that of the refrigerator cycle, and by adjusting the amplitude of the oscillator signal, the temperature fluctuations at the laser could be minimized. Residual fluctuations were about 0.003K peak-to-peak, at an operating temperature of 9.5K.

  17. Rapid PCR protocols for forensic DNA typing on six thermal cycling platforms.

    PubMed

    Butts, Erica L R; Vallone, Peter M

    2014-11-01

    Rapid PCR protocols for the amplification of typing STR multiplexes were evaluated on six different thermal cyclers. Through the use of a faster DNA polymerase coupled with the use of rapid thermal cyclers the amplification cycling times were reduced down to as little as 14 min using PCR primers from the commercially available multiplex STR typing kit Identifiler. Previously described two-step and three-step thermal cycling protocols were evaluated for the six thermal cyclers on 95 unique single-source DNA extracts. CE characterization of the PCR products indicates good peak balance between loci (median values greater than 0.84), and N minus four stutter ratios on averages were 30 to 40% higher than for standard Identifiler PCR conditions. Nonspecific amplification artifacts were observed, but were not observed to migrate within the allele calling bins. With the exception of one locus (D18S51) in a single sample, genotyping results were concordant with manufacturer's recommended amplification conditions utilizing standard thermal cycling procedures. Assay conditions were robust enough to routinely amplify 250 to 500 pg of template DNA. This work describes the protocols for the rapid PCR amplification of STR multiplexes on various PCR thermal cyclers with the future intent to support validation for typing single-source samples in a database laboratory.

  18. Effects of mechanical and thermal cycling on composite and hybrid laminates with residual stresses

    NASA Technical Reports Server (NTRS)

    Daniel, I. M.; Liber, T.

    1977-01-01

    The effects of tensile load cycling and thermal cycling on residual stiffness and strength properties of the following composite and hybrid angle-ply laminates were studied: boron/epoxy, boron/polyimide, graphite/low-modulus epoxy, graphite/high-modulus epoxy, graphite/polyimide, S-glass/epoxy, graphite/Kevlar 49/epoxy, and graphite/S-glass/epoxy. Specimens of the first six types were mechanically cycled up to 90% of static strength. Those that survived 10 million cycles were tested statically to failure, and no significant changes in residual strength and modulus were noted. Specimens of all types were subjected to thermal cycling between room temperature and 411 K for the epoxy-matrix composites and 533 K for the polyimide-matrix composites. The residual strength and stiffness remained largely unchanged, except for the graphite/low-modulus epoxy, which showed reductions in both of approximately 35%. When low-temperature thermal cycling under tensile load was applied, there was a noticeable reduction in modulus and strength in the graphite/low-modulus epoxy and some strength reduction in the S-glass/epoxy.

  19. Effect of Thermal Cycling on the Tensile Behavior of Polymer Composites Reinforced by Basalt and Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Khalili, S. Mohammad Reza; Najafi, Moslem; Eslami-Farsani, Reza

    2017-01-01

    The aim of the present work was to investigate the effect of thermal cycling on the tensile behavior of three types of polymer-matrix composites — a phenolic resin reinforced with woven basalt fibers, woven carbon fibers, and hybrid basalt and carbon fibers — in an ambient environment. For this purpose, tensile tests were performed on specimens previously subjected to a certain number of thermal cycles. The ultimate tensile strength of the specimen reinforced with woven basalt fibers had by 5% after thermal cycling, but the strength of the specimen with woven carbon fibers had reduced to a value by 11% higher than that before thermal cycling.

  20. Measurements of the thermal neutron flux for an accelerator-based photoneutron source.

    PubMed

    Taheri, Ali; Pazirandeh, Ali

    2016-12-01

    To have access to an appropriate neutron source is one of the most demanding requirements for neutron studies. This is important specially in laboratory and clinical applications, which need more compact and accessible sources. The most known neutron sources are fission reactors and natural isotopes, but there is an increasing interest for using accelerator based neutron sources because of their advantages. In this paper, we shall present a photo-neutron source prototype which is designed and fabricated to be used for different neutron researches including in-laboratory neutron activation analysis and neutron imaging, and also preliminary studies in boron neutron capture therapy (BNCT). Series of experimental tests were conducted to examine the intensity and quality of the neutron field produced by this source. Monte-Carlo simulations were also utilized to provide more detailed evaluation of the neutron spectrum, and determine the accuracy of the experiments. The experiments demonstrated a thermal neutron flux in the order of 10(7) (n/cm(2).s), while simulations affirmed this flux and showed a neutron spectrum with a sharp peak at thermal energy region. According to the results, about 60 % of produced neutrons are in the range of thermal to epithermal neutrons.

  1. Open cycle ocean thermal energy conversion system structure

    DOEpatents

    Wittig, J. Michael

    1980-01-01

    A generally mushroom-shaped, open cycle OTEC system and distilled water producer which has a skirt-conduit structure extending from the enlarged portion of the mushroom to the ocean. The enlarged part of the mushroom houses a toroidal casing flash evaporator which produces steam which expands through a vertical rotor turbine, partially situated in the center of the blossom portion and partially situated in the mushroom's stem portion. Upon expansion through the turbine, the motive steam enters a shell and tube condenser annularly disposed about the rotor axis and axially situated beneath the turbine in the stem portion. Relatively warm ocean water is circulated up through the radially outer skirt-conduit structure entering the evaporator through a radially outer portion thereof, flashing a portion thereof into motive steam, and draining the unflashed portion from the evaporator through a radially inner skirt-conduit structure. Relatively cold cooling water enters the annular condenser through the radially inner edge and travels radially outwardly into a channel situated along the radially outer edge of the condenser. The channel is also included in the radially inner skirt-conduit structure. The cooling water is segregated from the potable, motive steam condensate which can be used for human consumption or other processes requiring high purity water. The expansion energy of the motive steam is partially converted into rotational mechanical energy of the turbine rotor when the steam is expanded through the shaft attached blades. Such mechanical energy drives a generator also included in the enlarged mushroom portion for producing electrical energy. Such power generation equipment arrangement provides a compact power system from which additional benefits may be obtained by fabricating the enclosing equipment, housings and component casings from low density materials, such as prestressed concrete, to permit those casings and housings to also function as a floating

  2. Thermal Cycle Reliability of PBGA/CCGA 717 I/Os

    NASA Technical Reports Server (NTRS)

    Ghaffarian, Reza

    2006-01-01

    Status of thermal cycle test results for a nonfunctional daisy-chained peripheral ceramic column grid array (CCGA) and its plastic ball grid array (PBGA) version. both having 560 I/Os. were presented in last year's conference. Test results included environmental data for three different thermal cycle regimes (-55 C/125 C, -55 C/100 C, and -50 C /75 C). Update information on these - especially failure type for assemblies with high and low solder volumes-were presented. The thermal cycle test procedure followed those recommended IPC-9701 for tin-lead solder joint assemblies. Revision A of this specification covers guideline thermal cycle requirements for Pb-free solder joints. Some background information discussed during release of this specification with its current guideline recommendations were also presented. In a recent reliability investigation a fully populated CCGA with 717 I/Os was also considered for assembly reliability. evaluation. The functional package is a field-programmable gate array that has much higher processing power than its previous version. This new package is smaller in dimension, has no interposer, and has a thinner column wrapped with copper for reliability improvement. This paper will also present thermal cycle test results for this package assembly and its plastic version with 728 I/Os. both of which were exposed to three different cycle regimes. Two cycle profiles were those specified by IPC- 9701A for tin-lead, i.e. -55 to 100 C and -55 to 125 C and one was a cycle profile specified by Mil-Std-883, i.e.. -65 C/150 C which is generally used for ceramic hybrid packages. Per IPC-9701 A, test vehicles were built using daisy chain packages and were continuously monitored. The effects of many process and assembly variables-including corner staking commonly used for improving resistance to mechanical loading such as drop and vibration loads--were also considered as part of the test matrix. Optical photomicrographs were taken at various thermal

  3. Thermal Cycling Behavior of Quasi-Columnar YSZ Coatings Deposited by PS-PVD

    NASA Astrophysics Data System (ADS)

    Yang, Jiasheng; Zhao, Huayu; Zhong, Xinghua; Shao, Fang; Liu, Chenguang; Zhuang, Yin; Ni, Jinxing; Tao, Shunyan

    2017-01-01

    Columnar-structured thermal barrier coatings, owing to their high strain tolerance, are expected for their potential possibilities to substantially extend turbine lives and improve engine efficiencies. In this paper, plasma spray-physical vapor deposition (PS-PVD) process was used to deposit yttria partially stabilized zirconia (YSZ) coatings with quasi-columnar structures. Thermal cyclic tests on burner rigs and thermal shock tests by heating and water-quenching method were involved to evaluate the thermal cycling and thermal shock behaviors of such kind of structured thermal barrier coatings (TBCs). Evolution of the microstructures, phase composition, residual stresses and failure behaviors of quasi-columnar YSZ coatings before and after the thermal tests was investigated. The quasi-columnar coating obtained had an average life of around 623 cycles when the spallation area reached about 10% of the total coating surface during burner rig tests with the coating surface temperature of 1250 °C. Failure of the coating is mainly due to the break and pull-out of center columnar segments.

  4. Technical and economic feasibility of a Thermal Gradient Utilization Cycle (TGUC) power plant. Final report

    SciTech Connect

    Raiji, A.M.; Renfroe, D.A.; Lalk, T.R.

    1980-01-01

    The technical and economic feasibility of a Thermal Gradient Utilization Cycle (TGUC), a new concept in power generation, was investigated. Power is generated by exploiting the natural atmosheric temperature gradient. A low grade energy source is used to vaporize a fluid which rises in a pipe to a higher elevation where it is condensed. The cycle is completed by passing the condensed liquid through a turbine as it returns to the lower elevation. A digital computer model was developed and used to simulate the operation of the cycle and to conduct a parameteric study. Life cycle cost analysis and energy analyses were conducted for the specific case of a TGUC using the ambient air at the lower elevation as an energy source. Although the cycle has a low thermal efficiency and is site specific, it is technically feasible. Variations in mass flow rate of the working fluid and elevation were found to affect the cycle power output to a large extent. The investment cost of a hypothetical 10 megawatt TGUC power plant was determined to be $3,080 per kilowatt, with life cycle busbar costs of electricity ranging from 47 to 55 Mills per kilowatt-hour depending on the method of financing. Results of the energy analyses showed that a TGUC system would have a positive net energy and a second law efficiency of 23% for the case of a TGUC system using the atmosphere as an energy source.

  5. Thermal compensator for closed-cycle helium refrigerator. [assuring constant temperature for an infrared laser diode

    NASA Technical Reports Server (NTRS)

    Jennings, D. E.; Hillman, J. J. (Inventor)

    1979-01-01

    The wave length of an infrared, semiconductor laser diode having an output frequency that is dependent on the diode temperature is maintained substantially constant by maintaining the diode temperature constant. The diode is carried by a cold tip of a closed cycle helium refrigerator. The refrigerator has a tendency to cause the temperature of the cold tip to oscillate. A heater diode and a sensor diode are placed on a thermal heat sink that is the only highly conductive thermal path between the laser diode and the cold tip. The heat sink has a small volume and low thermal capacitance so that the sensing diode is at substantially the same temperature as the heater diode and substantially no thermal lag exists between them. The sensor diode is connected in a negative feedback circuit with the heater diode so that the tendency of the laser diode to thermally oscillate is virtually eliminated.

  6. The surface quasiliquid melt acceleration and the role of thermodynamic phase in the thermal decomposition of crystalline organic explosives

    SciTech Connect

    Henson, Bryan F

    2010-01-01

    We show that melt acceleration in the thermal decomposition of crystalline organic solids is a manifestation of the surface quasiliquid phase. We derive a single universal rate law for melt acceleration that is a simple function of the metastable liquid activity below the melting point, and has a zero order term proportional to the quasiliquid thickness. We argue that the underlying mechanisms of this model will provide a molecular definition for the stability of the class of secondary explosives.

  7. Corotating Interaction Regions in Stellar Winds: Particle Acceleration and Non-thermal Radio Emission in Hot Stars

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1985-01-01

    A co-rotating interaction region (CIR) forms in a stellar wind when a fast stream from a rotating star overtakes a slow stream. The CIR's were studied in detail in the solar wind over the past decade primarily because they are efficient sources of particle acceleration. Here, CIR's in OB star winds are used to explain two properties of such winds: deposition of non-radiative energy in the wind far from the stellar surfaces and acceleration of non-thermal particles.

  8. Improved thermal cycling durability and PCR compatibility of polymer coated quantum dot

    NASA Astrophysics Data System (ADS)

    Xun, Zhe; Zhao, Xiaoyun; Guan, Yifu

    2013-09-01

    Quantum dots have experienced rapid development in imaging, labeling and sensing in medicine and life science. To be suitable for polymerase chain reaction (PCR) assay, we have tested QD thermal cycling durability and compatibility, which have not been addressed in previous reports. In this study, we synthesized CdSe/ZnS QDs with a surface modification with high-MW amphiphilic copolymers and observed that Mg2+ ions in the PCR reaction could induce the QDs to precipitate and reduce their fluorescence signal significantly after thermal cycling. To overcome this problem, we used mPEG2000 to conjugate the QD surface for further protection, and found that this modification enables QDs to endure 40 thermal cycles in the presence of other components essential for PCR reactions. We have also identified that QDs have different effects on rTaq and Ex Taq polymerization systems. A high QD concentration could apparently reduce the PCR efficiency, but this inhibition was relieved significantly in the Ex PCR system as the concentration of Ex Taq polymerase was increased. Real-time PCR amplification results showed that QDs could provide a sufficiently measurable fluorescence signal without excessively inhibiting the DNA amplification. Based on this improved thermal cycling durability and compatibility with the PCR system, QDs have the potential to be developed as stable fluorescent sensors in PCR and real-time PCR amplification.

  9. Reducing dislocations in semiconductors utilizing repeated thermal cycling during multistage epitaxial growth

    DOEpatents

    Fan, John C. C.; Tsaur, Bor-Yeu; Gale, Ronald P.; Davis, Frances M.

    1986-12-30

    Dislocation densities are reduced in growing semiconductors from the vapor phase by employing a technique of interrupting growth, cooling the layer so far deposited, and then repeating the process until a high quality active top layer is achieved. The method of interrupted growth, coupled with thermal cycling, permits dislocations to be trapped in the initial stages of epitaxial growth.

  10. Reducing dislocations in semiconductors utilizing repeated thermal cycling during multistage epitaxial growth

    DOEpatents

    Fan, John C. C.; Tsaur, Bor-Yeu; Gale, Ronald P.; Davis, Frances M.

    1992-02-25

    Dislocation densities are reduced in growing semiconductors from the vapor phase by employing a technique of interrupting growth, cooling the layer so far deposited, and then repeating the process until a high quality active top layer is achieved. The method of interrupted growth, coupled with thermal cycling, permits dislocations to be trapped in the initial stages of epitaxial growth.

  11. Effect of weld thermal cycles on the HAZ toughness of SQV-2A pressure vessel steel

    SciTech Connect

    Matsuda, F.; Ikeuchi, K.; Liao, J.

    1996-12-31

    The toughness of coarse grained heat affected zone (CGHAZ) and intercritically reheated CGHAZ of SQV-2A pressure vessel steel has been investigated with particular attention to the behavior of M-A constituents. The effect of temper-bead thermal cycles on the toughness improvement in ICCGHAZs and temper-bead process. The occurrence of embrittlement in CGHAZs and ICCGHAZs was accompanied by the formation of the M-A constituent. Observations with a scanning electron microscope (SEM) showed that the M-A constituent acted as an initiation site of cleavage facets or secondary cracks. Temper-bead thermal cycles could improve the toughness of ICCGHAZs due to the decomposition of M-A constituents, but the toughness improvement by the temper-bead thermal cycle was influenced strongly by the cooling time {Delta}t{sub 8/5(2)eff} of the second thermal cycle. For short cooling time {Delta}t{sub 8/5(2)eff}, namely for low welding heat-input, the toughness improvement was significant.

  12. Synergistic effects of ultraviolet radiation, thermal cycling and atomic oxygen on altered and coated Kapton surfaces

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; Bruckner, Eric J.; Rodriguez, Elvin

    1992-01-01

    The photovoltaic (PV) power system for Space Station Freedom (SSF) uses solar array blankets which provide structural support for the solar cells and house the electrical interconnections. In the low earth orbital (LEO) environment where SSF will be located, surfaces will be exposed to potentially damaging environmental conditions including solar ultraviolet (UV) radiation, thermal cycling, and atomic oxygen. It is necessary to use ground based tests to determine how these environmental conditions would affect the mass loss and optical properties of candidate SSF blanket materials. Silicone containing, silicone coated, and SiO(x) coated polyimide film materials were exposed to simulated LEO environmental conditions to determine their durability and whether the environmental conditions of UV, thermal cycling and oxygen atoms act synergistically on these materials. A candidate PV blanket material called AOR Kapton, a polysiloxane polyimide cast from a solution mixture, shows an improvement in durability to oxygen atoms erosion after exposure to UV radiation or thermal cycling combined with UV radiation. This may indicate that the environmental conditions react synergistically with this material, and the damage predicted by exposure to atomic oxygen alone is more severe than that which would occur in LEO where atomic oxygen, thermal cycling and UV radiation are present together.

  13. Synergistic effects of ultraviolet radiation, thermal cycling and atomic oxygen on altered and coated Kapton surfaces

    SciTech Connect

    Dever, J.A.; Bruckner, E.J.; Rodriguez, E. Cleveland State University, OH )

    1992-01-01

    The photovoltaic (PV) power system for Space Station Freedom (SSF) uses solar array blankets which provide structural support for the solar cells and house the electrical interconnections. In the low earth orbital (LEO) environment where SSF will be located, surfaces will be exposed to potentially damaging environmental conditions including solar ultraviolet (UV) radiation, thermal cycling, and atomic oxygen. It is necessary to use ground based tests to determine how these environmental conditions would affect the mass loss and optical properties of candidate SSF blanket materials. Silicone containing, silicone coated, and SiO(x) coated polyimide film materials were exposed to simulated LEO environmental conditions to determine their durability and whether the environmental conditions of UV, thermal cycling and oxygen atoms act synergistically on these materials. A candidate PV blanket material called AOR Kapton, a polysiloxane polyimide cast from a solution mixture, shows an improvement in durability to oxygen atoms erosion after exposure to UV radiation or thermal cycling combined with UV radiation. This may indicate that the environmental conditions react synergistically with this material, and the damage predicted by exposure to atomic oxygen alone is more severe than that which would occur in LEO where atomic oxygen, thermal cycling and UV radiation are present together. 14 refs.

  14. Corrosion resistance of stainless steels during thermal cycling in alkali nitrate molten salts.

    SciTech Connect

    Bradshaw, Robert W.; Goods, Steven Howard

    2001-09-01

    The corrosion behavior of three austenitic stainless steels was evaluated during thermal cycling in molten salt mixtures consisting of NaNO{sub 3} and KNO{sub 3}. Corrosion tests were conducted with Types 316, 316L and 304 stainless steels for more than 4000 hours and 500 thermal cycles at a maximum temperature of 565 C. Corrosion rates were determined by chemically descaling coupons. Metal losses ranged from 5 to 16 microns and thermal cycling resulted in moderately higher corrosion rates compared to isothermal conditions. Type 316 SS was somewhat more corrosion resistant than Type 304 SS in these tests. The effect of carbon content on corrosion resistance was small, as 316L SS corroded only slightly slower than 316 SS. The corrosion rates increased as the dissolved chloride content of the molten salt mixtures increased. Chloride concentrations approximating 1 wt.%, coupled with thermal cycling, resulted in linear weight loss kinetics, rather than parabolic kinetics, which described corrosion rates for all other conditions. Optical microscopy and electron microprobe analysis revealed that the corrosion products consisted of iron-chromium spinel, magnetite, and sodium ferrite, organized as separate layers. Microanalysis of the elemental composition of the corrosion products further demonstrated that the chromium content of the iron-chromium spinel layer was relatively high for conditions in which parabolic kinetics were observed. However, linear kinetics were observed when the spinel layer contained relatively little chromium.

  15. Synergistic effects of ultraviolet radiation, thermal cycling, and atomic oxygen on altered and coated Kapton surfaces

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; Bruckner, Eric J.; Rodriguez, Elvin

    1992-01-01

    The photovoltaic (PV) power system for Space Station Freedom (SSF) uses solar array blankets which provide structural support for the solar cells and house the electrical interconnections. In the low Earth orbital (LEO) environment where SSF will be located, surfaces will be exposed to potentially damaging environmental conditions including solar ultraviolet (UV) radiation, thermal cycling, and atomic oxygen. It is necessary to use ground based tests to determine how these environmental conditions would affect the mass loss and optical properties of candidate SSF blanket materials. Silicone containing, silicone coated, and SiO(x) coated polyimide film materials were exposed to simulated LEO environmental conditions to determine there durability and whether the environmental conditions of UV, thermal cycling and oxygen atoms act synergistically on these materials. A candidate PV blanket material called AOR Kapton, a polysiloxane polyimide cast from a solution mixture, shows an improvement in durability to oxygen atoms erosion after exposure to UV radiation or thermal cycling combined with UV radiation. This may indicate that the environmental conditions react synergistically with this material, and the damage predicted by exposure to atomic oxygen alone is more severe than that which would occur in LEO where atomic oxygen, thermal cycling and UV radiation are present together.

  16. The Correlation of the TBC Lifetimes in Burner Cycling Test with Thermal Gradient and Furnace Isothermal Cycling Test by TGO Effects

    NASA Astrophysics Data System (ADS)

    Li, Chang-Jiu; Dong, Hui; Ding, Hang; Yang, Guan-Jun; Li, Cheng-Xin

    2017-02-01

    Two types of typical thermal cycling tests are used for the evaluation of thermal cycling lifetime of thermal barrier coatings. Those are the burner cycling test with a thermal gradient and the isothermal furnace cycling test. There are diverse explanations to test results up to now. Although certain correlations should exist between the results obtained by two types of the tests, no evident parameters in two tests were directly related, possibly due to large range of difference test conditions. In this investigation, a series of TBC samples with carefully prepared Al2O3-based TGO of different thicknesses were used for both the burner cycling and the furnace cycling tests. The relationships between thermal cycling lifetime and TGO thickness were obtained for two types of the tests. It was found that TGO thickness presents the same influence tendency despite of different types of thermal cycling test. The results reveal the existence of the critical TGO thickness by which the transition of failure mode takes place. Moreover, the values of the critical TGO thickness for two tests are comparable. The results evidently suggest that the lifetimes during different thermal cycling tests can be correlated by TGO effects on failure behavior. However, it is clear that the apparent dominant driving factors to TBC failure are different in two types of tests. Accordingly, the burner cycling test could be used for optimizing the durability of ceramic top coat by separating the effect of individual factors through test condition design, while the furnace cycling test results represent the integrated TBC durable performance of the bond coat and top ceramic coating.

  17. Monitoring chemical degradation of thermally cycled glass-fibre composites using hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Papadakis, V. M.; Müller, B.; Hagenbeek, M.; Sinke, J.; Groves, R. M.

    2016-04-01

    Nowadays, the application of glass-fibre composites in light-weight structures is growing. Although mechanical characterizations of those structures are commonly performed in testing, chemical changes of materials under stresses have not yet been well documented. In the present work coupon tests and Hyperspectral Imaging (HSI) have been used to categorise possible chemical changes of glass-fibre reinforced polymers (GFRP) which are currently used in the aircraft industry. HSI is a hybrid technique that combines spectroscopy with imaging. It is able to detect chemical degradation of surfaces and has already been successfully applied in a wide range of fields including astronomy, remote sensing, cultural heritage and medical sciences. GFRP specimens were exposed to two different thermal loading conditions. One thermal loading condition was a continuous thermal exposure at 120°C for 24h, 48 h and 96h, i.e. ageing at a constant temperature. The other thermal loading condition was thermal cycling with three different numbers of cycles (4000, 8000, 12000) and two temperature ranges (0°C to 120°C and -25°C to 95°C). The effects of both conditions were measured using both HSI and interlaminar shear (ILSS) tests. No significant changes of the physical properties of the thermally cycled GFRP specimens were detected using interlaminar shear strength tests and optical microscopy. However, when using HIS, differences of the surface conditions were detected. The results showed that the different thermal loading conditions could be successfully clustered in different colours, using the HSI linear unmixing technique. Each different thermal loading condition showed a different chemical degradation level on its surface which was indicated using different colours.

  18. Gas-dynamic acceleration of laser-ablation plumes: Hyperthermal particle energies under thermal vaporization

    SciTech Connect

    Morozov, A. A.; Evtushenko, A. B.; Bulgakov, A. V.

    2015-02-02

    The expansion of a plume produced by low-fluence laser ablation of graphite in vacuum is investigated experimentally and by direct Monte Carlo simulations in an attempt to explain hyperthermal particle energies for thermally vaporized materials. We demonstrate that the translation energy of neutral particles, ∼2 times higher than classical expectations, is due to two effects, hydrodynamic plume acceleration into the forward direction and kinetic selection of fast particles in the on-axis region. Both effects depend on the collision number within the plume and on the particles internal degrees of freedom. The simulations allow ablation properties to be evaluated, such as ablation rate and surface temperature, based on time-of-flight measurements. Available experimental data on kinetic energies of various laser-produced particles are well described by the presented model.

  19. Role of mechanical loads in inducing in-cycle tensile stress in thermally grown oxide

    SciTech Connect

    Diaz, R.; Jansz, M.; Mossaddad, M.; Raghavan, S.; Okasinski, J.S.; Almer, J.D.; Perez, H.P.; Imbrie, P.

    2012-01-01

    Experimental in situ synchrotron x-ray diffraction results tracking the strain behavior of the various layers during a cycle, under thermo-mechanical conditions are presented in this work. The quantitative strain measurements here show that the thermally grown oxide briefly experiences in-plane tensile stress ({sigma}{sub 22} = +36.4 MPa) with increased mechanical loading during ramp-up in the thermal cycle. These findings are the first in situ experimental observations of these strains under thermo-mechanical conditions, envisaged to serve as a catalyst for crack initiation. The depth resolved measurements of strain taken during applied thermal and mechanical load in this work are a significant step towards achieving realistic testing conditions.

  20. Finite Element Modeling of Thermal Cycling Induced Microcracking in Carbon/Epoxy Triaxial Braided Composites

    NASA Technical Reports Server (NTRS)

    Zhang, Chao; Binienda, Wieslaw K.; Morscher, Gregory; Martin, Richard E.

    2012-01-01

    The microcrack distribution and mass change in PR520/T700s and 3502/T700s carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between -55 C and 120 C. Transverse microcrack morphology was investigated using X-ray Computed Tomography. Different performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied. Keywords: Thermal cycles; Microcrack; Finite Element Model; Braided Composite

  1. Positron annihilation lifetime evaluation of thermal cycling effects in atactic polystyrene

    SciTech Connect

    Kasbekar, A.D.; Jones, P.L.

    1989-01-01

    Positron annihilation lifetime spectroscopy (PALS) is an atomic-level probing technique that has been shown to be extremely sensitive to vacancy-type defects in a wide variety of solids. In amorphous and semicrystalline polymers this technique is uniquely sensitive to free-volume-based structural changes such as the glass transition. As such, PALS complements conventional macroscopic polymer characterization techniques. Positron annihilation lifetime spectroscopy (PALS) was used to investigate the thermal-cycling characteristics of two different-molecular-weight atactic polystyrene reins. Annealed compression-molded samples were thermally cycled over the temperature range 253 to 393 K with PAL spectra taken in 10 K increments upon both cooling and heating. The longest-lived component lifetime and intensity, indicative of orthopositronium pick-off, exhibit thermal dependencies that can be interpreted in a manner consistent with anticipated free-volume changes associated with structural transitions.

  2. Thermomechanical loading of multilayered cylindrical geometries in thermal cycling from 300 to 1300 K

    NASA Astrophysics Data System (ADS)

    Hendricks, R. C.; McDonald, G.; Mullen, R. L.; Braun, M. J.; Chung, B. T.; Padovan, J.

    The principal of multiple material layering is well known as an effective method of reducing heat transfer; however, thermal gradients can impose significant loads and lead to delamination and subsequent component failure. An analysis is developed and experimental data are discussed for the thermomechanical effects of multilayered materials on a heat sink substrate of cylindrical geometry subject to thermal cycling. The geometry is heated in cross-flow by a high-velocity flame and cooled in crossflow by ambient-temperature air from a critical flow orifice. Each layer of material possesses a threshold beyond which small changes in temperature or mechanical loading greatly influence the life in thermal cycling of the layered materials. Comparisons are made between the thermomechanical loads predicted by various numerical codes for the linear case and by a simplified analytic model.

  3. On the thermal efficiency of power cycles in finite time thermodynamics

    NASA Astrophysics Data System (ADS)

    Momeni, Farhang; Morad, Mohammad Reza; Mahmoudi, Ashkan

    2016-09-01

    The Carnot, Diesel, Otto, and Brayton power cycles are reconsidered endoreversibly in finite time thermodynamics (FTT). In particular, the thermal efficiency of these standard power cycles is compared to the well-known results in classical thermodynamics. The present analysis based on FTT modelling shows that a reduction in both the maximum and minimum temperatures of the cycle causes the thermal efficiency to increase. This is antithetical to the existing trend in the classical references. Under the assumption of endoreversibility, the relation between the efficiencies is also changed to {η }{{Carnot}}\\gt {η }{{Brayton}}\\gt {η }{{Diesel}}\\gt {η }{{Otto}}, which is again very different from the corresponding classical results. The present results benefit a better understanding of the important role of irreversibility on heat engines in classical thermodynamics.

  4. Compatibility and accelerated aging study for Li(Si)/FeS/sub 2 thermally activated batteries

    NASA Astrophysics Data System (ADS)

    Mead, J. W.; Searcy, J. Q.; Neiswander, P. N.; Poole, R. L.

    1983-12-01

    Thermally activated batteries using the lithium (silicon) iron disulfide (Li(Si)/FeS2) electrochemical system are used in weapons having a required storage life of 25 years and high reliability. A review of known data revealed no information on the compatibility of Li(Si)/FeS2 with the organic materials used in the system. The compatibility question is studied. Accelerated-aging data on pairs of materials were produced. In addition, a group of production batteries was aged and tested. Three aging temperatures were used during the one-year study. Gas analyses, electrical tests and mechanical tests were compared for control and aged samples. Two results, the depletion of oxygen and an increase in hydrogen in the compatibility and accelerated-aging samples, stimulated additional studies. No unexpected or significant changes were observed in the electrical or mechanical properties of the organic materials. Calorific output and chloride ion content of heat pellets indicated no degradation with aging. Ignition sensitivity and burn rate measurements suggested no heat pellet degradation. Oxygen content in aged lithium (silicon) anodes remained within acceptable limits. Single-cell tests and battery test results showed no degradation with aging.

  5. Investigation of hypersonic ramjet propulsion cycles using a ram accelerator test facility

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Chew, G.; De Turenne, J. A.; Dunmire, B.

    1991-01-01

    Experimental research on hypersonic propulsion using a ram accelerator test facility is presented. The gasdynamics of the ram accelerator has been studied experimentally in a 38-mm bore facility over the Mach number range of 2.5 to 8.5, using methane- and ethylene-based propellant mixtures. Three different propulsive modes, centered on the Chapman-Jouguet (C-J) detonation speed of the combustible gas, have been experimentally observed. Projectiles have been accelerated smoothly from velocities below to above the C-J speed within a single propellant mixture.

  6. Solar panel thermal cycling testing by solar simulation and infrared radiation methods

    NASA Technical Reports Server (NTRS)

    Nuss, H. E.

    1980-01-01

    For the solar panels of the European Space Agency (ESA) satellites OTS/MAROTS and ECS/MARECS the thermal cycling tests were performed by using solar simulation methods. The performance data of two different solar simulators used and the thermal test results are described. The solar simulation thermal cycling tests for the ECS/MARECS solar panels were carried out with the aid of a rotatable multipanel test rig by which simultaneous testing of three solar panels was possible. As an alternative thermal test method, the capability of an infrared radiation method was studied and infrared simulation tests for the ultralight panel and the INTELSAT 5 solar panels were performed. The setup and the characteristics of the infrared radiation unit using a quartz lamp array of approx. 15 sq and LN2-cooled shutter and the thermal test results are presented. The irradiation uniformity, the solar panel temperature distribution, temperature changing rates for both test methods are compared. Results indicate the infrared simulation is an effective solar panel thermal testing method.

  7. Structural-Phase Transformations of CuZn Alloy Under Thermal-Impact Cycling

    NASA Astrophysics Data System (ADS)

    Potekaev, A. I.; Chaplygina, A. A.; Kulagina, V. V.; Chaplygin, P. A.; Starostenkov, M. D.; Grinkevich, L. S.

    2017-02-01

    Using the Monte Carlo method, special features of structural - phase transformations in β-brass are investigated during thermal impact using thermal cycling as an example (a number of successive order - disorder and disorder - order phase transitions in the course of several heating - cooling cycles). It is shown that a unique hysteresis is observed after every heating and cooling cycle, whose presence indicates irreversibility of the processes, which suggests a difference in the structural - phase states both in the heating and cooling stages. A conclusion is drawn that the structural - phase transformations in the heating and cooling stages occur within different temperature intervals, where the thermodynamic stimuli of one or the other structural - phase state are low. This is also demonstrated both in the plots of configurational energy, long- and short-range order parameter, atomic structure variations, and structural - phase state distributions. Simultaneously, there coexist ordered and disordered phases and a certain collection of superstructure domains. This implies the presence of low - stability states in the vicinity of the order - disorder phase transition. The results of investigations demonstrate that the structural - phase transitions within two successive heating and cooling cycles at the same temperature are different in both stages. These changes, though not revolutionary, occur in every cycle and decrease with the increasing cycle number. In fact, the system undergoes training with a tendency towards a certain sequence of structural - phase states.

  8. Thermal energy storage for low grade heat in the organic Rankine cycle

    NASA Astrophysics Data System (ADS)

    Soda, Michael John

    Limits of efficiencies cause immense amounts of thermal energy in the form of waste heat to be vented to the atmosphere. Up to 60% of unrecovered waste heat is classified as low or ultra-low quality, making recovery difficult or inefficient. The organic Rankine cycle can be used to generate mechanical power and electricity from these low temperatures where other thermal cycles are impractical. A variety of organic working fluids are available to optimize the ORC for any target temperature range. San Diego State University has one such experimental ORC using R245fa, and has been experimenting with multiple expanders. One limitation of recovering waste heat is the sporadic or cyclical nature common to its production. This inconsistency makes sizing heat recovery ORC systems difficult for a variety of reasons including off-design-point efficiency loss, increased attrition from varying loads, unreliable outputs, and overall system costs. Thermal energy storage systems can address all of these issues by smoothing the thermal input to a constant and reliable level and providing back-up capacity for times when the thermal input is deactivated. Multiple types of thermal energy storage have been explored including sensible, latent, and thermochemical. Latent heat storage involves storing thermal energy in the reversible phase change of a phase change material, or PCM, and can have several advantages over other modalities including energy storage density, cost, simplicity, reliability, relatively constant temperature output, and temperature customizability. The largest obstacles to using latent heat storage include heat transfer rates, thermal cycling stability, and potentially corrosive PCMs. Targeting 86°C, the operating temperature of SDSU's experimental ORC, multiple potential materials were explored and tested as potential PCMs including Magnesium Chloride Hexahydrate (MgCl2˙6H2O), Magnesium Nitrate Hexahydrate (Mg(NO3)2˙6H 2O), montan wax, and carnauba wax. The

  9. Development and Use of Life-Cycle Analysis Capabilites To Evaluate, Select, and Implement Plans to Accelerate Hanford Site Cleanup

    SciTech Connect

    Shay, Michael R.; Johnson, Wayne L.; Frey, Jeffrey A.

    2004-02-28

    Over the past year the U.S. Department of Energy (DOE) has made significant progress in developing and executing plans to transform and accelerate cleanup of the Hanford Site. Notable progress has been in the cleanup of the River Corridor, including the relocation of spent nuclear fuel to the Central Plateau, and the stabilization of plutonium materials. However, difficult work still remains. DOE has already accelerated the completion of the Environmental Management (EM) cleanup mission from 2070 to 2035 and believes its completion can be achieved even sooner by reducing excess conservatism, substantively changing technical strategy and management approach, and making new front-end investments. Work is well under way in the detailed planning, analyses and decision making required to implement and support the execution of the accelerated cleanup program at Hanford. Various cleanup, contract, and regulatory approaches are being explored. DOE has instituted a process that allows DOE to efficiently explore and test alternative cleanup approaches using a life-cycle model. This paper provides a means to share the planning approach and the life-cycle modeling and analysis tools used with other sites and interested parties. This paper will be of particular interest to analysts performing similar planning and evaluations at other sites as well as provide insight into the current status of Hanford’s cleanup program and DOE’s plans for the future.

  10. Thermal-Cycling Behavior of Plasma-Sprayed Partially Stabilized Zirconia Coatings on High-Density Graphite Substrate

    NASA Astrophysics Data System (ADS)

    Sure, Jagadeesh; Thyagarajan, K.; Mallika, C.; Mudali, U. Kamachi

    2015-08-01

    The thermal cycling behavior of partially stabilized zirconia (PSZ)-coated by plasma-spray process on NiCrAlY bond-coated high-density (HD) graphite substrate was investigated. Thermal cycling was carried out at 600 and 750 °C under vacuum, up to 200 cycles. Each cycle comprised a 10-min heating followed by forced air cooling for 10 min down to room temperature. Characterization of the microstructure and the phase analysis of thermal-cycled PSZ coatings by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction (XRD), and Raman spectroscopy revealed the correlation between the microstructural/crystallographic phases and the mechanical integrity of the coating up to 200 cycles. Segmented and vertical cracks generated on the coating during thermal cycling were observed to propagate with increase in the number of cycles. Macrocracks and variations in elemental compositions were not observed until 200 cycles at 600 and 750 °C. XRD and Raman spectroscopic analysis confirmed the presence of nontransformable tetragonal phase only in all the thermal-cycled PSZ coatings, irrespective of temperature up to 200 cycles.

  11. Thermal shock and thermal cycling behaviour of amorphous a-C:H films on molybdenum substrates

    NASA Astrophysics Data System (ADS)

    Kny, E.; Winter, J.; Littmark, U.; Friedbacher, G.; Grasserbauer, M.; Waelbroeck, F.

    1988-07-01

    The thermal behaviour of a-C: H films (a stands for amorphous) deposited by the TEXTOR carbonization technique on molybdenum substrates was investigated in high power electron beam testing device for single and multiple shot sequences. The stationary thermal behaviour was also measured. The results for single shot testing are presented in a threshold damage diagram and show that the stability of a-C: H films on molybdenum is superior to that on steel. At higher or repeated loadings the films are converted gradually to molybdenum carbide. AES and SIMS depth profiling was used to investigate the concentration profiles and interface compositions of the films after various heat treatments. Their 1-h thermal stability on molybdenum extends to approximately 700°C in a stationary test. Results show that a-C: H films on molybdenum should be effective in shielding the molybdenum substrate from the plasma in a fusion device as long as the stated loading limits are not exceeded.

  12. Accelerated screening methods for determining chemical and thermal stability of refrigerant-lubricant mixtures, Part 1: Method assessment. Final report

    SciTech Connect

    Kauffman, R.

    1993-04-01

    This report presents results of a literature search performed to identify analytical techniques suitable for accelerated screening of chemical and thermal stabilities of different refrigerant/lubricant combinations. Search focused on three areas: Chemical stability data of HFC-134a and other non-chlorine containing refrigerant candidates; chemical stability data of CFC-12, HCFC-22, and other chlorine containing refrigerants; and accelerated thermal analytical techniques. Literature was catalogued and an abstract was written for each journal article or technical report. Several thermal analytical techniques were identified as candidates for development into accelerated screening tests. They are easy to operate, are common to most laboratories, and are expected to produce refrigerant/lubricant stability evaluations which agree with the current stability test ANSI/ASHRAE (American National Standards Institute/American Society of Heating, Refrigerating, and Air-Conditioning Engineers) Standard 97-1989, ``Sealed Glass Tube Method to Test the Chemical Stability of Material for Use Within Refrigerant Systems.`` Initial results of one accelerated thermal analytical candidate, DTA, are presented for CFC-12/mineral oil and HCFC-22/mineral oil combinations. Also described is research which will be performed in Part II to optimize the selected candidate.

  13. Thermal Change and the Dynamics of Multi-Host Parasite Life Cycles in Aquatic Ecosystems

    PubMed Central

    Barber, Iain; Berkhout, Boris W.; Ismail, Zalina

    2016-01-01

    Altered thermal regimes associated with climate change are impacting significantly on the physical, chemical, and biological characteristics of the Earth’s natural ecosystems, with important implications for the biology of aquatic organisms. As well as impacting the biology of individual species, changing thermal regimes have the capacity to mediate ecological interactions between species, and the potential for climate change to impact host–parasite interactions in aquatic ecosystems is now well recognized. Predicting what will happen to the prevalence and intensity of infection of parasites with multiple hosts in their life cycles is especially challenging because the addition of each additional host dramatically increases the potential permutations of response. In this short review, we provide an overview of the diverse routes by which altered thermal regimes can impact the dynamics of multi-host parasite life cycles in aquatic ecosystems. In addition, we examine how experimentally amenable host–parasite systems are being used to determine the consequences of changing environmental temperatures for these different types of mechanism. Our overarching aim is to examine the potential of changing thermal regimes to alter not only the biology of hosts and parasites, but also the biology of interactions between hosts and parasites. We also hope to illustrate the complexity that is likely to be involved in making predictions about the dynamics of infection by multi-host parasites in thermally challenged aquatic ecosystems. PMID:27252219

  14. Analyzing Nuclear Fuel Cycles from Isotopic Ratios of Waste Products Applicable to Measurement by Accelerator Mass Spectrometry

    SciTech Connect

    Biegalski, S R; Whitney, S M; Buchholz, B

    2005-08-24

    An extensive study was conducted to determine isotopic ratios of nuclides in spent fuel that may be utilized to reveal historical characteristics of a nuclear reactor cycle. This forensic information is important to determine the origin of unknown nuclear waste. The distribution of isotopes in waste products provides information about a nuclear fuel cycle, even when the isotopes of uranium and plutonium are removed through chemical processing. Several different reactor cycles of the PWR, BWR, CANDU, and LMFBR were simulated for this work with the ORIGEN-ARP and ORIGEN 2.2 codes. The spent fuel nuclide concentrations of these reactors were analyzed to find the most informative isotopic ratios indicative of irradiation cycle length and reactor design. Special focus was given to long-lived and stable fission products that would be present many years after their creation. For such nuclides, mass spectrometry analysis methods often have better detection limits than classic gamma-ray spectroscopy. The isotopic ratios {sup 151}Sm/{sup 146}Sm, {sup 149}Sm/{sup 146}Sm, and {sup 244}Cm/{sup 246}Cm were found to be good indicators of fuel cycle length and are well suited for analysis by accelerator mass spectroscopy.

  15. RCC1-dependent activation of Ran accelerates cell cycle and DNA repair, inhibiting DNA damage–induced cell senescence

    PubMed Central

    Cekan, Pavol; Hasegawa, Keisuke; Pan, Yu; Tubman, Emily; Odde, David; Chen, Jin-Qiu; Herrmann, Michelle A.; Kumar, Sheetal; Kalab, Petr

    2016-01-01

    The coordination of cell cycle progression with the repair of DNA damage supports the genomic integrity of dividing cells. The function of many factors involved in DNA damage response (DDR) and the cell cycle depends on their Ran GTPase–regulated nuclear–cytoplasmic transport (NCT). The loading of Ran with GTP, which is mediated by RCC1, the guanine nucleotide exchange factor for Ran, is critical for NCT activity. However, the role of RCC1 or Ran⋅GTP in promoting cell proliferation or DDR is not clear. We show that RCC1 overexpression in normal cells increased cellular Ran⋅GTP levels and accelerated the cell cycle and DNA damage repair. As a result, normal cells overexpressing RCC1 evaded DNA damage–induced cell cycle arrest and senescence, mimicking colorectal carcinoma cells with high endogenous RCC1 levels. The RCC1-induced inhibition of senescence required Ran and exportin 1 and involved the activation of importin β–dependent nuclear import of 53BP1, a large NCT cargo. Our results indicate that changes in the activity of the Ran⋅GTP–regulated NCT modulate the rate of the cell cycle and the efficiency of DNA repair. Through the essential role of RCC1 in regulation of cellular Ran⋅GTP levels and NCT, RCC1 expression enables the proliferation of cells that sustain DNA damage. PMID:26864624

  16. Application of an ultraminiature thermal neutron monitor for irradiation field study of accelerator-based neutron capture therapy.

    PubMed

    Ishikawa, Masayori; Tanaka, Kenichi; Endo, Satrou; Hoshi, Masaharu

    2015-03-01

    Phantom experiments to evaluate thermal neutron flux distribution were performed using the Scintillator with Optical Fiber (SOF) detector, which was developed as a thermal neutron monitor during boron neutron capture therapy (BNCT) irradiation. Compared with the gold wire activation method and Monte Carlo N-particle (MCNP) calculations, it was confirmed that the SOF detector is capable of measuring thermal neutron flux as low as 10(5) n/cm(2)/s with sufficient accuracy. The SOF detector will be useful for phantom experiments with BNCT neutron fields from low-current accelerator-based neutron sources.

  17. Application of an ultraminiature thermal neutron monitor for irradiation field study of accelerator-based neutron capture therapy

    PubMed Central

    Ishikawa, Masayori; Tanaka, Kenichi; Endo, Satrou; Hoshi, Masaharu

    2015-01-01

    Phantom experiments to evaluate thermal neutron flux distribution were performed using the Scintillator with Optical Fiber (SOF) detector, which was developed as a thermal neutron monitor during boron neutron capture therapy (BNCT) irradiation. Compared with the gold wire activation method and Monte Carlo N-particle (MCNP) calculations, it was confirmed that the SOF detector is capable of measuring thermal neutron flux as low as 105 n/cm2/s with sufficient accuracy. The SOF detector will be useful for phantom experiments with BNCT neutron fields from low-current accelerator-based neutron sources. PMID:25589504

  18. Thermal analysis of heat and power plant with high temperature reactor and intermediate steam cycle

    NASA Astrophysics Data System (ADS)

    Fic, Adam; Składzień, Jan; Gabriel, Michał

    2015-03-01

    Thermal analysis of a heat and power plant with a high temperature gas cooled nuclear reactor is presented. The main aim of the considered system is to supply a technological process with the heat at suitably high temperature level. The considered unit is also used to produce electricity. The high temperature helium cooled nuclear reactor is the primary heat source in the system, which consists of: the reactor cooling cycle, the steam cycle and the gas heat pump cycle. Helium used as a carrier in the first cycle (classic Brayton cycle), which includes the reactor, delivers heat in a steam generator to produce superheated steam with required parameters of the intermediate cycle. The intermediate cycle is provided to transport energy from the reactor installation to the process installation requiring a high temperature heat. The distance between reactor and the process installation is assumed short and negligable, or alternatively equal to 1 km in the analysis. The system is also equipped with a high temperature argon heat pump to obtain the temperature level of a heat carrier required by a high temperature process. Thus, the steam of the intermediate cycle supplies a lower heat exchanger of the heat pump, a process heat exchanger at the medium temperature level and a classical steam turbine system (Rankine cycle). The main purpose of the research was to evaluate the effectiveness of the system considered and to assess whether such a three cycle cogeneration system is reasonable. Multivariant calculations have been carried out employing the developed mathematical model. The results have been presented in a form of the energy efficiency and exergy efficiency of the system as a function of the temperature drop in the high temperature process heat exchanger and the reactor pressure.

  19. Open-cycle Ocean Thermal Energy Conversion (OTEC): Status and potential

    NASA Astrophysics Data System (ADS)

    Bharathan, D.

    1984-08-01

    Tropical oceans with a 20 C or more temperature difference between surface and deep water represent a vast resource of renewable thermal energy. One of the methods of harnessing this resource is an open-cycle Ocean Thermal Energy Conversion (OTEC) system utilizing steam evaporated from the surface water for powering the turbine. In this paper, the state of the art of research and component development, as related to heat and mass transfer processes, power production, noncondensable gas handling, and seawater flow hydraulics, are described through an illustrated preliminary design study of a 1-MW facility.

  20. The Influence of TIG Welding Thermal Cycles on HSLA-100 Steel Plate

    DTIC Science & Technology

    1993-11-01

    THERMAL CYCLES ON HSLA-100 STEEL PLATE Alan G. Fox Sanjiwan D. Bhole November 1993 Approved for public release; distribution is unlimited Prepared for...Cycles on HSLA-100 Steel Plate I. AUTHOR(S) N00167-93-WR-30331 Alan G3. Fox and Sanjiwan D. Bhole 7. PERFORMING ORGANIZATION MAMES(S) AND ADORESS(ES...welds were performed on U.S. Navy HSLA-100 steel . Power variations in these welds was achieved by altering the welding speed, voltage and current and

  1. Human Physiological Responses to Cycle Ergometer Leg Exercise During +Gz Acceleration

    NASA Technical Reports Server (NTRS)

    Chou, J. L.; Stad, N. J.; Barnes, P. R.; Leftheriotis, G. P. N.; Arndt, N. F.; Simonson, S.; Greenleaf, J. E.

    1998-01-01

    Spaceflight and bed-rest deconditioning decrease maximal oxygen uptake (aerobic power), strength, endurance capacity, and orthostatic tolerance. In addition to extensive use of muscular exercise conditioning as a countermeasure for the reduction in aerobic power (VO(sub 2max)), stimuli from some form of +Gz acceleration conditioning may be necessary to attenuate the orthostatic intolerance component of this deconditioning. Hypothesis: There will be no significant difference in the physiological responses (oxygen uptake, heart rate, ventilation, or respiratory exchange ratio) during supine exercise with moderate +Gz acceleration.

  2. Cell cycle of primitive hematopoietic progenitors decelerated in senescent mice is reactively accelerated after 2-Gy whole-body irradiation.

    PubMed

    Hirabayashi, Yoko; Tsuboi, Isao; Kuramoto, Kazunao; Kusunoki, Yoichiro; Inoue, Tohru

    2016-03-01

    Aging is considered to be a functional retardation of continuous xenobiotic responses over a lifetime after the developmental period; thus, the effects of ionizing radiation over a lifetime may be somewhat accounted for by a modifier of aging effects. This study was conducted to evaluate the possible/synergic effects of radiation during aging by determining cell-cycle parameters of hematopoietic stem cells/hematopoietic progenitor cells (HSCs/HPCs), such as the percent of cells in cycling, the generation doubling time, and the cumulative cycling-cell fraction, by bromodeoxyuridine-ultraviolet assay, which enables the determination of their cycling capacity in vivo. Colony-forming progenitor cells, such as colony-forming unit (CFU)-granulocyte/macrophage (GM), CFU in the spleen on day 9 (CFU-S9), and CFU-S on day 13 (CFU-S13) for mature, less mature, and immature HPCs, respectively, were evaluated in young and old mice (6 weeks and 21 months of age, respectively) with or without 2-Gy whole-body irradiation and a 4-week recovery period. Then, cell-cycle parameters were evaluated and compared. As a result, the generation doubling time of all types of HPC was prolonged by the irradiation in both young and old mouse groups, except that of CFU-S13 in old mice, which showed acceleration of the cell cycle following the irradiation. In addition, only CFU-S13 in irradiated old mice showed a significant increase in the cumulative cycling-cell-fraction ratio. Significant changes due to the effects of aging and irradiation on HPCs were observed only in the immature HPCs, i.e., the cell cycle of immature HPCs was suppressed by aging without irradiation and was, in contrast, accelerated as the cells recovered from radiation-induced damage. This suggests that the mechanisms of peripheral blood recovery after 2-Gy whole-body irradiation are markedly different between young and old mice, although 21-month-old mice showed almost the same level of recovery as the young mice.

  3. Observational Signatures of Thermal and Suprathermal Ion Acceleration at CME-Driven Interplanetary Shocks

    NASA Astrophysics Data System (ADS)

    Desai, M. I.; Smith, C. W.; Lee, M. A.; Dayeh, M. A.; Mason, G. M.

    2009-12-01

    Coronal Mass Ejection- or CME-driven interplanetary (IP) shocks are responsible for causing the so-called energetic storm particle (ESP) events observed at Earth. However, despite recent observational and theoretical advances, many important questions regarding such CME-associated particle events remain unanswered. This is because ESP events occur due to a confluence of numerous poorly understood physical effects all of whose contributions can vary with time and location. These effects include: the origin, structure, and obliquity of the shocks, the nature of wave-particle interactions and the type of turbulence that is present near the shocks, the distribution and composition of the seed populations, and the type of injection and acceleration processes involved. In this paper, we combine observations of ~0.1-0.5 MeV/nucleon O and Fe ions with that of the magnetic field near four CME-driven IP shocks observed at the Advanced Composition Explorer spacecraft to differentiate between shocks where the seed population is most likely dominated by thermal solar wind ions and those events where it is dominated by pre-existing suprathermal ions. In particular, we use the temporal evolution of (1) O and Fe intensities, (2) power-law spectral indices of O, (3) the Fe/O and C/O ratios, and (4) the magnetic field power spectrum to identify unique signatures that provide strong clues regarding the origin of the seed population. Such observational signatures may also be useful in modeling the properties of the so-called large gradual solar energetic particle (SEP) events that are primarily accelerated by CME shocks near the Sun.

  4. Non-thermal Electron Acceleration in Low Mach Number Collisionless Shocks. II. Firehose-mediated Fermi Acceleration and its Dependence on Pre-shock Conditions

    NASA Astrophysics Data System (ADS)

    Guo, Xinyi; Sironi, Lorenzo; Narayan, Ramesh

    2014-12-01

    Electron acceleration to non-thermal energies is known to occur in low Mach number (Ms <~ 5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D) particle-in-cell (PIC) plasma simulations, we showed in Paper I that electrons are efficiently accelerated in low Mach number (Ms = 3) quasi-perpendicular shocks via a Fermi-like process. The electrons bounce between the upstream region and the shock front, with each reflection at the shock resulting in energy gain via shock drift acceleration. The upstream scattering is provided by oblique magnetic waves that are self-generated by the electrons escaping ahead of the shock. In the present work, we employ additional 2D PIC simulations to address the nature of the upstream oblique waves. We find that the waves are generated by the shock-reflected electrons via the firehose instability, which is driven by an anisotropy in the electron velocity distribution. We systematically explore how the efficiency of wave generation and of electron acceleration depend on the magnetic field obliquity, the flow magnetization (or equivalently, the plasma beta), and the upstream electron temperature. We find that the mechanism works for shocks with high plasma beta (gsim 20) at nearly all magnetic field obliquities, and for electron temperatures in the range relevant for galaxy clusters. Our findings offer a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  5. Non-thermal electron acceleration in low Mach number collisionless shocks. II. Firehose-mediated Fermi acceleration and its dependence on pre-shock conditions

    SciTech Connect

    Guo, Xinyi; Narayan, Ramesh; Sironi, Lorenzo

    2014-12-10

    Electron acceleration to non-thermal energies is known to occur in low Mach number (M{sub s} ≲ 5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D) particle-in-cell (PIC) plasma simulations, we showed in Paper I that electrons are efficiently accelerated in low Mach number (M{sub s} = 3) quasi-perpendicular shocks via a Fermi-like process. The electrons bounce between the upstream region and the shock front, with each reflection at the shock resulting in energy gain via shock drift acceleration. The upstream scattering is provided by oblique magnetic waves that are self-generated by the electrons escaping ahead of the shock. In the present work, we employ additional 2D PIC simulations to address the nature of the upstream oblique waves. We find that the waves are generated by the shock-reflected electrons via the firehose instability, which is driven by an anisotropy in the electron velocity distribution. We systematically explore how the efficiency of wave generation and of electron acceleration depend on the magnetic field obliquity, the flow magnetization (or equivalently, the plasma beta), and the upstream electron temperature. We find that the mechanism works for shocks with high plasma beta (≳ 20) at nearly all magnetic field obliquities, and for electron temperatures in the range relevant for galaxy clusters. Our findings offer a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  6. Monoenergetic acceleration of a target foil by circularly polarized laser pulse in RPA regime without thermal heating

    SciTech Connect

    Khudik, V.; Yi, S. A.; Siemon, C.; Shvets, G.

    2012-12-21

    A kinetic model of the monoenergetic acceleration of a target foil irradiated by the circularly polarized laser pulse is developed. The target moves without thermal heating with constant acceleration which is provided by chirping the frequency of the laser pulse and correspondingly increasing its intensity. In the accelerated reference frame, bulk plasma in the target is neutral and its parameters are stationary: cold ions are immobile while nonrelativistic electrons bounce back and forth inside the potential well formed by ponderomotive and electrostatic potentials. It is shown that a positive charge left behind of the moving target in the ion tail and a negative charge in front of the target in the electron sheath form a capacitor whose constant electric field accelerates the ions of the target. The charge separation is maintained by the radiation pressure pushing electrons forward. The scalings of the target thickness and electromagnetic radiation with the electron temperature are found.

  7. Cycle-powered short radius (1.9M) centrifuge: exercise vs. passive acceleration

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Gundo, D. P.; Watenpaugh, D. E.; Mulenburg, G. M.; Marchman, N.; Looft-Wilson, R.; Hargens, A. R.

    1996-01-01

    A human-powered short-arm centrifuge is described. This centrifuge could be used during spaceflight to provide +Gz acceleration while subjects performed exercise, thus supplying two forms of weightlessness countermeasures. Results from a study of cardiovascular responses while using the centrifuge are presented.

  8. Effects of high temperature brazing and thermal cycling on mechanical properties of Hastelloy X.

    NASA Technical Reports Server (NTRS)

    Dicus, D. L.; Buckley, J. D.

    1973-01-01

    Data are presented on the effects of brazing alloy, brazing operation, thermal cycling, and combinations of these on the yield strength, elongation, ultimate tensile strength, and fatigue life of thin gage Hastelloy X. These data show that brazing with a Ni-Pd-Au alloy at 1461 K resulted in reductions of 35 percent in yield strength and elongation, 6 percent in ultimate tensile strength, and 18 percent in fatigue limit of Hastelloy X, as compared with as-received material. Subsequent exposure to 200 thermal cycles between 533 K and 1144 K after brazing caused further losses of 4 percent in yield strength, 8 percent in ultimate tensile strength, and 6 percent in fatigue limit.

  9. Effect of thermal cycling on the mechanical properties of 350-grade maraging steel

    SciTech Connect

    Viswanathan, U.K.; Kishore, R.; Asundi, M.K.

    1996-03-01

    The effects of retained austenite produced by thermal cycling on the mechanical properties of a precipitation-hardened 350-grade commercial maraging steel were examined. The presence of retained austenite caused decreases in the yield strength (YS) and ultimate tensile strength (UTS) and effected a significant increase in the tensile ductility. Increased impact toughness was also produced by this treatment. The mechanical stability of retained austenite was evaluated by tension and impact tests at subambient temperatures. A deformation-induced transformation of the austenite was manifested as load drops on the load-elongation plots at subzero temperatures. This transformation imparts excellent low-temperature ductility to the material. A wide range of strength, ductility, and toughness can be obtained by subjecting the steel to thermal cycling before the precipitation-hardening treatment.

  10. Thermal Cycling Absorption Process (TCAP): Instrument and Simulation Development Status at Los Alamos National Laboratory

    SciTech Connect

    Arias, Angela A.; Schmierer, Eric N.; Gettemy, Donald; Howard, David W.; Wermer, Joseph R.; Tuggle, Dale G.

    2005-07-15

    The Thermal Cycling Absorption Process (TCAP) Project at Los Alamos National Laboratory has been a collaborative effort with Savannah River Site to demonstrate the Tube-in-Tube (TnT) column design and to improve TCAP science. TnT TCAP is an alternative design which uses a liquid to thermally cycle the metal hydride packed column. Inert gas displacement tests and deuterium pulse tests have been performed on the TnT TCAP column. The inert gas displacement tests are designed to measure plug flow in the column while the deuterium pulse tests determine the separation ability of the column. A residual gas analyzer measures the gases in the exit stream and the experimental results are compared with pulse test model results.

  11. Radiation and Thermal Cycling Effects on EPC1001 Gallium Nitride Power Transistors

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Scheick, Leif Z.; Lauenstein, Jean M.; Casey, Megan C.; Hammoud, Ahmad

    2012-01-01

    Electronics designed for use in NASA space missions are required to work efficiently and reliably under harsh environment conditions. These include radiation, extreme temperatures, and thermal cycling, to name a few. Information pertaining to performance of electronic parts and systems under hostile environments is very scarce, especially for new devices. Such data is very critical so that proper design is implemented in order to ensure mission success and to mitigate risks associated with exposure of on-board systems to the operational environment. In this work, newly-developed enhancement-mode field effect transistors (FET) based on gallium nitride (GaN) technology were exposed to various particles of ionizing radiation and to long-term thermal cycling over a wide temperature range. Data obtained on control (un-irradiated) and irradiated samples of these power transistors are presented and the results are discussed.

  12. Reconstruction of the welding thermal cycle and determination of residual stresses from isotherm traces

    NASA Astrophysics Data System (ADS)

    Goldstein, R. V.; Kozintsev, V. M.; Kurov, D. A.; Popov, A. L.; Chelyubeev, D. A.

    2013-01-01

    The earlier method for reconstructing the welding thermal cycle from the dislocation of the temper colors and the cold weld joint boundaries was applied in the case of contact flash welding of rod samples. The possibility of using this method to determine the key parameters of the welding processes such as the approach speed of the welded rods, the temperature at the weld center at the beginning of cooling, and the time in which the characteristic temperature isotherm moves to the largest distance from the weld center, which allow one to reconstruct the temperature distribution curve near the weld at any time after the heating termination, was shown. The reconstructed thermal cycle was used to determine the residual stresses in the weld and in the heat-affected zone.

  13. Microstructural characterization and thermal cycling reliability of solders under isothermal aging and electrical current

    NASA Astrophysics Data System (ADS)

    Chauhan, Preeti Singh

    Solder joints on printed circuit boards provide electrical and mechanical connections between electronic devices and metallized patterns on boards. These solder joints are often the cause of failure in electronic packages. Solders age under storage and operational life conditions, which can include temperature, mechanical loads, and electrical current. Aging occurring at a constant temperature is called isothermal aging. Isothermal aging leads to coarsening of the bulk microstructure and increased interfacial intermetallic compounds at the solder-pad interface. The coarsening of the solder bulk degrades the creep properties of solders, whereas the voiding and brittleness of interfacial intermetallic compounds leads to mechanical weakness of the solder joint. Industry guidelines on solder interconnect reliability test methods recommend preconditioning the solder assemblies by isothermal aging before conducting reliability tests. The guidelines assume that isothermal aging simulates a "reasonable use period," but do not relate the isothermal aging levels with specific use conditions. Studies on the effect of isothermal aging on the thermal cycling reliability of tin-lead and tin-silver-copper solders are limited in scope, and results have been contradictory. The effect of electrical current on solder joints has been has mostly focused on current densities above 104A/cm2 with high ambient temperature (≥100oC), where electromigration, thermomigration, and Joule heating are the dominant failure mechanisms. The effect of current density below 104A/cm2 on temperature cycling fatigue of solders has not been established. This research provides the relation between isothermal aging and the thermal cycling reliability of select Sn-based solders. The Sn-based solders with 3%, 1%, and 0% silver content that have replaced tin-lead are studied and compared against tin-lead solder. The activation energy and growth exponents of the Arrhenius model for the intermetallic growth in

  14. Effects of Elevated Temperatures and Thermal Cycling on Ceramic Composite Materials

    DTIC Science & Technology

    1989-12-01

    the facilities of the materials laboratory at will. Larry Zawada provided the plates for me to use and gave me much information on the processing and...Fabrication All plates were manufactured at the Air Force Materials Laboratory under the supervision of Mr. Larry Zawada . The following processing...the room temperature, elevated temperature, and thermal cycling I portions of this study were conducted. Specimen Preparation. Mr. Larry Zawada

  15. Heat transfer deterioration in tubes caused by bulk flow acceleration due to thermal and frictional influences

    SciTech Connect

    Jackson, J. D.

    2012-07-01

    Severe deterioration of forced convection heat transfer can be encountered with compressible fluids flowing through strongly heated tubes of relatively small bore as the flow accelerates and turbulence is reduced because of the fluid density falling (as the temperature rises and the pressure falls due to thermal and frictional influence). The model presented here throws new light on how the dependence of density on both temperature and pressure can affect turbulence and heat transfer and it explains why the empirical equations currently available for calculating effectiveness of forced convection heat transfer under conditions of strong non-uniformity of fluid properties sometimes fail to reproduce observed behaviour. It provides a criterion for establishing the conditions under which such deterioration of heat transfer might be encountered and enables heat transfer coefficients to be determined when such deterioration occurs. The analysis presented here is for a gaseous fluid at normal pressure subjected strong non-uniformity of fluid properties by the application of large temperature differences. Thus the model leads to equations which describe deterioration of heat transfer in terms of familiar parameters such as Mach number, Reynolds number and Prandtl number. It is applicable to thermal power plant systems such as rocket engines, gas turbines and high temperature gas-cooled nuclear reactors. However, the ideas involved apply equally well to fluids at supercritical pressure. Impairment of heat transfer under such conditions has become a matter of growing interest with the active consideration now being given to advanced water-cooled nuclear reactors designed to operate at pressures above the critical value. (authors)

  16. Mechanical Properties of Anisotropic Conductive Adhesive Film Under Hygrothermal Aging and Thermal Cycling

    NASA Astrophysics Data System (ADS)

    Gao, Li-Lan; Chen, Xu; Gao, Hong

    2012-07-01

    Mechanical properties of anisotropic conductive adhesive film (ACF) were investigated experimentally under various environmental conditions. The temperature sweep test was conducted to investigate the effects of temperature on dynamical mechanical properties of the ACF. The ACF exhibited transitions to the glass state, viscoelastic state, and rubber state with increasing temperature, and its glass-transition temperature ( T g) was determined to be 149°C. The creep-recovery behaviors of the ACF were investigated, and it was found that the initial strains, instantaneous strains, and creep or recovery rates increased with increasing temperature. No obvious creep phenomenon was observed at low temperatures (≤0°C). The creep strain and creep rates at any time decreased with increasing hygrothermal aging time. The uniaxial tensile behaviors of the ACF were also investigated under hygrothermal aging and thermal cycling. The results show that the Young's modulus and tensile strength of the ACF decrease with increasing hygrothermal aging time; however, they increase at first and then decrease with increasing thermal cycling time. T g decreases slightly for the ACF after hygrothermal aging; however, it increases after thermal cycling.

  17. Thermal Cycling and Isothermal Deformation Response of Polycrystalline NiTi: Simulations vs. Experiment

    NASA Technical Reports Server (NTRS)

    Manchiraju, Sivom; Gaydosh, Darrell; Benafan, Othmane; Noebe, Ronald; Vaidyanathan, Raj; Anderson, Peter M.

    2011-01-01

    A recent microstructure-based FEM model that couples crystal-based plasticity, the B2<-> MB190 phase transformation and anisotropic elasticity at the grain scale is calibrated to recent data for polycrystalline NiTi (49.9 at.% Ni). Inputs include anisotropic elastic properties, texture and differential scanning calorimetry data, as well as a subset of recent isothermal deformation and load-biased thermal cycling data. The model is assessed against additional experimental data. Several experimental trends are captured - in particular, the transformation strain during thermal cycling monotonically increases and reaches a peak with increasing bias stress. This is achieved, in part, by modifying the martensite hardening matrix proposed by Patoor et al. [Patoor E, Eberhardt A, Berveiller M. J Phys IV 1996;6:277]. Some experimental trends are underestimated - in particular, the ratcheting of macrostrain during thermal cycling. This may reflect a model limitation that transformation-plasticity coupling is captured on a coarse (grain) scale but not on a fine (martensitic plate) scale.

  18. Thermal reliability analysis of a BLDC motor in a high-speed axial fan by the accelerated-life test and numerical methods

    NASA Astrophysics Data System (ADS)

    Hur, Jin-Huek; Lee, Tae-Gu; Moon, Sun-Ae; Lee, Sang-Jae; Yoo, Hoseon; Moon, Seung-Jae; Lee, Jae-Heon

    2008-09-01

    The thermal reliability of a closed-type BLDC motor for a high-speed fan is analyzed by an accelerated-life testing and numerical methods in this paper. Since a module and a motor part are integrated in a closed case, heat generated from a rotor in a motor and electronic components in the PCB module cannot be effectively removed to the outside. Therefore, the module will easily fail due to high temperature. The experiment for measuring the temperature and the surface heat flux of the electronic components is carried out to predict their surface temperature distributions and main heat sources. The accelerated-life test is accomplished to formulate the life equation depending on the environmental temperature. Moreover, the temperature of the PCB module is different from the environmental temperature since the heat generated from the motor cannot be effectively dissipated owing to the motor’s structure. Therefore a numerical method is used to predict the temperature of the PCB module, which is one of the life equation parameter, according to the environment. By numerically obtaining the maxima of the thermal stress and strain of the electronic components according to the operation environments with the temperature results, the fatigue cycle can be estimated.

  19. Thermal cycling reliability of indirect hybrid HgCdTe infrared detectors

    NASA Astrophysics Data System (ADS)

    Chen, Xing; He, Kai; Wang, Jian-xin; Zhang, Qin-yao

    2013-09-01

    Thermal cycling reliability is one of the most important issues whether the HgCdTe infrared focal plane array detectors can be applied to both military and civil fields. In this paper, a 3D finite element model for indirect hybrid HgCdTe infrared detectors is established. The thermal stress distribution and thermally induced warpage of the detector assembly as a function of the distance between the detector chip and Si-ROIC, the thickness and the materials properties of electrical lead board in cryogenic temperature are analyzed. The results show that all these parameters have influences on the thermal stress distribution and warpage of the detector assembly, especially the coefficient of thermal expansion(CTE) of electrical lead board. The thermal stress and warpage in the assembly can be avoided or minimized by choosing the appropriate electrical lead board. Additionally, the warpage of some indirect hybrid detectors assembly samples is measured in experiment. The experimental results are in good agreement with the simulation results, which verifies that the results are calculated by finite element method are reasonable.

  20. Simulation of the synergistic low Earth orbit effects of vacuum thermal cycling, vacuum UV radiation, and atomic oxygen

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; Degroh, Kim K.; Stidham, Curtis R.; Stueber, Thomas J.; Dever, Therese M.; Rodriguez, Elvin; Terlep, Judith A.

    1992-01-01

    In order to assess the low Earth orbit (LEO) durability of candidate space materials, it is necessary to use ground laboratory facilities which provide LEO environmental effects. A facility combining vacuum thermal cycling and vacuum ultraviolet (VUV) radiation has been designed and constructed at NASA Lewis Research Center for this purpose. This facility can also be operated without the VUV lamps. An additional facility can be used to provide VUV exposure only. By utilizing these facilities, followed by atomic oxygen exposure in an RF plasma asher, the effects of the individual vacuum thermal cycling and VUV environments can be compared to the effect of the combined vacuum thermal cycling/VUV environment on the atomic oxygen durability of materials. The synergistic effects of simulated LEO environmental conditions on materials were evaluated by first exposing materials to vacuum thermal cycling, VUV, and vacuum thermal cycling/VUV environments followed by exposure to atomic oxygen in an RP plasma asher. Candidate space power materials such as atomic oxygen protected polyimides and solar concentrator mirrors were evaluated using these facilities. Characteristics of the Vacuum Thermal Cycling/VUV Exposure Facility which simulates the temperature sequences and solar ultraviolet radiation exposure that would be experienced by a spacecraft surface in LEO are discussed. Results of durability evaluations of some candidate space power materials to the simulated LEO environmental conditions will also be discussed. Such results have indicated that for some materials, atomic oxygen durability is affected by previous exposure to thermal cycling and/or VUV exposure.

  1. Measured Thermal and Fast Neutron Fluence Rates for ATF-1 Holders During ATR Cycle 157D

    SciTech Connect

    Smith, Larry Don; Miller, David Torbet

    2016-03-01

    This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 157D which were measured by the Radiation Measurements Laboratory (RML) as requested by the Power Reactor Programs (ATR Experiments) Radiation Measurements Work Order. This report contains measurements of the fluence rates corresponding to the particular elevations relative to the 80-ft. core elevation. The data in this report consist of (1) a table of the ATR power history and distribution, (2) a hard copy listing of all thermal and fast neutron fluence rates, and (3) plots of both the thermal and fast neutron fluence rates. The fluence rates reported are for the average power levels given in the table of power history and distribution.

  2. Thermal analysis in a solar pumped laser for Mg energy cycle

    NASA Astrophysics Data System (ADS)

    Bagheri, Behgol; Uchidat, Shgeaki

    2012-10-01

    Thermal analysis of a high-power cw solar-pumped laser under development as a magnesium energy cycle driver has been conducted experimentally and analytically. The laser system is equipped with a Fresnel lens and a cone-shaped secondary mirror chamber (SMC). The SMC realizes a hybrid-pumping scheme combining axial- and side-pumping configurations to enhance solar light absorption to a rod-shaped laser medium. A non-uniform temperature profile was obtained during experiments due to combination of volumetric heating and surface cooling, which leads to a nonuniform variation of index of refraction in the laser medium. The thermal lensing and thermal stress-induced birefringence are analyzed.

  3. Thermal Modelling Analysis of Spiral Wound Supercapacitor under Constant-Current Cycling

    PubMed Central

    Wang, Kai; Li, Liwei; Yin, Huaixian; Zhang, Tiezhu; Wan, Wubo

    2015-01-01

    A three-dimensional modelling approach is used to study the effects of operating and ambient conditions on the thermal behaviour of the spiral wound supercapacitor. The transient temperature distribution during cycling is obtained by using the finite element method with an implicit predictor-multicorrector algorithm. At the constant current of 2A, the results show that the maximum temperature appears in core area. After 5 cycles, the maximum temperature is 34.5°C, while in steady state, it’s up to 42.5°C. This paper further studies the relationship between the maximum temperature and charge-discharge current. The maximum temperature will be more than 60°C after 5 cycles at the current of 4A, and cooling measurements should be taken at that time. It can provide thoughts on inner temperature field distribution and structure design of the spiral wound supercapacitor in working process. PMID:26444687

  4. Some effects of thermal-cycle-induced deformation in rocket thrust chambers

    NASA Technical Reports Server (NTRS)

    Hannum, N. P.; Price, R. G., Jr.

    1981-01-01

    The deformation process observed in the hot gas side wall of rocket combustion chambers was investigaged for three different liner materials. Five thrust chambers were cycled to failure by using hydrogen and oxygen as propellants at a chamber pressure of 4.14 MN/cu m. The deformation was observed nondestructively at midlife points and destructively after failure occurred. The cyclic life results are presented with an accompanying discussion about the problems of life prediction associated with the types of failures encountered in the present work. Data indicating the deformation of the thrust chamber liner as cycles are accumulated are presented for each of the test thrust chambers. From these deformation data and observation of the failure sites it is evident that modeling the failure process as classic low cycle thermal fatigue is inadequate as a life prediction method.

  5. Elastic-plastic finite-element analyses of thermally cycled single-edge wedge specimens

    NASA Technical Reports Server (NTRS)

    Kaufman, A.

    1982-01-01

    Elastic-plastic stress-strain analyses were performed for single-edge wedge alloys subjected to thermal cycling in fluidized beds. Three cases (NASA TAZ-8A alloy under one cycling condition and 316 stainless steel alloy under two cycling conditions) were analyzed by using the MARC nonlinear, finite-element computer program. Elastic solutions from MARC showed good agreement with previously reported solutions that used the NASTRAN and ISO3DQ computer programs. The NASA TAZ-8A case exhibited no plastic strains, and the elastic and elastic-plastic analyses gave identical results. Elastic-plastic analyses of the 316 stainless steel alloy showed plastic strain reversal with a shift of the mean stresses in the compressive direction. The maximum equivalent total strain ranges for these cases were 13 to 22 percent greater than that calculated from elastic analyses.

  6. Accelerating the Design of Solar Thermal Fuel Materials through High Throughput Simulations

    SciTech Connect

    Liu, Y; Grossman, JC

    2014-12-01

    Solar thermal fuels (STF) store the energy of sunlight, which can then be released later in the form of heat, offering an emission-free and renewable solution for both solar energy conversion and storage. However, this approach is currently limited by the lack of low-cost materials with high energy density and high stability. In this Letter, we present an ab initio high-throughput computational approach to accelerate the design process and allow for searches over a broad class of materials. The high-throughput screening platform we have developed can run through large numbers of molecules composed of earth-abundant elements and identifies possible metastable structures of a given material. Corresponding isomerization enthalpies associated with the metastable structures are then computed. Using this high-throughput simulation approach, we have discovered molecular structures with high isomerization enthalpies that have the potential to be new candidates for high-energy density STF. We have also discovered physical principles to guide further STF materials design through structural analysis. More broadly, our results illustrate the potential of using high-throughput ab initio simulations to design materials that undergo targeted structural transitions.

  7. Accelerating the design of solar thermal fuel materials through high throughput simulations.

    PubMed

    Liu, Yun; Grossman, Jeffrey C

    2014-12-10

    Solar thermal fuels (STF) store the energy of sunlight, which can then be released later in the form of heat, offering an emission-free and renewable solution for both solar energy conversion and storage. However, this approach is currently limited by the lack of low-cost materials with high energy density and high stability. In this Letter, we present an ab initio high-throughput computational approach to accelerate the design process and allow for searches over a broad class of materials. The high-throughput screening platform we have developed can run through large numbers of molecules composed of earth-abundant elements and identifies possible metastable structures of a given material. Corresponding isomerization enthalpies associated with the metastable structures are then computed. Using this high-throughput simulation approach, we have discovered molecular structures with high isomerization enthalpies that have the potential to be new candidates for high-energy density STF. We have also discovered physical principles to guide further STF materials design through structural analysis. More broadly, our results illustrate the potential of using high-throughput ab initio simulations to design materials that undergo targeted structural transitions.

  8. Marginal adaptation of class V composite restorations submitted to thermal and mechanical cycling

    PubMed Central

    CASSELLI, Denise Sá Maia; FARIA-E-SILVA, André Luis; CASSELLI, Henrique; MARTINS, Luis Roberto Marcondes

    2013-01-01

    Objective: This study evaluated the effect of the margin location and an adhesive system on the marginal adaptation of composite restorations. Material and Methods: Class V cavities were prepared in bovine teeth with the gingival margin on the dentin and the incisal margin on the enamel. The cavities were restored with a micro-hybrid composite resin using an etch-and-rinse [Single Bond 2 (SB)] or a self-etching adhesive [Clearfil SE Bond (CL)]. After finishing and polishing the restorations, epoxy replicas were prepared. The marginal adaptation was analyzed using scanning electronic microscopy (SEM, 500 x magnification). The higher gap width in each margin was recorded (T0). After the first evaluation, the samples were submitted to thermal cycling (2,000 cycles of 5ºC±2ºC followed by 55ºC±2ºC - T1) and mechanical cycling (100,000 cycles of 50 kN and 2 Hz - T2). Replicas of samples were rebuilt after each cycling and analyzed under SEM. The data were submitted to Mann-Whitney, Wilcoxon and Friedman testing (a=0.05). Results: The SB presented higher gaps in the dentin than the enamel, while there was no difference between the substrate for the CL. In the dentin, the CL showed better marginal sealing than the SB. The opposite occurred in the enamel. There were no significant differences between the baseline, thermal and mechanical cycling for any experimental condition. Conclusions: The outcomes of the present study showed that the adhesive system and margin location have an important effect on the marginal adaptation of composite restorations. PMID:23559115

  9. The Effect of Interface Roughness and Oxide Film Thickness on the Inelastic Response of Thermal Barrier Coatings to Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Pindera, Marek-Jerzy; Aboudi, Jacob; Arnold, Steven M.

    1999-01-01

    The effects of interfacial roughness and oxide film thickness on thermally-induced stresses in plasma-sprayed thermal barrier coatings subjected to thermal cycling are investigated using the recently developed higher-order theory for functionally graded materials. The higher-order theory is shown to be a viable alternative to the finite-element approach, capable of modeling different interfacial roughness architectures in the presence of an aluminum oxide layer and capturing the high stress gradients that occur at the top coat/bond coat interface. The oxide layer thickness is demonstrated to have a substantially greater effect on the evolution of residual stresses than local variations in interfacial roughness. Further, the location of delamination initiation in the top coat is predicted to change with increasing oxide layer thickness. This result can be used to optimize the thickness of a pre-oxidized layer introduced at the top coat/bond coat interface in order to enhance TBC durability as suggested by some researchers. The results of our investigation also support a recently proposed hypothesis regarding delamination initiation and propagation in the presence of an evolving bond coat oxidation, while pointing to the importance of interfacial roughness details and specimen geometry in modeling this phenomenon.

  10. Nitrogen cycling in Yellowstone National Park thermal features: using gene expression to reveal ecological function

    NASA Astrophysics Data System (ADS)

    Lafree, S. T.; Burton, M. S.; Meyer-Dombard, D. R.

    2010-12-01

    Studies of biodiversity, metabolic strategies, and functional ecology in modern hydrothermal systems have the potential to provide insight into the metabolism and evolution of life. The geochemical and microbial diversity present at Yellowstone National Park (YNP), Wyoming, USA, makes it an ideal place for studying the functional ecology and metabolic processes of prokaryotic organisms. While much work in terrestrial hydrothermal features is focused on phylogenetic and geochemical analyses, a few recent investigations in YNP and other hydrothermal areas have focused on “gene hunting”: screening thermal sediment and biofilm samples for the presence of genes utilized in specific metabolic processes [2, 3, 6, 7, 8]. Although research has evaluated and confirmed the presence of many of these genes in various thermophilic microbial communities, the existence of a gene in the DNA of an organism does not verify its use, and few researchers have done work to confirm the utilization (expression) of the genes discovered in thermal samples [1, 6, 7, 8]. Disequilibrium between reduced hydrothermal fluid of YNP thermal features and the atmosphere provides a copious source of potential energy to be harnessed through microbial metabolic processes, with NO3- and NO2- serving as the preferred electron acceptors and top energy sources after O2 [4, 5]. Consequentially, nitrogen cycling likely plays a vital role in microbial metabolic processes, as well as nutrient availability. This study explores the presence and utilization of functional genes that are key in steps of the nitrogen cycle, such as nitrogen fixation (NifH), denitrification (nirKS), and ammonia oxidation (amoA). Both DNA and RNA were extracted from thermal sediment and streamer biofilm communities collected in the chemosynthetic zone of various thermal features of the Sentinel Meadows Group in Lower Geyser Basin, YNP. Extracted DNA and reverse transcribed RNA (cDNA) were amplified using the polymerase chain

  11. Thermal-hydraulic design of the target/blanket for the accelerator production of tritium conceptual design

    SciTech Connect

    Willcutt, G.J.E. Jr.; Kapernick, R.J.

    1997-11-01

    A conceptual design was developed for the target/blanket system of an accelerator-based system to produce tritium. The target/blanket system uses clad tungsten rods for a spallation target and clad lead rods as a neutron multiplier in a blanket surrounding the target. The neutrons produce tritium in {sup 3}He, which is contained in aluminum tubes located in the decoupler and blanket regions. This paper presents the thermal-hydraulic design of the target, decoupler, and blanket developed for the conceptual design of the Accelerator Production of Tritium Project, and demonstrates there is adequate margin in the design at full power operation.

  12. Thermal Cycling Behavior of Thermal Barrier Coatings with MCrAlY Bond Coat Irradiated by High-Current Pulsed Electron Beam.

    PubMed

    Cai, Jie; Lv, Peng; Guan, Qingfeng; Xu, Xiaojing; Lu, Jinzhong; Wang, Zhiping; Han, Zhiyong

    2016-11-30

    Microstructural modifications of a thermally sprayed MCrAlY bond coat subjected to high-current pulsed electron beam (HCPEB) and their relationships with thermal cycling behavior of thermal barrier coatings (TBCs) were investigated. Microstructural observations revealed that the rough surface of air plasma spraying (APS) samples was significantly remelted and replaced by many interconnected bulged nodules after HCPEB irradiation. Meanwhile, the parallel columnar grains with growth direction perpendicular to the coating surface were observed inside these bulged nodules. Substantial Y-rich Al2O3 bubbles and varieties of nanocrystallines were distributed evenly on the top of the modified layer. A physical model was proposed to describe the evaporation-condensation mechanism taking place at the irradiated surface for generating such surface morphologies. The results of thermal cycling test showed that HCPEB-TBCs presented higher thermal cycling resistance, the spalling area of which after 200 cycles accounted for only 1% of its total area, while it was about 34% for APS-TBCs. The resulting failure mode, i.e., in particular, a mixed delamination crack path, was shown and discussed. The irradiated effects including compact remelted surface, abundant nanoparticles, refined columnar grains, Y-rich alumina bubbles, and deformation structures contributed to the formation of a stable, continuous, slow-growing, and uniform thermally grown oxide with strong adherent ability. It appeared to be responsible for releasing stress and changing the cracking paths, and ultimately greatly improving the thermal cycling behavior of HCPEB-TBCs.

  13. The cost of transport of human running is not affected, as in walking, by wide acceleration/deceleration cycles.

    PubMed

    Minetti, Alberto E; Gaudino, Paolo; Seminati, Elena; Cazzola, Dario

    2013-02-15

    Although most of the literature on locomotion energetics and biomechanics is about constant-speed experiments, humans and animals tend to move at variable speeds in their daily life. This study addresses the following questions: 1) how much extra metabolic energy is associated with traveling a unit distance by adopting acceleration/deceleration cycles in walking and running, with respect to constant speed, and 2) how can biomechanics explain those metabolic findings. Ten males and ten females walked and ran at fluctuating speeds (5 ± 0, ± 1, ± 1.5, ± 2, ± 2.5 km/h for treadmill walking, 11 ± 0, ± 1, ± 2, ± 3, ± 4 km/h for treadmill and field running) in cycles lasting 6 s. Field experiments, consisting of subjects following a laser spot projected from a computer-controlled astronomic telescope, were necessary to check the noninertial bias of the oscillating-speed treadmill. Metabolic cost of transport was found to be almost constant at all speed oscillations for running and up to ±2 km/h for walking, with no remarkable differences between laboratory and field results. The substantial constancy of the metabolic cost is not explained by the predicted cost of pure acceleration/deceleration. As for walking, results from speed-oscillation running suggest that the inherent within-stride, elastic energy-free accelerations/decelerations when moving at constant speed work as a mechanical buffer for among-stride speed fluctuations, with no extra metabolic cost. Also, a recent theory about the analogy between sprint (level) running and constant-speed running on gradients, together with the mechanical determinants of gradient locomotion, helps to interpret the present findings.

  14. Dislocation fiber interactions in short fiber reinforced metal matrix composites during creep and during thermal cycling

    SciTech Connect

    Eggeler, G.F.; Earthman, J.C.

    1997-12-22

    Short fiber reinforced metal matrix composites (SFR MMCs) are attractive engineering materials because they exhibit increased strength and wear resistance as compared to the fiber free matrix materials. For example, an aluminum alloy containing 15 volume percent of Al{sub 2}O{sub 3} fibers with average dimensions of 200 {micro}m length and 3 {micro}m diameter exhibits an improved creep strength with respect to the fiber free matrix. In addition to extended periods of isothermal and static creep loading high temperature components are subjected to temperature changes which are associated with thermal stresses. Thermal cycles can be due to start up and shut down events and can also be a consequence of anisothermal operating conditions. In short fiber reinforced aluminum alloys, in the stress and temperature range of interest, dislocation creep governs the deformation behavior of the MMC`s metallic matrix. It is therefore interesting to discuss the role of dislocations during creep and during thermal cycling of SFR MMCs. In the present paper the authors describe some basic dislocation mechanisms near the fiber/matrix-interface (FMI) of SFR MMCs. They first consider dislocation structures which are associated with the processing of SFR MMCs. Then dislocation processes which are associated with (1) static isothermal creep and (2) thermal cycling are discussed. Common and distinct features of the associated dislocation structures in the matrix zone near the FMI are highlighted. The authors then use the insight they have gained to qualitatively understand the role of dislocations in the macroscopic response of a SFR MMC under more complex load profiles.

  15. Systemic response to thermal injury in rats. Accelerated protein degradation and altered glucose utilization in muscle.

    PubMed Central

    Clark, A S; Kelly, R A; Mitch, W E

    1984-01-01

    Negative nitrogen balance and increased oxygen consumption after thermal injury in humans and experimental animals is related to the extent of the burn. To determine whether defective muscle metabolism is restricted to the region of injury, we studied protein and glucose metabolism in forelimb muscles of rats 48 h after a scalding injury of their hindquarters. This injury increased muscle protein degradation (PD) from 140 +/- 5 to 225 +/- 5 nmol tyrosine/g per h, but did not alter protein synthesis. Muscle lactate release was increased greater than 70%, even though plasma catecholamines and muscle cyclic AMP were not increased. Insulin dose-response studies revealed that the burn decreased the responsiveness of muscle glycogen synthesis to insulin but did not alter its sensitivity to insulin. Rates of net glycolysis and glucose oxidation were increased and substrate cycling of fructose-6-phosphate was decreased at all levels of insulin. The burn-induced increase in protein and glucose catabolism was not mediated by adrenal hormones, since they persisted despite adrenalectomy. Muscle PGE2 production was not increased by the burn and inhibition of prostaglandin synthesis by indomethacin did not inhibit proteolysis. The increase in PD required lysosomal proteolysis, since inhibition of cathepsin B with EP475 reduced PD. Insulin reduced PD 20% and the effects of EP475 and insulin were additive, reducing PD 41%. An inhibitor of muscle PD, alpha-ketoisocaproate, reduced burn-induced proteolysis 28% and lactate release 56%. The rate of PD in muscle of burned and unburned rats was correlated with the percentage of glucose uptake that was directed into lactate production (r = +0.82, P less than 0.01). Thus, a major thermal injury causes hypercatabolism of protein and glucose in muscle that is distant from the injury, and these responses may be linked to a single metabolic defect. PMID:6470144

  16. Thermal performance of gaseous-helium-purged tank-mounted multilayer insulation system during ground-hold and space-hold thermal cycling and exposure to water vapor

    NASA Technical Reports Server (NTRS)

    Sumner, I. E.

    1978-01-01

    An experimental investigation was conducted to determine (1) the ground-hold and space-hold thermal performance of a multilayer insulation (MLI) system mounted on a spherical, liquid-hydrogen propellant tank and (2) the degradation to the space-hold thermal performance of the insulation system that resulted from both thermal cycling and exposure to moisture. The propellant tank had a diameter of 1.39 meters (4.57ft). The MLI consisted of two blankets of insulation; each blanket contained 15 double-aluminized Mylar radiation shields separated by double silk net spacers. Nineteen tests simulating basic cryogenic spacecraft thermal (environmental) conditions were conducted. These tests typically included initial helium purge, liquid-hydrogen fill and ground-hold, ascent, space-hold, and repressurization. No significant degradation of the space-hold thermal performance due to thermal cycling was noted.

  17. Improvement of the duty cycle of an orthogonal acceleration time-of-flight mass spectrometer using ion gates.

    PubMed

    Brenton, A G; Krastev, T; Rousell, D J; Kennedy, M A; Craze, A S; Williams, C M

    2007-01-01

    A method to control the duty cycle of a time-of-flight mass spectrometer is described. The method relies on one or more ion gates placed in the beam path that have the function to transmit or stop the beam. These ion gates can switch from the open state to the closed state in tens of nanoseconds and effectively select portions of the mass range. The method is useful in circumstances where recording the complete mass spectrum is not an essential requirement, for example, in the analysis of known compounds where sensitivity and speed of operation are more important. It will be of benefit for applications in separation sciences with techniques involving fast chromatographic separations, where hundreds of mass spectra may be required per second. In such circumstances analytical identification may require only a limited number of masses (or mass regions) to be continuously monitored. Improvement of the duty cycle is particularly important for orthogonal-acceleration time-of-flight (oa-TOF) mass spectrometry instruments whose performance suffers from a low duty cycle. The duty cycle is not a constant for an instrument design but is a mass-dependent function and is least for smaller masses. The method described here is capable of raising the duty cycle to 100%. A theory is developed for one or more ion gate arrangements, for both linear- and reflectron-TOF systems. For a two-gate system the relationship between the positions of the first and second gates is described by a '2/3 rule'. Experimental results are shown for one-gate and two-gate operation, both in linear and in reflectron modes of operation, on an oa-TOF system built in-house.

  18. Thermodynamic systems analysis of open-cycle Ocean Thermal Energy Conversion (OTEC)

    NASA Astrophysics Data System (ADS)

    Parsons, B. K.; Bharathan, D.; Althof, J. A.

    1985-09-01

    This report describes an updated thermal-hydraulic systems analysis program called OTECSYS that studies the integrated performance of an open-cycle ocean thermal energy conversion (OTEC) plant, specifically, the effects of component performance, design parameters, and site specific resource data on the total system performance and plant size. OTECSYS can size the various open-cycle power cycle and hydraulic components. Models for the evaporator, mist eliminator, turbine-generator diffuser, direct-contact condenser, exhaust compressors, seawater pumps, and seawater piping are included, as are evaluations of the pressure drops associated with the intercomponent connections. It can also determine the required steam, cold seawater, and warm seawater flow rates. OTECSYS uses an approach similar to earlier work and integrates the most up-to-date developments in component performance and configuration. The program format allows the user to examine subsystem concepts not currently included by creating new component models. It will be useful to the OTEC plant designer who wants to quantify the design point sizing, performance, and power production using site-specific resource data. Detailed design trade-offs are easily evaluated, and several examples of these types of investigations are presented using plant size and power as criteria.

  19. Comparative Study on Accelerated Thermal Ageing of Vegetable Insulating Oil-paperboard and Mineral Oil-paperboard

    NASA Astrophysics Data System (ADS)

    Zhou, Zhu-Jun; Hu, Ting; Cheng, Lin; Tian, Kai; Yang, Jun; Wang, Xuan; Fang, Fu-Xin; Kong, Hai-Yang; Qian, Hang

    2016-05-01

    To comparatively study the insulation ageing life of vegetable insulating oil-paperboard and mineral oil-paperboard, we conducted accelerated thermal ageing experiments at 170°C. Then according to the temperature rise of vegetable insulating oil transformer, we conducted accelerated thermal ageing experiments at 150°C for vegetable insulating oil-paperboard and at 140°C for mineral oil-paperboard. The appearance, polymerization degree, and SEM microstructure of the paperboard after different ageing experiments were comparative analyzed. The results show that after the oil-paperboard system is accelerated ageing for 1 000 h at 170°C, that is equivalent to 20 years natural ageing, the structure of paperboard in vegetable insulating oil is damaged severely, which indicates that the lifetime of transformer are in the late stage; while the structure of paperboard in mineral oil maintain complete, and the polymerization degree is still above 500, which indicate that the lifetime of transformer are in the middle stage. The accelerated ageing rate of the vegetable insulating oil-paperboard system at 150°C is slower than that of the mineral oil-paperboard system, which indicates that the lifetime of the vegetable insulating oil-paperboard is longer than that of the mineral oil-paperboard.

  20. Asexual Queen Succession mediates an accelerated colony life cycle in the termite Silvestritermes minutus.

    PubMed

    Fougeyrollas, R; Křivánek, J; Roy, V; Dolejšová, K; Frechault, S; Roisin, Y; Hanus, R; Sillam-Dussès, D

    2017-03-09

    Mixed modes of reproduction, combining sexual processes with thelytokous parthenogenesis, occur in all major clades of social insects. In several species of termites, queens maximize their genetic input into non-dispersing replacement queens through parthenogenesis, while maintaining genetically diverse sterile offspring and dispersing reproductives via sexual reproduction. This so-called Asexual Queen Succession (AQS) has multiple independent origins and its presumed advantages are diverse as well, ranging from multiplication of colony reproductive potential to extension of its lifespan beyond that of the foundress. However, how AQS shapes colony life cycles under natural conditions remains poorly known. The neotropical termite Silvestritermes minutus inhabits small but conspicuous nests, offering a unique opportunity to investigate the impact of AQS on life history. We report on its breeding system, life cycle and sex allocation using social structure census in 137 nests and genotyping of 12 colonies at 12 microsatellite loci. We show that colonies are established by an outbred pair of primary reproductives. In less than two years, the foundress is replaced by multiple neotenic queens, arising mostly through automixis with central fusion. Sterile castes, male and most (93%) female dispersers are produced sexually. Colony reproduction is usually restricted to a single dispersal of alates with unbiased sex ratio, taking place after three years. We conclude that S. minutus benefits from AQS to maximize colony growth rate and alate production within a very short life cycle rather than to extend colony lifespan. This highlights the versatile role of AQS in different cases of its polyphyletic origin. This article is protected by copyright. All rights reserved.

  1. Simulated Solar Flare X-Ray and Thermal Cycling Durability Evaluation of Hubble Space Telescope Thermal Control Candidate Replacement Materials

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Banks, Bruce A.; Sechkar, Edward A.; Scheiman, David A.

    1998-01-01

    During the Hubble Space Telescope (HST) second servicing mission (SM2), astronauts noticed that the multilayer insulation (MLI) covering the telescope was damaged. Large pieces of the outer layer of MLI (aluminized Teflon fluorinated ethylene propylene (Al-FEP)) were torn in several locations around the telescope. A piece of curled up Al-FEP was retrieved by the astronauts and was found to be severely embrittled, as witnessed by ground testing. Goddard Space Flight Center (GSFC) organized a HST MLI Failure Review Board (FRB) to determine the damage mechanism of FEP in the HST environment, and to recommend replacement insulation material to be installed on HST during the third servicing mission (SM3) in 1999. Candidate thermal control replacement materials were chosen by the FRB and tested for environmental durability under various exposures and durations. This paper describes durability testing of candidate materials which were exposed to charged particle radiation, simulated solar flare x-ray radiation and thermal cycling under load. Samples were evaluated for changes in solar absorptance and tear resistance. Descriptions of environmental exposures and durability evaluations of these materials are presented.

  2. Acceleration of the Epoxy Resin-Dicyandiamide Cure Cycle by Trisubstituted Ureas.

    DTIC Science & Technology

    1981-06-01

    EPOXY RESIN- DICYANDIAMIDE CURE CYCLE BY TRISUBSTITUTED UREAS BERNARD R. LaLIBERTE, ROBERT E. SACHER, and JOSEPH BORNSTEIN POLYMER RESEARCH DIVISION...OEE ACCEERAIONOF THE EPOXY RESIN- DICYANDIAMIDE Finale t &EYCEBY YYISUBSTITUTED IJRtAS , PERPlIOOINCG EPORT NUER 7’-A~t!Q"aLS CONTRACT OR GRANT NUMBER(s...N’,N’-dimethylurea, or Diuron, N-(3,4-dichlorophenyl)-N’,Nl-dimethylurea, to epoxy resin- dicyandiamide mixtures significantly decreases the

  3. Analysis of Orbit Prediction Sensitivity to Thermal Emissions Acceleration Modeling for High Area-to-mass Ratio Objects

    NASA Astrophysics Data System (ADS)

    Kelecy, T.; Jah, M.

    High area-to-mass ratio (A/m) inactive resident space objects (RSOs) in the geosynchronous orbit (GEO) regime pose a hazard to active GEO RSOs. The combination of solar radiation pressure (SRP) and solar and lunar gravitational perturbations causes perturbations in the orbits of these RSOs. The high A/m nature of these RSOs results in greater sensitivity to SRP forces resulting in the perturbation of mean motion, inclination and eccentricity. The subsequent drift with respect to the Earth, combined with time varying orientation with respect to the sun and transitions into and out of Earth's shadow, results in many of these RSOs being "lost" after initial acquisition as they transition through periods of days to weeks out of view of observing sites. This work examines the sensitivity of the prediction accuracies to inadequate modeling of the thermal emissions component of the SRP acceleration in the force models. The simplest models treat the thermal emission term either implicitly, or as a term that is a function of a fixed surface temperature and area. In reality, the temperature can vary with time for inert objects (e.g. orbital debris) transitioning in to and out of Earth shadow. Additionally, the orientation dynamics result in thermal acceleration components that vary relative to the inertial reference frame, and in general, have components orthogonal to the sun-object line. The prediction uncertainties associated with thermal modeling, orientation dynamics and materials uncertainties are examined in terms of the SRP acceleration perturbations for a range of representative high A/m object characteristics. Results indicate that significant prediction errors result from inadequate accounting for the thermal emissions component when compared to the standard SRP models used. These errors need to be addressed in the orbit determination and prediction to allow for more accurate re-acquisition and tracking.

  4. The effect of laser treatment of WC-Co coatings on their failure under thermal cycling

    NASA Astrophysics Data System (ADS)

    Kasterov, Artur; Shugurov, Artur; Kazachenok, Marina; Panin, Alexey; Cheng, Chin-Hsiang; Chang, I.-Ling

    2016-11-01

    The given paper studies the effect of surface laser treatment of WC-Co coatings on their surface morphology, phase composition and thermal cycling behavior. The coatings were sprayed on stainless steel substrates with the use of a high velocity oxy fuel spraying process. Application of the scanning electron microscopy and X-ray diffraction showed that re-melting of the coating surface layer during laser treatment induced changes in its phase composition as well as the formation of regular rows of globular asperities on the coating surface. The latter resulted in a sharp increase in thermal shock resistance of the laser treated WC-Co coatings under water quench tests; its underlying mechanism are proposed and discussed in the paper.

  5. A photoelectrochemical-thermal hydrogen producing cycle involving a semiconductor liquid junction cell

    NASA Astrophysics Data System (ADS)

    Gissler, W.

    A photoelectrochemical-thermal hydrogen producing cycle is proposed involving a semiconductor liquid junction solar cell. In contrast with direct photoelectrolysis, the proposal is based upon a photoelectrochemical oxidation or reduction of the n- or p-type semiconductor electrode respectively in an aqueous electrolyte. In subsequent thermal reaction steps the water splitting process is completed, and the semiconductor electrode is regenerated. The advantage of the method is that semiconductors of band gap energies which are well matched to the solar spectrum can be used and correspondingly high solar energy conversion efficiencies can be obtained. The drawback is that the electrode regeneration process is in general quite complicated. The method is demonstrated by using a trigonal selenium electrode which allows a relatively simple regeneration. First experimental results on the photoelectrochemical reaction step are reported.

  6. Seawater test results of Open-Cycle Ocean Thermal Energy Conversion (OC-OTEC) components

    NASA Astrophysics Data System (ADS)

    Zangrando, F.; Bharathan, D.; Link, H.; Panchal, C. B.

    Key components of open-cycle ocean thermal energy conversion systems- the flash evaporator, mist eliminator, passive predeaerator, two surface condenser stages, and two direct-contact condenser stages- have been tested using seawater. These components operate at lower steam pressures and higher inlet noncondensable gas concentrations than do conventional power plant heat exchangers. The rate of heat exchanged between the evaporator and the condenser is on the order of 1.25MW-thermal, requiring a warm seawater flow of about 0.1 cu m/s; the cold seawater flow is on the order of half the warm water flow. In addition to characterizing the performance of the various components, the system has produced potable water from condensation of the steam produced in the evaporator. The information obtained in these tests is being used to design a larger scale experiment in which net power production is expected to be demonstrate for the first time using OC-OTEC technology.

  7. Improvements on APTC (Ambient Pressure Thermal Cycling) Chamber Regarding Temperature Homogeneity and Energy Consumption

    NASA Astrophysics Data System (ADS)

    Sollner, B.; Doring, D.

    2014-06-01

    This paper describes the working principles of IABG's Ambient Pressure Thermal Cycling chamber (an alternative to thermal-vacuum tests for some cases) and our activities to characterize and improve the system. For example a 3D grid of 64 temperature sensors was installed inside the test volume, in order to determine reliable temperature distribution data for standard operating conditions. Camera monitoring inside the temperature control / fan box allowed us to study the processes. A modification of the direct injection of liquid nitrogen (for efficient cooling) by installation of defined spray nozzles improved the temperature distribution. The characteristics of the original LN2 injection valve caused enormous consumption of liquid nitrogen and electrical power even at constant chamber temperatures. A new valve with a different control characteristic reduced this standby consumption remarkably.

  8. Heat-induced darkening and spectral broadening in photodarkened ytterbium-doped fiber under thermal cycling.

    PubMed

    Söderlund, Mikko J; Montiel i Ponsoda, Joan J; Koplow, Jeffrey P; Honkanen, Seppo

    2009-06-08

    We study thermal bleaching of photodarkening-induced loss in a 20-microm core diameter, large-mode-area ytterbium-doped silica fiber. Pristine and photodarkened samples are subjected to thermal cycling pulses. Recovery of the photodarkened fiber absorption coefficient initiates at approximately 350 degrees C and complete recovery is reached at approximately 625 degrees C. However, prior to recovery, the photodarkened fiber exhibits further heat-induced increase of absorption loss. This increase of loss is attributed to both a permanent increase of loss-inducing color centers and a temperature-dependent broadening of the absorption spectrum. Post-irradiation heat-induced formation of color centers suggests the presence of an intermediate energy state in the near-infrared photochemical mechanism for photodarkening.

  9. The Kepler Light Curve of V344 LYR: Constraining the Thermal-Viscous Limit Cycle Instability

    NASA Technical Reports Server (NTRS)

    Cannizzo, J. K.; Still, M. D.; Howell, S. B.; Wood, M. A.; Smale, A. P.

    2010-01-01

    We present time dependent modeling based on the accretion disk limit cycle model for a 90 d light curve of the short period SU UMa-type dwarf nova V344 Lyr taken by Kepler. The unprecedented precision and cadence (1 minute) far surpass that generally available for long term light curves. The data encompass a super outburst, preceded by three normal (i.e., short) outbursts and followed by two normal outbursts. The main decay of the super outburst is nearly perfectly exponential, decaying at a rate approx.12 d/mag, while the much more rapid decays of the normal outbursts exhibit a faster-than-exponential shape. We show that the standard limit cycle model can account for the light curve, without the need for either the thermal-tidal instability or enhanced mass transfer.

  10. Environmental cycling of cellulosic thermal insulation and its influence on fire performance

    SciTech Connect

    Lawson, J.R.

    1984-08-01

    A study was conducted on climatological data for eleven cities located throughout the United States. Findings from this environmental study were used to develop conditioning cycles for a research project on the influence of environments on the fire performance of loose-fill cellulosic thermal insulation. Six cellulosic insulation materials with different compositions of fire retardant chemicals at an add-on level of 25% by weight were specially manufactured for this study. These materials were tested for fire performance using the smoldering combustion test and the attic flooring radiant panel test to establish a baseline. After the materials were exposed to the various environmental cycles, they were tested for fire performance. Results from these tests show that environmental exposure can have a significant effect on the fire performance of cellulosic insulation materials and indicates that long term fire protection provided by fire retardant compounds may be limited.

  11. Axisymmetric deformation of plates and shells with phase trasformations under thermal cycling

    NASA Astrophysics Data System (ADS)

    Shkutin, L. I.

    2008-03-01

    A mathematical formulation is given of nonlinear axisymmetric buckling problems for plates and shells in the two-phase zones of austenite-to-martensite transformation. Numerical solutions of the direct-and inverse-transformation problems are used to construct hysteresis loops for thermomechanically cycled, pressure-loaded circular plates and shallow spherical domes of titanium nickelide (NiTi) alloy. It is shown that dynamic instability of the dome deformation process can occur during transformation under loads notably lower than the upper critical values for the isothermal states of the material outside the transformation zone. A theoretical analysis gives external loads below which the dome remains stable in the thermally cycled material with phase transformations.

  12. Diagnosis of Thermal Efficiency of Advanced Combined Cycle Power Plants Using Optical Torque Sensors

    NASA Astrophysics Data System (ADS)

    Umezawa, Shuichi

    A new optical torque measurement method was applied to diagnosis of thermal efficiency of advanced combined cycle, i.e. ACC, plants. Since the ACC power plant comprises a steam turbine and a gas turbine and both of them are connected to the same generator, it is difficult to identify which turbine in the plant deteriorates the performance when the plant efficiency is reduced. The sensor measures axial distortion caused by power transmission by use of He-Ne laser beams, small stainless steel reflectors having bar-code patterns, and a technique of signal processing featuring high frequency. The sensor was applied to the ACC plants of TOKYO ELECTRIC POWER COMPANY, TEPCO, following the success in the application to the early combined cycle plants of TEPCO. The sensor performance was inspected over a year. After an improvement related to the signal process, it is considered that the sensor performance has reached a practical use level.

  13. Open cycle OTEC thermal-hydraulic systems analysis and parametric studies

    NASA Astrophysics Data System (ADS)

    Patsons, B.; Bharathan, D.; Althof, J.

    1984-06-01

    An analytic thermohydraulic systems model of the power cycle an seawater supply systems for an open cycle ocean thermal energy conversion (OTEC) plant has been developed that allows ready examination of the effects of system and component operating points on plant size and parasitic power requirements. This paper presents the results of three parametric studies on the effects of system temperature distribution, plant gross electric capacity, and the allowable seawater velocity in the supply and discharge pipes. The paper also briefly discusses the assumptions and equations used in the model and the state-of-the-art component limitations. The model provides a useful tool for an OTEC plant designer to evaluate system trade-offs and define component interactions and performance.

  14. Rate equations modeling for hydrogen inventory studies during a real tokamak material thermal cycle

    NASA Astrophysics Data System (ADS)

    Bonnin, X.; Hodille, E.; Ning, N.; Sang, C.; Grisolia, Ch.

    2015-08-01

    Prediction and control of tritium inventory in plasma-facing components (PFCs) is a critical nuclear safety issue for ITER and future fusion devices. This goal can be achieved through rate equations models as presented here. We calibrate our models with thermal desorption spectrometry results to obtain a validated set of material parameters relevant to hydrogen inventory processes in bulk tungsten. The best fits are obtained with two intrinsic trap types, deep and shallow, and an extrinsic trap created by plasma irradiation and plastic deformation of the tungsten matrix associated with blister formation. We then consider a realistic cycle of plasma discharges consisting of 400 s of plasma exposure followed by a resting period of 1000 s, repeating for several hours. This cycle is then closed by a long "overnight" period, thus providing an estimate of the amount of tritium retained in the PFCs after a full day of standard operation.

  15. A complex life cycle in a warming planet: gene expression in thermally stressed sponges.

    PubMed

    Webster, N; Pantile, R; Botté, E; Abdo, D; Andreakis, N; Whalan, S

    2013-04-01

    Sponges are abundant, diverse and functionally important components of aquatic biotopes with crucial associations for many reef fish and invertebrates. Sponges have strict temperature optima, and mass mortality events have occurred after unusually high temperatures. To assess how sponges may adapt to thermal stress associated with a changing climate, we applied gene expression profiling to both stages of their bipartite life cycles. Adult Rhopaloeides odorabile are highly sensitive to thermal stress (32 °C), yet their larvae can withstand temperatures up to 36 °C. Here, we reveal the molecular mechanisms that underpin these contrasting thermal tolerances, which may provide sponges with a means to successfully disperse into cooler waters. Heat shock protein 70 was induced by increasing temperature in adult sponges, and genes involved in important biological functions including cytoskeleton rearrangement, signal transduction, protein synthesis/degradation, oxidative stress and detoxification were all negatively correlated with temperature. Conversely, gene expression in larvae was not significantly affected until 36 °C when a stress response involving extremely rapid activation of heat shock proteins occurred. This study provides the first transcriptomic assessment of thermal stress on both life history stages of a marine invertebrate facilitating better predictions of the long-term consequences of climate change for sponge population dynamics.

  16. Thermal effects on the clearance and stiffness of foil journal bearings for a Brayton cycle turboalternator

    NASA Technical Reports Server (NTRS)

    Eshel, A.

    1972-01-01

    An analysis of foil journal bearings for a NASA Brayton Cycle Unit (BRU) is presented. The study represents an extension of previous work in that it includes the effects of thermal expansion of foil-bearing components, as well as an improved model of the influence of foil flexure. The results presented give the bearing film thickness, the bearing stiffness, and the foil tension as functions of the operating temperatures and the elasto-hydrodynamic and geometrical parameters pertinent to the design of BRU foil bearings. A computer program for the evaluation of design data and for parametric studies is included.

  17. Effects of thermal and moisture cycling on the internal structure of stitched RTM laminates

    NASA Technical Reports Server (NTRS)

    Walker, Jeff; Roundy, Lance; Goering, Jon

    1993-01-01

    Conventional aerospace composites are strong and stiff in the directions parallel to the carbon fibers, but they are prone to delaminations and damage in the through-the-thickness directions. Recent research has shown that substantial improvements in damage tolerance are obtained from textile composites with Z-direction reinforcement provided by stitching, weaving, or braiding. Because of the mismatch in thermal and moisture expansion properties of the various material components, there is a potential for microcracks to develop in the resin matrix. These cracks can form to relieve the mechanical stresses that are generated during curing or in-service temperature cycles.

  18. Recent Advances in SRS on Hydrogen Isotope Separation Using Thermal Cycling Absorption Process

    DOE PAGES

    Xiao, Xin; Sessions, Henry T.; Heung, L. Kit

    2015-02-01

    The recent Thermal Cycling Absorption Process (TCAP) advances at Savannah River Site (SRS) include compressor-free concept for heating/cooling, push and pull separation using an active inverse column, and compact column design. The new developments allow significantly higher throughput and better reliability from 1/10th of the current production system’s footprint while consuming 60% less energy. Various versions are derived in the meantime for external customers to be used in fusion energy projects and medical isotope production.

  19. Structural and thermal interface characteristics of Stirling cycle cryocoolers for space applications

    NASA Technical Reports Server (NTRS)

    Boyle, R.; James, E.; Miller, P.; Arillo, V.; Sparr, L.; Castles, S.

    1991-01-01

    Integration of a Stirling cycle cryocooler into a flight system will require careful attention to the thermal, structural, and electrical interfaces between the cryocooler, the instrument and the spacecraft. These issues are currently under investigation by National Aeronautics and Space Administration/Goddard Space Flight Center personnel in laboratory tests of representative longlife cryocoolers. An 80 K cryocooler has been instrumented as a testbed for vibration control systems characterization. Initial vibration data using a new six-DOF force dynamometer is presented in this report.

  20. Thermal and Cycle-Life Behavior of Commercial Li-ion and Li-Polymer Cells

    NASA Technical Reports Server (NTRS)

    Zimmerman, Albert H.; Quinzio, M. V.

    2001-01-01

    Accelerated and real-time LEO cycle-life test data will be presented for a range of commercial Li-ion and Li-polymer (gel type) cells indicating the ranges of performance that can be obtained, and the performance screening tests that must be done to assure long life. The data show large performance variability between cells, as well as a highly variable degradation signature during non-cycling periods within the life tests. High-resolution Dynamic Calorimetry data will be presented showing the complex series of reactions occurring within these Li cells as they are cycled. Data will also be presented for cells being tested using an Adaptive Charge Control Algorithm (ACCA) that continuously adapts itself to changes in cell performance, operation, or environment to both find and maintain the optimum recharge over life. The ACCA has been used to prevent all unneeded overcharge for Li cells, NiCd cells and NiH2 cells. While this is important for all these cell types, it is most critical for Li-ion cells, which are not designed with electrochemical tolerance for overcharge.

  1. A Literature Review of Shock Sensitivity Changes of TATB Due to Thermal Cycling

    SciTech Connect

    Ritter, Boyd

    2016-07-15

    Insensitive high explosives (IHEs) based on 1,3,5-triamino 2,4,6-trinitro-benzene (TATB) are the IHEs of choice for use in nuclear warheads over conventional high explosives when safety is the only consideration, because they are very insensitive to thermal or mechanical initiation stimuli. It is this inherent insensitivity to high temperatures, shock, and impact, which provides detonation design challenges when designing TATB explosive systems while at the same time providing a significant level of protection against accidental initiation. Although classified as IHE, over the past few years the focus on explosive safety has demonstrated that the shock sensitivity of TATB is influenced with respect to temperature. A number of studies have been performed on TATB and TATB formulations, plastic bonded explosives (PBX) 9502, and LX-17-01 (LX-17), which demonstrates the increase in shock sensitivity of the explosive after it has been preheated or thermally cycled over various temperature ranges. Many studies suggest the change in sensitivity is partly due to the decomposition rates of the temperature elevated TATB. Others point to the coefficient of thermal expansion, the crystalline structures of TATB and/or the combination of all factors, which create voids which can become active hot spots. During thermal cycling, TATB is known to undergo an irreversible increase in specific volume called ratchet growth. This increase in specific volume correlates to a decrease in density. This decrease in density and increase in volume, demonstrate the creations of additional void spaces which could serve as potential new initiation hot spots thus, increasing the overall sensitivity of the HE. This literature review evaluates the published works to understand why the shock sensitivity of TATB-based plastic bonded explosives (PBXs) changes with temperature.

  2. Impact of cycling at low temperatures on the safety behavior of 18650-type lithium ion cells: Combined study of mechanical and thermal abuse testing accompanied by post-mortem analysis

    NASA Astrophysics Data System (ADS)

    Friesen, Alex; Horsthemke, Fabian; Mönnighoff, Xaver; Brunklaus, Gunther; Krafft, Roman; Börner, Markus; Risthaus, Tim; Winter, Martin; Schappacher, Falko M.

    2016-12-01

    The impact of cycling at low temperatures on the thermal and mechanical abuse behavior of commercial 18650-type lithium ion cells was compared to fresh cells. Post-mortem analyses revealed a deposition of high surface area lithium (HSAL) metal on the graphite surface accompanied by severe electrolyte decomposition. Heat wait search (HWS) tests in an accelerating rate calorimeter (ARC) were performed to investigate the thermal abuse behavior of aged and fresh cells under quasi-adiabatic conditions, showing a strong shift of the onset temperature for exothermic reactions. HSAL deposition promotes the reduction of the carbonate based electrolyte due to the high reactivity of lithium metal with high surface area, leading to a thermally induced decomposition of the electrolyte to produce volatile gaseous products. Nail penetration tests showed a change in the thermal runaway (TR) behavior affected by the decomposition reaction. This study indicates a greater thermal hazard for LIB cells at higher SOC and experiencing aging at low temperature.

  3. The effect of thermal cycling on the shear bond strength of porcelain/Ti-6Al-4V interfaces.

    PubMed

    Sendão, Isabel A; Alves, Alexandra C; Galo, Rodrigo; Toptan, Fatih; Silva, Filipe S; Ariza, Edith

    2015-04-01

    The aim of the study was to evaluate the effect of thermal cycling on the shear bond strength of the porcelain/Ti-6Al-4V interfaces prepared by two different processing routes and metallic surface conditions. Polished and SiO2 particle abraded Ti-6Al-4V alloy and Triceram bonder porcelain were used to produce the interfaces. Porcelain-to-metal specimens were processed by conventional furnace firing and hot pressing. Thermal cycling was performed in Fusayama's artificial saliva for 5000 cycles between 5 ± 1 and 60 ± 2°C. After thermal cycling, shear bond tests were carried out by using a custom-made stainless steel apparatus. The results were analyzed using t-Student test and non-parametric Kruskal-Wallis test (p<0.01). Most of the polished-fired specimens were fractured during thermal cycling; thus, it was not possible to obtain the shear bond strength results for this group. Sandblasted-fired, polished-hot pressed, and sandblasted-hot pressed specimens presented the shear bond strength values of 76.2 ± 15.9, 52.2 ± 23.6, and 59.9 ± 22.0 MPa, respectively. Statistical analysis indicated that thermal cycling affected the polished specimens processed by firing, whereas a significant difference was not observed on the other groups.

  4. Critical current retention of potted and unpotted REBCO Roebel cables under transverse pressure and thermal cycling

    NASA Astrophysics Data System (ADS)

    Talantsev, E. F.; Badcock, R. A.; Mataira, R.; Chong, S. V.; Bouloukakis, K.; Hamilton, K.; Long, N. J.

    2017-04-01

    Coated conductor Roebel cables are an effective way to create a high current density, fully transposed cable. However, despite REBCO tapes being robust against transverse stress, the Roebel architecture can concentrate transverse stress in non-trivial and random patterns depending on the exact arrangement of strands. If stands are embedded in a solid media which consolidates all strands then a transverse stress concentration will not occur. We tested this idea through mechanical and thermo-cycling tests on 5 strand Roebel cables. For non-impregnated cable irreversible degradation in critical currents is initiated at transverse pressures in a range of 4–34 MPa. Optical examination of the cables shows stress concentration patterns beyond those predicted by thickness variations. For cables impregnated with epoxy filled with SiO2 nanopowder, which has a similar thermal expansion coefficient to the metallic substrate of the strands, the irreversibility point is increased above our highest experimentally available pressure of 270 MPa. Thermo-cycling experiments confirmed a closely matched thermal expansion coefficient between the embedding media and metallic substrate is critical to avoid wire failures.

  5. X-ray measurements of the self-organization of martensitic variants during thermal cycling

    NASA Astrophysics Data System (ADS)

    Perez, Daniel; Sutton, Mark; Rogers, Michael

    The deformation of most types of metals involves an irreversible flow of crystallographic dislocations. This allows for their ductility. The deformation of a metallic shape memory alloy (SMA), on the other hand, is accommodated by a solid-solid phase transition. If deformed in the low-temperature martensitic phase, an SMA can be returned to its original shape by raising its temperature to the point where it changes back to its high-temperature parent phase. When the reverse occurs and the transformation is from parent to martensitic phase, an SMA goes from a high-symmetry to a low-symmetry state in which a number of martensitic variants are produced. We monitored the self-organization of these variants during cycles of periodic thermal driving. This was done using in situ X-ray Photon Correlation Scectroscopy (XPCS), which uses correlation from X-ray speckle to quantify the degree of microstructural change in a material. Our measurements revealed enhanced reversibility in the organization of the martensitic variants as the system evolved during repeated thermal cycling.

  6. Open-cycle ocean thermal energy conversion surface-condenser design analysis and computer program

    SciTech Connect

    Panchal, C.B.; Rabas, T.J.

    1991-05-01

    This report documents a computer program for designing a surface condenser that condenses low-pressure steam in an ocean thermal energy conversion (OTEC) power plant. The primary emphasis is on the open-cycle (OC) OTEC power system, although the same condenser design can be used for conventional and hybrid cycles because of their highly similar operating conditions. In an OC-OTEC system, the pressure level is very low (deep vacuums), temperature differences are small, and the inlet noncondensable gas concentrations are high. Because current condenser designs, such as the shell-and-tube, are not adequate for such conditions, a plate-fin configuration is selected. This design can be implemented in aluminum, which makes it very cost-effective when compared with other state-of-the-art vacuum steam condenser designs. Support for selecting a plate-fin heat exchanger for OC-OTEC steam condensation can be found in the sizing (geometric details) and rating (heat transfer and pressure drop) calculations presented. These calculations are then used in a computer program to obtain all the necessary thermal performance details for developing design specifications for a plate-fin steam condenser. 20 refs., 5 figs., 5 tabs.

  7. Open-cycle ocean thermal energy conversion surface-condenser design analysis and computer program

    NASA Astrophysics Data System (ADS)

    Panchal, C. B.; Rabas, T. J.

    1991-05-01

    This report documents a computer program for designing a surface condenser that condenses low-pressure steam in an ocean thermal energy conversion (OTEC) power plant. The primary emphasis is on the open-cycle (OC) OTEC power system, although the same condenser design can be used for conventional and hybrid cycles because of their highly similar operating conditions. In an OC-OTEC system, the pressure level is very low (deep vacuums), temperature differences are small, and the inlet noncondensable gas concentrations are high. Because current condenser designs, such as the shell-and-tube, are not adequate for such conditions, a plate-fin configuration is selected. This design can be implemented in aluminum, which makes it very cost-effective when compared with other state-of-the-art vacuum steam condenser designs. Support for selecting a plate-fin heat exchanger for OC-OTEC steam condensation can be found in the sizing (geometric details) and rating (heat transfer and pressure drop) calculations presented. These calculations are then used in a computer program to obtain all the necessary thermal performance details for developing design specifications for a plate-fin steam condenser.

  8. Characterization of coarse bainite transformation in low carbon steel during simulated welding thermal cycles

    SciTech Connect

    Lan, Liangyun; Kong, Xiangwei; Qiu, Chunlin

    2015-07-15

    Coarse austenite to bainite transformation in low carbon steel under simulated welding thermal cycles was morphologically and crystallographically characterized by means of optical microscope, transmission electron microscope and electron backscattered diffraction technology. The results showed that the main microstructure changes from a mixture of lath martensite and bainitic ferrite to granular bainite with the increase in cooling time. The width of bainitic laths also increases gradually with the cooling time. For a welding thermal cycle with relatively short cooling time (e.g. t{sub 8/5} is 30 s), the main mode of variant grouping at the scale of individual prior austenite grains changes from Bain grouping to close-packed plane grouping with the progress of phase transformation, which results in inhomogeneous distribution of high angle boundaries. As the cooling time is increased, the Bain grouping of variants becomes predominant mode, which enlarges the effective grain size of product phase. - Highlights: • Main microstructure changes and the width of lath structure increases with cooling time. • Variant grouping changes from Bain zone to close-packed plane grouping with the transformation. • The change of variant grouping results in uneven distribution of high angle grain boundary. • Bain grouping is main mode for large heat input, which lowers the density of high angle boundary.

  9. Laser High-Cycle Thermal Fatigue of Pulse Detonation Engine Combustor Materials Tested

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Fox, Dennis S.; Miller, Robert A.

    2001-01-01

    Pulse detonation engines (PDE's) have received increasing attention for future aerospace propulsion applications. Because the PDE is designed for a high-frequency, intermittent detonation combustion process, extremely high gas temperatures and pressures can be realized under the nearly constant-volume combustion environment. The PDE's can potentially achieve higher thermodynamic cycle efficiency and thrust density in comparison to traditional constant-pressure combustion gas turbine engines (ref. 1). However, the development of these engines requires robust design of the engine components that must endure harsh detonation environments. In particular, the detonation combustor chamber, which is designed to sustain and confine the detonation combustion process, will experience high pressure and temperature pulses with very short durations (refs. 2 and 3). Therefore, it is of great importance to evaluate PDE combustor materials and components under simulated engine temperatures and stress conditions in the laboratory. In this study, a high-cycle thermal fatigue test rig was established at the NASA Glenn Research Center using a 1.5-kW CO2 laser. The high-power laser, operating in the pulsed mode, can be controlled at various pulse energy levels and waveform distributions. The enhanced laser pulses can be used to mimic the time-dependent temperature and pressure waves encountered in a pulsed detonation engine. Under the enhanced laser pulse condition, a maximum 7.5-kW peak power with a duration of approximately 0.1 to 0.2 msec (a spike) can be achieved, followed by a plateau region that has about one-fifth of the maximum power level with several milliseconds duration. The laser thermal fatigue rig has also been developed to adopt flat and rotating tubular specimen configurations for the simulated engine tests. More sophisticated laser optic systems can be used to simulate the spatial distributions of the temperature and shock waves in the engine. Pulse laser high-cycle

  10. Brief constant light accelerates serotonergic re-entrainment to large shifts of the daily light/dark cycle.

    PubMed

    Kaur, G; Thind, R; Glass, J D

    2009-04-10

    Brief ( approximately 2 day) constant light exposure (LL(b)) in hamsters dramatically enhances circadian phase-resetting induced by the 5-HT receptor agonist, (+/-)-2-dipropyl-amino-8-hydroxyl-1,2,3,4-tetrahydronapthalene (8-OH-DPAT) and other nonphotic stimuli. The present study was undertaken to determine if LL(b) can also amplify phase-resetting responses to endogenous 5-HT and accelerate re-entrainment to large-magnitude advance and delay shifts of the light/dark (LD) cycle. First, central serotonergic activity was increased by i.p. injection of L-tryptophan+/-the 5-HT reuptake inhibitor fluoxetine. Hamsters under LD or exposed to LL(b) received vehicle or drugs during the early morning, and phase-shifts of the locomotor activity rhythm were measured after release to constant darkness. Neither drug phase-shifted animals not exposed to LL(b) (P>0.5 vs. vehicle); however in animals receiving LL(b,)L-tryptophan with and without fluoxetine produced large phase-advance shifts (means=2.5+/-0.4 h and 2.6+/-0.2 h, respectively; both P<0.035 vs. vehicle). Next, the effects of LL(b) combined with 8-OH-DPAT or L-tryptophan+fluoxetine on serotonergic re-entrainment to 10 h phase-advance and phase-delay shifts of the LD cycle were assessed. In groups not exposed to LL(b), vehicle controls re-entrained slowly to the advance and delay shifts (means=16+/-1 and 24+/-4 days, respectively), but those treated with 8-OH-DPAT re-entrained faster (means=11+/-2 and 9+/-2 days, respectively; both P<0.05 vs. vehicle). In groups exposed to LL(b), vehicle controls re-entrained slowly to the advance and delay shifts (means=15+/-2 and 25+/-3 days, respectively); however those receiving 8-OH-DPAT rapidly re-entrained to the delay and advance shifts, with the majority (75%) requiring only 1-2 days (means=2+/-1 and 4+/-2 days, respectively; both P<0.05 vs. vehicle). Animals exposed to LL(b) and treated with L-tryptophan+fluoxetine also exhibited accelerated re-entrainment to a 10 h advance

  11. Low cycle thermal fatigue testing of beryllium grades for ITER plasma facing components

    SciTech Connect

    Watson, R.D.; Youchison, D.L.; Dombrowski, D.E.; Guiniatouline, R.N.; Kupriynov, I.B.

    1996-02-01

    A novel technique has been used to test the relative low cycle thermal fatigue resistance of different grades of US and Russian beryllium, which is proposed as plasma facing armor for fusion reactor first wall, limiter, and divertor components. The 30 kW electron beam test system at Sandia National Laboratories was used to sweep the beam spot along one direction at 1 Hz. This produces a localized temperature ``spike`` of 750{degree}C for each pass of the beam. Large thermal stresses in excess of the yield strength are generated due to very high spot heat flux, 250 MW/m{sup 2}. Cyclic plastic strains on the order of 0.6% produced visible cracking on the heated surface in less than 3000 cycles. An in-vacuo fiber optic borescope was used to visually inspect the beryllium surfaces for crack initiation. Grades of US beryllium tested included: S-65C, S- 65H, S-200F, S-200F-H, SR-200, I-400, extruded high purity, HIP`d spherical powder, porous beryllium (94% and 98% dense), Be/30% BeO, Be/60% BeO, and TiBe{sub 12}. Russian grades included: TGP-56, TShGT, DShG-200, and TShG-56. Both the number of cycles to crack initiation, and the depth of crack propagation, were measured. The most fatigue resistant grades were S-65C, DShG-200, TShGT, and TShG-56. Rolled sheet Be (SR-200) showed excellent crack propagation resistance in the plane of rolling, despite early formation of delamination cracks. Only one sample showed no evidence of surface melting, Extruded (T). Metallographic and chemical analyses are provided. Good agreement was found between the measured depth of cracks and a 2-D elastic-plastic finite element stress analysis.

  12. Accelerated sulfur cycle in coastal marine sediment beneath areas of intensive shellfish aquaculture.

    PubMed

    Asami, Hiroki; Aida, Masato; Watanabe, Kazuya

    2005-06-01

    Prokaryotes in marine sediments taken from two neighboring semi-enclosed bays (the Yamada and Kamaishi bays) at the Sanriku coast in Japan were investigated by the culture-independent molecular phylogenetic approach coupled with chemical and activity analyses. These two bays were chosen in terms of their similar hydrogeological and chemical characteristics but different usage modes; the Yamada bay has been used for intensive shellfish aquaculture, while the Kamaishi bay has a commercial port and is not used for aquaculture. Substantial differences were found in the phylogenetic composition of 16S rRNA gene clone libraries constructed for the Yamada and Kamaishi sediments. In the Yamada library, phylotypes affiliated with delta-Proteobacteria were the most abundant, and those affiliated with gamma-Proteobacteria were the second-most abundant. In contrast, the Kamaishi library was occupied by phylotypes affiliated with Planctomycetes, gamma-Proteobacteria, delta-Proteobacteria, and Crenarchaeota. In the gamma-Proteobacteria, many Yamada phylotypes were related to free-living and symbiotic sulfur oxidizers, whereas the Kamaishi phylotype was related to the genus Pseudomonas. These results allowed us to hypothesize that sulfate-reducing and sulfur-oxidizing bacteria have become abundant in the Yamada sediment. This hypothesis was supported by quantitative competitive PCR (qcPCR) with group-specific primers. The qcPCR also suggested that organisms closely related to Desulfotalea in the Desulfobulbaceae were the major sulfate-reducing bacteria in these sediments. In addition, potential sulfate reduction and sulfur oxidation rates in the sediment samples were determined, indicating that the sulfur cycle has become active in the Yamada sediment beneath the areas of intensive shellfish aquaculture.

  13. Biological soil crusts accelerate the nitrogen cycle through large NO and HONO emissions in drylands

    PubMed Central

    Wu, Dianming; Tamm, Alexandra; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J.; Su, Hang; Pöschl, Ulrich

    2015-01-01

    Reactive nitrogen species have a strong influence on atmospheric chemistry and climate, tightly coupling the Earth’s nitrogen cycle with microbial activity in the biosphere. Their sources, however, are not well constrained, especially in dryland regions accounting for a major fraction of the global land surface. Here, we show that biological soil crusts (biocrusts) are emitters of nitric oxide (NO) and nitrous acid (HONO). Largest fluxes are obtained by dark cyanobacteria-dominated biocrusts, being ∼20 times higher than those of neighboring uncrusted soils. Based on laboratory, field, and satellite measurement data, we obtain a best estimate of ∼1.7 Tg per year for the global emission of reactive nitrogen from biocrusts (1.1 Tg a−1 of NO-N and 0.6 Tg a−1 of HONO-N), corresponding to ∼20% of global nitrogen oxide emissions from soils under natural vegetation. On continental scales, emissions are highest in Africa and South America and lowest in Europe. Our results suggest that dryland emissions of reactive nitrogen are largely driven by biocrusts rather than the underlying soil. They help to explain enigmatic discrepancies between measurement and modeling approaches of global reactive nitrogen emissions. As the emissions of biocrusts strongly depend on precipitation events, climate change affecting the distribution and frequency of precipitation may have a strong impact on terrestrial emissions of reactive nitrogen and related climate feedback effects. Because biocrusts also account for a large fraction of global terrestrial biological nitrogen fixation, their impacts should be further quantified and included in regional and global models of air chemistry, biogeochemistry, and climate. PMID:26621714

  14. Biological soil crusts accelerate the nitrogen cycle through large NO and HONO emissions in drylands.

    PubMed

    Weber, Bettina; Wu, Dianming; Tamm, Alexandra; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J; Su, Hang; Pöschl, Ulrich

    2015-12-15

    Reactive nitrogen species have a strong influence on atmospheric chemistry and climate, tightly coupling the Earth's nitrogen cycle with microbial activity in the biosphere. Their sources, however, are not well constrained, especially in dryland regions accounting for a major fraction of the global land surface. Here, we show that biological soil crusts (biocrusts) are emitters of nitric oxide (NO) and nitrous acid (HONO). Largest fluxes are obtained by dark cyanobacteria-dominated biocrusts, being ∼20 times higher than those of neighboring uncrusted soils. Based on laboratory, field, and satellite measurement data, we obtain a best estimate of ∼1.7 Tg per year for the global emission of reactive nitrogen from biocrusts (1.1 Tg a(-1) of NO-N and 0.6 Tg a(-1) of HONO-N), corresponding to ∼20% of global nitrogen oxide emissions from soils under natural vegetation. On continental scales, emissions are highest in Africa and South America and lowest in Europe. Our results suggest that dryland emissions of reactive nitrogen are largely driven by biocrusts rather than the underlying soil. They help to explain enigmatic discrepancies between measurement and modeling approaches of global reactive nitrogen emissions. As the emissions of biocrusts strongly depend on precipitation events, climate change affecting the distribution and frequency of precipitation may have a strong impact on terrestrial emissions of reactive nitrogen and related climate feedback effects. Because biocrusts also account for a large fraction of global terrestrial biological nitrogen fixation, their impacts should be further quantified and included in regional and global models of air chemistry, biogeochemistry, and climate.

  15. Thermochemical cycles for energy storage: Thermal decomposition of ZnCO{sub 4} systems. Final topical report, January 1, 1982--December 31, 1984

    SciTech Connect

    Wentworth, W.E.

    1992-04-01

    The overall objective of our research has been to develop thermochemical cycles that can be used for energy storage. A specific cycle involving ammonium hydrogen sulfate (NH{sub 4}HSO{sub 4}) has been proposed. Each reaction in the proposed cycle has been examined experimentally. Emphasis has been placed on the basic chemistry of these reactions. In the concluding phase of this research, reported herein, we have shown that when NH{sub 4}HSO{sub 4} is mixed with ZnO and decomposed, the resulting products can be released stepwise (H{sub 2}A{sub (g)} at {approximately}163{degrees}C, NH{sub 3(g)} at 365--418{degrees}C, and a mixture of SO{sub 2(g)} and SO{sub 3(g)} at {approximately}900{degrees}C) and separated by controlling the reaction temperature. Side reactions do not appear to be significant and the respective yields are high as would be required for the successful use of this energy storage reaction in the proposed cycle. Thermodynamic, kinetic, and other reaction parameters have been measured for the various steps of the reaction. Finally we have completed a detailed investigation of one particular reaction: the thermal decomposition of zinc sulfate (ZnSO{sub 4}). We have demonstrated that this reaction can be accelerated and the temperature required reduced by the addition of excess ZnO, V{sub 2}A{sub 5} and possibly other metal oxides.

  16. Characterization of tin crystal orientation evolution during thermal cycling in lead-free solder joints

    NASA Astrophysics Data System (ADS)

    Zhou, Bite

    To address the long term reliability of lead-free solder joints in electronic devices during thermal cycling, the fundamental understanding of deformation mechanisms was studied using polarized light optical microscopy (PLM), electron backscatter diffraction (EBSD) in scanning electron microscopy (SEM), and synchrotron X-ray diffraction (XRD). Near-eutectic Sn-3.0(wt %) Ag-0.5(wt %) Cu (SAC305) lead-free solder joints were assessed in three different package designs: low-strain plastic ball grid array (PBGA), medium-strain fine-pitch ball grid array (BGA), and high-strain wafer-level-chip-scale package (WLCSP). The effect of microstructure evolution on solder failure is correlated with dislocation slip activities. The major failure mode in lead-free solder joints during thermal cycling that causes the electrical failure of the device is cracking in the bulk Sn near the Si chip/solder interface. Microstructure and Sn grain orientation evolution usually precedes crack development. A combined approach of both statistical analysis of a large number of solder joints, and detailed studies of individual solder balls was used to investigate the causes of fracture. Sn crystal orientation evolution and its effect on deformation was characterized in solder joints with different thermal histories, and compared with those from other package designs with different effective strain levels. The relationship between the initial dominant and localized recrystallized Sn grain orientations on crack development was investigated. It is found that in the low-strain package design, cracking is strongly correlated with Sn grain orientations with the [001] direction (c-axis) nearly aligned with the chip/solder interface. But no cracks were observed in solder balls with dominant orientations that have the c-axis normal to the interface plane. In higher-strain packages, however, cracking occurred in a variety of Sn grain orientations, and even solder balls with dominant orientations that are

  17. Accelerated aging of thermally activated batteries which utilize the Li/Si//LiCl-KCl/FeS2 system

    NASA Astrophysics Data System (ADS)

    Searcy, J. Q.; Neiswander, P. A.

    The thermally activated Li(Si)/LiCl-KCl/FeS2 batteries considered are intended for applications which require high reliability and a shelf life of 25 years. In order to determine the feasibility of achieving these requirements, an accelerated aging study was undertaken. The major objective of this work was to identify deleterious chemical reactions that could affect performance and reliability during the 25 year shelf life. The approach used was to accelerate the aging of batteries by storage at elevated temperature, and then to examine and analyze materials from some batteries, while discharging others. The results of the study indicate that the reaction of Li(Si) with water outgassed from the various battery parts is deleterious to shelf life. No other deleterious effects were observed.

  18. Computational fluid dynamic (CFD) investigation of thermal uniformity in a thermal cycling based calibration chamber for MEMS

    NASA Astrophysics Data System (ADS)

    Gui, Xulong; Luo, Xiaobing; Wang, Xiaoping; Liu, Sheng

    2015-12-01

    Micro-electrical-mechanical system (MEMS) has become important for many industries such as automotive, home appliance, portable electronics, especially with the emergence of Internet of Things. Volume testing with temperature compensation has been essential in order to provide MEMS based sensors with repeatability, consistency, reliability, and durability, but low cost. Particularly, in the temperature calibration test, temperature uniformity of thermal cycling based calibration chamber becomes more important for obtaining precision sensors, as each sensor is different before the calibration. When sensor samples are loaded into the chamber, we usually open the door of the chamber, then place fixtures into chamber and mount the samples on the fixtures. These operations may affect temperature uniformity in the chamber. In order to study the influencing factors of sample-loading on the temperature uniformity in the chamber during calibration testing, numerical simulation work was conducted first. Temperature field and flow field were simulated in empty chamber, chamber with open door, chamber with samples, and chamber with fixtures, respectively. By simulation, it was found that opening chamber door, sample size and number of fixture layers all have effects on flow field and temperature field. By experimental validation, it was found that the measured temperature value was consistent with the simulated temperature value.

  19. CO{sub 2} looping cycle performance of a high-purity limestone after thermal activation/doping

    SciTech Connect

    Vasilije Manovic; Edward J. Anthony; Gemma Grasa; J. Carlos Abanades

    2008-09-15

    The influence of thermal pretreatment on the performance of a high-purity limestone (La Blanca) during CO{sub 2} capture cycles is investigated in this paper. This limestone was chosen for more detailed investigation because, in earlier research, it failed to show any favorable effect as a result of thermal pretreatment. Here, the original sample, with a particle size of 0.4-0.6 mm, and ground samples were thermally pretreated at 1000-1200{sup o}C, for 6-24 h, and then subjected to several carbonation/calcination cycles in a thermogravimetric analyzer (TGA). This work shows that thermal pretreatment failed to produce a significant self-reactivation effect during CO{sub 2} cycles, despite the use of a wide range of conditions during pretreatment (grinding, temperature, and pretreatment duration) as well as during cycling (CO{sub 2} concentration and duration of the carbonation stage). Additional doping experiments showed that both high Na content and lack of Al in La Blanca limestone cause poor self-reactivation performance after thermal pretreatment. Scanning electron microscope-energy-dispersive X-ray (SEM-EDX) analyses also confirmed more pronounced sintering and loss of activity, which we believe are caused by the relatively high Na content. However, stabilization of sorbent particle morphology by Al can allow this limestone to show self-reactivation performance and higher conversions over a longer series of CO{sub 2} cycles. 35 refs., 12 figs., 2 tabs.

  20. Effect of thermal cycling on the strength and superconducting properties of laser floating zone textured Bi-2212 rods

    NASA Astrophysics Data System (ADS)

    Salazar, A.; Pastor, J. Y.; Llorca, J.; Natividad, E.; Gimeno, F. J.; Angurel, L. A.

    2003-02-01

    The influence of the thermal cycling on the flexure strength and superconducting properties of textured Bi 2Sr 2CaCu 2O 8+ δ rods processed by the laser-heated floating zone method was studied. Two different temperature ranges (77-300 and 77-393 K) were used to separate the contributions of chemical reactions with liquid water from those due to the thermo-elastic stresses. The rods showed excellent resistance to thermal cycling in both cases and neither the superconducting nor the mechanical properties were significantly affected. In particular, the variation of the critical current at 77 K was below ±4% after 50 thermal cycles. The flexure strength of rods increased or decreased by ≈10% after a few tens of thermal cycles, and crack deflection along the rod axis was observed in the specimens which showed a reduction in strength. This decrease was transitory, and the flexure strength after 50 thermal cycles was similar to that measured on the as-received rods.

  1. Effect of Particle Size on the Micro-cracking of Plasma-Sprayed YSZ Coatings During Thermal Cycle Testing

    NASA Astrophysics Data System (ADS)

    Huang, Jibo; Wang, Weize; Yu, Jingye; Wu, Liangmin; Feng, Zhengqu

    2017-03-01

    The failure of plasma-sprayed thermal barrier coatings (TBCs) during service or thermal cycle testing usually results from internal cracking in the top coat, erosion and CMAS (calcium-magnesium-alumina-silicate)-induced damage, etc. The microstructure of ceramic coatings affects their durability and other properties of TBCs. In the present study, yttria-stabilized zirconia (YSZ) coatings were deposited by atmospheric plasma spraying (APS) using feedstocks with different particle sizes. In addition, the effect of particle size on damage evolution in the top coat was investigated. It is found that the coatings deposited using coarse particles show the higher thermal cycle life. Crack length grew with increasing numbers of thermal cycles. The faster crack growth rate can be found for the coatings deposited from fine particles. The porosity of the coating made from the coarse powder is larger than the porosity of the coating made from fine powder both in the as-sprayed condition and after thermal cycling. The changes in crack growth rate and the porosity are related to the effect of sintering and stress evolution in coatings during the thermal cyclic tests.

  2. Thermal cycling life prediction of Sn-3.0Ag-0.5Cu solder joint using type-I censored data.

    PubMed

    Mi, Jinhua; Li, Yan-Feng; Yang, Yuan-Jian; Peng, Weiwen; Huang, Hong-Zhong

    2014-01-01

    Because solder joint interconnections are the weaknesses of microelectronic packaging, their reliability has great influence on the reliability of the entire packaging structure. Based on an accelerated life test the reliability assessment and life prediction of lead-free solder joints using Weibull distribution are investigated. The type-I interval censored lifetime data were collected from a thermal cycling test, which was implemented on microelectronic packaging with lead-free ball grid array (BGA) and fine-pitch ball grid array (FBGA) interconnection structures. The number of cycles to failure of lead-free solder joints is predicted by using a modified Engelmaier fatigue life model and a type-I censored data processing method. Then, the Pan model is employed to calculate the acceleration factor of this test. A comparison of life predictions between the proposed method and the ones calculated directly by Matlab and Minitab is conducted to demonstrate the practicability and effectiveness of the proposed method. At last, failure analysis and microstructure evolution of lead-free solders are carried out to provide useful guidance for the regular maintenance, replacement of substructure, and subsequent processing of electronic products.

  3. Thermal Cycling Life Prediction of Sn-3.0Ag-0.5Cu Solder Joint Using Type-I Censored Data

    PubMed Central

    Mi, Jinhua; Yang, Yuan-Jian; Huang, Hong-Zhong

    2014-01-01

    Because solder joint interconnections are the weaknesses of microelectronic packaging, their reliability has great influence on the reliability of the entire packaging structure. Based on an accelerated life test the reliability assessment and life prediction of lead-free solder joints using Weibull distribution are investigated. The type-I interval censored lifetime data were collected from a thermal cycling test, which was implemented on microelectronic packaging with lead-free ball grid array (BGA) and fine-pitch ball grid array (FBGA) interconnection structures. The number of cycles to failure of lead-free solder joints is predicted by using a modified Engelmaier fatigue life model and a type-I censored data processing method. Then, the Pan model is employed to calculate the acceleration factor of this test. A comparison of life predictions between the proposed method and the ones calculated directly by Matlab and Minitab is conducted to demonstrate the practicability and effectiveness of the proposed method. At last, failure analysis and microstructure evolution of lead-free solders are carried out to provide useful guidance for the regular maintenance, replacement of substructure, and subsequent processing of electronic products. PMID:25121138

  4. Conformal cooling and rapid thermal cycling in injection molding with 3D printed tools

    NASA Astrophysics Data System (ADS)

    Xu, Xiaorong

    Solid Freeform Fabrication processes such as 3D Printing have demonstrated the potential to produce tools with complex internal geometry. This work explores the application of this capability to improved thermal management for injection molding tooling through: (i)cooling lines which are conformal to the mold surface which provide improved uniformity and stability of mold temperature and (ii)tools with low thermal inertia which, in combination with conformal fluid channels allow for rapid heating and cooling of tooling, thereby facilitating isothermal filling of the mold cavity. This work presents a systematic, modular, approach to the design of conformal cooling channels. Recognizing that the cooling is local to the surface of the tool, the tool is divided up into geometric regions and a channel system is designed for each region. Each channel system is itself modeled as composed of cooling elements, typically the region spanned by two channels. Six criteria are applied including; a transient heat transfer condition which dictates a maximum distance from mold surface to cooling channel, considerations of pressure and temperature drop along the flow channel and considerations of strength of the mold. These criteria are treated as constraints and successful designs are sought which define windows bounded by these constraints. The methodology is demonstrated in application to a complex core and cavity for injection molding. In the area of rapid thermal cycling, this work utilizes the design methods for conformal channels for the heating phases and adds analysis of the packing and cooling phases. A design is created which provides thermal isolation and accommodation of cyclic thermal stresses though an array of bendable support columns which support the molding portion of the tool where the heating/cooling channels are contained. Designed elasticity of the tool is used to aid in packing of the polymer during the cooling phase. Methodology for the design of this

  5. Thermal cycles from a two-zone accreting model - X-ray bursts and shell flashes

    NASA Astrophysics Data System (ADS)

    Regev, O.; Livio, M.

    1984-05-01

    The mechanisms of red-giant shell-flash emission and neutron-star X-ray bursts are investigated theoretically, extending the two-zone model of Barranco et al. (1980) by means of a third time-dependent nonlinear equation to account for the accretion process. The physical assumptions are explained, the equations are derived, and the results of numerical integration are presented graphically for a set of standard input parameters and several variants. Two types of limit-cycle oscillations are identified: thermal oscillations arising from nuclear burning in a thin shell of red giants (leading to shell flashes) and oscillations driven by both nuclear burning and mass accretion in the high-density thermonuclear-ignition region at the surface of neutron stars (leading to X-ray bursts). The two-zone model is shown to account for such burster properties as high-accretion rate stabilization, core heat-exchange effects, and double-peaked bursts.

  6. The Effect of Thermal Cycling on Crystal-Liquid Separation During Lunar Magma Ocean Differentiation

    NASA Technical Reports Server (NTRS)

    Mills, Ryan D.

    2013-01-01

    Differentiation of magma oceans likely involves a mixture of fractional and equilibrium crystallization [1]. The existence of: 1) large volumes of anorthosite in the lunar highlands and 2) the incompatible- rich (KREEP) reservoir suggests that fractional crystallization may have dominated during differentiation of the Moon. For this to have occurred, crystal fractionation must have been remarkably efficient. Several authors [e.g. 2, 3] have hypothesized that equilibrium crystallization would have dominated early in differentiation of magma oceans because of crystal entrainment during turbulent convection. However, recent numerical modeling [4] suggests that crystal settling could have occurred throughout the entire solidification history of the lunar magma ocean if crystals were large and crystal fraction was low. These results indicate that the crystal size distribution could have played an important role in differentiation of the lunar magma ocean. Here, I suggest that thermal cycling from tidal heating during lunar magma ocean crystallization caused crystals to coarsen, leading to efficient crystal-liquid separation.

  7. A study of thermal cycling and radiation effects on indium and solder bump bonding

    SciTech Connect

    Selcuk Cihangir et al.

    2001-09-12

    The BTeV hybrid pixel detector is constructed of readout chips and sensor arrays which are developed separately. The detector is assembled by flip-chip mating of the two parts. This method requires the availability of highly reliable, reasonably low cost fine-pitch flip-chip attachment technology. We have tested the quality of two bump-bonding technologies; indium bumps (by Advanced Interconnect Technology Ltd. (AIT) of Hong Kong) and fluxless solder bumps (by MCNC in North Carolina, USA). The results have been presented elsewhere[1]. In this paper we describe tests we performed to further evaluate these technologies. We subjected 15 indium bump-bonded and 15 fluxless solder bump-bonded dummy detectors through a thermal cycle and then a dose of radiation to observe the effects of cooling, heating and radiation on bump-bonds.

  8. Vacuum ultraviolet radiation and thermal cycling effects on atomic oxygen protective photovoltaic array blanket materials

    NASA Technical Reports Server (NTRS)

    Brady, J.; Banks, B.

    1990-01-01

    The importance of synergistic environmental exposure is demonstrated through the evaluation of DuPont 93-1 in simulated LEO environment. Changes in optical properties, surface condition, and mass loss data are described. The qualitative results indicate the necessity for exposure of materials to a series of simulated LEO environments in order to properly determine synergistic effects and demonstrate the overall LEO durability of candidate materials. It is shown that synergistic effects may occur with vacuum thermal cycling combined with VUV radiation followed by atomic oxygen exposure. Testing the durability of candidate solar array blanket materials in a test sequence with necessary synergistic effects makes it possible to determine the appropriate material for providing structural support and maintaining the proper operating temperature for solar cells in the SSF Photovaltaic Power System.

  9. Diagnosis of Thermal Efficiency of Combined Cycle Power Plants Using Optical Torque Sensors

    NASA Astrophysics Data System (ADS)

    Umezawa, Shuichi

    A new optical torque measurement method is proposed for diagnosis of thermal efficiency of combined cycle power plants. In the case that the plant comprises a steam turbine and a gas turbine, both of which are connected to the same generator, it is difficult to identify which turbine causes deterioration of performance when the plant efficiency is reduced. Therefore, an optical torque sensor has been developed to measure the output of each turbine, which are important data to analyze performance of each machineries in a plant. The sensor measures axial distortion caused by power transmission by use of He-Ne laser beams, small stainless steel reflectors having bar-code patterns, and a technique of signal processing featuring high frequency. It was applied to TOKYO ELECTRIC POWER COMPANY (TEPCO) commercial plants. Following system improvements, it is concluded that error factors can be eliminated and sensor performance can reach a practical use level.

  10. Personal, closed-cycle cooling and protective apparatus and thermal battery therefor

    DOEpatents

    Klett, James W.; Klett, Lynn B.

    2004-07-20

    A closed-cycle apparatus for cooling a living body includes a heat pickup body or garment which permits evaporation of an evaporating fluid, transmission of the vapor to a condenser, and return of the condensate to the heat pickup body. A thermal battery cooling source is provided for removing heat from the condenser. The apparatus requires no external power and provides a cooling system for soldiers, race car drivers, police officers, firefighters, bomb squad technicians, and other personnel who may utilize protective clothing to work in hostile environments. An additional shield layer may simultaneously provide protection from discomfort, illness or injury due to harmful atmospheres, projectiles, edged weapons, impacts, explosions, heat, poisons, microbes, corrosive agents, or radiation, while simultaneously removing body heat from the wearer.

  11. Systems analysis techniques for annual cycle thermal energy storage solar systems

    SciTech Connect

    Baylin, F.; Sillman, S.

    1980-07-01

    Community-scale annual cycle thermal energy storage (ACTES) solar systems are promising options for building heat and cooling. A variety of approaches are feasible in modeling ACTES solar systems. The key parameter in such efforts, average collector efficiency, is first examined, followed by several approaches for simple and effective modeling. Methods are also examined for modeling building loads for structures based on both conventional and passive architectural designs. Two simulation models for sizing solar heating systems with annual storage are presented next. Validation is presented by comparison with the results of a study of seasonal storage systems based on SOLANSIM, an hour-by-hour simulation. These models are presently being used to examine the economic trade-off between collector field area and storage capacity. Finally, programs in the US Department of Energy directed toward developing either other system components such as improved tanks and solar ponds or design tools for ACTES solar systems are examined.

  12. Recent advances in SRS on hydrogen isotope separation using thermal cycling absorption process

    SciTech Connect

    Xiao, X.; Kit Heung, L.; Sessions, H.T.

    2015-03-15

    TCAP (Thermal Cycling Absorption Process) is a gas chromatograph in principle using palladium in the column packing, but it is unique in the fact that the carrier gas, hydrogen, is being isotopically separated and the system is operated in a semi-continuous manner. TCAP units are used to purify tritium. The recent TCAP advances at Savannah River Site (SRS) include compressor-free concept for heating/cooling, push and pull separation using an active inverse column, and compact column design. The new developments allow significantly higher throughput and better reliability from 1/10 of the current production system's footprint while consuming 60% less energy. Various versions are derived in the meantime for external customers to be used in fusion energy projects.

  13. Study of hydraulic air compression for Ocean Thermal Energy Conversion open-cycle application

    NASA Astrophysics Data System (ADS)

    Golshani, A.; Chen, F. C.

    1983-01-01

    A hydraulic air compressor, which requires no mechanical moving parts and operates in a nearly isothermal mode, can be an alternative for the noncondensible gas disposal of an Ocean Thermal Energy Conversion (OTEC) open-cycle power system. The compressor requires only a downward flow of water to accomplish air compression. An air compressor test loop was assembled and operated to obtain test data that would lead to the design of an OTEC hydraulic air compressor. A one dimensional, hydraulic gas compressor, computer model was employed to simulate the laboratory experiments, and it was tuned to fit the test results. A sensitivity study that shows the effects of various parameters on the applied head of the hydraulic air compression is presented.

  14. Elastic-plastic finite-element analyses of thermally cycled double-edge wedge specimens

    NASA Technical Reports Server (NTRS)

    Kaufman, A.; Hunt, L. E.

    1982-01-01

    Elastic-plastic stress-strain analyses were performed for double-edge wedge specimens subjected to thermal cycling in fluidized beds at 316 and 1088 C. Four cases involving different nickel-base alloys (IN 100, Mar M-200, NASA TAZ-8A, and Rene 80) were analyzed by using the MARC nonlinear, finite element computer program. Elastic solutions from MARC showed good agreement with previously reported solutions obtained by using the NASTRAN and ISO3DQ computer programs. Equivalent total strain ranges at the critical locations calculated by elastic analyses agreed within 3 percent with those calculated from elastic-plastic analyses. The elastic analyses always resulted in compressive mean stresses at the critical locations. However, elastic-plastic analyses showed tensile mean stresses for two of the four alloys and an increase in the compressive mean stress for the highest plastic strain case.

  15. Effects on the long term storage container by thermal cycling alpha plutonium

    SciTech Connect

    Flamm, B.F.; Prenger, F.C.; Veirs, D.K.; Hill, D.D.; Isom, G.M.

    1998-03-01

    Experiments were conducted to determine the validity of the steady state temperature limit of 100 C established by the DOE-STD-3013-96 for storing alpha plutonium metal. Studies with an alpha plutonium ingot combined with strain gauge measurements indicate that the stainless steel storage container, yields very little (0.005 in.) to the expanding plutonium metal as it undergoes alpha beta phase transformation at temperatures above 112 C. Another experiment using an alpha plutonium rod for point loading of the container wall showed no measured deformation of the container. The results of strain measurements for alpha beta and beta alpha transformations for twenty five thermal cycles are reported. Finite element modeling using the measured data predicts that the compressive yield strength is 3,500 psi versus the literature value of 13,000 psi.

  16. Evaluation of a Novel Thermal Accelerant for Augmentation of Microwave Energy during Image-guided Tumor Ablation

    PubMed Central

    Park, William Keun Chan; Maxwell, Aaron Wilhelm Palmer; Frank, Victoria Elizabeth; Primmer, Michael Patrick; Collins, Scott Andrew; Baird, Grayson Luderman; Dupuy, Damian Edward

    2017-01-01

    The primary challenge in thermal ablation of liver tumors (e.g. hepatocellular carcinoma and hepatic colorectal cancer) is the relatively high recurrence rate (~30%) for which incomplete ablation at the periphery of the tumor is the most common reason. In an attempt to overcome this, we have developed a novel thermal accelerant (TA) agent capable of augmenting microwave energy from a distance normally unattainable by a single microwave ablation antenna. This cesium-based block co-polymer compound transforms from a liquid to a gel at body temperature and is intrinsically visible by computed tomography. Using an agarose phantom model, herein we demonstrate that both the rate and magnitude of temperature increase during microwave ablation were significantly greater in the presence of TA when compared with controls. These results suggest robust augmentation of microwave energy, and may translate into larger ablation zone volumes within biologic tissues. Further work using in vivo techniques is necessary to confirm these findings. PMID:28382173

  17. Ion acceleration to supra-thermal energies in the near-Earth magnetotail

    NASA Astrophysics Data System (ADS)

    Elena, Kronberg

    2016-07-01

    We here present an analysis of ion composition measurements by the RAPID instruments onboard Cluster. We discuss the evidence for an acceleration of ions to energies above 100 keV in the near-Earth current sheet, in the vicinity of a possible near-Earth neutral line, and we investigate the physical details of such an acceleration. We present observations of tailward bulk flows in the near-Earth tail associated with plasmoid-like magnetic structures. These flows are superimposed by low-frequency magnetic and electric field fluctuations. Observations and modelling show that resonant interactions between ions and low-frequency electromagnetic fluctuations facilitate the ion energization inside plasmoids.

  18. The effects of high-temperature brazing and thermal cycling on the mechanical properties of Hastelloy X

    NASA Technical Reports Server (NTRS)

    Dicus, D. L.; Buckley, J. D.

    1972-01-01

    Data are presented on the effects of brazing alloy, brazing operation, thermal cycling, and combinations of these on the yield strength, elongation, tensile strength, and fatigue life of thin gage Hastelloy X. These data show that brazing at 1461 K (2170 F) with a Ni-Pd-Au alloy and subsequent exposure to 200 service thermal cycles between 533 and 1144 K (500 and 1600 F) result in reduction of as much as 39 percent in yield strength, 33 percent in elongation, 14 percent in tensile strength, and 26 percent in fatigue limit of Hastelloy X, as compared to as-received materials. These property losses are primarily caused by the brazing operation rather than the subsequent service thermal cycles.

  19. In situ study of dislocation behavior in columnar Al thin film on Si substrate during thermal cycling

    SciTech Connect

    Allen, C. W.; Schroeder, H.; Hiller, J. M.

    1999-12-13

    In situ transmission electron microscopy (150 kV) has been employed to study the evolution of dislocation microstructure during relatively rapid thermal cycling of a 200 nm Al thin film on Si substrate. After a few thermal cycles between 150 and 500 C, nearly stable Al columnar grain structure is established with average grain less than a {micro}m. On rapid cooling (3--30+ C/s) from 500 C, dislocations first appear at a nominal temperature of 360--380 C, quickly multiplying and forming planar glide plane arrays on further cooling. From a large number of such experiments the authors have attempted to deduce the dislocation evolution during thermal cycling in these polycrystalline Al films and to account qualitatively for the results on a simple dislocation model.

  20. Thermal energy storage for integrated gasification combined-cycle power plants

    SciTech Connect

    Drost, M.K.; Antoniak, Z.I.; Brown, D.R.; Somasundaram, S.

    1990-07-01

    There are increasingly strong indications that the United States will face widespread electrical power generating capacity constraints in the 1990s; most regions of the country could experience capacity shortages by the year 2000. The demand for new generating capacity occurs at a time when there is increasing emphasis on environmental concerns. The integrated gasification combined-cycle (IGCC) power plant is an example of an advanced coal-fired technology that will soon be commercially available. The IGCC concept has proved to be efficient and cost-effective while meeting all current environmental regulations on emissions; however, the operating characteristics of the IGCC system have limited it to base load applications. The integration of thermal energy storage (TES) into an IGCC plant would allow it to meet cyclic loads while avoiding undesirable operating characteristics such as poor turn-down capability, impaired part-load performance, and long startup times. In an IGCC plant with TES, a continuously operated gasifier supplies medium-Btu fuel gas to a continuously operated gas turbine. The thermal energy from the fuel gas coolers and the gas turbine exhaust is stored as sensible heat in molten nitrate salt; heat is extracted during peak demand periods to produce electric power in a Rankine steam power cycle. The study documented in this report was conducted by Pacific Northwest Laboratory (PNL) and consists of a review of the technical and economic feasibility of using TES in an IGCC power plant to produce intermediate and peak load power. The study was done for the US Department of Energy's (DOE) Office of Energy Storage and Distribution. 11 refs., 5 figs., 18 tabs.

  1. Effects induced by the brazing thermal cycle on the structural properties of materials in steel brazed joints

    NASA Astrophysics Data System (ADS)

    Brossa, M.; Guerreschi, U.

    1988-07-01

    Specimens of AISI 316 austenitic steel, 9Cr-1Mo modified martensitic steel, and 2.25Cr-1Mo ferritic steel have been brazed in a furnace under vacuum conditions. Several thermal cycles were followed in order to investigate their influence on the final characteristics of the joints and the materials. Various kinds of high-melting Ni-based brazing alloys having properties similar to the base materials were used. The growth of the austenitic grain size was measured in order to assess its dependence on the brazing cycle of the different alloys. Metallurgical analyses were carried out and, in a few cases, repeated after the specimens underwent a second thermal cycle or destructive tests. No precipitation of carbides was observed in the base materials after the brazing cycles, confirming that the cooling rate is above the critical range.

  2. Coupled Mechanical-Electrochemical-Thermal Modeling for Accelerated Design of EV Batteries; NREL (National Renewable Energy Laboratory)

    SciTech Connect

    Pesaran, Ahmad; Zhang, Chao; Kim, Gi-heon; Santhanagopalan, Shriram

    2015-06-10

    The physical and chemical phenomena occurring in a battery are many and complex and in many different scales. Without a better knowledge of the interplay among the multi-physics occurring across the varied scales, it is very challenging and time consuming to design long-lasting, high-performing, safe, affordable large battery systems, enabling electrification of the vehicles and modernization of the grid. The National Renewable Energy Laboratory, a U.S. Department of Energy laboratory, has been developing thermal and electrochemical models for cells and battery packs. Working with software producers, carmakers, and battery developers, computer-aided engineering tools have been developed that can accelerate the electrochemical and thermal design of batteries, reducing time to develop and optimize them and thus reducing the cost of the system. In the past couple of years, we initiated a project to model the mechanical response of batteries to stress, strain, fracture, deformation, puncture, and crush and then link them to electrochemical and thermal models to predict the response of a battery. This modeling is particularly important for understanding the physics and processes that happen in a battery during a crush-inducing vehicle crash. In this paper, we provide an overview of electrochemical-thermal-mechanical models for battery system understanding and designing.

  3. Carnot cycle for interacting particles in the absence of thermal noise.

    PubMed

    Curado, Evaldo M F; Souza, Andre M C; Nobre, Fernando D; Andrade, Roberto F S

    2014-02-01

    A thermodynamic formalism is developed for a system of interacting particles under overdamped motion, which has been recently analyzed within the framework of nonextensive statistical mechanics. It amounts to expressing the interaction energy of the system in terms of a temperature θ, conjugated to a generalized entropy s(q), with q = 2. Since θ assumes much higher values than those of typical room temperatures T ≪ θ, the thermal noise can be neglected for this system (T/θ ≃ 0). This framework is now extended by the introduction of a work term δW which, together with the formerly defined heat contribution (δ Q = θ ds(q)), allows for the statement of a proper energy conservation law that is analogous to the first law of thermodynamics. These definitions lead to the derivation of an equation of state and to the characterization of s(q) adiabatic and θ isothermic transformations. On this basis, a Carnot cycle is constructed, whose efficiency is shown to be η = 1-(θ(2)/θ(1)), where θ(1) and θ(2) are the effective temperatures of the two isothermic transformations, with θ(1)>θ(2). The results for a generalized thermodynamic description of this system open the possibility for further physical consequences, like the realization of a thermal engine based on energy exchanges gauged by the temperature θ.

  4. Economic analysis of community solar heating systems that use annual cycle thermal energy storage

    SciTech Connect

    Baylin, F.; Monte, R.; Sillman, S.; Hooper, F.C.; McClenahan, J.D.

    1981-02-01

    The economics of community-scale solar systems that incorporate a centralized annual cycle thermal energy storage (ACTES) coupled to a distribution system is examined. Systems were sized for three housing configurations: single-unit dwellings, 10-unit, and 200-unit apartment complexes in 50-, 200-, 400-, and 1000-unit communities in 10 geographic locations in the United States. Thermal energy is stored in large, constructed, underground tanks. Costs were assigned to each component of every system in order to allow calculation of total costs. Results are presented as normalized system costs per unit of heat delivered per building unit. These methods allow: (1) identification of the relative importance of each system component in the overall cost; and (2) identification of the key variables that determine the optimum sizing of a district solar heating system. In more northerly locations, collectors are a larger component of cost. In southern locations, distribution networks are a larger proportion of total cost. Larger, more compact buildings are, in general, less expensive to heat. For the two smaller-scale building configurations, a broad minima in total costs versus system size is often observed.

  5. Seawater test results of open-cycle ocean thermal energy conversion (OC-OTEC) components

    SciTech Connect

    Zangrando, F.; Bharathan, D.; Link, H. ); Panchal, C.B. )

    1994-01-01

    Key components of open-cycle ocean thermal energy conversion systems--the flash evaporator, mist eliminator, passive predeaerator, two surface condenser stages, and two direct-contact condenser stages--have been tested using seawater. These components operate at lower steam pressures and higher inlet noncondensable gas concentrations than do conventional power plant heat exchangers. The rate of heat exchanged between the evaporator and the condenser is on the order of 1.25MW-thermal, requiring a warm seawater flow of about 0.1 m[sup 3]/s; the cold seawater flow is on the order of half the warm water flow. In addition to characterizing the performance of the various components, the system has produced potable water from condensation of the steam produced in the evaporator. The information obtained in these tests is being used to design a larger scale experiment in which net power production is expected to be demonstrate for the first time using OC-OTEC technology.

  6. Efficiency Study of a Commercial Thermoelectric Power Generator (TEG) Under Thermal Cycling

    NASA Astrophysics Data System (ADS)

    Hatzikraniotis, E.; Zorbas, K. T.; Samaras, I.; Kyratsi, Th.; Paraskevopoulos, K. M.

    2010-09-01

    Thermoelectric generators (TEGs) make use of the Seebeck effect in semiconductors for the direct conversion of heat to electrical energy. The possible use of a device consisting of numerous TEG modules for waste heat recovery from an internal combustion (IC) engine could considerably help worldwide efforts towards energy saving. However, commercially available TEGs operate at temperatures much lower than the actual operating temperature range in the exhaust pipe of an automobile, which could cause structural failure of the thermoelectric elements. Furthermore, continuous thermal cycling could lead to reduced efficiency and lifetime of the TEG. In this work we investigate the long-term performance and stability of a commercially available TEG under temperature and power cycling. The module was subjected to sequential hot-side heating (at 200°C) and cooling for long times (3000 h) in order to measure changes in the TEG’s performance. A reduction in Seebeck coefficient and an increase in resistivity were observed. Alternating-current (AC) impedance measurements and scanning electron microscope (SEM) observations were performed on the module, and results are presented and discussed.

  7. The Paleocene-Eocene Thermal Maximum and the Global Carbon Cycle: Progress and Promise

    NASA Astrophysics Data System (ADS)

    Zachos, J. C.

    2005-12-01

    The initial documentation of a short-lived, but extreme global warming event (Paleocene-Eocene Thermal Maximum; PETM) and carbon isotope excursion (CIE) coincident with a major benthic foraminiferal extinction horizon at the end of the Paleocene (Kennett & Stott, 1991) represents one of the more exciting and important contributions to the field of Paleoceanography. In the time since this discovery, substantial progress has been made toward developing a comprehensive understanding of key aspects of this event including the character of the global carbon cycle perturbation, and impacts on climate, biogeochemical cycles, and marine and terrestrial ecosystems. In this presentation, I review the latest findings of investigations of pelagic and shallow marine sequences designed to provide new constraints on both the tempo and magnitude of the CIE and associated geochemical anomalies. In particular, I will focus on bulk and planktonic carbon isotope and proxy records of carbonate dissolution generated from analyses of Pacific and Atlantic deep sea cores, and discuss implications for changes in ocean carbon chemistry and the mass of carbon added to the ocean during this event. I will also explore several outstanding issues regarding the rate and magnitude of carbon fluxes during the PETM, and possible strategies to address these issues. Kennett, J. P., and L.D. Stott, Abrupt deep-sea warming, palaeoceanographic changes and benthic extinctions at the end of the Palaeocene, Nature, 353, 225-229, 1991.

  8. Innovative turbine concepts for open-cycle OTEC (Ocean Thermal Energy Conversion)

    NASA Astrophysics Data System (ADS)

    1989-12-01

    The results are summarized of preliminary studies conducted to identify and evaluate three innovative concepts for an open cycle ocean thermal energy conversion (OTEC) steam turbine that could significantly reduce the cost of OTEC electrical power plants. The three concepts are: (1) a crossflow turbine, (2) a vertical axis, axial flow turbine, and (3) a double flow, radial inflow turbine with mixed flow blading. In all cases, the innovation involves the use of lightweight, composite plastic blading and a physical geometry that facilitates efficient fluid flow to and from the other major system components and reduces the structural requirements for both the turbine or the system vacuum enclosure, or both. The performance, mechanical design, and cost of each of the concepts are developed to varying degrees but in sufficient detail to show that the potential exists for cost reductions to the goals established in the U.S. Department of Energy's planning documents. Specifically, results showed that an axial turbine operating with 33 percent higher steam throughput and 7 percent lower efficiency than the most efficient configuration provides the most cost effective open-cycle OTEC system. The vacuum enclosure can be significantly modified to reduce costs by establishing better interfaces with the system.

  9. Innovative turbine concepts for open-cycle OTEC (ocean thermal energy conversion)

    SciTech Connect

    Not Available

    1989-12-01

    This report summarizes the results of preliminary studies conducted to identify and evaluate three innovative concepts for an open-cycle ocean thermal energy conversion (OTEC) steam turbine that could significantly reduce the cost of OTEC electrical power plants. The three concepts are (1) a crossflow turbine, (2) a vertical-axis, axial-flow turbine, and (3) a double-flow, radial-inflow turbine with mixed-flow blading. In all cases, the innovation involves the use of lightweight, composite plastic blading and a physical geometry that facilitates efficient fluid flow to and from the other major system components and reduces the structural requirements for both the turbine or the system vacuum enclosure, or both. The performance, mechanical design, and cost of each of the concepts are developed to varying degrees but in sufficient detail to show that the potential exists for cost reductions to the goals established in the US Department of Energy's planning documents. Specifically, results showed that an axial turbine operating with 33% higher steam throughput and 7% lower efficiency than the most efficient configuration provides the most cost-effective open-cycle OTEC system. The vacuum enclosure can be significantly modified to reduce costs by establishing better interfaces with the system. 33 refs., 26 figs., 11 tabs.

  10. Physiological cost and thermal envelope: a novel approach to cycle garment evaluation during a representative protocol.

    PubMed

    Corbett, J; Barwood, M J; Tipton, M J

    2015-04-01

    This study aimed to examine thermoregulation in different clothing assemblies during a representative cycling exercise protocol. Six men undertook cycling exercise simulating representative thermal exchange challenges while wearing low (LOW), intermediate (INT1 and INT2), or high (HI) amounts of clothing. Exercise was conducted at 14.5 °C, 46.8% relative humidity and included a "flat" [45 min at 35% peak power output (PPO), wind speed 8.3 m/s], "uphill" (30 min at 55% PPO, wind speed 3.6 m/s), and "downhill" (20 min at 50 W, wind speed 16.7 m/s) stage. Rectal temperature changed with the exercise stage and was independent of clothing assembly. In contrast, an "envelope" was evident for mean body temperature, resulting from differences in mean skin temperature between the LOW and HI conditions. The elevated mean body temperature in HI was associated with increased physiological "cost," in the form of increased sweat production and heart rate. Physiological cost provides a better index of clothing performance than deep body temperature in the "thermoregulatory zone," as a consequence sports clothing should attempt to optimize the balance between comfort and reduced physiological cost.

  11. Wakefield-acceleration of relativistic electrons with few-cycle laser pulses at kHz-repetition-rate

    NASA Astrophysics Data System (ADS)

    Guenot, Diego; Gustas, Dominykas; Vernier, Aline; Boehle, Frederik; Beaurepaire, Benoit; Lopez-Martens, Rodrigo; Faure, Jerome; Appli Team

    2016-10-01

    The generation of relativistic electron beams using laser wakefield acceleration has become a standard technique, providing low emittance electron bunches with femtosecond durations. However, this technique usually requires multi-ten-terawatt lasers and is thus limited to low repetition-rate (typically 10 Hz or less). We have recently demonstrated the generation of few MeV electrons using 2.5-mJ, 4-fs, 1-kHz repetition-rate laser pulses, focused to relativistic intensity onto a gas jet with electron density 1020 cm-3. We have investigated the influence of the pulse duration, the gas density. We demonstrated that an electron beam with a charge in the range of 10-fC/shot, with a divergence of 20-mrad and a peaked spectrum with energies between 2 and 4 MeV can be generated at kHz repetition-rate. These results confirm the possibility of using few-cycle laser pulses with very low energy for exciting wakefields in the bubble regime and for trapping electrons, as predicted by PIC simulations. This kHz electron source is ideally suited for performing electron diffraction experiments with very high temporal resolution. Our results also open the way to other applications, such as the generation of a kHz ultrafast X-ray source. ERC femtoelec.

  12. Hubble Space telescope thermal cycle test report for large solar array samples with BSFR cells (Sample numbers 703 and 704)

    NASA Technical Reports Server (NTRS)

    Alexander, D. W.

    1992-01-01

    The Hubble space telescope (HST) solar array was designed to meet specific output power requirements after 2 years in low-Earth orbit, and to remain operational for 5 years. The array, therefore, had to withstand 30,000 thermal cycles between approximately +100 and -100 C. The ability of the array to meet this requirement was evaluated by thermal cycle testing, in vacuum, two 128-cell solar cell modules that exactly duplicated the flight HST solar array design. Also, the ability of the flight array to survive an emergency deployment during the dark (cold) portion of an orbit was evaluated by performing a cold-roll test using one module.

  13. Use of Guided Acoustic Waves to Assess the Effects of Thermal-Mechanical Cycling on Composite Stiffness

    NASA Technical Reports Server (NTRS)

    Seale, Michael D.; Madaras, Eric I.

    2000-01-01

    The introduction of new, advanced composite materials into aviation systems requires it thorough understanding of the long-term effects of combined thermal and mechanical loading. As part of a study to evaluate the effects of thermal-mechanical cycling, it guided acoustic (Lamb) wave measurement system was used to measure the bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the velocity dispersion curve. A series of 16 and 32-ply composite laminates were subjected to it thermal-mechanical loading profile in load frames equipped with special environmental chambers. The composite systems studied were it graphite fiber reinforced amorphous thermoplastic polyimide and it graphite fiber reinforced bismaleimide thermoset. The samples were exposed to both high and low temperature extremes its well as high and low strain profiles. The bending and out-of-plane stiffnesses for composite sample that have undergone over 6,000 cycles of thermal-mechanical loading are reported. The Lamb wave generated elastic stiffness results have shown decreases of up to 20% at 4,936 loading cycles for the graphite/thermoplastic samples and up to 64% at 4,706 loading cycles for the graphite/thermoset samples.

  14. Role of interfacial and matrix creep during thermal cycling of continuous fiber reinforced metal-matrix composites

    SciTech Connect

    Dutta, I.

    2000-03-14

    A uni-dimensional micro-mechanical model for thermal cycling of continuous fiber reinforced metal-matrix composites is developed. The model treats the fiber and matrix as thermo-elastic and thermo-elasto-plastic-creeping solids, respectively, and allows the operation of multiple matrix creep mechanisms at various stages of deformation through the use of unified creep laws. It also incorporates the effect of interfacial sliding by an interface-diffusion-controlled diffusional creep mechanism proposed earlier (Funn and Dutta, Acta mater., 1999, 47, 149). The results of thermal cycling simulations based on a graphite fiber reinforced pure aluminum-matrix composite were compared with experimental data on a P100 graphite-6061 Al composite. The model successfully captured all the important features of the observed heating/cooling rate dependence, strain hysteresis, residual permanent strain at the end of a cycle, as well as both intrusion and protrusion of the fiber-ends relative to the matrix at the completion of cycling. The analysis showed that the dominant deformation mechanism operative in the matrix changes continually during thermal cycling due to continuous stress and temperature revision. Based on these results, a framework for the construction of a transient deformation mechanism map for thermal excursions of continuous fiber composites is proposed.

  15. The Dependence of the Change in the Coefficient of Thermal Expansion of Graphite Fiber Reinforced Polyimide IM7-K3B on Microcracking due to Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Stewart, Melissa C.

    1995-01-01

    Composite IM7-K3B was subjected to a simulated high speed aircraft thermal environment to determine the effects of microcracking on the change in CTE. IM7-K3B is a graphite fiber reinforced polyimide laminate, manufactured by Dupont. The lay-up for the material was (0.90((Sub 3)(Sub s))). The specimens were placed in a laser-interferometric dilatometer to obtain thermal expansion measurements and were then repeatedly cycled between -65 F and 350 F up to 1000 cycles. After cycling they were scanned for microcracks at a magnification of 400x. The material was expected not to crack and to have a near zero CTE. Some microcracking did occur in all specimens and extensive microcracking occurred in one specimen. Further testing is required to determine how closely the CTE and microcracking are related.

  16. Thermal electron acceleration by electric field spikes in the outer radiation belt: generation of field-aligned pitch angle distributions

    NASA Astrophysics Data System (ADS)

    Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

    2015-12-01

    Van Allen Probes observations in the outer radiation belt have demonstrated an abundance non-linear electrostatic stucture called Time Domain Structures (TDS). One of the type of TDS is electrostatic electron-acoustic double layers (DL). Observed DLs are frequently accompanied by field-aligned (bi-directional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV (rarely up to tens of keV). We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e. due to reflections from DL potential humps. Due to this interaction some fraction of electrons is scattered into the loss cone. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi mechanism electrons can be trapped by DLs in their generation region and accelerated due to transport to higher latitudes. Both mechanisms result in formation of field-aligned PADs for electrons with energies comparable to those found in observations. The Fermi mechanism provides field-aligned PADs for <1 keV electrons, while the trapping mechanism extends field-aligned PADs to higher energy electrons.

  17. Thermal electron acceleration by electric field spikes in the outer radiation belt: Generation of field-aligned pitch angle distributions

    NASA Astrophysics Data System (ADS)

    Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.; Artemyev, A. V.

    2015-10-01

    Van Allen Probes observations in the outer radiation belt have demonstrated an abundance of electrostatic electron-acoustic double layers (DL). DLs are frequently accompanied by field-aligned (bidirectional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV. We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e., due to reflections from DL potential humps. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi mechanism, electrons can be trapped by DLs in their generation region and accelerated due to transport to higher latitudes. Both mechanisms result in formation of field-aligned PADs for electrons with energies comparable to those found in observations. The Fermi mechanism provides field-aligned PADs for <1 keV electrons, while the trapping mechanism extends field-aligned PADs to higher-energy electrons. It is shown that the Fermi mechanism can result in scattering into the loss cone of up to several tenths of percent of electrons with flux peaking at energies up to several hundred eVs.

  18. Investigation of a putative nitrogen cycle in a subsurface radioactive thermal spring

    NASA Astrophysics Data System (ADS)

    Gerbl, Friedrich; Breitfuss, Angelika; Weidler, Gerhard; Stan-Lotter, Helga

    2010-05-01

    Background: Previous studies on the microbial diversity [1] of the slightly radioactive thermal springs near Bad Gastein, Salzburg, Austria, suggested the occurrence of a nitrogen cycle in this subterranean environment. Microcosm experiments were performed to prove if nitrogen compounds may be used as energy sources for certain members of the microbial community of this spring Methods: 2 x 25 l of thermal mineral water were sampled and filtered through a 0.22 µm Stericup (Millipore). Filters were excised and used as inocula for one microcosm. Stable isotope probing (SIP), was performed by using labeled nitrogen compounds to identify microorganisms, which were able to use nitrogen as the only energy source. 2 x 35 ml of natural grown biofilm were collected and used also as inocula for microcosms. Incubation was carried out as batch cultures in the dark at 30 °C or 40 °C, respectively. Two different types of media were used for incubation. Ammonium, nitrite and nitrate were measured 3-4 times a week. PH-value was also measured and adjusted to ca. 7.5 - 7.7 if necessary. DNA extraction was performed after 3 and 8 weeks of incubation, followed by an isopycnic centrifugation step. Clone libraries were performed only from microcosms incubated at 40 °C. To compare putative differences between the microbial communities at 30 °C with those at 40 °C, as well as the two different media, DGGE analyses were carried out. Results: A continuous decrease of the initial amount of ammonium was detected while the amounts of nitrite and nitrate increased simultaneously. No alterations of the initial amount of ammonium and nitrite or nitrate, could be detected with negative controls. Mass spectrometric measurements demonstrated that the extracted DNA was highly labeled. Phylogenetic analysis of DNA bands obtained from CsCl gradients led to differences in archaeal and bacterial communities of microcosms, which may reflect the different composition of media. Two of the archaeal

  19. Fused deposition modeling (FDM) fabricated part behavior under tensile stress, thermal cycling, and fluid pressure

    NASA Astrophysics Data System (ADS)

    Hossain, Mohammad Shojib

    using visual feedback method led to an increase in UTS of 16% in XYZ, 7% in XZY, and 22% in ZXY. The FDM fabricated parts using PC were tested under thermal cycling of -30° C to 85° C. A series of experiments were performed (e.g., tensile test, deformation of fabricated part, glass transition measurement) to evaluate the possibility of FDM fabricated parts in the harsh environment (embedded electronics, wiring in automotive industry, etc.). The UTS results showed that the results were not significantly different using statistical analysis after 150 thermal cycles while average Young's modulus increased from 1389 MPa to 1469 MPa after 150 thermal cycles. The highest warping of the specimen was found to be 78 microm which was the result of continuous thermal expansion and contraction. A sealing algorithm was developed using LabVIEW and MATLAB programming. The LabVIEW program was developed to obtain the edge information of each layer of a 3D model part. The MATLAB programming was used to gather the output information from LabVIEW and calculate the suggested RW providing least amount of gap in between rasters and contours. As a result, each layer became sealed and was able to withstand air pressure within a pressure vessel. A test specimen was fabricated according to the developed sealing algorithm parameters and used to show entirely sealed walls capable of withstanding up to 138 kPa air pressure.

  20. Thermodynamic and design considerations of organic Rankine cycles in combined application with a solar thermal gas turbine

    NASA Astrophysics Data System (ADS)

    Braun, R.; Kusterer, K.; Sugimoto, T.; Tanimura, K.; Bohn, D.

    2013-12-01

    Concentrated Solar Power (CSP) technologies are considered to provide a significant contribution for the electric power production in the future. Different kinds of technologies are presently in operation or under development, e.g. parabolic troughs, central receivers, solar dish systems and Fresnel reflectors. This paper takes the focus on central receiver technologies, where the solar radiation is concentrated by a field of heliostats in a receiver on the top of a tall tower. To get this CSP technology ready for the future, the system costs have to reduce significantly. The main cost driver in such kind of CSP technologies are the huge amount of heliostats. To reduce the amount of heliostats, and so the investment costs, the efficiency of the energy conversion cycle becomes an important issue. An increase in the cycle efficiency results in a decrease of the solar heliostat field and thus, in a significant cost reduction. The paper presents the results of a thermodynamic model of an Organic Rankine Cycle (ORC) for combined cycle application together with a solar thermal gas turbine. The gas turbine cycle is modeled with an additional intercooler and recuperator and is based on a typical industrial gas turbine in the 2 MW class. The gas turbine has a two stage radial compressor and a three stage axial turbine. The compressed air is preheated within a solar receiver to 950°C before entering the combustor. A hybrid operation of the gas turbine is considered. In order to achieve a further increase of the overall efficiency, the combined operation of the gas turbine and an Organic Rankine Cycle is considered. Therefore an ORC has been set up, which is thermally connected to the gas turbine cycle at two positions. The ORC can be coupled to the solar-thermal gas turbine cycle at the intercooler and after the recuperator. Thus, waste heat from different cycle positions can be transferred to the ORC for additional production of electricity. Within this investigation

  1. Effect of thermal cycling in a Mach 0.3 burner rig on properties and structure of directionally solidified gamma/gamma prime - delta eutectic

    NASA Technical Reports Server (NTRS)

    Gray, H. R.; Sanders, W. A.

    1975-01-01

    Tensile and stress rupture properties at 1040 C of a thermally cycled gamma/gamma prime - delta eutectic were essentially equivalent to the as-grown properties. Tensile strength and rupture life at 760 C appeared to decrease slightly by thermal cycling. Thermal cycling resulted in gamma prime coarsening and Widmanstatten delta precipitation in the gamma phase. An unidentified precipitate, presumably gamma prime, was observed within the delta phase. The eutectic alloy exhibited a high rate of oxidation-erosion weight loss during thermal cycling in the Mach 0.3 burner rig.

  2. Evaluation of accelerated UV and thermal testing for benzene formation in beverages containing benzoate and ascorbic acid.

    PubMed

    Nyman, Patricia J; Wamer, Wayne G; Begley, Timothy H; Diachenko, Gregory W; Perfetti, Gracia A

    2010-04-01

    Under certain conditions, benzene can form in beverages containing benzoic and ascorbic acids. The American Beverage Assn. (ABA) has published guidelines to help manufacturers mitigate benzene formation in beverages. These guidelines recommend accelerated testing conditions to test product formulations, because exposure to ultraviolet (UV) light and elevated temperature over the shelf life of the beverage may result in benzene formation in products containing benzoic and ascorbic acids. In this study, the effects of UVA exposure on benzene formation were determined. Benzene formation was examined for samples contained in UV stabilized and non-UV stabilized packaging. Additionally, the usefulness of accelerated thermal testing to simulate end of shelf-life benzene formation was evaluated for samples containing either benzoic or ascorbic acid, or both. The 24 h studies showed that under intense UVA light benzene levels increased by as much as 53% in model solutions stored in non-UV stabilized bottles, whereas the use of UV stabilized polyethylene terephthalate bottles reduced benzene formation by about 13% relative to the non-UV stabilized bottles. Similar trends were observed for the 7 d study. Retail beverages and positive and negative controls were used to study the accelerated thermal testing conditions. The amount of benzene found in the positive controls and cranberry juice suggests that testing at 40 degrees C for 14 d may more reliably simulate end of shelf-life benzene formation in beverages. Except for cranberry juice, retail beverages were not found to contain detectable amounts of benzene (<0.05 ng/g) at the end of their shelf lives.

  3. The effect of thermal cycling on the structure and properties of a Co, Cr, Ni-TaC directionally solidified eutectic composite

    NASA Technical Reports Server (NTRS)

    Dunlevey, F. M.; Wallace, J. F.

    1973-01-01

    The effect of thermal cycling on the structure and properties of a cobalt, chromium, nickel, tantalum carbide directionally solidified eutectic composite is reported. It was determined that the stress rupture properties of the alloy were decreased by the thermal cycling. The loss in stress rupture properties varied with the number of cycles with the loss in properties after about 200 cycles being relatively high. The formation of serrations and the resulting changes in the mechanical properties of the material are discussed.

  4. Ocean Thermal Energy Conversion Life Cycle Cost Assessment, Final Technical Report, 30 May 2012

    SciTech Connect

    Martel, Laura; Smith, Paul; Rizea, Steven; Van Ryzin, Joe; Morgan, Charles; Noland, Gary; Pavlosky, Rick; Thomas, Michael; Halkyard, John

    2012-05-30

    The Ocean Thermal Energy Conversion (OTEC) Life Cycle Cost Assessment (OLCCA) is a study performed by members of the Lockheed Martin (LM) OTEC Team under funding from the Department of Energy (DOE), Award No. DE-EE0002663, dated 01/01/2010. OLCCA objectives are to estimate procurement, operations and maintenance, and overhaul costs for two types of OTEC plants: -Plants moored to the sea floor where the electricity produced by the OTEC plant is directly connected to the grid ashore via a marine power cable (Grid Connected OTEC plants) -Open-ocean grazing OTEC plant-ships producing an energy carrier that is transported to designated ports (Energy Carrier OTEC plants) Costs are developed using the concept of levelized cost of energy established by DOE for use in comparing electricity costs from various generating systems. One area of system costs that had not been developed in detail prior to this analysis was the operations and sustainment (O&S) cost for both types of OTEC plants. Procurement costs, generally referred to as capital expense and O&S costs (operations and maintenance (O&M) costs plus overhaul and replacement costs), are assessed over the 30 year operational life of the plants and an annual annuity calculated to achieve a levelized cost (constant across entire plant life). Dividing this levelized cost by the average annual energy production results in a levelized cost of electricity, or LCOE, for the OTEC plants. Technical and production efficiency enhancements that could result in a lower value of the OTEC LCOE were also explored. The thermal OTEC resource for Oahu, Hawaii and projected build out plan were developed. The estimate of the OTEC resource and LCOE values for the planned OTEC systems enable this information to be displayed as energy supplied versus levelized cost of the supplied energy; this curve is referred to as an Energy Supply Curve. The Oahu Energy Supply Curve represents initial OTEC deployment starting in 2018 and demonstrates the

  5. Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, High-Cycle and Low-Cycle Mechanical Fatigue, Creep and Thermal Fatigue Effects

    NASA Technical Reports Server (NTRS)

    Bast, Callie C.; Boyce, Lola

    1995-01-01

    The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

  6. Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Bigelow, Glen S.; Padula, Santo A.; Noebe, Ronald D.; Garg, Anita; Gaydosh, Darrell

    2010-01-01

    While NiTiPd alloys have been extensively studied for proposed use in high-temperature shape-memory applications, little is known about the shape-memory response of these materials under stress. Consequently, the isobaric thermal cyclic responses of five (Ni,Pd)49.5Ti50.5 alloys with constant stoichiometry and Pd contents ranging from 15 to 46 at. pct were investigated. From these tests, transformation temperatures, transformation strain (which is proportional to work output), and unrecovered strain per cycle (a measure of dimensional instability) were determined as a function of stress for each alloy. It was found that increasing the Pd content over this range resulted in a linear increase in transformation temperature, as expected. At a given stress level, work output decreased while the amount of unrecovered strain produced during each load-biased thermal cycle increased with increasing Pd content, during the initial thermal cycles. However, continued thermal cycling at constant stress resulted in a saturation of the work output and nearly eliminated further unrecovered strain under certain conditions, resulting in stable behavior amenable to many actuator applications.

  7. Evaluation of roughness and micromorphology of epoxy paint on cobalt-chromium alloy before and after thermal cycling.

    PubMed

    Nascimento, Alessandra Cardoso da Silva; Muzilli, Carlos Alberto; Miranda, Milton Edson; Flório, Flávia Martão; Basting, Roberta Tarkany

    2013-01-01

    It has been suggested that the epoxy paint used to coat metal substrates in industrial electrostatic painting applications could also be used to mask metal clasps in removable dental prostheses (RDP). The purpose of this study was to evaluate both the influence of thermal cycling and the in vitro roughness of a surface after application of epoxy paint, as well as to assess the micromorphology of a cobalt-chromium (CoCr) based metal structure. Sixty test specimens were fabricated from a CoCr alloy. The specimens were separated into three groups (n = 20) according to surface treatment: Group 1 (Pol) - polished with abrasive stone and rubbers; Group 2 (Pol+Epo) - polished and coated with epoxy paint; Group 3 (Epo) - air-abraded with aluminum oxide particles and coated with epoxy paint. The surface roughness was evaluated before and after 1000 thermal cycles (5°C and 50°C). The surface micromorphology was verified by scanning electron microscopy (SEM). The two-way repeated measures ANOVA showed significant differences among surface treatments (p < 0.0001), but no difference was found before and after thermal cycling (p = 0.6638). The CoCr-based metal alloy surfaces treated with epoxy paint (Groups 2 and 3) were rougher than the surfaces that were only polished (Group 1). Thermal cycling did not influence surface roughness, or lead to chipping or detachment of the epoxy paint.

  8. Accelerated thermal recovery for flash-lamp-pumped solid-state laser amplifiers final report for 97-ERD-133

    SciTech Connect

    Erlandson, A C; London, R; Manes, K; Marshall, C; Petty, C; Pierce, R; Smith, L; Sutton, S; Zapata, L

    1999-09-03

    We have developed a cost-effective method for accelerating the thermal wavefront recovery and shot rate of large, flashlamp-pumped, Nd:glass, Brewster-angle slab lasers of the type used for studying inertial confinement fusion (ICF) and laser-plasma interactions. This method removes waste pump heat by flowing slightly-chilled, turbulent gas over the flashlamps and blastshields after each shot, with the cooled blastshields serving as heat sinks for radiatively extracting residual heat deposited in the laser slabs. We performed both experiments and modeling to characterize residual optical distortions arising from both temperature gradients within the laser slabs as well as from buoyantly-driven convection currents in the amplifier cavity and attached beam tubes. The most rapid thermal recovery was achieved by reducing the temperature of the cooling gas by 0.5-1 C below the ambient temperature for about two hours after the shot. Model predictions for the 1.8-MJ National Ignition Facility (NIF) laser now being built at Lawrence Livermore National Laboratory (LLNL) show that such chilled-gas cooling would increase the thermal-distortion-limited shot rate from about one shot every eight hours to one shot every three to four hours, thus significantly increasing the potential scientific productivity of this major Department of Energy (DOE) facility.

  9. Optimization and experimental validation of a thermal cycle that maximizes entropy coefficient fisher identifiability for lithium iron phosphate cells

    NASA Astrophysics Data System (ADS)

    Mendoza, Sergio; Rothenberger, Michael; Hake, Alison; Fathy, Hosam

    2016-03-01

    This article presents a framework for optimizing the thermal cycle to estimate a battery cell's entropy coefficient at 20% state of charge (SOC). Our goal is to maximize Fisher identifiability: a measure of the accuracy with which a parameter can be estimated. Existing protocols in the literature for estimating entropy coefficients demand excessive laboratory time. Identifiability optimization makes it possible to achieve comparable accuracy levels in a fraction of the time. This article demonstrates this result for a set of lithium iron phosphate (LFP) cells. We conduct a 24-h experiment to obtain benchmark measurements of their entropy coefficients. We optimize a thermal cycle to maximize parameter identifiability for these cells. This optimization proceeds with respect to the coefficients of a Fourier discretization of this thermal cycle. Finally, we compare the estimated parameters using (i) the benchmark test, (ii) the optimized protocol, and (iii) a 15-h test from the literature (by Forgez et al.). The results are encouraging for two reasons. First, they confirm the simulation-based prediction that the optimized experiment can produce accurate parameter estimates in 2 h, compared to 15-24. Second, the optimized experiment also estimates a thermal time constant representing the effects of thermal capacitance and convection heat transfer.

  10. Difference in water accumulation patterns between solid and closed hollow obturators under a thermal cycle.

    PubMed

    Tsuboi, Akito; Sakurai, Takeshi; Watanabe, Makoto

    2012-09-01

    Water accumulation in the hollow space of a maxillary obturator is a continuing problem, and it is unclear whether the porosity of acrylic resin is involved in the mechanism. The purposes of the study were to evaluate the effect of a hollow space in the resin obturator on water sorption under a thermal cycle and to determine factors associated with water accumulation in the obturator. Twenty solid spheres (30-mm diameter) and 40 hemispheres (30-mm diameter, 1.5 mm thickness) were fabricated from heat-polymerized acrylic resin. Closed hollow specimens consisted of 2 hemispheres joined with autopolymerizing resin. Ten solid and 10 closed hollow specimens were immersed in distilled water, whereas the other specimens were stored at 100% relative humidity. Each specimen was thermocycled (5°C-37°C) with a dwell time of 12 hours and weighed every 12 hours for 180 days. Of the 20 closed hollow specimens, 16 showed no water accumulation (8 in distilled water, 8 at 100% humidity). The weight of these specimens became saturated by day 90, with increases from the initial weight of 1.41% at 5°C and 1.36% at 37°C. By day 180, the weights of the solid specimens had increased by 0.96% at 5°C and 0.94% at 37°C. Weight fluctuation associated with temperature was observed for both types of specimens and for all storage conditions. It is concluded that water accumulation inside a closed hollow obturator is not directly related to the water absorption properties of the acrylic resin but is related to thermal damage of the obturator.

  11. The extent of non-thermal particle acceleration in relativistic, electron-positron reconnection

    SciTech Connect

    Werner, Greg; Guo, Fan

    2015-07-21

    Reconnection is studied as an explanation for high-energy flares from the Crab Nebula. The production of synchrotron emission >100 MeV challenges classical models of acceleration. 3D simulation shows that reconnection, converting magnetic energy to kinetic energy, can accelerate beyond γrad. The power-law index and high-energy cutoff are important for understanding the radiation spectrum dN/dγ = f(γ) ∝ γ. α and cutoff were measured vs. L and σ, where L is system (simulation) size and σ is upstream magnetization (σ = B2/4πnmc2). α can affect the high-energy cutoff. In conclusion, for collisionless relativistic reconnection in electron-positron plasma, without guide field, nb/nd=0.1: (1) relativistic magnetic reconnection yields power-law particle spectra, (2) the power law index decreases as σ increases, approaching ≈1.2. (3) the power law is cut off at an energy related to acceleration within a single current layer, which is proportional to the current layer length (for small systems, that length is the system length, yielding γc2 ≈ 0.1 L/ρ0; for large systems, the layer length is limited by secondary tearing instability, yielding γc1 ≈ 4σ; the transition from small to large is around L/ρ0 = 40σ.). (4) although the large-system energy cutoff is proportional to the average energy per particle, it is significantly higher than the average energy per particle.

  12. On the non-thermal electron-to-proton ratio at cosmic ray acceleration sites

    NASA Astrophysics Data System (ADS)

    Merten, Lukas; Becker Tjus, Julia; Eichmann, Björn; Dettmar, Ralf-Jürgen

    2017-04-01

    The luminosity ratio of electrons to protons as it is produced in stochastic acceleration processes in cosmic ray sources is an important quantity relevant for several aspects of the modeling of the sources themselves. It is usually assumed to be around 1: 100 in the case of Galactic sources, while a value of 1: 10 is typically assumed when describing extragalactic sources. It is supported by observations that the average ratios should be close to these values. At this point, however, there is no possibility to investigate how each individual source behaves. When looking at the physics aspects, a 1: 100 ratio is well supported in theory when making the following assumptions: (1) the total number of electrons and protons that is accelerated are the same; (2) the spectral index of both populations after acceleration is αe =αp ≈ 2.2 . In this paper, we reinvestigate these assumptions. In particular, assumption (2) is not supported by observational data of the sources and PIC simulation yield different spectral indices as well. We present the detailed calculation of the electron-to-proton ratio, dropping the assumption of equal spectral indices. We distinguish between the ratio of luminosities and the ratio of the differential spectral behavior, which becomes necessary for cases where the spectral indices of the two particle populations are not the same. We discuss the possible range of values when allowing for different spectral indices concerning the spectral behavior of electrons and protons. Additionally, it is shown that the minimum energy of the accelerated population can have a large influence on the results. We find, in the case of the classical minimum energy of T0 , e =T0 , p = 10 keV, that when allowing for a difference in the spectral indices of up to 0.1 with absolute spectral indices varying between 2.0 < α < 2.3, the luminosity ratio varies between 0.008 < Kep < 0.12. The differential particle number ratio is in the range 0.008

  13. Micro solid oxide fuel cell fabricated on porous stainless steel: a new strategy for enhanced thermal cycling ability

    NASA Astrophysics Data System (ADS)

    Kim, Kun Joong; Park, Byung Hyun; Kim, Sun Jae; Lee, Younki; Bae, Hongyeul; Choi, Gyeong Man

    2016-03-01

    Miniaturized solid oxide fuel cells (micro-SOFCs) are being extensively studied as a promising alternative to Li batteries for next generation portable power. A new micro-SOFC is designed and fabricated which shows enhanced thermal robustness by employing oxide-based thin-film electrode and porous stainless steel (STS) substrate. To deposit gas-tight thin-film electrolyte on STS, nano-porous composite oxide is proposed and applied as a new contact layer on STS. The micro-SOFC fabricated on composite oxide- STS dual layer substrate shows the peak power density of 560 mW cm‑2 at 550 °C and maintains this power density during rapid thermal cycles. This cell may be suitable for portable electronic device that requires high power-density and fast thermal cycling.

  14. Micro solid oxide fuel cell fabricated on porous stainless steel: a new strategy for enhanced thermal cycling ability.

    PubMed

    Kim, Kun Joong; Park, Byung Hyun; Kim, Sun Jae; Lee, Younki; Bae, Hongyeul; Choi, Gyeong Man

    2016-03-01

    Miniaturized solid oxide fuel cells (micro-SOFCs) are being extensively studied as a promising alternative to Li batteries for next generation portable power. A new micro-SOFC is designed and fabricated which shows enhanced thermal robustness by employing oxide-based thin-film electrode and porous stainless steel (STS) substrate. To deposit gas-tight thin-film electrolyte on STS, nano-porous composite oxide is proposed and applied as a new contact layer on STS. The micro-SOFC fabricated on composite oxide- STS dual layer substrate shows the peak power density of 560 mW cm(-2) at 550 °C and maintains this power density during rapid thermal cycles. This cell may be suitable for portable electronic device that requires high power-density and fast thermal cycling.

  15. Micro solid oxide fuel cell fabricated on porous stainless steel: a new strategy for enhanced thermal cycling ability

    PubMed Central

    Kim, Kun Joong; Park, Byung Hyun; Kim, Sun Jae; Lee, Younki; Bae, Hongyeul; Choi, Gyeong Man

    2016-01-01

    Miniaturized solid oxide fuel cells (micro-SOFCs) are being extensively studied as a promising alternative to Li batteries for next generation portable power. A new micro-SOFC is designed and fabricated which shows enhanced thermal robustness by employing oxide-based thin-film electrode and porous stainless steel (STS) substrate. To deposit gas-tight thin-film electrolyte on STS, nano-porous composite oxide is proposed and applied as a new contact layer on STS. The micro-SOFC fabricated on composite oxide- STS dual layer substrate shows the peak power density of 560 mW cm−2 at 550 °C and maintains this power density during rapid thermal cycles. This cell may be suitable for portable electronic device that requires high power-density and fast thermal cycling. PMID:26928921

  16. Effects of Thermal Cycling on Thermal Expansion and Mechanical Properties of Sic Fiber-reinforced Reaction-bonded Si3n4 Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, R. T.; Palczer, A. R.

    1994-01-01

    Thermal expansion curves for SiC fiber-reinforced reaction-bonded Si3N4 matrix composites (SiC/RBSN) and unreinforced RBSN were measured from 25 to 1400 C in nitrogen and in oxygen. The effects of fiber/matrix bonding and cycling on the thermal expansion curves and room-temperature tensile properties of unidirectional composites were determined. The measured thermal expansion curves were compared with those predicted from composite theory. Predicted thermal expansion curves parallel to the fiber direction for both bonding cases were similar to that of the weakly bonded composites, but those normal to the fiber direction for both bonding cases resulted in no net dimensional changes at room temperature, and no loss in tensile properties from the as-fabricated condition. In contrast, thermal cycling in oxygen for both composites caused volume expansion primarily due to internal oxidation of RBSN. Cyclic oxidation affected the mechanical properties of the weakly bonded SiC/RBSN composites the most, resulting in loss of strain capability beyond matrix fracture and catastrophic, brittle fracture. Increased bonding between the SiC fiber and RBSN matrix due to oxidation of the carbon-rich fiber surface coating and an altered residual stress pattern in the composite due to internal oxidation of the matrix are the main reasons for the poor mechanical performance of these composites.

  17. Effect of Acid Etching, Silane and Thermal Cycling on the Bond Strength of Metallic Brackets to Ceramic.

    PubMed

    Matos, Natália Regina Santos de; Costa, Ana Rosa; Valdrighi, Heloísa Cristina; Correr, Américo Bortolazzo; Vedovello, Silvia Amélia; Santamaria, Milton; Correr-Sobrinho, Lourenço

    2016-01-01

    The aim of this study was to evaluate the effect of silanes, thermal cycling and acid etching on the shear bond strength (SBS) of metallic brackets to feldspathic ceramic. Feldspathic ceramic cylinders (Groups 1, 2, 5 and 6) were etched for 60 s with 10% hydrofluoric acid and Groups 3, 4, 7 and 8, without acid etching. Two layers of silane Clearfil Ceramic Primer (CCP, Groups 1 to 4) and two layers of RelyX Ceramic Primer (RCP, groups 5 to 8) were applied and dried for 60 s. Brackets were bonded to the cylinders with Transbond XT and light-activated for 40 s with Bluephase G2. All specimens were stored in deionized water at 37 °C for 24 h, and the specimens of groups 1, 3, 5 and 7 were submitted to 7,000 thermal cycles (5 °C/55 °C). After storage, the SBS test was performed at a crosshead speed of 1 mm/min. Data were subjected to three-way ANOVA and Tukey's post hoc test (α=0.05). The adhesive remnant index (ARI) was evaluated at 8x magnification. The SBS of CCP was significantly greater than of RCP (p<0.05), with or without thermal cycling. Thermal cycling significantly reduced the SBS (p<0.05). The groups submitted to acid etching showed significantly higher SBS than those without acid etching (p<0.05). In conclusion, thermal cycling reduced SBS for all groups. The best ceramic surface treatment for bracket bonding was achieved by acid etching and CCP silane. The ARI results showed predominance of score 0 for all groups.

  18. Probabilistic material strength degradation model for Inconel 718 components subjected to high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue effects

    NASA Technical Reports Server (NTRS)

    Bast, Callie C.; Boyce, Lola

    1995-01-01

    This report presents the results of both the fifth and sixth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA). The research included on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for five variables, namely, high temperature, high-cycle and low-cycle mechanical fatigue, creep and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using an updated version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of high-cycle mechanical fatigue, creep and thermal fatigue was performed. Then using the current version of PROMISS, entitled PROMISS94, a second sensitivity study including the effect of low-cycle mechanical fatigue, as well as, the three previous effects was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of high-cycle mechanical

  19. Analysis of Anderson Acceleration on a Simplified Neutronics/Thermal Hydraulics System

    SciTech Connect

    Toth, Alex; Kelley, C. T.; Slattery, Stuart R; Hamilton, Steven P; Clarno, Kevin T; Pawlowski, R. P. P.

    2015-01-01

    ABSTRACT A standard method for solving coupled multiphysics problems in light water reactors is Picard iteration, which sequentially alternates between solving single physics applications. This solution approach is appealing due to simplicity of implementation and the ability to leverage existing software packages to accurately solve single physics applications. However, there are several drawbacks in the convergence behavior of this method; namely slow convergence and the necessity of heuristically chosen damping factors to achieve convergence in many cases. Anderson acceleration is a method that has been seen to be more robust and fast converging than Picard iteration for many problems, without significantly higher cost per iteration or complexity of implementation, though its effectiveness in the context of multiphysics coupling is not well explored. In this work, we develop a one-dimensional model simulating the coupling between the neutron distribution and fuel and coolant properties in a single fuel pin. We show that this model generally captures the convergence issues noted in Picard iterations which couple high-fidelity physics codes. We then use this model to gauge potential improvements with regard to rate of convergence and robustness from utilizing Anderson acceleration as an alternative to Picard iteration.

  20. Thermal activation of CaO-based sorbent and self-reactivation during CO{sub 2} capture looping cycles

    SciTech Connect

    Vasilije Manovic; Edward J. Anthony

    2008-06-01

    In this study, the thermal activation of different types of CaO-based sorbents was examined. Pretreatments were performed at different temperatures (800-1300{sup o}C) and different durations (6-48 h) using four Canadian limestones. Sieved fractions of the limestones, powders obtained by grinding, and hydroxides produced following multiple carbonation/calcination cycles achieved in a tube furnace were examined. Pretreated samples were evaluated using two types of thermogravimetric reactors/analyzers. The most important result was that thermal pretreatment could improve sorbent performance. In comparison to the original, pretreated sorbents showed better conversions over a longer series of CO{sub 2} cycles. Moreover, in some cases, sorbent activity actually increased with cycle number, and this effect was especially pronounced for powdered samples preheated at 1000{sup o}C. In these experiments, the increase of conversion with cycle number (designated as self-reactivation) after 30 cycles produced samples that were about 50% carbonated for the four sorbents examined here, and there appeared to be the potential for additional increase. These results were explained with the newly proposed pore-skeleton model. This model suggests, in addition to changes in the porous structure of the sorbent, that changes in the pore-skeleton produced during pretreatment strongly influence subsequent carbonation/calcination cycles. 31 refs., 8 figs.

  1. Cool-down acceleration of G-M cryocoolers with thermal oscillations passively damped by helium

    NASA Astrophysics Data System (ADS)

    Webber, R. J.; Delmas, J.

    2015-12-01

    4 K Gifford-McMahon cryocoolers suffer from inherent temperature oscillations which can be a problem for certain attached electronic instrumentation. Sumitomo Heavy Industries has exploited the high volumetric specific heat of super-critical He to quell these oscillations (approx. 10 dB) by strongly thermally linking a separate vessel of He to the second stage; no significant thermal resistance is added between the payload and the working gas of the cryocooler. A noticeable effect of the helium damper is to increase the cool-down time of the second stage below 10 K. For the operation of niobium-based superconducting electronics (NbSCE), a common practice is to warm the circuits above the critical temperature (∼9 K) and then cool to the operating point in order to redistribute trapped magnetic fluxons, so for NbSCE users, the time to cool from 10 K is important. The gas in the helium damper is shared between a room-temperature buffer tank and the 2nd stage vessel, which are connected by a capillary tube. We show that the total cool-down time below 10 K can be substantially reduced by introducing a combination of thermal linkages between the cryocooler and the capillary tube and in-line relief valves, which control the He mass distribution between the warm canister and cold vessel. The time to reach operating temperature from the superconducting transition has been reduced to <25% of the time needed without these low-cost modifications.

  2. Fiber-reinforced composite analysis using optical coherence tomography after mechanical and thermal cycling

    NASA Astrophysics Data System (ADS)

    Kyotoku, B. B. C.; Braz, A. K. S.; Braz, R.; Gomes, A. S. L.

    2007-02-01

    Fiber-reinforced composites are new materials which have been used for a variety of dental applications, including tooth splinting, replacement of missing teeth, treatment of dental emergencies, reinforcement of resin provisional fixed prosthodontic restorations, orthodontic retention, and other clinical applications. Different fiber types are available, but little clinical information has been disseminated. The traditional microscopy investigation, most commonly used to study this material, is a destructive technique, which requires specimen sectioning and are essentially surface measurements. On the basis of these considerations, the aim of this research is to analyze the interior of a dental sample reinforced with fiber after a mechanical and thermal cycling to emulate oral conditions using optical coherence tomography (OCT). The device we are using is a home built Fourier domain OCT working at 800 nm with 6 μm resolution. The results are compared with microscopy images to validate OCT as a working method. In long term, fractures allow bacterial invasion provoking plaque and calculus formation that can cause caries and periodontal disease. Therefore, non invasive imaging of the bridge fiber enables the possibility of periodic clinical evaluation to ensure the patient health. Furthermore, OCT images can provide a powerful method for quantitative analysis of crack propagation, and can potentially be used for in vivo assessment.

  3. A study of thermal cycling and radiation effects on indium and solder bump bonds

    SciTech Connect

    Simon Kwan et al.

    2001-12-11

    The BTeV hybrid pixel detector is constructed of readout chips and sensor arrays which are developed separately. The detector is assembled by flip-chip mating of the two parts. This method requires the availability of highly reliable, reasonably low cost fine-pitch flip-chip attachment technology. We have tested the quality of two bump-bonding technologies; indium bumps (by Advanced Interconnect Technology Ltd. (AIT) of Hong Kong) and fluxless solder bumps (by MCNC in North Carolina, USA). The results have been presented elsewhere [1]. In this paper we describe tests we performed to further evaluate these technologies. We subjected 15 indium bump-bonded and 15 fluxless solder bump-bonded dummy detectors through a thermal cycle and then a dose of radiation to observe the effects of cooling, heating and radiation on bump-bonds. We also exercised the processes of HDI mounting and wire bonding to some of the dummy detectors to see the effect of these processes on bump bonds.

  4. Life Cycle Assessment of Thermal Energy Storage: Two-Tank Indirect and Thermocline

    SciTech Connect

    Heath, G.; Turchi, C.; Burkhardt, J.; Kutscher, C.; Decker, T.

    2009-07-01

    In the United States, concentrating solar power (CSP) is one of the most promising renewable energy (RE) technologies for reduction of electric sector greenhouse gas (GHG) emissions and for rapid capacity expansion. It is also one of the most price-competitive RE technologies, thanks in large measure to decades of field experience and consistent improvements in design. One of the key design features that makes CSP more attractive than many other RE technologies, like solar photovoltaics and wind, is the potential for including relatively low-cost and efficient thermal energy storage (TES), which can smooth the daily fluctuation of electricity production and extend its duration into the evening peak hours or longer. Because operational environmental burdens are typically small for RE technologies, life cycle assessment (LCA) is recognized as the most appropriate analytical approach for determining their environmental impacts of these technologies, including CSP. An LCA accounts for impacts from all stages in the development, operation, and decommissioning of a CSP plant, including such upstream stages as the extraction of raw materials used in system components, manufacturing of those components, and construction of the plant. The National Renewable Energy Laboratory (NREL) is undertaking an LCA of modern CSP plants, starting with those of parabolic trough design.

  5. Evidence of Transformation Bursts During Thermal Cycling of a Pu-Ga Alloy

    SciTech Connect

    Blobaum, K M; Krenn, C R; Mitchell, J N; Haslam, J J; Wall, M A; Massalski, T B; Schwartz, A J

    2005-02-09

    The thermodynamics and kinetics of the fcc (delta) to monoclinic (alpha-prime) phase transformation and its reversion in a plutonium-gallium alloy have been studied using differential scanning calorimetry, resistometry, and dilatometry. Under ambient conditions, the delta phase is metastable in a Pu-2.0 at% Ga alloy. Thermal cycling to below the ambient temperature results in a partial transformation to the alpha-prime phase; this transformation is composition-invariant and exhibits martensitic behavior. Because this transformation results in an unusually invariant large 25% volume contraction that cannot be fully accommodated by purely elastic adjustments, the transformation mode is expected to involve burst formation of individual alpha-prime particles. However, upon cooling, these individual bursts were not resolved by the above techniques, although signals corresponding to the overall accumulation of many alpha-prime particles were observed. On the other hand, upon heating, signals from differential scanning calorimetry, resistometry, and dilatometry showed a series of discrete changes occurring in periodic increments beginning at approximately 32 C. These features correspond to the cooperative reversion of many alpha-prime particles to the delta phase; they appear to be the result of an interplay between the autocatalytically driven reversion of a cascade of individual martensite units, and self-quenching caused by small changes of temperature and/or stress accompanying each individual transformation burst. The heat of the delta/alpha-prime transformation is estimated to be about + 4 kJ/mole.

  6. Life cycle assessment of thermal waste-to-energy technologies: review and recommendations.

    PubMed

    Astrup, Thomas Fruergaard; Tonini, Davide; Turconi, Roberto; Boldrin, Alessio

    2015-03-01

    Life cycle assessment (LCA) has been used extensively within the recent decade to evaluate the environmental performance of thermal Waste-to-Energy (WtE) technologies: incineration, co-combustion, pyrolysis and gasification. A critical review was carried out involving 250 individual case-studies published in 136 peer-reviewed journal articles within 1995 and 2013. The studies were evaluated with respect to critical aspects such as: (i) goal and scope definitions (e.g. functional units, system boundaries, temporal and geographic scopes), (ii) detailed technology parameters (e.g. related to waste composition, technology, gas cleaning, energy recovery, residue management, and inventory data), and (iii) modeling principles (e.g. energy/mass calculation principles, energy substitution, inclusion of capital goods and uncertainty evaluation). Very few of the published studies provided full and transparent descriptions of all these aspects, in many cases preventing an evaluation of the validity of results, and limiting applicability of data and results in other contexts. The review clearly suggests that the quality of LCA studies of WtE technologies and systems including energy recovery can be significantly improved. Based on the review, a detailed overview of assumptions and modeling choices in existing literature is provided in conjunction with practical recommendations for state-of-the-art LCA of Waste-to-Energy.

  7. The seasonal cycle of water vapour on Mars from assimilation of Thermal Emission Spectrometer data

    NASA Astrophysics Data System (ADS)

    Steele, Liam J.; Lewis, Stephen R.; Patel, Manish R.; Montmessin, Franck; Forget, François; Smith, Michael D.

    2014-07-01

    We present for the first time an assimilation of Thermal Emission Spectrometer (TES) water vapour column data into a Mars global climate model (MGCM). We discuss the seasonal cycle of water vapour, the processes responsible for the observed water vapour distribution, and the cross-hemispheric water transport. The assimilation scheme is shown to be robust in producing consistent reanalyses, and the global water vapour column error is reduced to around 2-4 pr μm depending on season. Wave activity is shown to play an important role in the water vapour distribution, with topographically steered flows around the Hellas and Argyre basins acting to increase transport in these regions in all seasons. At high northern latitudes, zonal wavenumber 1 and 2 stationary waves during northern summer are responsible for spreading the sublimed water vapour away from the pole. Transport by the zonal wavenumber 2 waves occurs primarily to the west of Tharsis and Arabia Terra and, combined with the effects of western boundary currents, this leads to peak water vapour column abundances here as observed by numerous spacecraft. A net transport of water to the northern hemisphere over the course of one Mars year is calculated, primarily because of the large northwards flux of water vapour which occurs during the local dust storm around LS=240-260°. Finally, outlying frost deposits that surround the north polar cap are shown to be important in creating the peak water vapour column abundances observed during northern summer.

  8. Experiments on oxygen desorption from surface warm seawater under open-cycle ocean thermal energy conversion

    SciTech Connect

    Pesaran, A.A. )

    1992-11-01

    This paper presents the results of scoping deaeration experiments conducted with warm surface seawater under open-cycle ocean thermal energy conversion (OC-OTEC) conditions. Concentrations of dissolved oxygen in seawater at three locations (in the supply water, water leaving the predeaerator, and discharge water from an evaporator) were measured and used to estimate oxygen desorption levels. The results suggest that 7 percent to 60 percent of the dissolved oxygen in the supply water was desorbed from seawater in the predeaerator for pressures ranging from 35 to 9 kPa. Bubble injection in the upcomer increased the oxygen desorption rate by 20 percent to 60 percent. The data also indicated that at typical OC-OTEC evaporator pressures, when flash evaporation in the evaporator occurred, 75 percent to 95 percent of the dissolved oxygen was desorbed overall from the warm seawater. The results were used to find the impact of a single-stage predeaeration scheme on the power to remove noncondensable gases in an OC-OTEC plant.

  9. The Seasonal Cycle of Water Vapour on Mars from Assimilation of Thermal Emission Spectrometer Data

    NASA Technical Reports Server (NTRS)

    Steele, Liam J.; Lewis, Stephen R.; Patel, Manish R.; Montmessin, Franck; Forget, Francois; Smith, Michael D.

    2014-01-01

    We present for the first time an assimilation of Thermal Emission Spectrometer (TES) water vapour column data into a Mars global climate model (MGCM). We discuss the seasonal cycle of water vapour, the processes responsible for the observed water vapour distribution, and the cross-hemispheric water transport. The assimilation scheme is shown to be robust in producing consistent reanalyses, and the global water vapour column error is reduced to around 2-4 pr micron depending on season. Wave activity is shown to play an important role in the water vapour distribution, with topographically steered flows around the Hellas and Argyre basins acting to increase transport in these regions in all seasons. At high northern latitudes, zonal wavenumber 1 and 2 stationary waves during northern summer are responsible for spreading the sublimed water vapour away from the pole. Transport by the zonal wavenumber 2 waves occurs primarily to the west of Tharsis and Arabia Terra and, combined with the effects of western boundary currents, this leads to peak water vapour column abundances here as observed by numerous spacecraft. A net transport of water to the northern hemisphere over the course of one Mars year is calculated, primarily because of the large northwards flux of water vapour which occurs during the local dust storm around L(sub S) = 240-260deg. Finally, outlying frost deposits that surround the north polar cap are shown to be important in creating the peak water vapour column abundances observed during northern summer.

  10. Surface degradation of CeO2 stabilized acrylic polyurethane coated thermally treated jack pine during accelerated weathering

    NASA Astrophysics Data System (ADS)

    Saha, Sudeshna; Kocaefe, Duygu; Boluk, Yaman; Pichette, Andre

    2013-07-01

    The thermally treated wood is a new value-added product and is very important for the diversification of forestry products. It drew the attention of consumers due to its attractive dark brown color. However, it loses its color when exposed to outside environment. Therefore, development of a protective coating for this value added product is necessary. In the present study, the efficiency of CeO2 nano particles alone or in combination with lignin stabilizer and/or bark extracts in acrylic polyurethane polymer was investigated by performing an accelerated weathering test. The color measurement results after accelerated weathering demonstrated that the coating containing CeO2 nano particles was the most effective whereas visual assessment suggested the coating containing CeO2 nano particles and lignin stabilizer as the most effective coating. The surface polarity changed for all the coatings during weathering and increase in contact angle after weathering suggested cross linking and reorientation of the polymer chain during weathering. The surface chemistry altered during weathering was evaluated by ATR-FTIR analysis. It suggested formation of different carbonyl byproducts during weathering. The chain scission reactions of the urethane linkages were not found to be significant during weathering.

  11. Effects of thermal cycling and thermal aging on the hermeticity and strength of silver-copper oxide air-brazed seals

    NASA Astrophysics Data System (ADS)

    Scott Weil, K.; Coyle, Christopher A.; Darsell, Jens T.; Xia, Gordon G.; Hardy, John S.

    Thermal cycle and exposure tests were conducted on ceramic-to-metal joints prepared by a new sealing technique. Known as reactive air brazing, this joining method is currently being considered for use in sealing various high-temperature solid-state electrochemical devices, including planar solid oxide fuel cells (pSOFC). In order to simulate a typical pSOFC application, test specimens were prepared by joining ceramic anode/electrolyte bilayers to metal washers, of the same composition as the common frame materials employed in pSOFC stacks, using a filler metal composed of 4 mol% CuO in silver. The brazed samples were exposure tested at 750 °C for 200, 400, and 800 h in both simulated fuel and air environments and thermally cycled at rapid rate (75 °C min -1) between room temperature and 750 °C for as many as 50 cycles. Subsequent joint strength testing and microstructural analysis indicated that the samples exposure tested in air displayed little degradation with respect to strength, hermeticity, or microstructure out to 800 h of exposure. Those tested in fuel showed no change in rupture strength or loss in hermeticity after 800 h of high-temperature exposure, but did undergo microstructural change due to the dissolution of hydrogen into the silver-based braze material. Air-brazed specimens subjected to rapid thermal cycling exhibited no loss in joint strength or hermeticity, but displayed initial signs of seal delamination along the braze-electrolyte interface after 50 cycles.

  12. Generic Repository Concepts and Thermal Analysis for Advanced Fuel Cycles - 12477

    SciTech Connect

    Hardin, Ernest; Blink, James; Carter, Joe; Fratoni, Massimiliano; Greenberg, Harris; Sutton, Mark; Howard, Robert

    2012-07-01

    A geologic disposal concept for spent nuclear fuel (SNF) or high-level waste (HLW) consists of three components: waste inventory, geologic setting, and concept of operations. A set of reference geologic disposal concepts has been developed by the U.S. Department of Energy (DOE), Used Fuel Disposition campaign. Reference concepts are identified for crystalline rock, clay/shale, bedded salt, and deep borehole (crystalline basement) geologic settings. These were analyzed for waste inventory cases representing a range of waste types that could be produced by advanced nuclear fuel cycles. Concepts of operation consisting of emplacement mode, repository layout, and engineered barrier descriptions, were selected based on international progress. All of these disposal concepts are enclosed emplacement modes, whereby waste packages are in direct contact with encapsulating engineered or natural materials. Enclosed modes have less capacity to dissipate heat than open modes such as that proposed for a repository at Yucca Mountain. Thermal analysis has identified important relationships between waste package size and capacity, and the duration of surface decay storage needed to meet temperature limits for different disposal concepts. For the crystalline rock and clay/shale repository concepts, a waste package surface temperature limit of 100 deg. C was assumed to prevent changes in clay-based buffer material or clay-rich host rock. Surface decay storage of 50 to 100 years is needed for disposal of high-burnup LWR SNF in 4-PWR packages, or disposal of HLW glass from reprocessing LWR uranium oxide (UOX) fuel. High-level waste (HLW) from reprocessing of metal fuel used in a fast reactor could be disposed after decay storage of 50 years or less. For disposal in salt the rock thermal conductivity is significantly greater, and higher temperatures (200 deg. C) can be tolerated at the waste package surface. Decay storage of 10 years or less is needed for high-burnup LWR SNF in 4-PWR

  13. Prognostics of Power Mosfets Under Thermal Stress Accelerated Aging Using Data-Driven and Model-Based Methodologies

    NASA Technical Reports Server (NTRS)

    Celaya, Jose; Saxena, Abhinav; Saha, Sankalita; Goebel, Kai F.

    2011-01-01

    An approach for predicting remaining useful life of power MOSFETs (metal oxide field effect transistor) devices has been developed. Power MOSFETs are semiconductor switching devices that are instrumental in electronics equipment such as those used in operation and control of modern aircraft and spacecraft. The MOSFETs examined here were aged under thermal overstress in a controlled experiment and continuous performance degradation data were collected from the accelerated aging experiment. Dieattach degradation was determined to be the primary failure mode. The collected run-to-failure data were analyzed and it was revealed that ON-state resistance increased as die-attach degraded under high thermal stresses. Results from finite element simulation analysis support the observations from the experimental data. Data-driven and model based prognostics algorithms were investigated where ON-state resistance was used as the primary precursor of failure feature. A Gaussian process regression algorithm was explored as an example for a data-driven technique and an extended Kalman filter and a particle filter were used as examples for model-based techniques. Both methods were able to provide valid results. Prognostic performance metrics were employed to evaluate and compare the algorithms.

  14. INSTRUMENTS AND METHODS OF INVESTIGATION: Giant pulses of thermal neutrons in large accelerator beam dumps. Possibilities for experiments

    NASA Astrophysics Data System (ADS)

    Stavissky, Yurii Ya

    2006-12-01

    A short review is presented of the development in Russia of intense pulsed neutron sources for physical research — the pulsating fast reactors IBR-1, IBR-30, IBR-2 (Joint Institute for Nuclear Research, Dubna), and the neutron-radiation complex of the Moscow meson factory — the 'Troitsk Trinity' (RAS Institute for Nuclear Research, Troitsk, Moscow region). The possibility of generating giant neutron pulses in beam dumps of superhigh energy accelerators is discussed. In particular, the possibility of producing giant pulsed thermal neutron fluxes in modified beam dumps of the large hadron collider (LHD) under construction at CERN is considered. It is shown that in the case of one-turn extraction ov 7-TeV protons accumulated in the LHC main rings on heavy targets with water or zirconium-hydride moderators placed in the front part of the LHC graphite beam-dump blocks, every 10 hours relatively short (from ~100 µs) thermal neutron pulses with a peak flux density of up to ~1020 neutrons cm-2 s-1 may be produced. The possibility of applying such neutron pulses in physical research is discussed.

  15. Global Carbon Cycle Perturbations and Implications for Arctic Hydrology during the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Cui, Y.; Kump, L.; Diefendorf, A. F.; Freeman, K. H.

    2011-12-01

    The Paleocene-Eocene Thermal Maximum (PETM; ca. 55.9 Ma) was an interval of geologically abrupt global warming lasting ~200 ka. It has been proposed as an ancient analogue for future climate response to CO2 emission from fossil fuel burning. The onset of this event is fueled by a large release of 13C-depleted carbon into the ocean-atmosphere system. However, there is a large discrepancy in the magnitude of the carbon isotope excursion (CIE) between marine and terrestrial records. Here we present new organic geochemical data and stable carbon isotope records from n-alkanes and pristane extracted from core materials representing the most expanded PETM section yet recovered from a nearshore marine early Cenozoic succession from Spitsbergen. The low hydrogen index and oxygen index indicate that organic matter has been thermally altered, consistent with n-alkanes that do not show a clear odd-over-even predominance as reflected by the low and constant carbon preference index. The δ13C records of long chain n-alkanes from core BH9-05 track the δ13C recorded in total organic carbon, but are ~3% more negative prior to the CIE, ~4.5% more negative during the CIE, and ~4% more negative after the CIE. An orbital age model derived from the same core suggests the CIE from n-alkanes appears more abruptly onset than the bulk organic carbon, indicating possibly climate-induced modification to the observed feature in n-alkanes. In addition, the carbon isotope values of individual long-chain (n-C27 to n-C31) n-alkanes tend to become less negative with increasing chain length resulting in the smallest magnitude CIEs in longer chain lengths (i.e. n-C31) and the largest magnitude CIEs in shorter chain lengths (i.e. n-C27). We are currently considering the effect of plant community and paleoclimate on the observed pattern of CIE in n-alkanes to evaluate carbon cycle perturbations and Arctic hydrology changes during the PETM. One interpretation of these patterns is that there was an

  16. 17beta-estradiol combined with testosterone promotes chicken osteoblast proliferation and differentiation by accelerating the cell cycle and inhibiting apoptosis in vitro.

    PubMed

    Chen, Xiuxia; Deng, Yifeng; Zhou, Zhenlei; Tao, Qingshu; Zhu, Jie; Li, Xiaolan; Chen, Jinli; Hou, Jiafa

    2010-02-01

    Medullary bone is a unique tissue in the long bones cavities of lay hens, and plays an important role as a calcium reservoir for egg-shell formation. Medullary bone formation requires the synergistic action of estrogen and androgen on osteoblasts during the early stage of sexual maturity. The objective of the current study was to investigate the effects of 17beta-estradiol, testosterone, and the combination on the proliferation, alkaline phosphatase (ALP) activity, apoptosis, the cell cycle of chicken osteoblasts in vitro. The proliferation of osteoblasts was examined with the MTT assay. Apoptosis and the cell cycle were assessed with flow cytometry. Either 17beta-estradiol (200 pg ml(-1)) or testosterone (100 pg ml(-1)) or the combination (100 pg ml(-1) each) significantly enhanced osteoblast proliferation and ALP activity, accelerated the osteoblast cell cycle, and stimulated osteoblast DNA synthesis in a period of 24 h. 17beta-estradiol, used alone or with testosterone, inhibited chicken osteoblast apoptosis; However, testosterone alone induced cell apoptosis. In conclusion, 17beta-estradiol combined with testosterone promoted osteoblast proliferation and ALP activity, accelerated the osteoblast cell cycle, inhibited osteoblast apoptosis.

  17. First evidence of non-Gaussian solar flare EUV spectral line profiles and accelerated non-thermal ion motion

    NASA Astrophysics Data System (ADS)

    Jeffrey, Natasha L. S.; Fletcher, Lyndsay; Labrosse, Nicolas

    2016-05-01

    Context. The properties of solar flare plasma can be determined from the observation of optically thin lines. The emitting ion distribution determines the shape of the spectral line profile, with an isothermal Maxwellian ion distribution producing a Gaussian profile. Non-Gaussian line profiles may indicate more complex ion distributions. Aims: We investigate the possibility of determining flare-accelerated non-thermal ion and/or plasma velocity distributions. Methods: We study EUV spectral lines produced during a flare SOL2013-05-15T01:45 using the Hinode EUV Imaging Spectrometer (EIS). The flare is located close to the eastern solar limb with an extended loop structure, allowing the different flare features: ribbons, hard X-ray (HXR) footpoints and the loop-top source to be clearly observed in UV, EUV and X-rays. EUV line spectroscopy is performed in seven different regions covering the flare. We study the line profiles of the isolated and unblended Fe XVI lines (λ262.9760 Å ) mainly formed at temperatures of ~2 to 4 MK. Suitable Fe XVI line profiles at one time close to the peak soft X-ray emission and free of directed mass motions are examined using: 1. a higher moments analysis, 2. Gaussian fitting, and 3. by fitting a kappa distribution line profile convolved with a Gaussian to account for the EIS instrumental profile. Results: Fe XVI line profiles in the flaring loop-top, HXR footpoint and ribbon regions can be confidently fitted with a kappa line profile with an extra variable κ, giving low, non-thermal κ values between 2 and 3.3. An independent higher moments analysis also finds that many of the spectral line kurtosis values are higher than the Gaussian value of 3, even with the presence of a broad Gaussian instrumental profile. Conclusions: A flare-accelerated non-thermal ion population could account for both the observed non-Gaussian line profiles, and for the Fe XVI "excess" broadening found from Gaussian fitting, if the emitting ions are interacting

  18. The study of crack resistance of TiAlN coatings under mechanical loading and thermal cycle testing

    SciTech Connect

    Akulinkin, Alexandr Shugurov, Artur Sergeev, Viktor; Panin, Alexey; Cheng, C.-H.

    2015-10-27

    The effect of preliminary ion bombardment of 321 stainless steel substrate on crack resistance of TiAlN coatings at uniaxial tension and thermal cycling is studied. The ion-beam treatment of the substrate is shown to substantially improve the adhesion strength of the coatings that prevents their delamination and spalling under uniaxial tension. The resistance to crack propagation and spalling by the thermal shock is higher in the TiAlN coating deposited onto the substrate subjected to Ti ion bombardment as compared to that in the TiAlN coating deposited onto the initial substrate.

  19. Elastic modulus and thermal stress in coating during heat cycling with different substrate shapes

    NASA Astrophysics Data System (ADS)

    Gaona, Daniel; Valarezo, Alfredo

    2015-09-01

    The elastic modulus of a deposit ( E d) can be obtained by monitoring the temperature (Δ T) and curvature (Δ k) of a one-side coated long plate, namely, a onedimensional (1D) deformation model. The aim of this research is to design an experimental setup that proves whether a 1D deformation model can be scaled for complex geometries. The setup includes a laser displacement sensor mounted on a robotic arm capable of scanning a specimen surface and measuring its deformation. The reproducibility of the results is verified by comparing the present results with Stony Brook University Laboratory's results. The Δ k-Δ T slope error is less than 8%, and the E d estimation error is close to 2%. These values reveal the repeatability of the experiments. Several samples fabricated with aluminum as the substrate and 100MXC nanowire (Fe and Cr alloy) as the deposit are analyzed and compared with those in finite element (FE) simulations. The linear elastic behavior of 1D (flat long plate) and 2D (squared plate) specimens during heating/cooling cycles is demonstrated by the high linearity of all Δ k-Δ T curves (over 97%). The E d values are approximately equal for 1D and 2D analyses, with a median of 96 GPa and standard deviation of 2 GPa. The correspondence between the experimental and simulated results for the 1D and 2D specimens reveals that deformation and thermal stress in coated specimens can be predicted regardless of specimen geometry through FE modeling and by using the experimental value of E d. An example of a turbine-bladeshaped substrate is presented to validate the approach.

  20. Modeling the small-scale dish-mounted solar thermal Brayton cycle

    NASA Astrophysics Data System (ADS)

    Le Roux, Willem G.; Meyer, Josua P.

    2016-05-01

    The small-scale dish-mounted solar thermal Brayton cycle (STBC) makes use of a sun-tracking dish reflector, solar receiver, recuperator and micro-turbine to generate power in the range of 1-20 kW. The modeling of such a system, using a turbocharger as micro-turbine, is required so that optimisation and further development of an experimental setup can be done. As a validation, an analytical model of the small-scale STBC in Matlab, where the net power output is determined from an exergy analysis, is compared with Flownex, an integrated systems CFD code. A 4.8 m diameter parabolic dish with open-cavity tubular receiver and plate-type counterflow recuperator is considered, based on previous work. A dish optical error of 10 mrad, a tracking error of 1° and a receiver aperture area of 0.25 m × 0.25 m are considered. Since the recuperator operates at a very high average temperature, the recuperator is modeled using an updated ɛ-NTU method which takes heat loss to the environment into consideration. Compressor and turbine maps from standard off-the-shelf Garrett turbochargers are used. The results show that for the calculation of the steady-state temperatures and pressures, there is good comparison between the Matlab and Flownex results (within 8%) except for the recuperator outlet temperature, which is due to the use of different ɛ-NTU methods. With the use of Matlab and Flownex, it is shown that the small-scale open STBC with an existing off-the-shelf turbocharger could generate a positive net power output with solar-to-mechanical efficiency of up to 12%, with much room for improvement.

  1. Effect of Restorative System and Thermal Cycling on the Tooth-Restoration Interface - OCT Evaluation.

    PubMed

    Sampaio, C S; Rodrigues, R V; Souza-Junior, E J; Freitas, A Z; Ambrosano, G M B; Pascon, F M; Puppin-Rontani, R M

    2016-01-01

    The present study evaluated the tooth/noncarious cervical lesion restoration interface when using different adhesive systems and resin composites, submitted to thermal cycling (TC), using optical coherence tomography (OCT). Noncarious cervical lesion (NCCL) preparations (0.7 mm depth × 2 mm diameter) were performed on 60 human third molars and randomly divided into six groups, according to the adhesive system and resin composite used: group 1 = Adper Single Bond 2 (SB2) + Aelite LS Posterior (AP); group 2 = SB2 + Venus Diamond (VD); group = SB2 + Filtek Z250XT (Z250); group 4 = Clearfil SE Bond (CSE) + AP; group 5 = CSE + VD; group 6 = CSE + Z250. Selective enamel etching was performed for 30 seconds on groups 4, 5, and 6, while groups 1, 2, and 3 were etched for 30 seconds in enamel and 15 seconds in dentin. All groups were evaluated using OCT before and after TC (n=10). Images were analyzed using Image J software; enamel and dentin margins were separately evaluated. Data from OCT were submitted to PROC MIXED for repeated measurements and Tukey Kramer test (α = 0.05). No marginal gaps were observed in etched enamel, either before or after TC, for all adhesive and resin composite systems. A significant interaction was found between adhesive system and TC for the dentin groups; after TC, restorations with CSE showed smaller gaps at the dentin/restoration interface compared with SB2 for all resin composites. Increased gap percentages were noticed after TC compared with the gaps before TC for all groups. In conclusion, TC affected marginal integrity only in dentin margins, whereas etched enamel margins remained stable even after TC. Dentin margins restored with CSE adhesive system showed better marginal adaptation than those restored with SB2. Resin composites did not influence marginal integrity of NCCL restorations.

  2. A quantitative evaluation of closed-cycle ocean thermal energy conversion (OTEC) technology in central station applications

    NASA Astrophysics Data System (ADS)

    Gritton, E. C.; Pei, R. Y.; Aroesty, J.; Balaban, M. M.; Gazley, C.; Hess, R. W.; Krase, W. H.

    1980-05-01

    An evaluation of a closed cycle Ocean Thermal Energy Conversion (OTEC) system for delivery of electric power to the United States is presented. Performance and costs of complete commercial OTEC systems are analyzed at the system level using inputs from component analyses and thermal resource data in the Gulf of Mexico. Such sites could feed the Gulf Coast from the west coast of Florida to the New Orleans area. By exploiting the temperature difference between warm surface waters and cold water from the depths to operate a thermodynamic cycle to generate electricity, OTEC acts as a heat engine that taps the surface waters of tropical and subtropical oceans as a heat source and the cold water originating in the polar regions as a heat sink. Results of the engineering analysis indicate that the system and platform appear to be within the state-of-the-art.

  3. Effect of thermal cycling on the microstructure of a directionally solidified Fe, Cr, Al-TaC eutectic alloy

    NASA Technical Reports Server (NTRS)

    Harf, F. H.; Tewari, S. N.

    1977-01-01

    Cylindrical bars (1.2 cm diameter) of Fe-13.6Cr-3.7Al-9TaC (wt %) eutectic alloy were directionally solidified in a modified Bridgman type furnace at 1 cm/h. The alloy microstructure consisted of aligned TaC fibers imbedded in a bcc Fe-Cr-Al matrix. Specimens of the alloy were thermally cycled from 1100 to 425 C in a burner rig. The effects of 1800 thermal cycles on the microstructure was examined by scanning electron microscopy, revealing a zig-zag shape of TaC fibers aligned parallel to the growth direction. The mechanism of carbide solution and reprecipitation on the (111) easy growth planes, suggested previously to account for the development of irregular serrations in Co-Cr-Ni matrix alloys, is believed to be responsible for these zig-zag surfaces.

  4. Compatability and accelerated aging study for Li(Si)FeS2 thermally activated batteries

    NASA Astrophysics Data System (ADS)

    Poole, R. L.; Mead, J. W.; Searcy, J. Q.; Neiswander, P. A.

    1982-04-01

    Thermally activated batteries using the Li(Si)/FeS2 system are being developed by Sandia National Laboratories. These components ae used in systems which require a storage life of 25 years and high reliability. A previous aging study was completed on this system, but no organic materials other than those in the electrical match and heat paper fuse strips were included. The present study incorporates all of the materials in the system, both organic and inorganic, except for the electric match and heat paper. There are two main parts in this study: (1) a compatibility study in which the four organic materials under investigation are placed in a hermetically sealed stainless steel container with battery components; (2) an aging study of pairs of material and individual materials in which one organic material is placed in a hermetically sealed stainless steel container with battery components. The compatibility study examines effects of some materials upon others (outgassing, etc.) which would cause degradation and/or functional failure.

  5. Recombinant growth factor mixtures induce cell cycle progression and the upregulation of type I collagen in human skin fibroblasts, resulting in the acceleration of wound healing processes.

    PubMed

    Lee, Do Hyun; Choi, Kyung-Ha; Cho, Jae-We; Kim, So Young; Kwon, Tae Rin; Choi, Sun Young; Choi, Yoo Mi; Lee, Jay; Yoon, Ho Sang; Kim, Beom Joon

    2014-05-01

    Application of growth factor mixtures has been used for wound healing and anti-wrinkles agents. The aim of this study was to evaluate the effect of recombinant growth factor mixtures (RGFM) on the expression of cell cycle regulatory proteins, type I collagen, and wound healing processes of acute animal wound models. The results showed that RGFM induced increased rates of cell proliferation and cell migration of human skin fibroblasts (HSF). In addition, expression of cyclin D1, cyclin E, cyclin-dependent kinase (Cdk)4, and Cdk2 proteins was markedly increased with a growth factor mixtures treatment in fibroblasts. Expression of type I collagen was also increased in growth factor mixtures-treated HSF. Moreover, growth factor mixtures-induced the upregulation of type I collagen was associated with the activation of Smad2/3. In the animal model, RGFM-treated mice showed accelerated wound closure, with the closure rate increasing as early as on day 7, as well as re-epithelization and reduced inflammatory cell infiltration than phosphate-buffered saline (PBS)-treated mice. In conclusion, the results indicated that RGFM has the potential to accelerate wound healing through the upregulation of type I collagen, which is partly mediated by activation of Smad2/3-dependent signaling pathway as well as cell cycle progression in HSF. The topical application of growth factor mixtures to acute and chronic skin wound may accelerate the epithelization process through these molecular mechanisms.

  6. Fibrin biomatrix-conjugated platelet-derived growth factor AB accelerates wound healing in severe thermal injury.

    PubMed

    Mittermayr, Rainer; Branski, Ludwik; Moritz, Martina; Jeschke, Marc G; Herndon, David N; Traber, Daniel; Schense, Jason; Gampfer, Jörg; Goppelt, Andreas; Redl, Heinz

    2016-05-01

    Controlled delivery of growth factors from biodegradable biomatrices could accelerate and improve impaired wound healing. The study aim was to determine whether platelet-derived growth factor AB (PDGF.AB) with a transglutaminase (TG) crosslinking substrate site released from a fibrin biomatrix improves wound healing in severe thermal injury. The binding and release kinetics of TG-PDGF.AB were determined in vitro. Third-degree contact burns (dorsum of Yorkshire pigs) underwent epifascial necrosectomy 24 h post-burn. Wound sites were covered with autologous meshed (3:1) split-thickness skin autografts and either secured with staples or attached with sprayed fibrin sealant (FS; n = 8/group). TG-PDGF.AB binds to the fibrin biomatrix using the TG activity of factor XIIIa, and is subsequently released through enzymatic cleavage. Three doses of TG-PDGF.AB in FS (100 ng, 1 µg and 11 µg/ml FS) were tested. TG-PDGF.AB was bound to the fibrin biomatrix as evidenced by western blot analysis and subsequently released by enzymatic cleavage. A significantly accelerated and improved wound healing was achieved using sprayed FS containing TG-PDGF.AB compared to staples alone. Low concentrations (100 ng-1 µg TG-PDGF.AB/ml final FS clot) demonstrated to be sufficient to attain a nearly complete closure of mesh interstices 14 days after grafting. TG-PDGF.AB incorporated in FS via a specific binding technology was shown to be effective in grafted third-degree burn wounds. The adhesive properties of the fibrin matrix in conjunction with the prolonged growth factor stimulus enabled by this binding technology could be favourable in many pathological situations associated with wound-healing disturbances. Copyright © 2013 John Wiley & Sons, Ltd.

  7. Thermally Accelerated Oxidative Degradation of Quercetin Using Continuous Flow Kinetic Electrospray-Ion Trap-Time of Flight Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Barnes, Jeremy S.; Foss, Frank W.; Schug, Kevin A.

    2013-10-01

    Thermally accelerated oxidative degradation of aqueous quercetin at pH 5.9 and 7.4 was kinetically measured using an in-house built online continuous flow device made of concentric capillary tubes, modified to fit to the inlet of an electrospray ionization-ion trap-time-of-flight-mass spectrometer (ESI-IT-TOF-MS). Time-resolved mass spectral measurements ranging from 2 to 21 min were performed in the negative mode to track intermediate degradation products and to evaluate the degradation rate of the deprotonated quercetin ion, [Q-H]-. Upon heating solutions in the presence of dissolved oxygen, degradation of [Q-H]- was observed and was accelerated by an increase in pH and temperature. Regardless of the condition, the same degradation pathways were observed. Degradation mechanisms and structures were determined using higher order tandem mass spectrometry (up to MS3) and high mass accuracy. The observed degradation mechanisms included oxidation, hydroxylation, and ring-cleavage by nucleophilic attack. A chalcan-trione structure formed by C-ring opening after hydroxylation at C2 was believed to be a precursor for other degradation products, formed by hydroxylation at the C2, C3, and C4 carbons from attack by nucleophilic species. This resulted in A-type and B-type ions after cross-ring cleavage of the C-ring. Based on time of appearance and signal intensity, nucleophilic attack at C3 was the preferred degradation pathway, which generated 2,4,6-trihydroxymandelate and 2,4,6-trihydroxyphenylglyoxylate ions. Overall, 23 quercetin-related ions were observed.

  8. Supersonic inflation of the radio lobes of NGC 1052: evidence for non-thermal particle acceleration

    NASA Astrophysics Data System (ADS)

    Morris, Taylor Andrew; Kraft, Ralph P.; Jones, Christine

    2016-01-01

    We analyze archival Chandra data of the nearby AGN NGC 1052 to determine the nature of the interaction of the radio lobes with the ambient hot gas. NGC 1052 is typically classified as a Seyfert galaxy, but has a radio bright core and extended diffuse radio lobes on kpc scales. We report the detection of X-ray bright shells around the radio lobes, suggestive of compression of the ISM by the supersonic inflation of the lobes. We determine the temperature and density of the gas in these shells and of the ambient ISM. We find that the temperature of the ISM is 0.8 keV, and that of the shells around the E and W radio lobes are 0.72 and 0.69 keV, respectively fitting a single temperature APEC model. The statistical quality of the fits is low, so systematic uncertainties dominate our ability to distinguish temperature variations between regions. NGC 1052's outburst is relatively young (9 x 1013 sec) and comparatively low power (1.9 x 1041 erg/sec). Interestingly, the density jump between the shells and the ambient ISM is larger than the maximum compression allows by the Rankine-Hugoniot conditions, suggesting that the emission from the shells is not thermal. We propose that the bubbles are highly supersonic (Mach number >5) and that the emission of the shell is due to synchrotron radiation from a population of ultrarelativistic electrons created by the powerful shock. If this interpretation is correct, NGC 1052 would be only the second AGN in which this process has been observed. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  9. Structure and thermal cycling stability of a hafnium monocarbide reinforced directionally solidified cobalt-base eutectic alloy

    NASA Technical Reports Server (NTRS)

    Kim, Y. G.

    1975-01-01

    A nominal composition of Co-15Cr-2ONi-10.5 Hf-0.7 C (NASA-HAFCO-11) was directionally solidified at 0.8 cm/hr growth rate to produce aligned HfC in a cobalt matrix alloy. The aligned HfC fibers were present as rod and plate types. The diameter of the aligned fibers was about 1 micron, with volume fraction in the range of 11 to 15 percent. The growth direction of the fibers was parallel to the 100. The NASA-HAFCO-11 alloy was subjected to thermal cycling between 425 deg and 1100 C, using a 2.5 minute cycle. No microstructural degradation of the HfC fibers in the alloy was observed after 2500 cycles.

  10. Al-Li alloy AA2198's very high cycle fatigue crack initiation mechanism and its fatigue thermal effect

    NASA Astrophysics Data System (ADS)

    Xu, Luopeng; Cao, Xiaojian; Chen, Yu; Wang, Qingyuan

    2015-10-01

    AA2198 alloy is one of the third generation Al-Li alloys which have low density, high elastic modulus, high specific strength and specific stiffness. Compared With the previous two generation Al-Li alloys, the third generation alloys have much improved in alloys strength, corrosion resistance and weldable characteristic. For these advantages, the third generation Al-Li alloys are used as aircraft structures, such as C919 aviation airplane manufactured by China and Russia next generation aviation airplane--MS-21. As we know, the aircraft structures are usually subjected to more than 108 cycles fatigue life during 20-30 years of service, however, there is few reported paper about the third generation Al-Li alloys' very high cycle fatigue(VHCF) which is more than 108 cycles fatigue. The VHCF experiment of AA2198 have been carried out. The two different initiation mechanisms of fatigue fracture have been found in VHCF. The cracks can initiate from the interior of the testing material with lower stress amplitude and more than 108 cycles fatigue life, or from the surface or subsurface of material which is the dominant reason of fatigue failures. During the experiment, the infrared technology is used to monitor the VHCF thermal effect. With the increase of the stress, the temperature of sample is also rising up, increasing about 15 °C for every 10Mpa. The theoretical thermal analysis is also carried out.

  11. Enhanced Employment of the Xanthophyll Cycle and Thermal Energy Dissipation in Spinach Exposed to High Light and N Stress.

    PubMed Central

    Verhoeven, A. S.; Demmig-Adams, B.; Adams III, W. W.

    1997-01-01

    The involvement of the xanthophyll cycle in photoprotection of N-deficient spinach (Spinacia oleracea L. cv Nobel) was investigated. Spinach plants were fertilized with 14 mM nitrate (control, high N) versus 0.5 mM (low N) fertilizer, and grown under both high- and low-light conditions. Plants were characterized from measurements of photosynthetic oxygen exchange and chlorophyll fluorescence, as well as carotenoid and cholorophyll analysis. Compared with the high-N plants, the low-N plants showed a lower capacity for photosynthesis and a lower chlorophyll content, as well as a lower rate of photosystem II photosynthetic electron transport and a corresponding increase in thermal energy dissipation activity measured as nonphotochemical fluorescence quenching. The low-N plants displayed a greater fraction of the total xanthophyll cycle pool as zeaxanthin and antheraxanthin at midday, and an increase in the ratio of xanthophyll cycle pigments to total chlorophyll. These results indicate that under N limitation both the light-collecting system and the photosynthetic rate decrease. However, the increased dissipation of excess energy shows that there is excess light absorbed at midday. We conclude that spinach responds to N limitation by a combination of decreased light collection and increased thermal dissipation involving the xanthophyll cycle. PMID:12223645

  12. University of Minnesota aquifer thermal energy storage (ATES) project report on the second long-term cycle

    SciTech Connect

    Hoyer, M.C.; Hallgren, J.P.; Lauer, J.L.; Walton, M.; Eisenreich, S.J.; Howe, J.T.; Splettstoesser, J.F.

    1991-12-01

    The technical feasibility of high-temperature [>100{degrees}C (>212{degrees}F)] aquifer thermal energy storage (ATES) in a deep, confined aquifer was tested in a series of experimental cycles at the University of Minnesota`s St. Paul field test facility (FTF). This report describes the second long-term cycle (LT2), which was conducted from October 1986 through April 1987. Heat recovery; operational experience; and thermal, chemical, hydrologic, and geologic effects are reported. Approximately 61% of the 9.21 GWh of energy added to the 9.38 {times} 10{sup 4} m{sup 3} of ground water stored during LT2 was recovered. Temperatures of the water stored and recovered averaged 118{degrees}C (244{degrees}F) and 85{degrees}C (185{degrees}F), respectively. Results agreed with previous cycles conducted at the FTF. System operation during LT2 was nearly as planned. Operational experience from previous cycles at the FTF was extremely helpful. Ion-exchange softening of the heated and stored aquifer water prevented scaling in the system heat exchangers and the storage well, and changed the major-ion chemistry of the stored water. Sodium bicarbonate replaced magnesium and calcium bicarbonate as primary ions in the softened water. Water recovered form storage was approximately at equilibrium with respect to dissolved ions. Silica, calcium, and magnesium were significantly higher in recovered water than in injected water. Sodium was significantly lower in water recovered than in water stored.

  13. University of Minnesota aquifer thermal energy storage (ATES) project report on the second long-term cycle

    SciTech Connect

    Hoyer, M.C.; Hallgren, J.P.; Lauer, J.L.; Walton, M.; Eisenreich, S.J.; Howe, J.T.; Splettstoesser, J.F. )

    1991-12-01

    The technical feasibility of high-temperature (>100{degrees}C (>212{degrees}F)) aquifer thermal energy storage (ATES) in a deep, confined aquifer was tested in a series of experimental cycles at the University of Minnesota's St. Paul field test facility (FTF). This report describes the second long-term cycle (LT2), which was conducted from October 1986 through April 1987. Heat recovery; operational experience; and thermal, chemical, hydrologic, and geologic effects are reported. Approximately 61% of the 9.21 GWh of energy added to the 9.38 {times} 10{sup 4} m{sup 3} of ground water stored during LT2 was recovered. Temperatures of the water stored and recovered averaged 118{degrees}C (244{degrees}F) and 85{degrees}C (185{degrees}F), respectively. Results agreed with previous cycles conducted at the FTF. System operation during LT2 was nearly as planned. Operational experience from previous cycles at the FTF was extremely helpful. Ion-exchange softening of the heated and stored aquifer water prevented scaling in the system heat exchangers and the storage well, and changed the major-ion chemistry of the stored water. Sodium bicarbonate replaced magnesium and calcium bicarbonate as primary ions in the softened water. Water recovered form storage was approximately at equilibrium with respect to dissolved ions. Silica, calcium, and magnesium were significantly higher in recovered water than in injected water. Sodium was significantly lower in water recovered than in water stored.

  14. Suppressing Thermal Energy Drift In The LLNL Flash X-Ray Accelerator Using Linear Disk Resistor Stacks

    SciTech Connect

    Kreitzer, B R; Houck, T L; Luchterhand, O C

    2011-07-19

    This paper addresses thermal drift in sodium thiosulfate liquid resistors and their replacement with linear disk resistors from HVR Advanced Power Components. Sodium thiosulfate resistors in the FXR induction linear accelerator application have a temperature coefficient of {approx}1.8%/C. The FXR Marx banks send an 8kJ pulse through eight 524 cm{sup 3} liquid resistors at a repetition rate of up to 1 every 45 seconds. Every pulse increases the temperature of the solution by {approx}0.4 C which produces a 0.7% change in resistance. The typical cooling rate is {approx}0.4 C per minute which results in {approx}0.1% energy drop per pulse during continuous pulsed operations. A radiographic accelerator is extraordinarily sensitive to energy variations. Changes in beam energy produce movement in beam transport, changes in spot size, and large dose variations. If self-heating were the only problem, we could predict the increase in input voltage required to compensate for the energy loss. However, there are other variables that influence the temperature of the resistors such as focus magnet heating, changes in room temperature, changes in cooling water, where the cell is located, etc. Additionally not all of the resistors have equivalent cooling rates and as many as 32 resistors are driven from a single power source. The FXR accelerator group elected to replace the sodium thiosulfate resistors with HVR Linear Disk Resistors in a stack type configuration. With data limited for these resistors when used in oil and at low resistance values, a full characterization needed to be performed. High currents (up to 15kA), high voltages (up to 400kV), and Fast Rise times (<10ns) made a resistor choice difficult. Other solid resistors have been tried and had problems at the connection points and with the fact that the resistivity changed as they absorbed oil. The selected HVR resistors have the advantage of being manufactured with the oil impregnated in to them so this characteristic

  15. Effects of arc current on the life in burner rig thermal cycling of plasma sprayed ZrOsub2-Ysub2Osub3

    NASA Astrophysics Data System (ADS)

    Hendricks, R. C.; McDonald, G.

    1982-02-01

    An analysis of thermal cycle life data for four sets of eight thermal barrier coated specimens representing arc currents (plasma gun power) of 525, 600, 800, or 950 amps is presented. The ZrO2-8Y2O3/NiCrAlY plasma spray coated Rene 41 rods were thermal cycled to 1040 C in a Mach 0.3-Jet A/air burner flame. The experimental results indicate the existance of a minimum or threshold power level which coating life expectancy is less than 500 cycles. Above the threshold power level, coating life expectancy more than doubles and increases with arc current.

  16. Three-dimensional simulations of the non-thermal broadband emission from young supernova remnants including efficient particle acceleration

    SciTech Connect

    Ferrand, Gilles; Safi-Harb, Samar; Decourchelle, Anne E-mail: samar@physics.umanitoba.ca

    2014-07-01

    Supernova remnants are believed to be major contributors to Galactic cosmic rays. In this paper, we explore how the non-thermal emission from young remnants can be used to probe the production of energetic particles at the shock (both protons and electrons). Our model couples hydrodynamic simulations of a supernova remnant with a kinetic treatment of particle acceleration. We include two important back-reaction loops upstream of the shock: energetic particles can (1) modify the flow structure and (2) amplify the magnetic field. As the latter process is not fully understood, we use different limit cases that encompass a wide range of possibilities. We follow the history of the shock dynamics and of the particle transport downstream of the shock, which allows us to compute the non-thermal emission from the remnant at any given age. We do this in three dimensions, in order to generate projected maps that can be compared with observations. We observe that completely different recipes for the magnetic field can lead to similar modifications of the shock structure, although to very different configurations of the field and particles. We show how this affects the emission patterns in different energy bands, from radio to X-rays and γ-rays. High magnetic fields (>100 μG) directly impact the synchrotron emission from electrons, by restricting their emission to thin rims, and indirectly impact the inverse Compton emission from electrons and also the pion decay emission from protons, mostly by shifting their cut-off energies to respectively lower and higher energies.

  17. Development of a thermal scheme for a cogeneration combined-cycle unit with an SVBR-100 reactor

    NASA Astrophysics Data System (ADS)

    Kasilov, V. F.; Dudolin, A. A.; Krasheninnikov, S. M.

    2017-02-01

    At present, the prospects for development of district heating that can increase the effectiveness of nuclear power stations (NPS), cut down their payback period, and improve protection of the environment against harmful emissions are being examined in the nuclear power industry of Russia. It is noted that the efficiency of nuclear cogeneration power stations (NCPS) is drastically affected by the expenses for heat networks and heat losses during transportation of a heat carrier through them, since NPSs are usually located far away from urban area boundaries as required for radiation safety of the population. The prospects for using cogeneration power units with small or medium power reactors at NPSs, including combined-cycle units and their performance indices, are described. The developed thermal scheme of a cogeneration combined-cycle unit (CCU) with an SBVR-100 nuclear reactor (NCCU) is presented. This NCCU should use a GE 6FA gasturbine unit (GTU) and a steam-turbine unit (STU) with a two-stage district heating plant. Saturated steam from the nuclear reactor is superheated in a heat-recovery steam generator (HRSG) to 560-580°C so that a separator-superheater can be excluded from the thermal cycle of the turbine unit. In addition, supplemental fuel firing in HRSG is examined. NCCU effectiveness indices are given as a function of the ambient air temperature. Results of calculations of the thermal cycle performance under condensing operating conditions indicate that the gross electric efficiency η el NCCU gr of = 48% and N el NCCU gr = 345 MW can be achieved. This efficiency is at maximum for NCCU with an SVBR-100 reactor. The conclusion is made that the cost of NCCU installed kW should be estimated, and the issue associated with NCCUs siting with reference to urban area boundaries must be solved.

  18. Recent geographic convergence in diurnal and annual temperature cycling flattens global thermal profiles

    NASA Astrophysics Data System (ADS)

    Wang, George; Dillon, Michael E.

    2014-11-01

    Warming mean temperatures over the past century have probably shifted distributions, altered phenologies, increased extinction risks, and impacted agriculture and human health. However, knowledge of mean temperatures alone does not provide a complete understanding either of changes in the climate itself or of how changing climate will affect organisms. Temporal temperature variation, primarily driven by daily and annual temperature cycles, has profound effects on organism physiology and ecology, yet changes in temperature cycling over the past 40 years are still poorly understood. Here we estimate global changes in the magnitudes of diurnal and annual temperature cycles from 1975 to 2013 from an analysis of over 1.4 billion hourly temperature measurements from 7,906 weather stations. Increases in daily temperature variation since 1975 in polar (1.4 °C), temperate (1.0 °C) and tropical (0.3 °C) regions parallel increases in mean temperature. Concurrently, magnitudes of annual temperature cycles decreased by 0.6 °C in polar regions, increased by 0.4 °C in temperate regions, and remained largely unchanged in tropical regions. Stronger increases in daily temperature cycling relative to changes in annual temperature cycling in temperate and polar regions mean that, with respect to diurnal and annual cycling, the world is flattening as temperate and polar regions converge on tropical temperature cycling profiles.

  19. Long-term calcination/carbonation cycling and thermal pretreatment for CO{sub 2} capture by limestone and dolomite

    SciTech Connect

    Zhongxiang Chen; Hoon Sub Song; Miguel Portillo; C. Jim Lim; John R. Grace; E.J. Anthony

    2009-03-15

    Capturing carbon dioxide is vital for the future of climate-friendly combustion, gasification, and steam-re-forming processes. Dry processes utilizing simple sorbents have great potential in this regard. Long-term calcination/carbonation cycling was carried out in an atmospheric-pressure thermogravimetric reactor. Although dolomite gave better capture than limestone for a limited number of cycles, the advantage declined over many cycles. Under some circumstances, decreasing the carbonation temperature increased the rate of reaction because of the interaction between equilibrium and kinetic factors. Limestone and dolomite, after being pretreated thermally at high temperatures (1000 or 1100{sup o}C), showed a substantial increase in calcium utilization over many calcination/carbonation cycles. Lengthening the pretreatment interval resulted in greater improvement. However, attrition was significantly greater for the pretreated sorbents. Greatly extending the duration of carbonation during one cycle was found to be capable of restoring the CO{sub 2} capture ability of sorbents to their original behavior, offering a possible means of countering the long-term degradation of calcium sorbents for dry capture of carbon dioxide. 12 refs., 12 figs., 2 tabs.

  20. Effects of bonding bakeout thermal cycles on pre- and post irradiation microstructures, physical, and mechanical properties of copper alloys

    SciTech Connect

    Singh, B.N.; Eldrup, M.; Toft, P.; Edwards, D.J.

    1996-10-01

    At present, dispersion strengthened (DS) copper is being considered as the primary candidate material for the ITER first wall and divertor components. Recently, it was agreed among the ITER parties that a backup alloy should be selected from the two well known precipitation hardened copper alloys, CuCrZr and CuNiBe. It was therefore decided to carry out screening experiments to simulate the effect of bonding and bakeout thermal cycles on microstructure, mechanical properties, and electrical resistivity of CuCrZr and CuNiBe alloys. On the basis of the results of these experiments, one of the two alloys will be selected as a backup material. Tensile specimens of CuCrZr and CuNiBe alloys were given various heat treatments corresponding to solution anneal, prime ageing, and bonding thermal cycle followed by reageing and the reactor bakeout treatment at 623K for 100 hours. Tensile specimens of the DS copper were also given the heat treatment corresponding to the bonding thermal cycle. A number of these heat treated specimens of CuCrZr, CuNiBe, and DS copper were neutron irradiated at 523K to a dose level of {approx}0.3 dpa (NRT) in the DR-3 reactor at Riso. Both unirradiated and irradiated specimens with the various heat treatments were tensile tested at 532K. The dislocation, precipitate and void microstructures and electrical resistivity of these specimens were also determined. Results of these investigations will be reported and discussed in terms of thermal and irradiation stability of precipitates and irradiation-induced precipitation and recovery of dislocation microstructure. Results show that the bonding and bakeout thermal cycles are not likely to have any serious deleterious effects on the performance of these alloys. The CuNiBe alloys were found to be susceptible to radiation-induced embrittlement, however, the exact mechanism is not yet known. It is thought that radiation-induced precipitation and segregation of the beryllium may be responsible.

  1. Development of improved high pressure turbine outer gas path seal components. [abradability and thermal cycling test results

    NASA Technical Reports Server (NTRS)

    Shiembob, L. T.

    1980-01-01

    A plasma sprayed graded layered ceramic/metallic (ZrO2/CoCrAlY) seal was evaluated for JT9D turbine application by rig and engine tests. Four cyclic thermal shock rig tests were conducted during the program. Three completed 1000 simulated engine thermal cycle tests and the fourth completed 500 cycles without severe cracking or spalling. Three ceramic seals were installed in a JT9D experimental engine to evaluate the effect of the engine thermal environment on the seals. All three seals completed the test successfully without severe cracking or spalling. The three seals did have slight laminar cracks at the 85/15-40/60 ZrO2/CoCrAlY interface. The second engine test evaluated the rub capabilities of the seal. Six ceramic seals were installed in the engine with fourteen abrasive tip blades. Three of the six seals rubbed to a depth of 24 mils. Eight of the fourteen abrasive tip blades showed evidence of wear. Three of the eight blades wore a maximum of five mils. Engine rub test results demonstrated the potential of reducing turbine clearances and thereby improving engine performance by use of sprayed ceramic seals.

  2. Compliant alkali silicate sealing glass for solid oxide fuel cell applications: thermal cycle stability and chemical compatibility

    SciTech Connect

    Chou, Y. S.; Thomsen, Edwin C.; Williams, Riley T.; Choi, Jung-Pyung; Canfield, Nathan L.; Bonnett, Jeff F.; Stevenson, Jeffry W.; Shyam, Amit; Lara-Curzio, E.

    2011-03-01

    An alkali silicate glass (SCN-1) is currently being evaluated as a candidate sealing glass for solid oxide fuel (SOFC) applications. The glass containing ~17 mole% alkalis (K2O and Na2O) remains vitreous and compliant during SOFC operation, unlike conventional SOFC sealing glasses, which experience substantial devitrification after the sealing process. The non-crystallizing compliant sealing glass has lower glass transition and softening temperatures since the microstructure remains glassy without significant crystallite formation, and hence can relieve or reduce residual stresses and also has the potential for crack healing. Sealing approaches based on compliant glass will also need to satisfy all the mechanical, thermal, chemical, physical, and electrical requirements for SOFC applications, not only in bulk properties but also at sealing interfaces. In this first of a series of papers we will report the thermal cycle stability of the glass when sealed between two SOFC components, i.e., a NiO/YSZ anode supported YSZ bilayer and a coated ferritic stainless steel interconnect material. High temperature leak rates were monitored versus thermal cycles between 700-850oC using back pressures ranging from 0.2 psi to 1.0 psi. Isothermal stability was also evaluated in a dual environment consisting of flowing dilute H2 fuel versus ambient air. In addition, chemical compatibility at the alumina and YSZ interfaces was examined with scanning electron microscopy and energy dispersive spectroscopy. The results shed new light on the topic of SOFC glass seal development.

  3. Experimental investigation of neutron emissions during thermal cycling of TiD{sub x} (x {approx} 2.00)

    SciTech Connect

    Fernandez, J.F.; Cuevas, F.; Alguero, M.; Sanchez, C.

    1997-03-01

    The production of neutrons from D + D reactions in thermally cycled titanium deuteride (TiD{sub x}) (x {approx} 2) is investigated in depth. Special attention is given to cubic-tetragonal ({delta} - {epsilon}) phase transition that TiD{sub x} experiences near room temperature as a possible triggering mechanism of `cold nuclear fusion reactions.` The TiD{sub x} (x {approx} 2.00) samples, possessing well-known properties about the {delta} - {epsilon} transition, are cycled at temperatures (from -60 to 60{degree} C) where the phase transition takes place. The cold fusion signature is investigated by measuring the neutron flux of the sample during the experiments. No significant neutron signal above the background level is found during thermal cycling of the TiD{sub x} samples. It is concluded that in the samples investigated, no correlation exists between the {delta} - {epsilon} transition and the trigger of the D + D reactions. Background deviations give an upper limit of the rate of the D + D {yields} {sup 3}He + n reaction of {lambda} < 10{sup -23} fusion/p-d.s. 32 refs., 8 figs., 4 tabs.

  4. Comparison of Extensive Thermal Cycling Effects on Microstructure Development in Micro-alloyed Sn-Ag-Cu Solder Joints

    SciTech Connect

    Anderson, Iver E.; Boesenberg, Adam; Harringa, Joel; Riegner, David; Steinmetz, Andrew; Hillman, David

    2011-09-28

    Pb-free solder alloys based on the Sn-Ag-Cu (SAC) ternary eutectic have promise for widespread adoption across assembly conditions and operating environments, but enhanced microstructural control is needed. Micro-alloying with elements such as Zn was demonstrated for promoting a preferred solidification path and joint microstructure earlier in simple (Cu/Cu) solder joints studies for different cooling rates. This beneficial behavior now has been verified in reworked ball grid array (BGA) joints, using dissimilar SAC305 (Sn-3.0Ag-0.5Cu, wt.%) solder paste. After industrial assembly, BGA components joined with Sn-3.5Ag-0.74Cu-0.21Zn solder were tested in thermal cycling (-55 C/+125 C) along with baseline SAC305 BGA joints beyond 3000 cycles with continuous failure monitoring. Weibull analysis of the results demonstrated that BGA components joined with SAC + Zn/SAC305 have less joint integrity than SAC305 joints, but their lifetime is sufficient for severe applications in consumer, defense, and avionics electronic product field environments. Failure analysis of the BGA joints revealed that cracking did not deviate from the typical top area (BGA component side) of each joint, in spite of different Ag3Sn blade content. Thus, SAC + Zn solder has not shown any advantage over SAC305 solder in these thermal cycling trials, but other characteristics of SAC + Zn solder may make it more attractive for use across the full range of harsh conditions of avionics or defense applications.

  5. Accelerating Ground-Test Cycle Time: The Six-Minute Model Change and Other Visions for the 21st Century

    NASA Technical Reports Server (NTRS)

    Kegelman, Jerome T.

    1998-01-01

    The advantage of managing organizations to minimize product development cycle time has been well established. This paper provides an overview of the wind tunnel testing cycle time reduction activities at Langley Research Center (LaRC) and gives the status of several improvements in the wind tunnel productivity and cost reductions that have resulted from these activities. Processes have been examined and optimized. Metric data from monitoring processes provides guidance for investments in advanced technologies. The most promising technologies under implementation today include the use of formally designed experiments, a diverse array of quick disconnect technology and the judicious use of advanced electronic and information technologies.

  6. Inhibition of ovarian cancer cell proliferation by a cell cycle inhibitory peptide fused to a thermally responsive polypeptide carrier

    PubMed Central

    Massodi, Iqbal; Moktan, Shama; Rawat, Aruna; Bidwell, Gene L.; Raucher, Drazen

    2009-01-01

    Current treatment of solid tumors is limited by normal tissue tolerance, resulting in a narrow therapeutic index. To increase drug specificity and efficacy and to reduce toxicity in normal tissues, we have developed a polypeptide carrier for a cell cycle inhibitory peptide, which has the potential to be thermally targeted to the tumor site. The design of this polypeptide is based on elastin-like polypeptide (ELP). The coding sequence of ELP was modified by the addition of the cell penetrating peptide Bac-7 at the N-terminus and a 23 amino acid peptide derived from p21 at the C-terminus (Bac-ELP1-p21). Bac-ELP1-p21 is soluble in aqueous solutions below physiological temperature (37°C) but aggregates when the temperature is raised above 39°C, making it a promising thermally responsive therapeutic carrier that may be actively targeted to solid tumors by application of focused hyperthermia. While Bac-ELP1-p21 at 37°C did not have any effect on SKOV-3 cell proliferation, the use of hyperthermia increased the antiproliferative effect of Bac-ELP1-p21 compared with a thermally unresponsive control polypeptide. Bac-ELP1-p21 displayed both a cytoplasmic and nuclear distribution in the SKOV-3 cells, with nuclear-localized polypeptide enriched in the heated cells, as revealed by confocal microscopy. Using Western blotting, we show that Bac-ELP1-p21 caused a decrease in Rb phosphorylation levels in cells treated at 42°C. The polypeptide also induced caspase activation, PARP cleavage, and cell cycle arrest in S-phase and G2/M-phase. These studies indicate that ELP is a promising macromolecular carrier for the delivery of cell cycle inhibitory peptides to solid tumors. PMID:19588502

  7. Modeling Thermal Fatigue in CPV Cell Assemblies: Preprint

    SciTech Connect

    Bosco, N.; Silverman, T. J.; Kurtz, S.

    2011-07-01

    A finite element model has been created to quantify the thermal fatigue damage of the CPV die attach. Simulations are used to compare to results of empirical thermal fatigue equations originally developed for accelerated chamber cycling. While the empirical equations show promise when extrapolated to the lower temperature cycles characteristic of weather-induced temperature changes in the CPV die attach, it is demonstrated that their damage does not accumulate linearly: the damage a particular cycle contributes depends on the preceding cycles. Simulations of modeled CPV cell temperature histories provided for direct comparison of the FEM and empirical methods, and for calculation of equivalent times provided by standard accelerated test sequences.

  8. Ultraviolet irradiation at elevated temperatures and thermal cycling in vacuum of FEP-A covered silicon solar cells

    NASA Technical Reports Server (NTRS)

    Broder, J. D.; Marsik, S. J.

    1978-01-01

    Experiments were designed and performed on silicon solar cells covered with heat-bonded FEP-A in an effort to explain the rapid degeneration of open-circuit voltage and maximum power observered on cells of this type included in an experiment on the ATS-6 spacecraft. Solar cells were exposed to ultraviolet light in vacuum at temperatures ranging from 30 to 105 C. The samples were then subjected to thermal cycling from 130 to -130 C. Inspection following irradiation indicated that all the covers remained physically intact. However, during the temperature cycling heat-bonded covers showed cracking. The test showed that heat-bonded FEP-A covers embrittle during UV exposure and the embrittlement is dependent upon sample temperature during irradiation. The results of the experiment suggest a probable mechanism for the degradation of the FEP-A cells on ATS-6.

  9. A review of test results on solar thermal power modules with dish-mounted Stirling and Brayton cycle engines

    NASA Technical Reports Server (NTRS)

    Jaffe, Leonard D.

    1988-01-01

    This paper presents results of development tests of various solar thermal parabolic dish modules and assemblies that used dish-mounted Brayton or Stirling cycle engines for production of electric power. These tests indicate that early modules achieve net efficiencies up to 29 percent in converting sunlight to electricity, as delivered to the grid. Various equipment deficiencies were observed and a number of malfunctions occurred. The performance measurements, as well as the malfunctions and other test experience, provided information that should be of value in developing systems with improved performance and reduced maintenance.

  10. Chloride-dependent acceleration of cell cycle via modulation of Rb and cdc2 in osteoblastic cells

    SciTech Connect

    Maki, Masahiro; Miyazaki, Hiroaki; Nakajima, Ken-ichi; Yamane, Junko; Niisato, Naomi; Morihara, Toru; Kubo, Toshikazu; Marunaka, Yoshinori

    2007-10-05

    In the present study, we investigated if Cl{sup -} regulates the proliferation of the MC3T3-E1 osteoblastic cells. The proliferation of MC3T3-E1 osteoblastic cells was diminished by lowering the extracellular Cl{sup -} concentration ([Cl{sup -}]{sub o}) in the culture medium. The lowered in [Cl{sup -}]{sub o} increased the periods of the G{sub 0}/G{sub 1} and the G{sub 2}/M phases in cell cycle. We further studied the effects of [Cl{sup -}]{sub o} on the key enzymes, Rb and cdc2, playing key roles in checking points of the G{sub 0}/G{sub 1} and the G{sub 2}/M phases in cell cycle. The lowered in [Cl{sup -}]{sub o} diminished the active forms of enzymes, Rb and cdc2. We further found that the action of lowered [Cl{sup -}]{sub o} on the cell proliferation, the cell cycle, Rb and cdc2 was abolished by the presence of 2 mM glutamine, but not by that of pyruvate as another Krebs cycle substrate. Taken together, these observations indicate here for the first time that Cl{sup -} modulates Rb and cdc2, enhancing the proliferation of the MC3T3-E1 osteoblastic cells.

  11. A Chandra view of non-thermal emission in the northwestern region of supernova remnant RCW 86: Particle acceleration and magnetic fields

    SciTech Connect

    Castro, Daniel; Lopez, Laura A.; Figueroa-Feliciano, Enectali; Slane, Patrick O.; Yamaguchi, Hiroya; Ramirez-Ruiz, Enrico

    2013-12-10

    The shocks of supernova remnants are believed to accelerate particles to cosmic ray (CR) energies. The amplification of the magnetic field due to CRs propagating in the shock region is expected to have an impact on both the emission from the accelerated particle population as well as the acceleration process itself. Using a 95 ks observation with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory, we map and characterize the synchrotron emitting material in the northwest region of RCW 86. We model spectra from several different regions, both filamentary and diffuse, where emission appears to be dominated by synchrotron radiation. The fine spatial resolution of Chandra allows us to obtain accurate emission profiles across three different non-thermal rims in this region. The narrow width (l ≈ 10''-30'') of these filaments constrains the minimum magnetic field strength at the post-shock region to approximately 80 μG.

  12. Effect of Gaseous Impurities on Long-Term Thermal Cycling and Aging Properties of Complex Hydrides for Hydrogen Storage

    SciTech Connect

    Chandra, Dhanesh; Lamb, Joshua; Chien, Wen-Ming; Talekar, Anjali; and Pal, Narendra

    2011-03-28

    This program was dedicated to understanding the effect of impurities on Long-Term Thermal Cycling and aging properties of Complex Hydrides for Hydrogen Storage. At the start of the program we found reversibility between Li2NH+LiH LiH+LiNH2 (yielding ~5.8 wt.%H capacity). Then we tested the effect of impurity in H2 gas by pressure cycling at 255°C; first with industrial gas containing ppm levels of O2 and H2O as major impurities. Both these impurities had a significant impact on the reversibility and decreased the capacity by 2.65 wt.%H. Further increase in number of cycles from 500 to 1100 showed only a 0.2 wt%H more weight loss, showing some capacity is still maintained after a significant number of cycles. The loss of capacity is attributed to the formation of ~55 wt% LiH and ~30% Li2O, as major contaminant phases, along with the hydride Li2NH phase; suggesting loss of nitrogen during cycling. The effect of 100 ppm H2O in H2 also showed a decrease of ~2.5 wt.%H (after 560 cycles), and 100ppm O2 in H2; a loss of ~4.1 wt.%. Methane impurity (100 ppm, 100cycles), showed a very small capacity loss of 0.9 wt.%H under similar conditions. However, when Li3N was pressure cycled with 100ppmN2-H2 there were beneficial effects were observed (255oC); the reversible capacity increased to 8.4wt.%H after 853 cycles. Furthermore, with 20 mol.%N2-H2 capacity increased to ~10 wt.%H after 516 cycles. We attribute this enhancement to the reaction of nitrogen with liquid lithium during cycling as the Gibbs free energy of formation of Li3N (Go = -98.7 kJ/mol) is more negative than that of LiH (Go = -50.3 kJ/mol). We propose that the mitigation of hydrogen capacity losses is due to the destabilization of the LiH phase that tends to accumulate during cycling. Also more Li2NH phase was found in the cycled product. Mixed Alanates (3LiNH2:Li3AlH6) showed that 7 wt% hydrogen desorbed under dynamic vacuum. Equilibrium experiments (maximum 12 bar H2) showed up to 4wt% hydrogen reversibly

  13. Accelerator-driven subcritical fission in molten salt core: Closing the nuclear fuel cycle for green nuclear energy

    SciTech Connect

    McIntyre, Peter; Assadi, Saeed; Badgley, Karie; Baker, William; Comeaux, Justin; Gerity, James; Kellams, Joshua; McInturff, Al; Pogue, Nathaniel; Sattarov, Akhdiyor; Sooby, Elizabeth; Tsvetkov, Pavel; Phongikaroon, Supathorn; Simpson, Michael

    2013-04-19

    A technology for accelerator-driven subcritical fission in a molten salt core (ADSMS) is being developed as a basis for the destruction of the transuranics in used nuclear fuel. The molten salt fuel is a eutectic mixture of NaCl and the chlorides of the transuranics and fission products. The core is driven by proton beams from a strong-focusing cyclotron stack. This approach uniquely provides an intrinsically safe means to drive a core fueled only with transuranics, thereby eliminating competing breeding terms.

  14. Exogenous hydrogen sulfide exerts proliferation, anti-apoptosis, migration effects and accelerates cell cycle progression in multiple myeloma cells via activating the Akt pathway.

    PubMed

    Zheng, Dong; Chen, Ziang; Chen, Jingfu; Zhuang, Xiaomin; Feng, Jianqiang; Li, Juan

    2016-10-01

    Hydrogen sulfide (H2S), regarded as the third gaseous transmitter, mediates and induces various biological effects. The present study investigated the effects of H2S on multiple myeloma cell progression via amplifying the activation of Akt pathway in multiple myeloma cells. The level of H2S produced in multiple myeloma (MM) patients and healthy subjects was measured using enzyme-linked immunosorbent assay (ELISA). MM cells were treated with 500 µmol/l NaHS (a donor of H2S) for 24 h. The expression levels of phosphorylated-Akt (p-Akt), Bcl-2 and caspase-3 were measured by western blot assay. Cell viability was detected by Cell Counting Kit 8 (CCK-8). The cell cycle was analyzed by flow cytometry. Our results show that the concentration of H2S was higher in MM patients and that it increased in parallel with disease progression. Treating MM cells with 500 µmol/l NaHS for 24 h markedly increased the expression level of Bcl-2 and the activation of p-Akt, however, the expression level of caspase-3 was decreased, cell viability was increased, and cell cycle progression was accelerated in MM cells. NaHS also induced migration in MM cells in transwell migration assay. Furthermore, co-treatment of MM cells with 500 µmol/l NaHS and 50 µmol/l LY294002 for 24 h significantly overset these effects. In conclusion, our findings demonstrate that the Akt pathway contributes to NaHS-induced cell proliferation, migration and acceleration of cell cycle progression in MM cells.

  15. Amplitude of the diurnal temperature cycle as observed by thermal infrared and microwave radiometers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Land surface temperature (LST) is a key input to physically-based retrieval algorithms of hydrological states and fluxes, and global measurements of LST are provided by many satellite platforms. Passive microwave (MW) observations offer an alternative to conventional thermal infrared (TIR) LST retri...

  16. Methods for separation/purification utilizing rapidly cycled thermal swing sorption

    DOEpatents

    Tonkovich, Anna Lee Y.; Monzyk, Bruce F.; Wang, Yong; VanderWiel, David P.; Perry, Steven T.; Fitzgerald, Sean P.; Simmons, Wayne W.; McDaniel, Jeffrey S.; Weller, Jr., Albert E.

    2004-11-09

    The present invention provides apparatus and methods for separating fluid components. In preferred embodiments, the apparatus and methods utilize microchannel devices with small distances for heat and mass transfer to achieve rapid cycle times and surprisingly large volumes of fluid components separated in short times using relatively compact hardware.

  17. The effect of bonding and bakeout thermal cycles on the properties of copper alloys irradiated at 100 C

    SciTech Connect

    Edwards, D.J.; Singh, B.N.; Toft, P.; Eldrup, M.

    1998-03-01

    This report describes the final irradiation experiment in a series of screening experiments aimed at investigating the effects of bonding and bakeout thermal cycles on irradiated copper alloys. Tensile specimens of CuCrZr and CuNiBe alloys were given various heat treatments corresponding to solution anneal, prime-ageing and bonding thermal treatment. The post-irradiation tests at 100 C revealed the greatest loss of ductility occurred in the CuCrZr alloys, irrespective of the pre-irradiation heat treatment, with the uniform elongation dropping to levels of less than 1.5%. The yield and ultimate strengths for all of the individual heat treated samples increased substantially after irradiation. The same trend was observed for the CuNiBe alloys, which overall exhibited a factor of 3 higher uniform elongation after irradiation with almost double the strength. In both alloys irradiation-induced precipitation lead to a large increase in the strength of the solution annealed specimens with a noticeable decrease in uniform elongation. The Al25 alloy also experienced an increase in the overall strength of the alloy after irradiation, accompanied by approximately a 50% decrease in the uniform and total elongation. The additional bakeout treatments given to the CuCrZr and CuNiBe before irradiation served to increase the strength, but in terms of the ductility no improvement or degradation resulted from the additional thermal exposure. The results of this experiment confirm that the al25 possesses the most resistant microstructure to thermal and irradiation-induced changes, while the competing effects of ballistic dissolution and reprecipitation lead to important changes in the two precipitation strengthened alloys. This study and others have repeatedly shown that these materials can only be used if the very low uniform elongation (1% or less) can be accounted for in the design since pre-irradiation thermal processing cannot mitigate the irradiation embrittlement.

  18. Influence of dopant on the behavior under thermal cycling of two plasma- sprayed zirconia coatings Part 2: residual stresses

    NASA Astrophysics Data System (ADS)

    Hamacha, R.; Fauchais, P.; Nardou, F.

    1997-06-01

    The evolution of coating morphology and surface residual stresses was followed for three different pow-ders: zirconia stabilized with 8 wt% yttria (YSZ), 9.9 wt% dysprosia (DSZ), and 9.8 wt% ytterbia (YbSZ). The YSZ reference powder was fused and crushed (-45 +22 μm), and the other two were agglom-erated and sintered (-90 +10 μm). According to the size distributions and manufacturing process, the plasma-sprayed YSZ particles were fully molten, resulting in dense coatings with good contact between the splats; the DSZ and, especially, the YbSZ particles were partially molten. In general, the surface residual stresses were slightly compressive before thermal cycling. The YSZ and DSZ coatings were insensitive to aging (600 h in air at room temperature), as shown by the surface stress evolution, which was not the case for YbSZ coatings. Six hundred furnace thermal cycles from 1100 °C to room temperature indicated excellent behavior of YSZ and DSZ coatings, with almost no variation of sur-face residual stresses, compared to a high dispersion for YbSZ coatings with the development of macrocracks parallel and perpendicular to the substrate within the coating.

  19. Effects of Thermal and Mechanical Load Cycling on the Dentin Microtensile Bond Strength of Single Bond-2

    PubMed Central

    Daneshkazemi, Alireza; Davari, Abdolrahim; Akbari, Mohammad Javad; Davoudi, Amin; Badrian, Hamid

    2015-01-01

    Background: Different studies have shown the uncertain effects of thermal cycling (TC) and mechanical load cycling (MC) on the dentin microtensile bond strength (µTBS) of composites. This study designed to investigate the effects of TC and MC on the dentin µTBS of single bond-2. Materials and Methods: Flat dentinal surface was prepared on 48 sound extracted human third molar teeth, and were bonded by single bond-2 adhesive and Z250 resin composite. The teeth were randomly divided into eight equal groups, according to the thermal/mechanical protocol. TC and MC were proceeded at 5-55°C and 90 N with 0.5 Hz. Then restorations were sectioned to shape the hour-glass form and subjected to µTBS testing at a speed of 0.5 mm/min. To evaluate the bonding failure, the specimens were observed under the scanning electron microscope. The results were statistically analyzed with analysis of variance, t-test, Tukey HSD and post-hoc by using SPSS software version 17 at a significant level of 0.05. Results: µTBS of all groups were significantly lower than the control group (P < 0.001). Adhesive failure was predominant in all groups and increased with TC and MC. Conclusions: TC and MC had an adverse effect on µTBS of the tested adhesive resin to dentin. PMID:26464532

  20. Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

    NASA Astrophysics Data System (ADS)

    Hidalgo, Javier; Santofimia, Maria Jesus

    2016-11-01

    Current trends in steels are focusing on refined martensitic microstructures to obtain high strength and toughness. An interesting manner to reduce the size of martensitic substructure is by reducing the size of the prior austenite grain (PAG). This work analyzes the effect of PAGS refinement by thermal cycling on different microstructural features of as-quenched lath martensite in a 0.3C-1.6Si-3.5Mn (wt pct) steel. The application of thermal cycling is found to lead to a refinement of the martensitic microstructures and to an increase of the density of high misorientation angle boundaries after quenching; these are commonly discussed to be key structural parameters affecting strength. Moreover, results show that as the PAGS is reduced, the volume fraction of retained austenite increases, carbides are refined and the concentration of carbon in solid solution as well as the dislocation density in martensite increase. All these microstructural modifications are related with the manner in which martensite forms from different prior austenite conditions, influenced by the PAGS.

  1. Reactor physics studies for the Advanced Fuel Cycle Initiative (AFCI) Reactor-Accelerator Coupling Experiments (RACE) Project

    NASA Astrophysics Data System (ADS)

    Stankovskiy, Evgeny Yuryevich

    In the recently completed RACE Project of the AFCI, accelerator-driven subcritical systems (ADS) experiments were conducted to develop technology of coupling accelerators to nuclear reactors. In these experiments electron accelerators induced photon-neutron reactions in heavy-metal targets to initiate fission reactions in ADS. Although the Idaho State University (ISU) RACE ADS was constructed only to develop measurement techniques for advanced experiments, many reactor kinetics experiments were conducted there. In the research reported in this dissertation, a method was developed to calculate kinetics parameters for measurement and calculation of the reactivity of ADS, a safety parameter that is necessary for control and monitoring of power production. Reactivity is measured in units of fraction of delayed versus prompt neutron from fission, a quantity that cannot be directly measured in far-subcritical reactors such as the ISU RACE configuration. A new technique is reported herein to calculate it accurately and to predict kinetic behavior of a far-subcritical ADS. Experiments conducted at ISU are first described and experimental data are presented before development of the kinetic theory used in the new computational method. Because of the complexity of the ISU ADS, the Monte-Carlo method as applied in the MCNP code is most suitable for modeling reactor kinetics. However, the standard method of calculating the delayed neutron fraction produces inaccurate values. A new method was developed and used herein to evaluate actual experiments. An advantage of this method is that its efficiency is independent of the fission yield of delayed neutrons, which makes it suitable for fuel with a minor actinide component (e.g. transmutation fuels). The implementation of this method is based on a correlated sampling technique which allows the accurate evaluation of delayed and prompt neutrons. The validity of the obtained results is indicated by good agreement between experimental

  2. Thermal Fatigue Evaluation of Pb-Free Solder Joints: Results, Lessons Learned, and Future Trends

    NASA Astrophysics Data System (ADS)

    Coyle, Richard J.; Sweatman, Keith; Arfaei, Babak

    2015-09-01

    Thermal fatigue is a major source of failure of solder joints in surface mount electronic components and it is critically important in high reliability applications such as telecommunication, military, and aeronautics. The electronic packaging industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu alloys first established as replacements for eutectic SnPb. This paper discusses the results from Pb-free solder joint reliability programs sponsored by two industry consortia. The characteristic life in accelerated thermal cycling is reported for 12 different Pb-free solder alloys and a SnPb control in 9 different accelerated thermal cycling test profiles in terms of the effects of component type, accelerated thermal cycling profile and dwell time. Microstructural analysis on assembled and failed samples was performed to investigate the effect of initial microstructure and its evolution during accelerated thermal cycling test. A significant finding from the study is that the beneficial effect of Ag on accelerated thermal cycling reliability (measured by characteristic lifetime) diminishes as the severity of the accelerated thermal cycling, defined by greater ΔT, higher peak temperature, and longer dwell time increases. The results also indicate that all the Pb-free solders are more reliable in accelerated thermal cycling than the SnPb alloy they have replaced. Suggestions are made for future work, particularly with respect to the continued evolution of alloy development for emerging application requirements and the value of using advanced analytical methods to provide a better understanding of the effect of microstructure and its evolution on accelerated thermal cycling performance.

  3. Die Attachment for -120 C to +20 C Thermal Cycling of Microelectronics for Future Mars Rovers: An Overview

    NASA Technical Reports Server (NTRS)

    Kirschman, Randall K.; Sokolowski, Witold M.; Kolawa, Elizabeth A.

    1999-01-01

    Active thermal control for electronics on Mars Rovers imposes a serious penalty in weight, volume, power consumption, and reliability. Thus, we propose that thermal control be eliminated for future Rovers. From a functional standpoint there is no reason that the electronics could not operate over the entire temperature range of the Martian environment, which can vary from a low of approximately equal -90 C to a high of approximately equal +20 C during the Martian night and day. The upper end of this range is well within that for conventional electronics. Although the lower end is considerably below that for which conventional--even high-reliability electronics is designed or tested, it is well established that electronic devices can operate to such low temperatures. The primary concern is reliability of the overall electronic system, especially in regard to the numerous daily temperature cycles that it would experience over the duration of a mission on Mars. Accordingly, key reliability issues have been identified for elimination of thermal control on future Mars Rovers. One of these is attachment of semiconductor die onto substrates and into packages. Die attachment is critical since it forms a mechanical, thermal and electrical interface between the electronic device and the substrate or package. This paper summarizes our initial investigation of existing information related to this issue, in order to form an opinion whether die attachment techniques exist, or could be developed with reasonable effort, to withstand the Mars thermal environment for a mission duration of approximately I year. Our conclusion, from a review of literature and personal contacts. is that die attachment can be made sufficiently reliable to satisfy the requirements of future Mars Rovers. Moreover, it appears that there are several possible techniques from which to choose and that the requirements could be met by judicious selection from existing methods using hard solders, soft solders

  4. Special Aspects of Structural-Phase Transformations in the CuZn Alloy Under Thermal Cycling

    NASA Astrophysics Data System (ADS)

    Chaplygina, A. A.; Potekaev, A. I.; Chaplygin, P. A.; Kulagina, V. V.; Starostenkov, M. D.; Grinkevich, L. S.

    2016-09-01

    Using the Monte Carlo approach, special features of structural and energy characteristics of β-brass are investigated under cycling conditions. As a result of the heating-cooling cycle, a unique hysteresis loop is observed, which suggests irreversibility of the processes and implies differences in the structural-phase states in the heating and cooling stages. An analysis of the atomic and phase structure of the system during heating and cooling, i.e., in the course of order-disorder and disorder-order phase transitions, has demonstrated that the system is found in different structural-phase states. Upon completion of the disorder-order phase transition, two domains of the B2 superstructure are formed.

  5. Physical exercise accelerates reentrainment of human sleep-wake cycle but not of plasma melatonin rhythm to 8-h phase-advanced sleep schedule.

    PubMed

    Yamanaka, Yujiro; Hashimoto, Satoko; Tanahashi, Yusuke; Nishide, Shin-Ya; Honma, Sato; Honma, Ken-Ichi

    2010-03-01

    Effects of timed physical exercise were examined on the reentrainment of sleep-wake cycle and circadian rhythms to an 8-h phase-advanced sleep schedule. Seventeen male adults spent 12 days in a temporal isolation facility with dim light conditions (<10 lux). The sleep schedule was phase-advanced by 8 h from their habitual sleep times for 4 days, which was followed by a free-run session for 6 days, during which the subjects were deprived of time cues. During the shift schedule, the exercise group (n = 9) performed physical exercise with a bicycle ergometer in the early and middle waking period for 2 h each. The control group (n = 8) sat on a chair at those times. Their sleep-wake cycles were monitored every day by polysomnography and/or weight sensor equipped with a bed. The circadian rhythm in plasma melatonin was measured on the baseline day before phase shift: on the 4th day of shift schedule and the 5th day of free-run. As a result, the sleep-onset on the first day of free-run in the exercise group was significantly phase-advanced from that in the control and from the baseline. On the other hand, the circadian melatonin rhythm was significantly phase-delayed in the both groups, showing internal desynchronization of the circadian rhythms. The sleep-wake cycle resynchronized to the melatonin rhythm by either phase-advance or phase-delay shifts in the free-run session. These findings indicate that the reentrainment of the sleep-wake cycle to a phase-advanced schedule occurs independent of the circadian pacemaker and is accelerated by timed physical exercise.

  6. Unexpectedly large mass loss during the thermal pulse cycle of the red giant star R Sculptoris.

    PubMed

    Maercker, M; Mohamed, S; Vlemmings, W H T; Ramstedt, S; Groenewegen, M A T; Humphreys, E; Kerschbaum, F; Lindqvist, M; Olofsson, H; Paladini, C; Wittkowski, M; de Gregorio-Monsalvo, I; Nyman, L-A

    2012-10-11

    The asymptotic-giant-branch star R Sculptoris is surrounded by a detached shell of dust and gas. The shell originates from a thermal pulse during which the star underwent a brief period of increased mass loss. It has hitherto been impossible to constrain observationally the timescales and mass-loss properties during and after a thermal pulse--parameters that determine the lifetime of the asymptotic giant branch and the amount of elements returned by the star. Here we report observations of CO emission from the circumstellar envelope and shell around R Sculptoris with an angular resolution of 1.3″. What was previously thought to be only a thin, spherical shell with a clumpy structure is revealed to also contain a spiral structure. Spiral structures associated with circumstellar envelopes have been previously seen, leading to the conclusion that the systems must be binaries. Combining the observational data with hydrodynamic simulations, we conclude that R Sculptoris is a binary system that underwent a thermal pulse about 1,800 years ago, lasting approximately 200 years. About 3 × 10(-3) solar masses of material were ejected at a velocity of 14.3 km s(-1) and at a rate around 30 times higher than the pre-pulse mass-loss rate. This shows that about three times more mass was returned to the interstellar medium during and immediately after the pulse than previously thought.

  7. Simulations and Measurements for a concept of powering CALICE-AHCAL at a train-cycled accelerator

    NASA Astrophysics Data System (ADS)

    Göttlicher, P.

    2013-01-01

    Improving calorimetry by usage of the particle-flow algorithm requires to record the details of the shower development. Therefore a high granularity analogue readout hadron calorimeter (AHCAL) with small sensors and with electronics handling the enormous amount of channels, ≈ 40 000/m3, is required. Homogeneity is maintained by avoiding cooling tubes in the active volume and only cooling at the service end. For this concept low power consumption per channel, 40 μW, is essential. Future linear e+e-- collider designs, ILC or CLIC, foresee duty cycles for the bunch delivery. At ILC bunch trains of 1 ms duration are followed by long breaks of 200 ms. Power cycling the front end electronics with the train structure can reduce power consumption by a factor 100. However for a full scale CALICE-AHCAL switched currents reach magnitudes of kilo-amperes. This paper describes the design chain from front end PCB's through to external power supplies. By simulations a concept is developed, in which effects of electromagnetic interferences are kept small and localized. The goal is to keep current loops small, to limit the switched current to the region near the switched consumer and to allow only small frequency currents to spread out further into the system. By that analogue performance can be kept high and parasitic couplings to the surrounding metal structures and other sub-detectors will be minimized. Measurements with existing prototypes support the validity of the simulations.

  8. The influence of chronological age on periods of accelerated adaptation of stretch-shortening cycle performance in pre and postpubescent boys.

    PubMed

    Lloyd, Rhodri S; Oliver, Jon L; Hughes, Michael G; Williams, Craig A

    2011-07-01

    Although it is suggested that periods of naturally occurring accelerated adaptation may exist for various physical parameters, it would appear that no such evidence exists for stretch-shortening cycle (SSC) development. Two hundred and fifty male youths aged 7-17 years were tested for squat (SJ) and countermovement jump (CMJ) height, reactive strength index (RSI), and leg stiffness, with analyses of variance used to establish any significant between-group differences. Additionally, to ascertain the existence of periods of accelerated adaptation, inferences were made about the magnitudes of change between consecutive chronological age groups in relation to the smallest worthwhile change. The largest mean differences (±90% confidence limits) occurred between age groups 10 and 11 (G10-G11) for squat jump (SJ) height (21.61 ± 12.08-31.94%), CMJ height (20.80 ± 11.1-44.1%), and RSI (26.51 ± 11.07-44.10%); and between G12 and G13 for SJ (15.31 ± 7.47-23.73%) and CMJ (16.09 ± 7.50-25.38%) height. Negative mean differences occurred between G11 and G12 for SJ height (-1.32 ± -9.30 to 7.37%), CMJ jump height (-7.68 ± -15.15 to 0.45%) and RSI (-11.48 ± -22.21 to 0.74%); and between G10 and G11 for leg stiffness (-8.87 ± -18.85 to 2.34%). It would appear almost certain that windows of accelerated adaptation may exist for SJ and CMJ height and RSI in male youths; however, leg stiffness results would suggest that fast-SSC function may follow a different developmental trend.

  9. Accelerated ageing in testing bricks used in the conservation of historic buildings

    NASA Astrophysics Data System (ADS)

    Pavlendová, Gabriela; Podoba, Rudolf; Baník, Ivan

    2014-11-01

    The effect of accelerated climate ageing on historical bricks in the laboratory is investigated in the paper. Differences in thermal properties are experimentally determined and studied before and after bricks exposure to climate ageing, which consists of 60 freeze-thaw cycles. For measuring thermal conductivity, diffusivity and specific heat, pulse method is used.

  10. Experimental evaluation of the Battelle accelerated test design for the solar array at Mead, Nebraska

    NASA Technical Reports Server (NTRS)

    Frickland, P. O.; Repar, J.

    1982-01-01

    A previously developed test design for accelerated aging of photovoltaic modules was experimentally evaluated. The studies included a review of relevant field experience, environmental chamber cycling of full size modules, and electrical and physical evaluation of the effects of accelerated aging during and after the tests. The test results indicated that thermally induced fatigue of the interconnects was the primary mode of module failure as measured by normalized power output. No chemical change in the silicone encapsulant was detectable after 360 test cycles.

  11. Strength Evolution in the Sintering of Bronze Powder Metal Compacts and Application to Thermal Cycle Design

    DTIC Science & Technology

    2007-11-02

    Annealing 25 2.5.3 Sinter Strengthening 26 2.5.4 Thermal Softening 29 2.6 Statement of Hypothesis 29 Chapter 3. Experimental Procedures...VI 6.1.1 Annealing of Green Strength 131 6.1.2 Sinter Strengthening 135 6.1.2.1 MSC Equivalent Energy 137 6.1.2.2 MSC - Sinter Strength...nonisothermal annealing in low carbon steels . Wang et al. [51 ] used the JMA equation to model transformation rates during the annealing of nickel

  12. Economic analysis of community solar heating systems that use annual cycle thermal energy storage

    NASA Astrophysics Data System (ADS)

    Baylin, F.; Monte, R.; Sillman, S.; Hooper, F. C.; McClenahan, J. D.

    1981-02-01

    Systems were sized for three housing configurations: single unit dwellings, 10 unit, and 200 unit apartment complexes in 50, 200, 400, and 1000 unit communities in 10 geographic locations in the United States. Thermal energy is stored in large, constructed, underground tanks. Costs were assigned to each component of every system in order to allow calculation of total costs. Results are presented as normalized system costs per unit of heat delivered per building unit. These methods allow: identification of the relative importance of each system component in the overall cost; and identification of the key variables that determine the optimum sizing of a district solar heating system.

  13. The Annual Cycle of Water Vapor on Mars as Observed by the Thermal Emission Spectrometer

    NASA Technical Reports Server (NTRS)

    Smith, Michael D.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Spectra taken by the Mars Global Surveyor Thermal Emission Spectrometer (TES) have been used to monitor the latitude, longitude, and seasonal dependence of water vapor for over one full Martian year (March 1999-March 2001). A maximum in water vapor abundance is observed at high latitudes during mid-summer in both hemispheres, reaching a maximum value of approximately 100 pr-micrometer in the north and approximately 50 pr-micrometer in the south. Low water vapor abundance (<5 pr-micrometer) is observed at middle and high latitudes in the fall and winter of both hemispheres. There are large differences in the hemispheric (north versus south) and seasonal (perihelion versus aphelion) behavior of water vapor. The latitudinal and seasonal dependence of the decay of the northern summer water vapor maximum implies cross-equatorial transport of water to the southern hemisphere, while there is little or no corresponding transport during the decay of the southern hemisphere summer maximum. The latitude-longitude dependence of annually-averaged water vapor (corrected for topography) has a significant positive correlation with albedo and significant negative correlations with thermal inertia and surface pressure. Comparison of TES results with those retrieved from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) experiments shows some similar features, but also many significant differences. The southern hemisphere maximum observed by TES was not observed by MAWD and the large latitudinal gradient in annually-averaged water vapor observed by MAWD does not appear in the TES results.

  14. Use of thermal cycling to reduce adhesion of OTS coated coated MEMS cantilevers

    NASA Astrophysics Data System (ADS)

    Ali, Shaikh M.; Phinney, Leslie M.

    2003-01-01

    °Microelectromechanical systems (MEMS) have enormous potential to contribute in diverse fields such as automotive, health care, aerospace, consumer products, and biotechnology, but successful commercial applications of MEMS are still small in number. Reliability of MEMS is a major impediment to the commercialization of laboratory prototypes. Due to the multitude of MEMS applications and the numerous processing and packaging steps, MEMS are exposed to a variety of environmental conditions, making the prediction of operational reliability difficult. In this paper, we investigate the effects of operating temperature on the in-use adhesive failure of electrostatically actuated MEMS microcantilevers coated with octadecyltrichlorosilane (OTS) films. The cantilevers are subjected to repeated temperature cycles and electrostatically actuated at temperatures between 25°C and 300°C in ambient air. The experimental results indicate that temperature cycling of the OTS coated cantilevers in air reduces the sticking probability of the microcantilevers. The sticking probability of OTS coated cantilevers was highest during heating, which decreased during cooling, and was lowest during reheating. Modifications to the OTS release method to increase its yield are also discussed.

  15. Running hotter, faster, shallower: acceleration of the marine nitrogen cycle from the Last Glacial Maximum to the pre-industrial, and implications for the future

    NASA Astrophysics Data System (ADS)

    Galbraith, E. D.

    2015-12-01

    Biologically-available nitrogen is the primary limiting nutrient in the global ocean. The complex physical-biological interdependencies of nitrogen fixation and denitrification, the source and sink of bioavailable nitrogen, have led to uncertainty over their future trajectories under higher CO2. Sedimentary nitrogen isotope evidence suggests that the global rate of denitrification was on the order of 50% lower during the last glacial maximum, and reveals that significant changes in denitrification have occurred on a decadal-centennial timescale. Coupled atmosphere-ocean-biogeochemistry models simulate similar changes, through physically-driven changes in anoxia, which then feed back on nitrogen fixation through the availability of phosphorus to diazotrophs. In addition, diazotroph culture experiments suggest that nitrogen fixation was further limited during glacial maxima by low CO2, causing an additional slowdown of the nitrogen cycle. The emergent picture suggests that deglaciation accelerated both sides of the N cycle, with more rapid loss encouraged by expanded shallow anoxia, and more rapid gain encouraged by higher CO2. It will be argued that the net effect on the nitrogen inventory can be approximated by knowing the distribution of surface ocean PO4, given the observed correlation of surface PO4 concentrations on the P:C ratio of exported organic matter.

  16. The effects of free and bonded sulfur both in the presence and absence of vulcanization accelerators on the rheological, technological, aging, and thermal stability of asphalts

    SciTech Connect

    Onabajo, A.; Kopsch, H.

    1987-01-01

    Rheological and technological experiments have been carried out on sulfur-modified asphalts in the temperature range of 353 K to 453 K over a wide range of shear rates (0-4800 sec/sup -1/). The results indicated that the activation energy of the viscous flow increased with increasing amount of bonded sulfur. The irreversible shear degradation observed in sulfur-modified asphalts is caused by the high shear forces which rupture the aggregated molecules. Thermogravimetric analysis and aging experiments on asphalts and their sulfurized products, containing varying amounts of free sulfur (0-5.5 wt.-%) and vulcanization accelerators (0.5-2.5 wt.-%), have shown that mixes containing vulcanization accelerators have higher thermal stabilities and are more resistant to thermal and non-thermal aging than the unaccelerated asphalt-sulfur mixed prepared at the same or higher temperatures. The changes in the rheological and physical properties of the mixes with time is not only explained by the changes in the physical state of unreacted free sulfur, that is, from plastic to crystalline state (physical process), but also attributable to the effect of chemical reactions.

  17. Accelerated stress testing of terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.; Hawkins, D. C.; Prince, J. L.; Walker, H. A.

    1982-01-01

    The development of an accelerated test schedule for terrestrial solar cells is described. This schedule, based on anticipated failure modes deduced from a consideration of IC failure mechanisms, involves bias-temperature testing, humidity testing (including both 85-85 and pressure cooker stress), and thermal-cycle thermal-shock testing. Results are described for 12 different unencapsulated cell types. Both gradual electrical degradation and sudden catastrophic mechanical change were observed. These effects can be used to discriminate between cell types and technologies relative to their reliability attributes. Consideration is given to identifying laboratory failure modes which might lead to severe degradation in the field through second quadrant operation. Test results indicate that the ability of most cell types to withstand accelerated stress testing depends more on the manufacturer's design, processing, and worksmanship than on the particular metallization system. Preliminary tests comparing accelerated test results on encapsulated and unencapsulated cells are described.

  18. Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof

    DOEpatents

    Sarin, V.K.

    1990-08-21

    An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications is disclosed. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al[sub x]N[sub y]O[sub z] layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al[sub x]N[sub y]O[sub z] layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

  19. Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof

    DOEpatents

    Sarin, Vinod K.

    1990-01-01

    An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al.sub.x N.sub.y O.sub.z layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al.sub.x N.sub.y O.sub.z layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

  20. Low Temperature Creep of Hot-Extruded Near-Stoichiometric NiTi Shape Memory Alloy. Part 2; Effect of Thermal Cycling

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Noebe, R. D.

    2013-01-01

    This paper is the first report on the effect prior low temperature creep on the thermal cycling behavior of NiTi. The isothermal low temperature creep behavior of near-stoichiometric NiTi between 300 and 473 K was discussed in Part I. The effect of temperature cycling on its creep behavior is reported in the present paper (Part II). Temperature cycling tests were conducted between either 300 or 373 K and 473 K under a constant applied stress of either 250 or 350 MPa with hold times lasting at each temperature varying between 300 and 700 h. Each specimen was pre-crept either at 300 or at 473 K for several months under an identical applied stress as that used in the subsequent thermal cycling tests. Irrespective of the initial pre-crept microstructures, the specimens exhibited a considerable increase in strain with each thermal cycle so that the total strain continued to build-up to 15 to 20 percent after only 5 cycles. Creep strains were immeasurably small during the hold periods. It is demonstrated that the strains in the austenite and martensite are linearly correlated. Interestingly, the differential irrecoverable strain, in the material measured in either phase decreases with increasing number of cycles, similar to the well-known Manson-Coffin relation in low cycle fatigue. Both phases are shown to undergo strain hardening due to the development of residual stresses. Plots of true creep rate against absolute temperature showed distinct peaks and valleys during the cool-down and heat-up portions of the thermal cycles, respectively. Transformation temperatures determined from the creep data revealed that the austenitic start and finish temperatures were more sensitive to the pre-crept martensitic phase than to the pre-crept austenitic phase. The results are discussed in terms of a phenomenological model, where it is suggested that thermal cycling between the austenitic and martensitic phase temperatures or vice versa results in the deformation of the austenite and

  1. University of Minnesota aquifer thermal energy storage (ATES) project report on the third long-term cycle

    SciTech Connect

    Hoyer, M.C.; Hallgren, J.P.; Uebel, M.H.; Delin, G.N.; Eisenreich, S.J.; Sterling, R.L.

    1994-12-01

    The University of Minnesota aquifer thermal energy storage (ATES) system has been operated as a field test facility (FTF) since 1982. The objectives were to design, construct, and operate the facility to study the feasibility of high-temperature ATES in a confined aquifer. Four short-term and two long-term cycles were previously conducted, which provided a greatly increased understanding of the efficiency and geochemical effects of high-temperature aquifer thermal energy storage. The third long-term cycle (LT3) was conducted to operate the ATES system in conjunction with a real heating load and to further study the geochemical impact that heated water storage had on the aquifer. For LT3, the source and storage wells were modified so that only the most permeable portion, the Ironton-Galesville part, of the Franconia-Ironton-Galesville aquifer was used for storage. This was expected to improve storage efficiency by reducing the surface area of the heated volume and simplify analysis of water chemistry results by reducing the number of aquifer-related variables which need to be considered. During LT3, a total volume of 63.2 {times} 10{sup 3} m {sup 3} of water was injected at a rate of 54.95 m{sup 3}/hr into the storage well at a mean temperature of 104.7{degrees}C. Tie-in to the reheat system of the nearby Animal Sciences Veterinary Medicine (ASVM) building was completed after injection was completed. Approximately 66 percent (4.13 GWh) of the energy added to the aquifer was recovered. Approximately 15 percent (0.64 GWh) of the usable (10 building. Operations during heat recovery with the ASVM building`s reheat system were trouble-free. Integration into more of the ASVM (or other) building`s mechanical systems would have resulted in significantly increasing the proportion of energy used during heat recovery.

  2. Energy losses in thermally cycled optical fibers constrained in small bend radii

    SciTech Connect

    Guild, Eric; Morelli, Gregg

    2012-09-23

    High energy laser pulses were fired into a 365μm diameter fiber optic cable constrained in small radii of curvature bends, resulting in a catastrophic failure. Q-switched laser pulses from a flashlamp pumped, Nd:YAG laser were injected into the cables, and the spatial intensity profile at the exit face of the fiber was observed using an infrared camera. The transmission of the radiation through the tight radii resulted in an asymmetric intensity profile with one half of the fiber core having a higher peak-to-average energy distribution. Prior to testing, the cables were thermally conditioned while constrained in the small radii of curvature bends. Single-bend, double-bend, and U-shaped eometries were tested to characterize various cable routing scenarios.

  3. Effects of Hygrothermal Cycling on the Chemical, Thermal, and Mechanical Properties of 862/W Epoxy Resin

    NASA Technical Reports Server (NTRS)

    Miller, Sandi G.; Roberts, Gary D.; Copa, Christine C.; Bail, Justin L.; Kohlman, Lee W.; Binienda, Wieslaw K.

    2011-01-01

    The hygrothermal aging characteristics of an epoxy resin were characterized over 1 year, which included 908 temperature and humidity cycles. The epoxy resin quickly showed evidence of aging through color change and increased brittleness. The influence of aging on the material s glass transition temperature (Tg) was evaluated by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The Tg remained relatively constant throughout the year long cyclic aging profile. The chemical composition was monitored by Fourier Transform Infrared Spectroscopy (FTIR) where evidence of chemical aging and advancement of cure was noted. The tensile strength of the resin was tested as it aged. This property was severely affected by the aging process in the form of reduced ductility and embrittlement. Detailed chemical evaluation suggests many aging mechanisms are taking place during exposure to hygrothermal conditions. This paper details the influence of processes such as: advancement of cure, chemical degradation, and physical aging on the chemical and physical properties of the epoxy resin.

  4. Long-period Intensity Pulsations in Coronal Loops Explained by Thermal Non-equilibrium Cycles

    NASA Astrophysics Data System (ADS)

    Froment, C.; Auchère, F.; Aulanier, G.; Mikić, Z.; Bocchialini, K.; Buchlin, E.; Solomon, J.

    2017-02-01

    In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon that can occur when the heating is both highly stratified and quasi-constant. Unambiguous observational identification of TNE would thus permit us to strongly constrain heating scenarios. While TNE is currently the standard interpretation of coronal rain, the long-term periodic evolution predicted by simulations has never been observed. However, the detection of long-period intensity pulsations (periods of several hours) has been recently reported with the Solar and Heliospheric Observatory/EIT, and this phenomenon appears to be very common in loops. Moreover, the three intensity-pulsation events that we recently studied with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) show strong evidence for TNE in warm loops. In this paper, a realistic loop geometry from linear force-free field (LFFF) extrapolations is used as input to 1D hydrodynamic simulations. Our simulations show that, for the present loop geometry, the heating has to be asymmetrical to produce TNE. We analyze in detail one particular simulation that reproduces the average thermal behavior of one of the pulsating loop bundle observed with AIA. We compare the properties of this simulation with those deduced from the observations. The magnetic topology of the LFFF extrapolations points to the presence of sites of preferred reconnection at one footpoint, supporting the presence of asymmetric heating. In addition, we can reproduce the temporal large-scale intensity properties of the pulsating loops. This simulation further strengthens the interpretation of the observed pulsations as signatures of TNE. This consequently provides important information on the heating localization and timescale for these loops.

  5. The annual cycle of water vapor on Mars as observed by the Thermal Emission Spectrometer

    NASA Astrophysics Data System (ADS)

    Smith, M. D.

    2001-12-01

    We report here on the latitude, longitude, and seasonal dependence of water vapor abundance for over one full Martian year as observed by the Mars Global Surveyor Thermal Emission Spectrometer (TES). A maximum in water vapor abundance is observed at high latitudes during mid-summer in both hemispheres, reaching a maximum value of ~100 pr-μ m in the north and ~50 pr-μ m in the south. Low water vapor abundance (<5 pr-μ m) is observed at middle and high latitudes in the fall and winter of both hemispheres. There are large differences in the hemispheric (north versus south) and seasonal (perihelion versus aphelion) behavior of water vapor. The latitudinal and seasonal dependence of the decay of the northern summer water vapor maximum implies cross-equatorial transport of water to the southern hemisphere, while there is little or no corresponding transport during the decay of the southern hemisphere summer maximum. A very steep latitudinal gradient in water vapor abundance (high in the north) forms during early northern summer (Ls= 90o--150o), while water vapor is distributed more uniformly in latitude during early southern summer (Ls= 270o--330o). The annually-averaged amount of water vapor in the Martian atmosphere is 17 pr-μ m in the northern hemisphere and 9.5 pr-μ m in the southern hemisphere. However, when referenced to a 6.1 mbar pressure surface to remove the effect of topography, the annually-averaged amount of water vapor becomes 17 pr-μ m in the latitude band from 10oS--40oN, and 12 pr-μ m everywhere else. The latitude-longitude dependence of annually-averaged water vapor (corrected for topography) has a significant positive correlation with albedo and significant negative correlations with thermal inertia and surface pressure.

  6. Life cycle assessment of hemp cultivation and use of hemp-based thermal insulator materials in buildings.

    PubMed

    Zampori, Luca; Dotelli, Giovanni; Vernelli, Valeria

    2013-07-02

    The aim of this research is to assess the sustainability of a natural fiber, such as hemp (Cannabis sativa), and its use as thermal insulator for building applications. The sustainability of hemp was quantified by life cycle assessment (LCA) and particular attention was given to the amount of CO2eq of the whole process, and the indicator greenhouse gas protocol (GGP) was selected to quantify CO2eq emissions. In this study also CO2 uptake of hemp was considered. Two different allocation procedures (i.e., mass and economic) were adopted. Other indicators, such as Cumulative Energy Demand (CED) and EcoIndicator99 H were calculated. The production of 1 ha yielded 15 ton of hemp, whose global warming potential (GWP100) was equal to about -26.01 ton CO2eq: the amount allocated to the technical fiber (20% of the total amount of hemp biomass) was -5.52 ton CO2eq when mass allocation was used, and -5.54 ton CO2eq when economic allocation was applied. The sustainability for building applications was quantified by considering an insulation panel made by hemp fiber (85%) and polyester fiber (15%) in 1 m(2) of wall having a thermal transmittance (U) equal to 0.2 W/m(2)_K. The environmental performances of the hemp-based panel were compared to those of a rockwool-based one.

  7. Leap Frog and Time Step Sub-Cycle Scheme for Coupled Neutronics and Thermal-Hydraulic Codes

    SciTech Connect

    Lu, S.

    2002-07-01

    As the result of the advancing TCP/IP based inter-process communication technology, more and more legacy thermal-hydraulic codes have been coupled with neutronics codes to provide best-estimate capabilities for reactivity related reactor transient analysis. Most of the coupling schemes are based on closely coupled serial or parallel approaches. Therefore, the execution of the coupled codes usually requires significant CPU time, when a complicated system is analyzed. Leap Frog scheme has been used to reduce the run time. The extent of the decoupling is usually determined based on a trial and error process for a specific analysis. It is the intent of this paper to develop a set of general criteria, which can be used to invoke the automatic Leap Frog algorithm. The algorithm will not only provide the run time reduction but also preserve the accuracy. The criteria will also serve as the base of an automatic time step sub-cycle scheme when a sudden reactivity change is introduced and the thermal-hydraulic code is marching with a relatively large time step. (authors)

  8. Scaling of Thermal-Hydraulic Experiments for a Space Rankine Cycle and Selection of a Preconceptual Scaled Experiment Design

    SciTech Connect

    Sulfredge, CD

    2006-01-27

    To assist with the development of a space-based Rankine cycle power system using liquid potassium as the working fluid, a study has been conducted on possible scaled experiments with simulant fluids. This report will consider several possible working fluids and describe a scaling methodology to achieve thermal-hydraulic similarity between an actual potassium system and scaled representations of the Rankine cycle boiler or condenser. The most practical scaling approach examined is based on the selection of perfluorohexane (FC-72) as the simulant. Using the scaling methodology, a series of possible solutions have been calculated for the FC-72 boiler and condenser. The possible scaled systems will then be compared and preconceptual specifications and drawings given for the most promising design. The preconceptual design concept will also include integrating the scaled boiler and scaled condenser into a single experimental loop. All the preconceptual system specifications appear practical from a fabrication and experimental standpoint, but further work will be needed to arrive at a final experiment design.

  9. Cycling performance and thermal stability of lithium polymer cells assembled with ionic liquid-containing gel polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Yun, Ye Sun; Kim, Jin Hee; Lee, Sang-Young; Shim, Eun-Gi; Kim, Dong-Won

    Gel polymer electrolytes containing 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and a small amount of additive (vinylene carbonate, fluoroethylene carbonate, and ethylene carbonate) are prepared, and their electrochemical properties are investigated. The cathodic limit of the gel polymer electrolytes can be extended to 0 V vs. Li by the formation of a protective solid electrolyte interphase on the electrode surface. Using these gel polymer electrolytes, lithium metal polymer cells composed of a lithium anode and a LiNi 1/3Co 1/3Mn 1/3O 2 cathode are assembled, and their cycling performances are evaluated at room temperature. The cells show good cycling performance, comparable to that of a cell assembled with gel polymer electrolyte containing standard liquid electrolyte (1.0 M LiPF 6 in ethylene carbonate/diethylene carbonate). Flammability tests and differential scanning calorimetry studies show that the presence of the ionic liquid in the gel polymer electrolyte considerably improves the safety and thermal stability of the cells.

  10. Aging study of Li(Si)/FeS/sub 2/ thermally activated batteries. [Results of accelerated aging at 130/sup 0/C

    SciTech Connect

    Searcy, J. Q.; Neiswander, P. A.

    1980-05-01

    A technique for accelerating the aging process of thermally activated batteries that use iron disulfide was developed. In this approach, storage at 130/sup 0/C for one week was assumed equivalent to a shelf life of five years. Some of the batteries stored at 130/sup 0/C were discharged to test for functionality changes, and others were disassembled and carefully analyzed for evidence of deleterious reactions. Some functionality anomalies were observed. The only deleterious reaction observed was that of Li(Si) reacting with water vapor. 3 figures, 6 tables.

  11. Impact of Total Ionizing Dose Radiation Testing and Long-Term Thermal Cycling on the Operation of CMF20120D Silicon Carbide Power MOSFET

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Scheidegger, Robert J.; Lauenstein, Jean-Marie; Casey, Megan; Scheick, Leif; Hammoud, Ahmad

    2013-01-01

    Power systems designed for use in NASA space missions are required to work reliably under harsh conditions including radiation, thermal cycling, and extreme temperature exposures. Silicon carbide devices show great promise for use in future power electronics systems, but information pertaining to performance of the devices in the space environment is very scarce. A silicon carbide N-channel enhancement-mode power MOSFET called the CMF20120 is of interest for use in space environments. Samples of the device were exposed to radiation followed by long-term thermal cycling to address their reliability for use in space applications. The results of the experimental work are presentd and discussed.

  12. The effect of thermal cycling to 1100 degree C on the alpha (Mo) phase in directionally solidified gamma/gamma prime-alpha alloys

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1981-01-01

    In gamma/gamma prime - alpha eutectic alloys (Ni-Mo-Al), the resistance of the alpha phase to morphological changes during thermal cycling was found to be dependent on the structure formed during directional solidification. Fine, smooth alpha fibers survived up to 1000 five minute cycles to 1100 C with minor microstructural contour changes, while coarser and irregularly shaped alpha fibers tended to spheroidize. A mechanism to explain this phenomenon is proposed. It is suggested that on heating to 1100 C, the alpha phase is likely to undergo morphological changes, until differential thermal expansion creates a stress free interface between the alpha phase and the gamma/gamma prime matrix.

  13. Cosmic ray heating in cool core clusters II: Self-regulation cycle and non-thermal emission

    NASA Astrophysics Data System (ADS)

    Jacob, Svenja; Pfrommer, Christoph

    2017-01-01

    Self-regulated feedback by active galactic nuclei (AGNs) appears to be critical in balancing radiative cooling of the low-entropy gas at the centres of galaxy clusters and in regulating star formation in central galaxies. In a companion paper, we found steady state solutions of the hydrodynamic equations that are coupled to the CR energy equation for a large cluster sample. In those solutions, radiative cooling in the central region is balanced by streaming CRs through the generation and dissipation of resonantly generated Alfvén waves and by thermal conduction at large radii. Here we demonstrate that the predicted non-thermal emission resulting from hadronic CR interactions in the intra-cluster medium exceeds observational radio (and gamma-ray) data in a subsample of clusters that host radio mini halos (RMHs). In contrast, the predicted non-thermal emission is well below observational data in cooling galaxy clusters without RMHs. These are characterised by exceptionally large AGN radio fluxes, indicating high CR yields and associated CR heating rates. We suggest a self-regulation cycle of AGN feedback in which non-RMH clusters are heated by streaming CRs homogeneously throughout the central cooling region. We predict radio micro halos surrounding the AGNs of these CR-heated clusters in which the primary emission may predominate the hadronically generated emission. Once the CR population has streamed sufficiently far and lost enough energy, the cooling rate increases, which explains the increased star formation rates in clusters hosting RMHs. Those could be powered hadronically by CRs that have previously heated the cluster core.

  14. Massive thermal acceleration of the emergence of primordial chemistry, the incidence of spontaneous mutation, and the evolution of enzymes.

    PubMed

    Wolfenden, Richard

    2014-10-31

    Kelvin considered it unlikely that sufficient time had elapsed on the earth for life to have reached its present level of complexity. In the warm surroundings in which life first appeared, however, elevated temperatures would have reduced the kinetic barriers to reaction. Recent experiments disclose the profound extent to which very slow reactions are accelerated by elevated temperatures, collapsing the time that would have been required for early events in primordial chemistry before the advent of enzymes. If a primitive enzyme, like model catalysts and most modern enzymes, accelerated a reaction by lowering its enthalpy of activation, then the rate enhancement that it produced would have increased automatically as the environment cooled, quite apart from any improvements in catalytic activity that arose from mutation and natural selection. The chemical events responsible for spontaneous mutation are also highly sensitive to temperature, furnishing an independent mechanism for accelerating evolution.

  15. Massive Thermal Acceleration of the Emergence of Primordial Chemistry, the Incidence of Spontaneous Mutation, and the Evolution of Enzymes*

    PubMed Central

    Wolfenden, Richard

    2014-01-01

    Kelvin considered it unlikely that sufficient time had elapsed on the earth for life to have reached its present level of complexity. In the warm surroundings in which life first appeared, however, elevated temperatures would have reduced the kinetic barriers to reaction. Recent experiments disclose the profound extent to which very slow reactions are accelerated by elevated temperatures, collapsing the time that would have been required for early events in primordial chemistry before the advent of enzymes. If a primitive enzyme, like model catalysts and most modern enzymes, accelerated a reaction by lowering its enthalpy of activation, then the rate enhancement that it produced would have increased automatically as the environment cooled, quite apart from any improvements in catalytic activity that arose from mutation and natural selection. The chemical events responsible for spontaneous mutation are also highly sensitive to temperature, furnishing an independent mechanism for accelerating evolution. PMID:25210030

  16. Four-wall turbine airfoil with thermal strain control for reduced cycle fatigue

    DOEpatents

    Cambell, Christian X

    2013-09-17

    A turbine airfoil (20B) with a thermal expansion control mechanism that increases the airfoil camber (60, 61) under operational heating. The airfoil has four-wall geometry, including pressure side outer and inner walls (26, 28B), and suction side outer and inner walls (32, 34B). It has near-wall cooling channels (31F, 31A, 33F, 33A) between the outer and inner walls. A cooling fluid flow pattern (50C, 50W, 50H) in the airfoil causes the pressure side inner wall (28B) to increase in curvature under operational heating. The pressure side inner wall (28B) is thicker than walls (26, 34B) that oppose it in camber deformation, so it dominates them in collaboration with the suction side outer wall (32), and the airfoil camber increases. This reduces and relocates a maximum stress area (47) from the suction side outer wall (32) to the suction side inner wall (34B, 72) and the pressure side outer wall (26).

  17. Thermal Stability of Cyclopentane as an Organic Rankine Cycle Working Fluid

    SciTech Connect

    Daniel M. Ginosar; Lucia M. Petkovic; Donna Post Guillen

    2011-08-01

    Laboratory experiments were performed to aid in determining the maximum operating temperature for cyclopentane as an Organic Rankine Cycle working fluid. The thermochemical decomposition of cyclopentane was measured in a recirculation loop at 240 C, 300 C and 350 C at 43 bar in a glass-lined heated tube. It was determined that in the absence of air at the lower two temperatures, decomposition was minor after more than twelve days of continuous operation. At 240 C, the total cyclopentane decomposition products were approximately 65 parts per million (ppm) and at 300 C, total decomposition products were on the order of 270 ppm at the end of the experiment. At 350 C, decomposition products were significantly higher and reached 1,500 ppm. When the feed was contacted with air, the decomposition rate increased dramatically. Residues found in the reactor after the decomposition experiments were examined by a number of different techniques. The mass of the residues increased with experimental temperature, but was lower at the same temperature when the feed was contacted with air. Analysis of the residues suggested that the residues were primarily heavy saturated hydrocarbons.

  18. The Effects of a Maximal Power Training Cycle on the Strength, Maximum Power, Vertical Jump Height and Acceleration of High-Level 400-Meter Hurdlers

    PubMed Central

    Balsalobre-Fernández, Carlos; Tejero-González, Carlos Mª; del Campo-Vecino, Juan; Alonso-Curiel, Dionisio

    2013-01-01

    The aim of this study was to determine the effects of a power training cycle on maximum strength, maximum power, vertical jump height and acceleration in seven high-level 400-meter hurdlers subjected to a specific training program twice a week for 10 weeks. Each training session consisted of five sets of eight jump-squats with the load at which each athlete produced his maximum power. The repetition maximum in the half squat position (RM), maximum power in the jump-squat (W), a squat jump (SJ), countermovement jump (CSJ), and a 30-meter sprint from a standing position were measured before and after the training program using an accelerometer, an infra-red platform and photo-cells. The results indicated the following statistically significant improvements: a 7.9% increase in RM (Z=−2.03, p=0.021, δc=0.39), a 2.3% improvement in SJ (Z=−1.69, p=0.045, δc=0.29), a 1.43% decrease in the 30-meter sprint (Z=−1.70, p=0.044, δc=0.12), and, where maximum power was produced, a change in the RM percentage from 56 to 62% (Z=−1.75, p=0.039, δc=0.54). As such, it can be concluded that strength training with a maximum power load is an effective means of increasing strength and acceleration in high-level hurdlers. PMID:23717361

  19. Thermal cycling reliability of Cu/SnAg double-bump flip chip assemblies for 100 μm pitch applications

    NASA Astrophysics Data System (ADS)

    Son, Ho-Young; Kim, Ilho; Lee, Soon-Bok; Jung, Gi-Jo; Park, Byung-Jin; Paik, Kyung-Wook

    2009-01-01

    A thick Cu column based double-bump flip chip structure is one of the promising alternatives for fine pitch flip chip applications. In this study, the thermal cycling (T/C) reliability of Cu/SnAg double-bump flip chip assemblies was investigated, and the failure mechanism was analyzed through the correlation of T/C test and the finite element analysis (FEA) results. After 1000 thermal cycles, T/C failures occurred at some Cu/SnAg bumps located at the edge and corner of chips. Scanning acoustic microscope analysis and scanning electron microscope observations indicated that the failure site was the Cu column/Si chip interface. It was identified by a FEA where the maximum stress concentration was located during T/C. During T/C, the Al pad between the Si chip and a Cu column bump was displaced due to thermomechanical stress. Based on the low cycle fatigue model, the accumulation of equivalent plastic strain resulted in thermal fatigue deformation of the Cu column bumps and ultimately reduced the thermal cycling lifetime. The maximum equivalent plastic strains of some bumps at the chip edge increased with an increased number of thermal cycles. However, equivalent plastic strains of the inner bumps did not increase regardless of the number of thermal cycles. In addition, the z-directional normal plastic strain ɛ22 was determined to be compressive and was a dominant component causing the plastic deformation of Cu/SnAg double bumps. As the number of thermal cycles increased, normal plastic strains in the perpendicular direction to the Si chip and shear strains were accumulated on the Cu column bumps at the chip edge at low temperature region. Thus it was found that the Al pad at the Si chip/Cu column interface underwent thermal fatigue deformation by compressive normal strain and the contact loss by displacement failure of the Al pad, the main T/C failure mode of the Cu/SnAg flip chip assembly, then occurred at the Si chip/Cu column interface shear strain deformation

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

    NASA Astrophysics Data System (ADS)

    Fiedler, Brent Alan

    Environmental and human health concerns drove European parliament to mandate the Reduction of Hazardous Substances (RoHS) for electronics. This was enacted in July 2006 and has practically eliminated lead in solder interconnects. There is concern in the electronics packaging community because modern lead-free solder is rich in tin. Presently, near-eutectic tin-silver-copper solders are favored by industry. These solders are stiffer than the lead-tin near-eutectic alloys, have a higher melting temperature, fewer slip systems, and form intermetallic compounds (IMC) with Cu, Ni and Ag, each of which tend to have a negative effect on lifetime. In order to design more reliable interconnects, the experimental observation of cracking mechanisms is necessary for the correct application of existing theories. The goal of this research is to observe the failure modes resulting from mode II strain and to determine the damage mechanisms which describe fatigue failures in 95.5 Sn- 4.0 Ag - 0.5 Cu wt% (SAC405) lead-free solder interconnects. In this work the initiation sites and crack paths were characterized for SAC405 ball-grid array (BGA) interconnects with electroless-nickel immersion-gold (ENIG) pad-finish. The interconnects were arranged in a perimeter array and tested in fully assembled packages. Evaluation methods included monotonic and displacement controlled mechanical shear fatigue tests, and temperature cycling. The specimens were characterized using metallogaphy, including optical and electron microscopy as well as energy dispersive spectroscopy (EDS) and precise real-time electrical resistance structural health monitoring (SHM). In mechanical shear fatigue tests, strain was applied by the substrates, simulating dissimilar coefficients of thermal expansion (CTE) between the board and chip-carrier. This type of strain caused cracks to initiate in the soft Sn-rich solder and grow near the interface between the solder and intermetallic compounds (IMC). The growth near

  1. The Role of Elastic and Plastic Anisotropy of Sn in Recrystallization and Damage Evolution During Thermal Cycling in SAC305 Solder Joints

    SciTech Connect

    Bieler, Thomas R.; Zhou, Bite; Blair, Lauren; Zamiri, Amir; Darbandi, Payam; Pourboghrat, Farhang; Lee, Tae-Kyu; Liu, Kuo-Chuan

    2013-04-08

    Because failures in lead-free solder joints occur at locations other than the most highly shear-strained regions, reliability prediction is challenging. To gain physical understanding of this phenomenon, physically based understanding of how elastic and plastic deformation anisotropy affect microstructural evolution during thermomechanical cycling is necessary. Upon solidification, SAC305 (Sn-3.0Ag-0.5Cu) solder joints are usually single or tricrystals. The evolution of microstructures and properties is characterized statistically using optical and orientation imaging microscopy. In situ synchrotron x-ray measurements during thermal cycling are used to examine how crystal orientation and thermal cycling history change strain history. Extensive characterization of a low-stress plastic ball grid array (PBGA) package design at different stages of cycling history is compared with preliminary experiments using higher-stress package designs. With time and thermal history, microstructural evolution occurs mostly from continuous recrystallization and particle coarsening that is unique to each joint, because of the specific interaction between local thermal and displacement boundary conditions and the strong anisotropic elastic, plastic, expansion, and diffusional properties of Sn crystals. The rate of development of recrystallized microstructures is a strong function of strain and aging. Cracks form at recrystallized (random) boundaries, and then percolate through recrystallized regions. Complications arising from electromigration and corrosion are also considered.

  2. Thaumarchaeal ammonium oxidation and evidence for a nitrogen cycle in a subsurface radioactive thermal spring in the Austrian Central Alps

    PubMed Central

    Gerbl, Friedrich W.; Weidler, Gerhard W.; Wanek, Wolfgang; Erhardt, Angelika; Stan-Lotter, Helga

    2014-01-01

    Previous studies had suggested the presence of ammonium oxidizing Thaumarchaeota as well as nitrite oxidizing Bacteria in the subsurface spring called Franz Josef Quelle (FJQ), a slightly radioactive thermal mineral spring with a temperature of 43.6–47°C near the alpine village of Bad Gastein, Austria. The microbiological consortium of the FJQ was investigated for its utilization of nitrogen compounds and the putative presence of a subsurface nitrogen cycle. Microcosm experiments made with samples from the spring water, containing planktonic microorganisms, or from biofilms, were used in this study. Three slightly different media, enriched with vitamins and trace elements, and two incubation temperatures (30 and 40°C, respectively) were employed. Under aerobic conditions, high rates of conversion of ammonium to nitrite, as well as nitrite to nitrate were measured. Under oxygen-limited conditions nitrate was converted to gaseous compounds. Stable isotope probing with 15NH4Cl or (15NH4)2SO4as sole energy sources revealed incorporation of 15N into community DNA. Genomic DNA as well as RNA were extracted from all microcosms. The following genes or fragments of genes were successfully amplified, cloned and sequenced by standard PCR from DNA extracts: Ammonia monooxygenase subunit A (amoA), nitrite oxidoreductase subunits A and B (nxrA and nxrB), nitrate reductase (narG), nitrite reductase (nirS), nitric oxide reductases (cnorB and qnorB), nitrous oxide reductase (nosZ). Reverse transcription of extracted total RNA and real-time PCR suggested the expression of each of those genes. Nitrogen fixation (as probed with nifH and nifD) was not detected. However, a geological origin of NH+4 in the water of the FJQ cannot be excluded, considering the silicate, granite and gneiss containing environment. The data suggested the operation of a nitrogen cycle in the subsurface environment of the FJQ. PMID:24904540

  3. An X-ray Radiography Study of the Effect of Thermal Cycling on Damage Evolution in Large-Area Sn-3.5Ag Solder Joints

    NASA Astrophysics Data System (ADS)

    Muralidharan, Govindarajan; Kurumaddali, Kanth; Kercher, Andrew K.; Walker, Larry; Leslie, Scott G.

    2013-02-01

    There is a need for next-generation, high-performance power electronic packages and systems utilizing wide-band-gap devices to operate at high temperatures in automotive and electricity transmission applications. Sn-3.5Ag solder is a candidate for use in such packages with potential maximum operating temperatures of about 200°C. However, there is a need to understand the thermal cycling reliability of Sn-3.5Ag solders subject to such high-temperature operating conditions. The results of a study on the damage evolution occurring in large-area Sn-3.5Ag solder joints between silicon dies and direct bonded copper substrates with Au/Ni-P metallization subject to thermal cycling between 200°C and 5°C are presented in this paper. Interface structure evolution and damage accumulation were followed using high-resolution X-ray radiography, cross-sectional optical and scanning electron microscopies, and X-ray microanalysis in these joints for up to 3000 thermal cycles. Optical and scanning electron microscopy results showed that the stresses introduced by the thermal cycling result in cracking and delamination at the copper-intermetallic compound interface. X-ray microanalysis showed that stresses due to thermal cycling resulted in physical cracking and breakdown of the Ni-P barrier layer, facilitating Cu-Sn interdiffusion. This interdiffusion resulted in the formation of Cu-Sn intermetallic compounds underneath the Ni-P layer, subsequently leading to delamination between the Ni-rich layer and Cu-Sn intermetallic compounds.

  4. Accelerated long-term assessment of thermal and chemical stability of bio-based phase change materials

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Thermal energy storage (TES) systems incorporated with phase change materials (PCMs) have potential applications to control energy use by building envelopes. However, it is essential to evaluate long term performance of the PCMs and cost effectiveness prior to full scale implementation. For this rea...

  5. Conceptual Design Study of a Closed Brayton Cycle Turbogenerator for Space Power Thermal-To-Electric Conversion System

    NASA Technical Reports Server (NTRS)

    Hansen, Jeff L.

    2000-01-01

    A conceptual design study was completed for a 360 kW Helium-Xenon closed Brayton cycle turbogenerator. The selected configuration is comprised of a single-shaft gas turbine engine coupled directly to a high-speed generator. The engine turbomachinery includes a 2.5:1 pressure ratio compression system with an inlet corrected flow of 0.44 kg/sec. The single centrifugal stage impeller discharges into a scroll via a vaned diffuser. The scroll routes the air into the cold side sector of the recuperator. The hot gas exits a nuclear reactor radiator at 1300 K and enters the turbine via a single-vaned scroll. The hot gases are expanded through the turbine and then diffused before entering the hot side sector of the recuperator. The single shaft design is supported by air bearings. The high efficiency shaft mounted permanent magnet generator produces an output of 370 kW at a speed of 60,000 rpm. The total weight of the turbogenerator is estimated to be only 123 kg (less than 5% of the total power plant) and has a volume of approximately 0.11 cubic meters. This turbogenerator is a key element in achieving the 40 to 45% overall power plant thermal efficiency.

  6. Conceptual design of an open-cycle ocean thermal energy conversion net power-producing experiment (OC-OTEC NPPE)

    SciTech Connect

    Bharathan, D.; Green, H.J.; Link, H.F.; Parsons, B.K.; Parsons, J.M.; Zangrando, F.

    1990-07-01

    This report describes the conceptual design of an experiment to investigate heat and mass transfer and to assess the viability of open-cycle ocean thermal energy conversion (OC-OTEC). The experiment will be developed in two stages, the Heat- and Mass-Transfer Experimental Apparatus (HMTEA) and the Net Power-Producing Experiment (NPPE). The goal for the HMTEA is to test heat exchangers. The goal for the NPPE is to experimentally verify OC-OTEC's feasibility by installing a turbine and testing the power-generating system. The design effort met the goals of both the HMTEA and the NPPE, and duplication of hardware was minimal. The choices made for the design resource water flow rates are consistent with the availability of cold and warm seawater as a result of the seawater systems upgrade carried out by the US Department of Energy (DOE), the state of Hawaii, and the Pacific International Center for High Technology Research. The choices regarding configuration of the system were made based on projected performance, degree of technical risk, schedule, and cost. The cost for the future phase of the design and the development of the HMTEA/NPPE is consistent with the projected future program funding levels. The HMTEA and NPPE were designed cooperatively by PICHTR, Argonne National Laboratory, and Solar Energy Research Institute under the guidance of DOE. The experiment will be located at the DOE's Seacoast Test Facility at the Natural Energy Laboratory of Hawaii, Kailua-Kona, Hawaii. 71 refs., 41 figs., 34 tabs.

  7. Experiments on oxygen desorption from surface warm seawater under Open-Cycle Ocean Thermal Energy Conversion (OC-OTEC) conditions

    NASA Astrophysics Data System (ADS)

    Pesaran, Ahmad A.

    1989-12-01

    This paper reports the results of scoping deaeration experiments conducted with warm surface seawater under open-cycle ocean thermal energy conversion (OC-OTEC). Concentrations of dissolved oxygen in seawater at three locations (in the supply water, water leaving a predeaerator, and discharge water from an evaporator) were measured and used to estimate oxygen desorption levels. The results suggest that 7 pct to 60 pct of dissolved oxygen in the supply water was desorbed from seawater in the predeaerator for pressures ranging from 9 to 35 kPa. Bubble injection in the upcomer increased the oxygen desorption rate by 20 pct to 60 pct. The dependence of oxygen desorption with flow rate could not be determined. The data also indicated that at typical OC-OTEC evaporator pressures when flashing occurred, 75 pct to 95 pct of dissolved oxygen was desorbed overall from the warm seawater. The uncertainty in results is larger than one would desire. These uncertainties are attributed to the uncertainties and difficulties in the dissolved oxygen measurements. Methods to improve the measurements for future gas desorption studies for warm surface and cold deep seawater under OC-OTEC conditions are recommended.

  8. Results of scoping tests for open-cycle OTEC (Ocean Thermal Energy Conversion) components operating with seawater

    NASA Astrophysics Data System (ADS)

    Zangrando, F.; Bharathan, D.; Green, H. J.; Link, H. F.; Parsons, B. K.; Parsons, J. M.; Pesaran, A. A.; Panchal, C. B.

    1990-09-01

    This report presents comprehensive documentation of the experimental research conducted on open-cycle ocean thermal energy conversion (OC-OTEC) components operating with seawater as a working fluid. The results of this research are presented in the context of previous analysis and fresh-water testing; they provide a basis for understanding and predicting with confidence the performance of all components of an OC-OTEC system except the turbine. Seawater tests have confirmed the results that were obtained in fresh-water tests and predicted by the analytical models of the components. A sound technical basis has been established for the design of larger systems in which net power will be produced for the first time from OC-OTEC technology. Design and operation of a complete OC-OTEC system that produces power will provide sufficient confidence to warrant complete transfer of OC-OTEC technology to the private sector. Each components performance is described in a separate chapter written by the principal investigator responsible for technical aspects of the specific tests. Chapters have been indexed separately for inclusion on the data base.

  9. Experiments on oxygen desorption from surface warm seawater under open-cycle ocean thermal energy conversion (OC-OTEC) conditions

    SciTech Connect

    Pesaran, A A

    1989-12-01

    This paper reports the results of scoping deaeration experiments conducted with warm surface seawater under open-cycle ocean thermal energy conversion (OC-OTEC). Concentrations of dissolved oxygen in seawater at three locations (in the supply water, water leaving a predeaerator, and discharge water from an evaporator) were measured and used to estimate oxygen desorption levels. The results suggest that 7% to 60% of dissolved oxygen in the supply water was desorbed from seawater in the predeaerator for pressures ranging from 9 to 35 kPa. Bubble injection in the upcomer increased the oxygen desorption rate by 20% to 60%. The dependence of oxygen desorption with flow rate could not be determined. The data also indicated that at typical OC-OTEC evaporator pressures when flashing occurred, 75% to 95% of dissolved oxygen was desorbed overall from the warm seawater. The uncertainty in results is larger than one would desire. These uncertainties are attributed to the uncertainties and difficulties in the dissolved oxygen measurements. Methods to improve the measurements for future gas desorption studies for warm surface and cold deep seawater under OC-OTEC conditions are recommended. 14 refs., 5 figs., 2 tabs.

  10. Conceptual design of an Open-Cycle Ocean Thermal Energy Conversion Net Power-Producing Experiment (OC-OTEC NPPE)

    NASA Astrophysics Data System (ADS)

    Bharathan, D.; Green, H. J.; Link, H. F.; Parsons, B. K.; Parsons, J. M.; Zangrando, F.

    1990-07-01

    This report describes the conceptual design of an experiment to investigate heat and mass transfer and to assess the viability of open-cycle ocean thermal energy conversion (OC-OTEC). The experiment will be developed in two stages, the Heat- and Mass-Transfer Experimental Apparatus (HMTEA) and the Net Power-Producing Experiment (NPPE). The goal for the HMTEA is to test heat exchangers. The goal for the NPPE is to experimentally verify OC-OTEC's feasibility by installing a turbine and testing the power-generating system. The design effort met the goals of both the HMTEA and the NPPE, and duplication of hardware was minimal. The choices made for the design resource water flow rates are consistent with the availability of cold and warm seawater as a result of the seawater systems upgrade carried out by the U.S. Department of Energy (DOE), the state of Hawaii, and the Pacific International Center for High Technology Research. The choices regarding configuration of the system were made based on projected performance, degree of technical risk, schedule, and cost. The cost for the future phase of the design and the development of the HMTEA/NPPE is consistent with the projected future program funding levels. The HMTEA and NPPE were designed cooperatively by PICHTR, Argonne National Laboratory, and Solar Energy Research Institute under the guidance of DOE. The experiment will be located at the DOE's Seacoast Test Facility at the Natural Energy Laboratory of Hawaii, Kailua-Kona, Hawaii.

  11. The Philosophy which underlies the structural tests of a supersonic transport aircraft with particular attention to the thermal cycle

    NASA Technical Reports Server (NTRS)

    Ripley, E. L.

    1972-01-01

    The information presented is based on data obtained from the Concorde. Much of this data also applies to other supersonic transport aircraft. The design and development of the Concorde is a joint effort of the British and French, and the structural test program is shared, as are all the other activities. Vast numbers of small specimens have been tested to determine the behavior of the materials used in the aircraft. Major components of the aircraft structure, totalling almost a complete aircraft, have been made and are being tested to help the constructors in each country in the design and development of the structure. Tests on two complete airframes will give information for the certification of the aircraft. A static test was conducted in France and a fatigue test in the United Kingdom. Fail-safe tests are being made to demonstrate the crack-propagation characteristics of the structure and its residual strength. Aspects of the structural test program are described in some detail, dealing particularly with the problems associated with the thermal cycle. The biggest of these problems is the setting up of the fatigue test on the complete airframe; therefore, this is covered more extensively with a discussion about how the test time can be shortened and with a description of the practical aspects of the test.

  12. Results of scoping tests for open-cycle OTEC (ocean thermal energy conversion) components operating with seawater

    SciTech Connect

    Zangrando, F; Bharathan, D; Green, H J; Link, H F; Parsons, B K; Parsons, J M; Pesaran, A A; Panchal, C B

    1990-09-01

    This report presents comprehensive documentation of the experimental research conducted on open-cycle ocean thermal energy conversion (OC-OTEC) components operating with seawater as a working fluid. The results of this research are presented in the context of previous analysis and fresh-water testing; they provide a basis for understanding and predicting with confidence the performance of all components of an OC-OTEC system except the turbine. Seawater tests have confirmed the results that were obtained in fresh-water tests and predicted by the analytical models of the components. A sound technical basis has been established for the design of larger systems in which net power will be produced for the first time from OC-OTEC technology. Design and operation of a complete OC-OTEC system that produces power will provide sufficient confidence to warrant complete transfer of OC-OTEC technology to the private sector. Each components performance is described in a separate chapter written by the principal investigator responsible for technical aspects of the specific tests. Chapters have been indexed separately for inclusion on the data base.

  13. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  14. 2,2'-Biphenols via protecting group-free thermal or microwave-accelerated Suzuki-Miyaura coupling in water.

    PubMed

    Schmidt, Bernd; Riemer, Martin; Karras, Manfred

    2013-09-06

    User-friendly protocols for the protecting group-free synthesis of 2,2'-biphenols via Suzuki-Miyaura coupling of o-halophenols and o-boronophenol are presented. The reactions proceed in water in the presence of simple additives such as K2CO3, KOH, KF, or TBAF and with commercially available Pd/C as precatalyst. Expensive or laboriously synthesized ligands or other additives are not required. In the case of bromophenols, efficient rate acceleration and short reaction times were accomplished by microwave irradiation.

  15. HESS J1023-575: Non-Thermal Particle Acceleration Associated With the Young Stellar Cluster Westerlund 2

    SciTech Connect

    Reimer, O.; Hinton, J.; Hofmann, W.; Hoppe, S.; Masterson, C.; Raue, M.; /Hamburg U.

    2007-11-14

    The results from H.E.S.S. observations towards Westerlund 2 are presented. The detection of very-high-energy gamma-ray emission towards the young stellar cluster Westerlund 2 in the HII complex RCW49 by H.E.S.S. provides ample evidence that particle acceleration to extreme energies is associated with this region. A variety of possible emission scenarios is mentioned, ranging from high-energy gamma-ray production in the colliding wind zone of the massive Wolf-Rayet binary WR 20a, collective wind scenarios, diffusive shock acceleration at the boundaries of wind-blown bubbles in the stellar cluster, and outbreak phenomena from hot stellar winds into the interstellar medium. These scenarios are briefly compared to the characteristics of the associated new VHE gamma-ray source HESS J1023-575, and conclusions on the validity of the respective emission scenarios for high-energy gamma-ray production in the Westerlund 2 system are drawn.

  16. Thermal analysis of reactions in soda-lime silicate glass batches containing melting accelerants: II, multicomponent systems

    SciTech Connect

    Hong, Kug Sun; Lee, Sang Won; Speyer, R.F. )

    1993-03-01

    The glass melting reactions in a multicomponent system (sand-soda ash-calcite-dolomite-feldspar) were studied using data from DTA, TGA, and XRD interactively. The first-formed liquid phase occurred at 700C from eutectic melting among CaCO[sub 3], Na[sub 2]CO[sub 3], and MgO. Further liquid phase formed at the CaCO[sub 3]-Na[sub 2]CO[sub 3] eutectic at 785C and a fusion reaction among SiO[sub 2], CaO, and the molten phase at 812C. Reactions between molten soda ash and silica grains to form a sodium disilicate coating also occurred in this temperature range. The effects of reaction accelerant additions (Na[sub 2], SO[sub 4], NaNO[sub 3], NaCl) on batch fusion were analyzed. Sodium chloride was found to be the most effective melting accelerant due to the formation of a NaCl-Na[sub 2]CO[sub 3] eutectic liquid phase at [approximately]636C, which effectively attacked the silica relic. CO[sub 2] gas release terminated [approximately]80C earlier with 1 wt% NaCl additions to the base glass.

  17. Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue

    SciTech Connect

    Bosco, Nick; Silverman, Timothy J.; Wohlgemuth, John; Kurtz, Sarah; Inoue, Masanao; Sakurai, Keiichiro; Shioda, Tsuyoshi; Zenkoh, Hirofumi; Hirota, Kusato; Miyashita, Masanori; Tadanori, Tanahashi; Suzuki, Soh; Chen, Yifeng; Verlinden, Pierre J.

    2014-12-31

    Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours of testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

  18. Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue: Preprint

    SciTech Connect

    Bosco, N.; Silverman, T. J.; Wohlgemuth, J.; Kurtz, S.; Inoue, M.; Sakurai, K.; Shinoda, T.; Zenkoh, H.; Hirota, K.; Miyashita, M.; Tadanori, T.; Suzuki, S.

    2015-04-07

    Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours o testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

  19. Degradation of thermal barrier coatings on an Integrated Gasification Combined Cycle (IGCC) simulated film-cooled turbine vane pressure surface due to particulate fly ash deposition

    NASA Astrophysics Data System (ADS)

    Luo, Kevin

    Coal synthesis gas (syngas) can introduce contaminants into the flow of an Integrated Gasification Combined Cycle (IGCC) industrial gas turbine which can form molten deposits onto components of the first stage of a turbine. Research is being conducted at West Virginia University (WVU) to study the effects of particulate deposition on thermal barrier coatings (TBC) employed on the airfoils of an IGCC turbine hot section. WVU had been working with U.S. Department of Energy, National Energy Technology Laboratory (NETL) to simulate deposition on the pressure side of an IGCC turbine first stage vane to study the effects on film cooling. To simulate the particulate deposition, TBC coated, angled film-cooled test articles were subjected to accelerated deposition injected into the flow of a combustor facility with a pressure of approximately 4 atm and a gas temperature of 1560 K. The particle characteristics between engine conditions and laboratory are matched using the Stokes number and particulate loading. To investigate the degradation on the TBC from the particulate deposition, non-destructive evaluations were performed using a load-based multiple-partial unloading micro-indentation technique and were followed by scanning electron microscopy (SEM) evaluation and energy dispersive X-ray spectroscopy (EDS) examinations. The micro-indentation technique used in the study was developed by Kang et al. and can quantitatively evaluate the mechanical properties of materials. The indentation results found that the Young's Modulus of the ceramic top coat is higher in areas with deposition formation due to the penetration of the fly ash. The increase in the modulus of elasticity has been shown to result in a reduction of strain tolerance of the 7% yttria-stabilized zirconia (7YSZ) TBC coatings. The increase in the Young's modulus of the ceramic top coat is due to the stiffening of the YSZ columnar microstructure from the cooled particulate fly ash. SEM evaluation was used to

  20. Effect of thermal barrier coatings on the performance of steam and water-cooled gas turbine/steam turbine combined cycle system

    NASA Technical Reports Server (NTRS)

    Nainiger, J. J.

    1978-01-01

    An analytical study was made of the performance of air, steam, and water-cooled gas-turbine/steam turbine combined-cycle systems with and without thermal-barrier coatings. For steam cooling, thermal barrier coatings permit an increase in the turbine inlet temperature from 1205 C (2200 F), resulting in an efficiency improvement of 1.9 percentage points. The maximum specific power improvement with thermal barriers is 32.4 percent, when the turbine inlet temperature is increased from 1425 C (2600 F) to 1675 C (3050 F) and the airfoil temperature is kept the same. For water cooling, the maximum efficiency improvement is 2.2 percentage points at a turbine inlet temperature of 1683 C (3062 F) and the maximum specific power improvement is 36.6 percent by increasing the turbine inlet temperature from 1425 C (2600 F) to 1730 C (3150 F) and keeping the airfoil temperatures the same. These improvements are greater than that obtained with combined cycles using air cooling at a turbine inlet temperature of 1205 C (2200 F). The large temperature differences across the thermal barriers at these high temperatures, however, indicate that thermal stresses may present obstacles to the use of coatings at high turbine inlet temperatures.

  1. Real-time thermal imaging of microwave accelerated metal-enhanced fluorescence (MAMEF) based assays on sapphire plates.

    PubMed

    Previte, Michael J R; Zhang, Yongxia; Aslan, Kadir; Geddes, Chris D

    2007-11-01

    In this paper, we describe an optical geometry that facilitates our further characterization of the temperature changes above silver island films (SiFs) on sapphire plates, when exposed to microwave radiation. Since sapphire transmits IR, we designed an optical scheme to capture real-time temperature images of a thin water film on sapphire plates with and without SiFs during the application of a short microwave pulse. Using this optical scheme, we can accurately determine the temperature profile of solvents in proximity to metal structures when exposed to microwave irradiation. We believe that this optical scheme will provide us with a basis for further studies in designing metal structures to further improve plasmonic-fluorescence clinical sensing applications, such as those used in microwave accelerated metal-enhanced fluorescence (MAMEF).

  2. Impact of Cooling Rate-Induced Recrystallization on High G Mechanical Shock and Thermal Cycling in Sn-Ag-Cu Solder Interconnects

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Kyu; Bieler, Thomas R.; Kim, Choong-Un

    2016-01-01

    The mechanical stability and thermo-mechanical fatigue performance of solder joints with low silver content Sn-1.0Ag-0.5Cu (wt.%) (SAC105) alloy based on different cooling rates are investigated in high G level shock environment and thermal cycling conditions. The cooling rate-controlled samples ranging from 1°C/min to 75°C/min cooling rate, not only show differences in microstructure, where a fine poly-granular microstructure develops in the case of fast cooling versus normal cooling, but also show various shock performances based on the microstructure changes. The fast cooling rate improves the high G shock performance by over 90% compared to the normal cooled SAC105 alloy air-cooling environment commonly used after assembly reflow. The microstructure effect on thermal cycling performance is also discussed, which is analyzed based on the Sn grain orientation, interconnect stability, and solder joint bulk microstructure.

  3. Technical and economic evaluation of a Brayton-Rankine combined-cycle solar-thermal power plant

    SciTech Connect

    Wright, J. D.

    1981-05-01

    The objective of this study is to conduct an assessment of gas-liquid direct-contact heat exchange and of a new storage-coupled system (the open-cycle Brayton/steam Rankine combined cycle). Both technical and economic issues are evaluated. Specifically, the storage-coupled combined cycle is compared with a molten salt system. The open Brayton cycle system is used as a topping cycle, and the reject heat powers the molten salt/Rankine system. In this study the molten salt system is left unmodified, the Brayton cycle is integrated on top of a Martin Marietta description of an existing molten salt plant. This compares a nonoptimized combined cycle with an optimized molten salt system.

  4. Effect of Thermal Cycling on Creep Behavior of Powder-Metallurgy-Processed and Hot-Rolled Al and Al-SiC Particulate Composites

    NASA Astrophysics Data System (ADS)

    Pal, Sharmilee; Bhanuprasad, V. V.; Mitra, R.; Ray, K. K.

    2009-12-01

    The tensile creep behavior of powder metallurgy (P/M)-processed and hot-rolled commercially pure Al and Al-5 or Al-10 vol pct SiC particulate composites has been evaluated after subjecting to 0, 2, and 8 thermal cycles between 500 °C and 0 °C with rapid quenching. The images of microstructures obtained using scanning and transmission electron microscopy as well as changes in the electrical resistivity, Young’s modulus, and microhardness have been examined in the samples subjected to thermal cycling, in order to compare the effects of structural damage and strengthening by dislocation generation. The damage is caused by voids formed by vacancy coalescence, and is more severe in pure Al than in Al-SiCp composites, because the particle-matrix interfaces in the composites act as effective sinks for vacancies. Creep tests have shown that the application of 2 thermal cycles lowers the creep strain rates in both pure Al and Al-SiCp composites. However, the creep resistance of pure Al gets significantly deteriorated, unlike the mild deterioration in the Al-5 SiCp composite, while the time to rupture for the Al-10 SiCp composite is increased. The dislocation structure and subgrain sizes in the Al and in the matrices of the Al-SiCp composites in the as-rolled condition, after thermal cycling, and after creep tests, have been compared and related to the creep behavior. The dimple sizes of the crept fracture surfaces appear to be dependent on the void density, tertiary component of strain, and time to rupture.

  5. Synergistic effect of thermal energy on bactericidal action of photolysis of H₂O₂ in relation to acceleration of hydroxyl radical generation.

    PubMed

    Shirato, Midori; Ikai, Hiroyo; Nakamura, Keisuke; Hayashi, Eisei; Kanno, Taro; Sasaki, Keiichi; Kohno, Masahiro; Niwano, Yoshimi

    2012-01-01

    The purpose of the present study is to evaluate the effect of thermal energy on the yield of and the bactericidal action of hydroxyl radical generated by photolysis of H(2)O(2). Different concentrations of H(2)O(2) (250, 500, 750, and 1,000 mM) were irradiated with light-emitting diodes (LEDs) at a wavelength of 400 ± 20 nm at 25°C to generate hydroxyl radical. The 500 mM H(2)O(2) was irradiated with the LEDs at different temperatures (25, 35, 45, and 55°C). Electron spin resonance spin trapping analysis showed that the yield of hydroxyl radicals increased with the temperature, as well as the concentration of H(2)O(2). Streptococcus mutans and Enterococcus faecalis were used in the bactericidal assay. The LED-light irradiation of the bacterial suspensions in 500 mM H(2)O(2) at 25°C could hardly kill the bacteria within 3 min, while the bactericidal effect was markedly enhanced with the temperature rise. For instance, a temperature increase to 55°C resulted in >99.999% reduction of viable counts of both bacterial species only within 1 min. The photolysis of 500 mM H(2)O(2) at 55°C could reduce the viable counts of bacteria more efficiently than did the photolysis of 1,000 mM H(2)O(2) at 25°C, although the yields of hydroxyl radical were almost the same under the both conditions. These findings suggest that the thermal energy accelerates the generation of hydroxyl radical by photolysis of H(2)O(2), which in turn results in a synergistic bactericidal effect of hydroxyl radical and thermal energy.

  6. Power Cycle Testing of Power Switches: A Literature Survey

    DOE PAGES

    GopiReddy, Lakshmi Reddy; Tolbert, Leon M.; Ozpineci, Burak

    2014-09-18

    Reliability of power converters and lifetime prediction has been a major topic of research in the last few decades, especially for traction applications. The main failures in high power semiconductors are caused by thermomechanical fatigue. Power cycling and temperature cycling are the two most common thermal acceleration tests used in assessing reliability. The objective of this paper is to study the various power cycling tests found in the literature and to develop generalized steps in planning application specific power cycling tests. A comparison of different tests based on the failures, duration, test circuits, and monitored electrical parameters is presented.

  7. Thermal-Fatigue Crack-Growth Characteristics and Mechanical Strain Cycling Behavior of A-286 Discaloy, and 16-25-6 Austenitic Steels

    NASA Technical Reports Server (NTRS)

    Smith, Robert W.; Smith, Gordon T.

    1960-01-01

    Thermal-fatigue crack-growth characteristics of notched- and unnotched-disk specimens of A-286, Discaloy, hot-cold worked 16-25-6, and overaged 16-25-6 were experimentally studied. Separately controlled variables were total strain range (0.0043 to 0.0079 in./in.), maximum cycle temperature (1300 and 1100 F), and hold time at maximum temperature (O and 5 min). A limited number of mechanical, push-pull, constant-strain cycle tests at room temperature were made using notched and un-notched bars of the same materials. In these tests the number of cycles to failure as well as the variation of load change with accumulated cycles was measured, and the effects of mean stress were observed. Constant-strain-range mechanical-fatigue tests at room temperature revealed notched-bar fatigue life to be strongly influenced by mean stress. For a specific strain range, the longest fatigue life was always found to be associated with the least-tensile (or most compressive) mean stress. By defining thermal-fatigue life as the number of cycles required to produce a crack area of 6000 square mils, the relative thermal-fatigue resistances of the test materials were established. Notched-disk specimens of A-286 and Discaloy steels exhibited longer fatigue lives than either hot-cold worked or overaged 16-25-6. On the other hand, unnotched-disk specimens of Discaloy and hot-cold worked 16-25-6 had longer lives than A-286 and overaged 16-25-6. Separation of the crack-growth data into microstage and macrostage periods revealed that the macrostage period accounted for the greatest part of the difference among materials when tested in the notched configuration, while the microstage was largely responsible for the differences encountered in unnotched disks.

  8. Effect of thermal cycling in a Mach 0.3 burner rig on properties and structure of directionally solidified gamma/gamma prime-delta eutectic

    NASA Technical Reports Server (NTRS)

    Gray, H. R.; Sanders, W. A.

    1976-01-01

    An experimental study was carried out to evaluate the effect of cyclic thermal exposures on the mechanical properties of a gamma/gamma prime-delta eutectic alloy parallel to the growth direction. The alloy had a nominal composition by weight of Ni-20 Nb-6 Cr-2.5 Al and was directionally solidified at 3 cm/hr in a furnace with a thermal gradient of at least 200 C/cm. Bars of the alloy were exposed in a Mach 0.3 burner rig and cycled 300 times between 1100 and 425 C. Oxidation-erosion characteristics of the alloy were determined by weight loss measurements at 300-cycle intervals. After cyclic exposure, stress rupture and tensile tests were performed at both 760 and 1040 C. Microstructural changes from cyclic exposure were determined. Thermal cycling resulted in gamma prime coarsening and Widmanstaetten delta precipitation in the gamma phase. An unidentified precipitate, presumably gamma prime, was observed within the delta phase. These microstructural changes did not affect the mechanical properties of the eutectic. High oxidation-erosion weight loss rate was observed.

  9. Synchrotron-based measurement of the impact of thermal cycling on the evolution of stresses in Cu through-silicon vias

    SciTech Connect

    Okoro, Chukwudi Obeng, Yaw; Levine, Lyle E.; Xu, Ruqing; Hummler, Klaus

    2014-06-28

    One of the main causes of failure during the lifetime of microelectronics devices is their exposure to fluctuating temperatures. In this work, synchrotron-based X-ray micro-diffraction is used to study the evolution of stresses in copper through-silicon via (TSV) interconnects, “as-received” and after 1000 thermal cycles. For both test conditions, significant fluctuations in the measured normal and shear stresses with depth are attributed to variations in the Cu grain orientation. Nevertheless, the mean hydrostatic stresses in the “as-received” Cu TSV were very low, at (16 ± 44) MPa, most likely due to room temperature stress relaxation. In contrast, the mean hydrostatic stresses along the entire length of the Cu TSV that had undergone 1000 thermal cycles (123 ± 37) MPa were found to be eight times greater, which was attributed to increased strain-hardening. The evolution in stresses with thermal cycling is a clear indication that the impact of Cu TSVs on front-end-of-line (FEOL) device performance will change through the lifetime of the 3D stacked dies, and ought to be accounted for during FEOL keep-out-zone design rules development.

  10. The effect of thermal cycling to 1100 C on the alpha /Mo/ phase in directionally solidified gamma/gamma-prime-alpha alloys

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1981-01-01

    Specimens of gamma/gamma-prime-alpha (Mo) eutectic alloy were thermally cycled or isothermally exposed at temperatures of 1075 to 1100 C. Transmission electron microscopy examination of cycled specimens indicated that even an exposure of 10 minutes effected noticeable changes in the shape of the alpha phase, and that the changes were cumulative as more cycles were added. The cross sections of fine, smooth fibers changed from rectangles to octagons, while lamellae and irregular shapes spheroidized. These effects are attributed to the differences in thermal expansion coefficients between the alpha phase and the gamma/gamma-prime matrix, and to the higher diffusion rates prevailing at elevated temperatures. Where the configuration of the alpha phase is a simple shape, such as a fiber, increasing the temperature eventually brings about a stress free interface between the alpha phase and the matrix by differential thermal expansion. Where the shape of the alpha phase is more complex, a stressed interface persists to higher temperatures where diffusion produces the more drastic morphological changes.

  11. Coupled modeling of a directly heated tubular solar receiver for supercritical carbon dioxide Brayton cycle: Optical and thermal-fluid evaluation

    SciTech Connect

    Ortega, Jesus; Khivsara, Sagar; Christian, Joshua; Ho, Clifford; Yellowhair, Julius; Dutta, Pradip

    2016-05-30

    In single phase performance and appealing thermo-physical properties supercritical carbon dioxide (s-CO2) make a good heat transfer fluid candidate for concentrating solar power (CSP) technologies. The development of a solar receiver capable of delivering s-CO2 at outlet temperatures ~973 K is required in order to merge CSP and s-CO2 Brayton cycle technologies. A coupled optical and thermal-fluid modeling effort for a tubular receiver is undertaken to evaluate the direct tubular s-CO2 receiver’s thermal performance when exposed to a concentrated solar power input of ~0.3–0.5 MW. Ray tracing, using SolTrace, is performed to determine the heat flux profiles on the receiver and computational fluid dynamics (CFD) determines the thermal performance of the receiver under the specified heating conditions. Moreover, an in-house MATLAB code is developed to couple SolTrace and ANSYS Fluent. CFD modeling is performed using ANSYS Fluent to predict the thermal performance of the receiver by evaluating radiation and convection heat loss mechanisms. Understanding the effects of variation in heliostat aiming strategy and flow configurations on the thermal performance of the receiver was achieved through parametric analyses. Finally, a receiver thermal efficiency ~85% was predicted and the surface temperatures were observed to be within the allowable limit for the materials under consideration.

  12. Coupled modeling of a directly heated tubular solar receiver for supercritical carbon dioxide Brayton cycle: Optical and thermal-fluid evaluation

    DOE PAGES

    Ortega, Jesus; Khivsara, Sagar; Christian, Joshua; ...

    2016-05-30

    In single phase performance and appealing thermo-physical properties supercritical carbon dioxide (s-CO2) make a good heat transfer fluid candidate for concentrating solar power (CSP) technologies. The development of a solar receiver capable of delivering s-CO2 at outlet temperatures ~973 K is required in order to merge CSP and s-CO2 Brayton cycle technologies. A coupled optical and thermal-fluid modeling effort for a tubular receiver is undertaken to evaluate the direct tubular s-CO2 receiver’s thermal performance when exposed to a concentrated solar power input of ~0.3–0.5 MW. Ray tracing, using SolTrace, is performed to determine the heat flux profiles on the receivermore » and computational fluid dynamics (CFD) determines the thermal performance of the receiver under the specified heating conditions. Moreover, an in-house MATLAB code is developed to couple SolTrace and ANSYS Fluent. CFD modeling is performed using ANSYS Fluent to predict the thermal performance of the receiver by evaluating radiation and convection heat loss mechanisms. Understanding the effects of variation in heliostat aiming strategy and flow configurations on the thermal performance of the receiver was achieved through parametric analyses. Finally, a receiver thermal efficiency ~85% was predicted and the surface temperatures were observed to be within the allowable limit for the materials under consideration.« less