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Sample records for elevated temperatures part

  1. Elevated temperature fracture mechanics

    International Nuclear Information System (INIS)

    Tomkins, B.

    1979-01-01

    The application of fracture mechanics concepts to cracks at elevated temperatures is examined. Particular consideration is given to the characterisation of crack tip stress-strain fields and parameters controlling crack extension under static and cyclic loads. (author)

  2. Designing for elevated temperature

    International Nuclear Information System (INIS)

    Boer, G.A. de

    1982-01-01

    The reasons for the application of higher process temperatures are explained. The properties of stainless steel are compared with those of other materials such as molybdenum. Factors influencing the choice of the material such as availability of material data at high temperature, controllability, and strength of heat-affected zone are discussed. The process of designing a structure for safe and economic high-temperature application is outlined: design-by-analysis in contrast to the design-by-rule which is general practice for low-temperature applications. The rules laid down in the ASME Pressure Vessel Code Case N47 are explained as well as the procedure for inelastic stress calculations. (author)

  3. Vessels for elevated temperature service

    International Nuclear Information System (INIS)

    O'Donnell, W.J.; Porowski, J.S.

    1983-01-01

    The subject is covered in chapters, entitled: introduction (background; elevated temperature concerns; design tools); design of pressure vessels for elevated temperature per ASME code; basic elevated temperature failure modes; allowable stresses and strains per ASME code (basic allowable stress limits; ASME code limits for bending; time-fraction summations; strain limits; buckling and instability; negligible creep and stress-rupture effects); combined membrane and bending stresses in creep regime; thermal stress cycles; bounding methods based on elastic core concept (bounds on accumulated strains; more accurate bounds; strain ranges; maximum stresses; strains at discontinuities); elastic follow-up; creep strain concentrations; time-dependent fatigue (combined creep rupture and fatigue damage; limits for inelastic design analyses; limits for elastic design analyses); flaw evaluation techniques; type 316 stainless steel; type 304 stainless steel; steel 2 1/4Cr1Mo; Inconel 718; Incolloy 800; Hastelloy X; detailed inelastic design analyses. (U.K.)

  4. Amorphisation during elevated temperature implantation

    International Nuclear Information System (INIS)

    Carter, G.; Nobes, M.J.; Elliman, R.G.

    1994-01-01

    Transition state theory is employed to predict the rates of amorphous zone recrystallization by direct thermal and radiation mediated thermal annealing processes. These rates are functions of zone radius and are employed to describe the competition between amorphous zone generation and annealing during elevated temperature heavy ion implantation of, particularly, Si and the accumulation of amorphousness with increasing ion fluence. This analysis predicts a change from monotonic to sigmoidal to biexponential accumulation functions with increasing annealing rate or substrate temperature in agreement with experiments. A logarithmic dependence of ion flux density upon substrate temperature for the achievement of defined fractional amorphisation is predicted and is also in agreement with the experiment. (author)

  5. EFFECTS OF ELEVATED TEMPERATURE ON ELEVATED ...

    African Journals Online (AJOL)

    eobe

    various temperature regimes before testing. A concrete mix of 1:1:3 ... approach arising from statistical evidence is not out of place. ... This paper presents the results of concrete cubes tests ..... accelerated there by reducing the strength of the.

  6. Mechanism for elevated temperature leaching

    International Nuclear Information System (INIS)

    Kenna, B.T.; Murphy, K.D.

    1979-01-01

    Long-term, elevated temperature leaching and subsequent electron microprobe analysis of simulated waste glass and ceramic materials have been completed. A cyclic leaching pattern was found in all systems over a 20-month period. It appears that the leaching of mobile ions by simple diffusional processes is modified by more complex chemical interactions. The release of immobile ions is primarily a function of their chemical interactions in the matrix which suggests that these ions may be complex species when released into solution. A mechanism is proposed which incorporates these ideas and the cyclic phenomenon observed

  7. Magnesium sacrificial anode behavior at elevated temperature

    International Nuclear Information System (INIS)

    Othman, Mohsen Othman

    2006-01-01

    Magnesium sacrificial anode coupled to mild steel was tasted in sodium chloride and tap water environments at elevated temperatures. The anode failed to protect the mild steel specimens in tap water environment at all temperatures specified. This was partly due to low conductivity of this medium. The temperature factor did not help to activate the anode in this medium. In sodium chloride environment the anode demonstrated good protection for steel cathodes. The weight loss was high for magnesium in sodium chloride environment particularly beyond 60 degree centigrade. In tap water environment the weight loss was negligible for the anode. It also suffered localized shallow pitting corrosion. Magnesium anode cannot be utilized where high temperature is involved particularly in high conductivity mediums. Protection of structures containing high resistivity waters is not feasible using sacrificial anode system. (author)

  8. Bentonite Permeability at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Katherine A. Daniels

    2017-01-01

    Full Text Available Repository designs frequently favour geological disposal of radioactive waste with a backfill material occupying void space around the waste. The backfill material must tolerate the high temperatures produced by decaying radioactive waste to prevent its failure or degradation, leading to increased hydraulic conductivity and reduced sealing performance. The results of four experiments investigating the effect of temperature on the permeability of a bentonite backfill are presented. Bentonite is a clay commonly proposed as the backfill in repository designs because of its high swelling capacity and very low permeability. The experiments were conducted in two sets of purpose-built, temperature controlled apparatus, designed to simulate isotropic pressure and constant volume conditions within the testing range of 4–6 MPa average effective stress. The response of bentonite during thermal loading at temperatures up to 200 °C was investigated, extending the previously considered temperature range. The results provide details of bentonite’s intrinsic permeability, total stress, swelling pressure and porewater pressure during thermal cycles. We find that bentonite’s hydraulic properties are sensitive to thermal loading and the type of imposed boundary condition. However, the permeability change is not large and can mostly be accounted for by water viscosity changes. Thus, under 150 °C, temperature has a minimal impact on bentonite’s hydraulic permeability.

  9. Optimization Of Nakazima Test At Elevated Temperatures

    International Nuclear Information System (INIS)

    Turetta, A.; Ghiotti, A.; Bruschi, S.

    2007-01-01

    Nowadays hot forming of High Strength Steel is gaining the strict requirements of automotive producer: in fact deformation performed simultaneously with quenching assures a fully martensitic microstructure at room temperature and thus high strength properties that allow the thickness reduction of the body-in-white components. Basic aspects of hot stamping are still under investigation and supplementary achievements are expected for a successful application of sheet metal forming technologies at elevated temperatures. Among data needed to settle a numerical model of the process, information about material formability may help in better designing and optimizing hot stamping operations. In the first part of the work, a new experimental apparatus based on Nakazima concept is presented; process parameters are optimized in order to accurately replicate the thermo-mechanical conditions typical of the industrial process, paying particular attention to the thermal and microstructural evolution. On the other hand, as commercial FE codes require the implementation of Forming Limit Diagrams at constant temperature, numerical investigations have been performed in order to determine the proper testing conditions to obtain FLD at nearly constant temperature

  10. HCF + LCF Interactions at Elevated Temperature

    National Research Council Canada - National Science Library

    Byrne, James; Hall, R. F; Ding, J

    2005-01-01

    ...) crack propagation in Ti- 6Al-4V will be studied under combined HCF/low cycle fatigue (LCF) loading conditions at elevated temperatures up to 350 deg C where creep stress ratcheting and environmental effects may arise...

  11. Elevated temperature erosive wear of metallic materials

    International Nuclear Information System (INIS)

    Roy, Manish

    2006-01-01

    Solid particle erosion of metals and alloys at elevated temperature is governed by the nature of the interaction between erosion and oxidation, which, in turn, is determined by the thickness, pliability, morphology, adhesion characteristics and toughness of the oxide scale. The main objective of this paper is to critically review the present state of understanding of the elevated temperature erosion behaviour of metals and alloys. First of all, the erosion testing at elevated temperature is reviewed. This is followed by discussion of the essential features of elevated temperature erosion with special emphasis on microscopic observation, giving details of the erosion-oxidation (E-O) interaction mechanisms. The E-O interaction has been elaborated in the subsequent section. The E-O interaction includes E-O maps, analysis of transition criteria from one erosion mechanism to another mechanism and quantification of enhanced oxidation kinetics during erosion. Finally, the relevant areas for future studies are indicated. (topical review)

  12. Elevation in brain temperature during paradoxical sleep.

    Science.gov (United States)

    Kawamura, H; Sawyer, C H

    1965-11-12

    During ordinary sleep, the temperature of the rabbit brain tended to drop, but during paradoxical sleep it rose sharply 0.1 degrees to 0.4 degrees C, a greater elevation than was observed during arousal. Changes in body temperature generally did not parallel the alterations in brain temperature. Shifts of direct-current potential in the brain are basically independent of the changes in brain temperature.

  13. ELEVATED TEMPERATURE EFFECTS ON THE ELECTRICAL ...

    African Journals Online (AJOL)

    The effects of elevated temperatures on the electrical properties of Bi metal probe to Si thin films had been investigated for electric field values 10-100V/m. Measurements of current (I) – voltage (V) characteristics were obtained at temperatures 300,320,340,360,380 and 400K respectively. The results indicated linear I–V ...

  14. Elevated temperature effects on concrete properties

    International Nuclear Information System (INIS)

    Grant, P.R.; Gruber, R.S.; Van Katwijk, C.

    1993-08-01

    The design of facilities to process or store radioactive wastes presents many challenging engineering problems. Such facilities must not only provide for safe storage of radioactive wastes but they must also be able to maintain confinement of these materials during and after natural phenomena events. Heat generated by the radioactive decay of the wastes will cause the temperature of the concrete containment structure to increase to a magnitude higher than that found in conventional structures. These elevated temperatures will cause strength-related concrete properties to degrade over time. For concrete temperatures less than 150 degree F, no reduction in strength is taken and the provisions of ACI 349, which states that higher temperatures are allowed if tests are provided to evaluate the reduction in concrete strength properties, apply. Methods proposed in a Pacific Northwest Laboratory (PNL) report, Modeling of Time-Variant Concrete Properties at Elevated Temperatures, can be used to evaluate the effects of elevated temperatures on concrete properties. Using these modified concrete properties the capacity of a concrete structure, subjected to elevated temperatures, to resist natural phenomena hazards can be determined

  15. Strength properties of concrete at elevated temperatures

    International Nuclear Information System (INIS)

    Freskakis, G.N.; Burrow, R.C.; Debbas, E.B.

    1979-01-01

    A study is presented concerning the compressive strength, modulus of elasticity, and stress-strain relationships of concrete at elevated temperatures. A review of published results provides information for the development of upper and lower bound relationships for compressive strength and the modulus of elasticity and establishes exposure conditions for a lower bound thermal response. The relationships developed from the literature review are confirmed by the results of a verification test program. The strength and elasticity relationships provide a basis for the development of design stress-strain curves for concrete exposed to elevated temperatures

  16. Behavior of reinforced concrete at elevated temperatures

    International Nuclear Information System (INIS)

    Freskakis, G.N.

    1984-09-01

    A study is presented concerning the behavior of reinforced concrete sections at elevated temperatures. Material properties of concrete and reinforcing steel are discussed. Behavior studies are made by means of moment-curvature-axial force relationships. Particular attention is given to the load carrying capacity, thermal forces and moments, and deformation capacity. The effects on these properties of variations in the strength properties, the temperature level and distribution, the amount of reinforcing steel, and limiting values of strains are considered

  17. Cu cluster shell structure at elevated temperatures

    DEFF Research Database (Denmark)

    Christensen, Ole Bøssing; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    1991-01-01

    Equilibrium structures of small (3–29)-atom Cu clusters are determined by simulated annealing, and finite-temperature ensembles are simulated by Monte Carlo techniques using the effective-medium theory for the energy calculation. Clusters with 8, 18, and 20 atoms are found to be particularly stable....... The equilibrium geometrical structures are determined and found to be determined by a Jahn-Teller distortion, which is found to affect the geometry also at high temperatures. The ‘‘magic’’ clusters retain their large stability even at elevated temperatures....

  18. Elevated environmental temperature and methamphetamine neurotoxicity

    International Nuclear Information System (INIS)

    Miller, Diane B.; O'Callaghan, James P.

    2003-01-01

    Amphetamines have been of considerable research interest for the last several decades. More recent work has renewed interest in the role of ambient temperature in both the toxicity and neurotoxicity of these drugs. We have determined that the striatal dopaminergic neurotoxicity observed in the mouse is linked in some fashion to both body and environmental temperature. Most studies of d-methamphetamine (d-METH) neurotoxicity are conducted at standard laboratory ambient temperatures (e.g., ∼21-22 deg. C) and utilizing a repeated dosage regimen (e.g., three to four injections spaced 2 h apart). A lowering of the ambient temperature provides neuro protection, while an elevation increases neurotoxicity. d-METH causes long-term depletions of triatal dopamine (DA) that are accompanied by other changes that are indicative of nerve terminal degeneration. These include argyrophilia, as detected by silver degeneration stains, and an elevation in glial fibrillary acidic protein (GFAP), a marker of reactive gliosis in response to injury, as well as a long-term decrease in tyrosine hydroxylase (TH) protein levels. here we show that increasing the ambient temperature during and for some time following dosing increases the neurotoxicity of d-METH. Mice (female 57BL6/J) given a single dosage of d-METH (20 mg/kg s.c.) and maintained at the usual laboratory ambient temperature show minimal striatal damage (an ∼15% depletion of DA and an ∼ 86% increase in GFAP). substantial striatal damage (e.g., an ∼70% depletion of DA and an ∼200% elevation in GFAP) was induced by this regimen if mice were maintained at 27 deg. C for 24 or 72 h following dosing. An increase in neurotoxicity was also apparent in mice kept at an elevated temperature for only 5 or 9 h, but keeping animals at 27 deg. C for 24 or 72 h was the most effective in increasing the neurotoxicity of d-METH. Our data show how a relatively minor change in ambient temperature can have a major impact on the degree of

  19. Elevated temperature forming method and preheater apparatus

    Science.gov (United States)

    Krajewski, Paul E; Hammar, Richard Harry; Singh, Jugraj; Cedar, Dennis; Friedman, Peter A; Luo, Yingbing

    2013-06-11

    An elevated temperature forming system in which a sheet metal workpiece is provided in a first stage position of a multi-stage pre-heater, is heated to a first stage temperature lower than a desired pre-heat temperature, is moved to a final stage position where it is heated to a desired final stage temperature, is transferred to a forming press, and is formed by the forming press. The preheater includes upper and lower platens that transfer heat into workpieces disposed between the platens. A shim spaces the upper platen from the lower platen by a distance greater than a thickness of the workpieces to be heated by the platens and less than a distance at which the upper platen would require an undesirably high input of energy to effectively heat the workpiece without being pressed into contact with the workpiece.

  20. Analusis techniques for elevated temperature applications

    International Nuclear Information System (INIS)

    Lewis, D.J.; Hellen, T.K.

    1975-01-01

    This paper reviews some of the more generally used methods of analysis of stress and strain in structures at elevated temperatures, with particular emphasis on finite element methods. It is shown that where sufficiently large computers are available, and where cost is not a severe limitation, creep and plasticity behaviour can be computed for a wide range of components. Where these effects are encountered simultaneously, more knowledge of materials behaviour is required. Calculation of stress and strain is usually only a means to the designer's main aim, which is proving the life and integrity of his structure. The shortcomings of computational methods in this respect are discussed, and a brief review given of some of the 'short cut' methods of life assessment available to the designer. (author)

  1. PEM Water Electrolysis at Elevated Temperatures

    DEFF Research Database (Denmark)

    Hansen, Martin Kalmar

    . This is followed in chapter 4 by a description of the electrolysis setups and electrolysis cells used during the work. Two different setups were used, one operating at atmospheric pressure and another that could operate at elevated pressure so that liquid water electrolysis could be performed at temperature above...... such as porosity and resistance which were supported by images acquired using scanning electron microscopy (SEM). In chapters 6 and 7 the results of the steam electrolysis and pressurised water electrolysis, respectively, are presented and discussed. The steam electrolysis was tested at 130 °C and atmospheric...... needed and hence it has become acute to be able to store the energy. Hydrogen has been identified as a suitable energy carrier and water electrolysis is one way to produce it in a sustainable and environmentally friendly way. In this thesis an introduction to the subject (chapter 1) is given followed...

  2. Modeling of AlMg Sheet Forming at Elevated Temperatures

    NARCIS (Netherlands)

    van den Boogaard, Antonius H.; Bolt, P.; Werkhoven, R.

    2001-01-01

    The process limits of aluminum sheet forming processes can be improved by control-ling local flow behavior by means of elevated temperatures and temperature gradients. In order to accurately model the deep drawing or stretching of aluminum sheet at elevated temperatures, a model is required that

  3. Effect of elevated temperature on the compressive strength of ...

    African Journals Online (AJOL)

    Based on results of tests, partial replacement of cement with 10 % PSMS is recommended for use in concrete production and resistance to elevated temperature. The studies show that at this replacement, the concrete compressive strength is not adversely affected when the elevated temperature reaches 500°C. Keywords: ...

  4. Upshot of Elevated Temperature on Performance Facet of Fly Ash ...

    African Journals Online (AJOL)

    This study investigates the effects of elevated temperature variation on the compressive strength of Fly Ash/Ordinary Portland Cement (OPC) Laterized concrete ... and 10% Fly ash content at 2500C. This is an indication that the strength of Fly ash/OPC Laterized concrete is generally sufficient for use at elevated temperature ...

  5. Investigation of Asphaltene Precipitation at Elevated Temperature

    DEFF Research Database (Denmark)

    Andersen, Simon Ivar; Lindeloff, Niels; Stenby, Erling Halfdan

    1998-01-01

    In order to obtain quantitative data on the asphaltene precipitation induced by the addition of n-alkane (heptane) at temperatures above the normal boiling point of the precipitant, a high temperature/high pressure filtration apparatus has been constructed. Oil and alkane are mixed...

  6. Aluminium sheet forming at elevated temperatures

    NARCIS (Netherlands)

    van den Boogaard, Antonius H.; Bolt, P.J.; Werkhoven, R.J.

    2001-01-01

    The formability of aluminum sheet depends on the temperature of the material and the strain rate. E.g. the limiting drawing ratio can be improved by increasing the temperature uniformly, but even more by heating the flange and cooling the punch. To accurately simulate the deep drawing or stretching

  7. Carbon implantation into tungsten at elevated temperatures

    International Nuclear Information System (INIS)

    Eckstein, W.; Shulga, V.I.; Roth, J.

    1999-01-01

    The bombardment of W with 2.4 keV C at normal incidence in the temperature range between 293 and 973 K is investigated experimentally and by computer simulation. At room temperature the measured weight is at first increasing but then changing to a weight gain with the incident C fluence. This weight gain is reduced at temperatures above 750 K, and at 973 K a constant weight loss is observed. The computing approach was to couple the dynamic Monte Carlo program TRIDYN with the diffusion program PIDAT. Input data for C diffusion in W are taken from the literature. Agreement between experimental data and computed results can be achieved at temperatures around 800 K by using a smaller diffusion coefficient in the simulations than those found in the literature

  8. Arsenite adsorption on goethite at elevated temperatures

    International Nuclear Information System (INIS)

    Kersten, Michael; Vlasova, Nataliya

    2009-01-01

    Experimental closed-system ΔT acid-base titrations between 10 deg. C and 75 deg. C were used to constrain a temperature-dependent 1-pK basic Stern model of the goethite surface complexation reactions. Experimental data for the temperature dependence of pH PZC determined by the one-term Van't Hoff extrapolation yield a value for goethite surface protonation enthalpy of -49.6 kJ mol -1 in good agreement with literature data. Batch titration data between 10 deg. C and 75 deg. C with arsenite concentrations between 10 μM and 100 μM yield adsorption curves, which increases with pH, peak at a pH of 9, and decrease at higher pH values. The slope of this bend becomes steeper with increasing temperature. A 1-pK charge distribution model in combination with a basic Stern layer option could be established for the pH-dependent arsenite adsorption. Formation of two inner-sphere bidentate surface complexes best matched the experimental data in agreement with published EXAFS spectroscopic information. The temperature behaviour of the thus derived intrinsic equilibrium constants can be well represented by the linear Van't Hoff logK T int vs. 1/T plot. Adsorption of arsenite on the goethite surface is exothermic (negative Δ r H 298 values) and therefore becomes weaker with increasing temperature. Application of the new constants with the aqueous speciation code VMINTEQ predicts that the As(III) concentration in presence of goethite sorbent decreases by 10 times once the hydrothermal solution is cooled from 99 deg. C to 1 deg. C. The model curve matches data from a natural thermal water spring system. The increase of adsorption efficiency for As along the temperature gradient may well serve as an additional process to prevent ecosystem contamination by As-rich water seepage from geothermal energy generation facilities

  9. Effects of Elevated Temperature on Compressive Strength Of Concrete

    African Journals Online (AJOL)

    This study presents the results of investigation of the effects of elevated temperatures on the compressive strength of Grade 40 concrete. A total of thirty cube specimens were cast, cured in water at ambient temperature in the laboratory and subjected to various temperature regimes before testing. A concrete mix of 1:1:3 ...

  10. Arsenite adsorption on goethite at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Kersten, Michael [Environmental Geochemistry Group, Institute of Geosciences, Johannes Gutenberg-University, Mainz 55099 (Germany)], E-mail: kersten@uni-mainz.de; Vlasova, Nataliya [Environmental Geochemistry Group, Institute of Geosciences, Johannes Gutenberg-University, Mainz 55099 (Germany)

    2009-01-15

    Experimental closed-system {delta}T acid-base titrations between 10 deg. C and 75 deg. C were used to constrain a temperature-dependent 1-pK basic Stern model of the goethite surface complexation reactions. Experimental data for the temperature dependence of pH{sub PZC} determined by the one-term Van't Hoff extrapolation yield a value for goethite surface protonation enthalpy of -49.6 kJ mol{sup -1} in good agreement with literature data. Batch titration data between 10 deg. C and 75 deg. C with arsenite concentrations between 10 {mu}M and 100 {mu}M yield adsorption curves, which increases with pH, peak at a pH of 9, and decrease at higher pH values. The slope of this bend becomes steeper with increasing temperature. A 1-pK charge distribution model in combination with a basic Stern layer option could be established for the pH-dependent arsenite adsorption. Formation of two inner-sphere bidentate surface complexes best matched the experimental data in agreement with published EXAFS spectroscopic information. The temperature behaviour of the thus derived intrinsic equilibrium constants can be well represented by the linear Van't Hoff logK{sub T}{sup int} vs. 1/T plot. Adsorption of arsenite on the goethite surface is exothermic (negative {delta}{sub r}H{sub 298} values) and therefore becomes weaker with increasing temperature. Application of the new constants with the aqueous speciation code VMINTEQ predicts that the As(III) concentration in presence of goethite sorbent decreases by 10 times once the hydrothermal solution is cooled from 99 deg. C to 1 deg. C. The model curve matches data from a natural thermal water spring system. The increase of adsorption efficiency for As along the temperature gradient may well serve as an additional process to prevent ecosystem contamination by As-rich water seepage from geothermal energy generation facilities.

  11. Elevated temperature grouts and radioactive waste inventory

    International Nuclear Information System (INIS)

    Constable, M.; Fenton, A.; Lee, D.J.; Jones, D.V.C.; Wilding, C.R.

    1990-01-01

    The objective of this year's programme was to quantify the total volumes of cementitious immobilising material required to package radioactive waste arisings in the UK to 2010. These data form the basis for selection of cementitious matrices for further investigation of storage at likely repository temperatures, including the effect of γ irradiation and resaturation to determine their effects on the physical and chemical performance of the cement systems. (Author)

  12. effect of elevated temperature on the compressive strength

    African Journals Online (AJOL)

    HOD

    reducing cost whilst maintaining structural integrity. [1–4].The solid ... density and surface appearance are affected by temperature .... Table 1: Physical properties of Sand, Granite, cement .... The relationship between weight loss and elevated.

  13. Structural analysis for elevated temperature design of the LMFBR

    International Nuclear Information System (INIS)

    Griffin, D.S.

    1976-02-01

    In the structural design of LMFBR components for elevated temperature service it is necessary to take account of the time-dependent, creep behavior of materials. The accommodation of creep to assure design reliability has required (1) development of new design limits and criteria, (2) development of more detailed representations of material behavior, and (3) application of the most advanced analysis techniques. These developments are summarized and examples are given to illustrate the current state of technology in elevated temperature design

  14. Hypercoagulability in response to elevated body temperature and central hypovolemia

    DEFF Research Database (Denmark)

    Meyer, Martin; Ostrowski, Sisse R; Overgaard, Flemming Anders

    2013-01-01

    Coagulation abnormalities contribute to poor outcomes in critically ill patients. In trauma patients exposed to a hot environment, a systemic inflammatory response syndrome, elevated body temperature, and reduced central blood volume occur in parallel with changes in hemostasis and endothelial...... damage. The objective of this study was to evaluate whether experimentally elevated body temperature and reduced central blood volume (CBV) per se affects hemostasis and endothelial activation....

  15. Plastic responses to elevated temperature in low and high elevation populations of three grassland species.

    Science.gov (United States)

    Frei, Esther R; Ghazoul, Jaboury; Pluess, Andrea R

    2014-01-01

    Local persistence of plant species in the face of climate change is largely mediated by genetic adaptation and phenotypic plasticity. In species with a wide altitudinal range, population responses to global warming are likely to differ at contrasting elevations. In controlled climate chambers, we investigated the responses of low and high elevation populations (1200 and 1800 m a.s.l.) of three nutrient-poor grassland species, Trifolium montanum, Ranunculus bulbosus, and Briza media, to ambient and elevated temperature. We measured growth-related, reproductive and phenological traits, evaluated differences in trait plasticity and examined whether trait values or plasticities were positively related to approximate fitness and thus under selection. Elevated temperature induced plastic responses in several growth-related traits of all three species. Although flowering phenology was advanced in T. montanum and R. bulbosus, number of flowers and reproductive allocation were not increased under elevated temperature. Plasticity differed between low and high elevation populations only in leaf traits of T. montanum and B. media. Some growth-related and phenological traits were under selection. Moreover, plasticities were not correlated with approximate fitness indicating selectively neutral plastic responses to elevated temperature. The observed plasticity in growth-related and phenological traits, albeit variable among species, suggests that plasticity is an important mechanism in mediating plant responses to elevated temperature. However, the capacity of species to respond to climate change through phenotypic plasticity is limited suggesting that the species additionally need evolutionary adaptation to adjust to climate change. The observed selection on several growth-related and phenological traits indicates that the study species have the potential for future evolution in the context of a warming climate.

  16. Brassinosteroid signaling-dependent root responses to prolonged elevated ambient temperature.

    Science.gov (United States)

    Martins, Sara; Montiel-Jorda, Alvaro; Cayrel, Anne; Huguet, Stéphanie; Roux, Christine Paysant-Le; Ljung, Karin; Vert, Grégory

    2017-08-21

    Due to their sessile nature, plants have to cope with and adjust to their fluctuating environment. Temperature elevation stimulates the growth of Arabidopsis aerial parts. This process is mediated by increased biosynthesis of the growth-promoting hormone auxin. How plant roots respond to elevated ambient temperature is however still elusive. Here we present strong evidence that temperature elevation impinges on brassinosteroid hormone signaling to alter root growth. We show that elevated temperature leads to increased root elongation, independently of auxin or factors known to drive temperature-mediated shoot growth. We further demonstrate that brassinosteroid signaling regulates root responses to elevated ambient temperature. Increased growth temperature specifically impacts on the level of the brassinosteroid receptor BRI1 to downregulate brassinosteroid signaling and mediate root elongation. Our results establish that BRI1 integrates temperature and brassinosteroid signaling to regulate root growth upon long-term changes in environmental conditions associated with global warming.Moderate heat stimulates the growth of Arabidopsis shoots in an auxin-dependent manner. Here, Martins et al. show that elevated ambient temperature modifies root growth by reducing the BRI1 brassinosteroid-receptor protein level and downregulating brassinosteroid signaling.

  17. Modelling of aluminium sheet forming at elevated temperatures

    NARCIS (Netherlands)

    van den Boogaard, Antonius H.; Huetink, Han

    2004-01-01

    The formability of Al–Mg sheet can be improved considerably, by increasing the temperature. By heating the sheet in areas with large shear strains, but cooling it on places where the risk of necking is high, the limiting drawing ratio can be increased to values above 2.5. At elevated temperatures,

  18. A material model for aluminium sheet forming at elevated temperatures

    NARCIS (Netherlands)

    van den Boogaard, Antonius H.; Werkhoven, R.J.; Bolt, P.J.

    2001-01-01

    In order to accurately simulate the deep drawing or stretching of aluminum sheet at elevated temperatures, a model is required that incorporates the temperature and strain-rate dependency of the material. In this paper two models are compared: a phenomenological material model in which the

  19. Experiment and calculation of reinforced concrete at elevated temperatures

    CERN Document Server

    Guo, Zhenhai

    2011-01-01

    Concrete as a construction material goes through both physical and chemical changes under extreme elevated temperatures. As one of the most widely used building materials, it is important that both engineers and architects are able to understand and predict its behavior in under extreme heat conditions. Brief and readable, this book provides the tools and techniques to properly analysis the effects of high temperature of reinforced concrete which will lead to more stable, safer structures. Based on years of the author's research, Reinforced Concrete at Elevated Temperatures four par

  20. Ultrasonic Resonance of Metallic Spheres at Elevated Temperatures

    OpenAIRE

    Johnson , W.

    1996-01-01

    A unique ultrasonic system has been constructed for measuring resonant frequencies and damping of metallic spheres at elevated temperatures. This system employs electromagnetic-acoustic transduction, with a solenoid coil surrounding the sphere in a uniform magnetic field. Temperature is measured with an optical pyrometer. Since the acoustic and temperature measurements are noncontacting, the uncertainties associated with external damping are relatively small. The resonant frequency and Q of t...

  1. Elevated temperature drives kelp microbiome dysbiosis, while elevated carbon dioxide induces water microbiome disruption.

    Directory of Open Access Journals (Sweden)

    Jeremiah J Minich

    Full Text Available Global climate change includes rising temperatures and increased pCO2 concentrations in the ocean, with potential deleterious impacts on marine organisms. In this case study we conducted a four-week climate change incubation experiment, and tested the independent and combined effects of increased temperature and partial pressure of carbon dioxide (pCO2, on the microbiomes of a foundation species, the giant kelp Macrocystis pyrifera, and the surrounding water column. The water and kelp microbiome responded differently to each of the climate stressors. In the water microbiome, each condition caused an increase in a distinct microbial order, whereas the kelp microbiome exhibited a reduction in the dominant kelp-associated order, Alteromondales. The water column microbiomes were most disrupted by elevated pCO2, with a 7.3 fold increase in Rhizobiales. The kelp microbiome was most influenced by elevated temperature and elevated temperature in combination with elevated pCO2. Kelp growth was negatively associated with elevated temperature, and the kelp microbiome showed a 5.3 fold increase Flavobacteriales and a 2.2 fold increase alginate degrading enzymes and sulfated polysaccharides. In contrast, kelp growth was positively associated with the combination of high temperature and high pCO2 'future conditions', with a 12.5 fold increase in Planctomycetales and 4.8 fold increase in Rhodobacteriales. Therefore, the water and kelp microbiomes acted as distinct communities, where the kelp was stabilizing the microbiome under changing pCO2 conditions, but lost control at high temperature. Under future conditions, a new equilibrium between the kelp and the microbiome was potentially reached, where the kelp grew rapidly and the commensal microbes responded to an increase in mucus production.

  2. Study of elevated temperature design standard against thermal loads

    International Nuclear Information System (INIS)

    Kasahara, Naoto; Asayama, Tai; Morishita, Masaki

    2001-01-01

    Elevated temperature components must be designed against both pressure and thermal loads. In the case of sodium circuits of fast breeder reactors, a restriction from the pressure load becomes small because of the high boiling point of sodium. Design approaches for thermal loads (displacement-controlled) are compared with those against pressure loads (load-controlled). Considering differences between those two approaches, a concept of the elevated temperature design standard that takes the nature of thermal loads fully into account is proposed. This concept is a basis of load evaluation techniques and an inelastic analysis guide, that are being developed. Finally, problems and plans to realize the above concept are discussed. (author)

  3. Solution hardening and strain hardening at elevated temperatures

    International Nuclear Information System (INIS)

    Kocks, U.F.

    1982-10-01

    Solutes can significantly increase the rate of strain hardening; as a consequence, the saturation stress, at which strain hardening tends to cease for a given temperature and strain rate, is increased more than the yield stress: this is the major effect of solutes on strength at elevated temperatures, especially in the regime where dynamic strain-aging occurs. It is shown that local solute mobility can affect both the rate of dynamic recovery and the dislocation/dislocation interaction strength. The latter effect leads to multiplicative solution strengthening. It is explained by a new model based on repeated dislocation unlocking, in a high-temperature limit, which also rationalizes the stress dependence of static and dynamic strain-aging, and may help explain the plateau of the yield stress at elevated temperatures. 15 figures

  4. Structural changes of manganese spinel at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guohua; Iijima, Yukiko; Azuma, Hideto [Nishi Battery Laboratories, Sony Corporation, 4-16-1 Okata, Kanagawa 243-0021 Atsugi (Japan); Kudo, Yoshihiro [Technical Support Center, Sony Corporation, 4-16-1 Okata, Kanagawa 243-0021 Atsugi (Japan)

    2002-01-01

    A chemical synthesis route to Cr-doped and undoped Mn spinel was developed for the purpose of detailed structural analysis for elucidating the relationship between storage performance and structural changes at elevated temperatures. We identified a two-phase segregation in the lithium compositional range of 0.6elevated temperatures was observed for electrochemical cells. These two phases also coexist in Cr-doped spinel in the lithium compositional range of 0.4elevated temperatures. X-ray absorption fine structure (XAFS) analysis revealed that the Cr-doped samples showed less change in the local structure after storage than the undoped spinel samples. These results suggest that the Cr-doped spinel has higher structural stability at elevated temperatures than the undoped spinel.

  5. Plastic creep flow processes in fracture at elevated temperatures

    International Nuclear Information System (INIS)

    Rice, J.R.

    1979-01-01

    Recent theoretical developments on fracture at elevated temperature in the presence of overall plastic (dislocation) creep are discussed. Two topics are considered: stress fields at tips of macroscopic cracks in creeping solids; and diffusive growth of microscopic grain boundary cavities in creeping solids

  6. A materials test system for static compression at elevated temperatures

    Science.gov (United States)

    Korellis, J. S.; Steinhaus, C. A.; Totten, J. J.

    1992-06-01

    This report documents modifications to our existing computer-controlled compression testing system to allow elevated temperature testing in an evacuated environment. We have adopted an 'inverse' design configuration where the evacuated test volume is located within the induction heating coil, eliminating the expense and minimizing the evacuation time of a much larger traditional vacuum chamber.

  7. Air temperature variability in a high-elevation Himalayan catchment

    NARCIS (Netherlands)

    Heynen, Martin; Miles, Evan; Ragettli, Silvan; Buri, Pascal; Immerzeel, Walter W.; Pellicciotti, Francesca

    2016-01-01

    Air temperature is a key control of processes affecting snow and glaciers in high-elevation catchments, including melt, snowfall and sublimation. It is therefore a key input variable to models of land-surface-atmosphere interaction. Despite this importance, its spatial variability is poorly

  8. Stress envelope of silicon carbide composites at elevated temperatures

    International Nuclear Information System (INIS)

    Nozawa, Takashi; Kim, Sunghun; Ozawa, Kazumi; Tanigawa, Hiroyasu

    2014-01-01

    To identify a comprehensive stress envelope, i.e., strength anisotropy map, of silicon carbide fiber-reinforced silicon carbide matrix composite (SiC/SiC composite) for practical component design, tensile and compressive tests were conducted using the small specimen test technique specifically tailored for high-temperature use. In-plane shear properties were, however, estimated using the off-axial tensile method and assuming that the mixed mode failure criterion, i.e., Tsai–Wu criterion, is valid for the composites. The preliminary test results indicate no significant degradation to either proportional limit stress (PLS) or fracture strength by tensile loading at temperatures below 1000 °C. A similarly good tolerance of compressive properties was identified at elevated temperatures, except for a slight degradation in PLS. With the high-temperature test data of tensile, compressive and in-plane shear properties, the stress envelopes at elevated temperatures were finally obtained. A slight reduction in the design limit was obvious at elevated temperatures when the compressive mode is dominant, whereas a negligibly small impact on the design is expected by considering the tensile loading case

  9. Stress envelope of silicon carbide composites at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Nozawa, Takashi, E-mail: nozawa.takashi67@jaea.go.jp [Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan); Kim, Sunghun [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Ozawa, Kazumi; Tanigawa, Hiroyasu [Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan)

    2014-10-15

    To identify a comprehensive stress envelope, i.e., strength anisotropy map, of silicon carbide fiber-reinforced silicon carbide matrix composite (SiC/SiC composite) for practical component design, tensile and compressive tests were conducted using the small specimen test technique specifically tailored for high-temperature use. In-plane shear properties were, however, estimated using the off-axial tensile method and assuming that the mixed mode failure criterion, i.e., Tsai–Wu criterion, is valid for the composites. The preliminary test results indicate no significant degradation to either proportional limit stress (PLS) or fracture strength by tensile loading at temperatures below 1000 °C. A similarly good tolerance of compressive properties was identified at elevated temperatures, except for a slight degradation in PLS. With the high-temperature test data of tensile, compressive and in-plane shear properties, the stress envelopes at elevated temperatures were finally obtained. A slight reduction in the design limit was obvious at elevated temperatures when the compressive mode is dominant, whereas a negligibly small impact on the design is expected by considering the tensile loading case.

  10. Measurement of rock properties at elevated pressures and temperatures

    International Nuclear Information System (INIS)

    Pincus, H.J.; Hoskins, E.R.

    1985-01-01

    The papers in this volume were presented at an ASTM symposium held on 20 June 1983 in conjunction with the 24th Annual Rock Mechanics Symposium at Texas A and M University, College Station, TX. The purpose of these papers is to present recent developments in the measurement of rock properties at elevated pressures and temperatures, and to examine and interpret the data produced by such measurement. The need for measuring rock properties at elevated pressures and temperatures has become increasingly important in recent years. Location and design of nuclear waste repositories, development of geothermal energy sites, and design and construction of deep excavations for civil, military, and mining engineering require significantly improved capabilities for measuring rock properties under conditions substantially different from those prevailing in most laboratory and in situ work. The development of high-pressure, high-temperature capabilities is also significant for the analysis of tectonic processes

  11. Elevated temperature mechanical properties of line pipe steels

    Science.gov (United States)

    Jacobs, Taylor Roth

    The effects of test temperature on the tensile properties of four line pipe steels were evaluated. The four materials include a ferrite-pearlite line pipe steel with a yield strength specification of 359 MPa (52 ksi) and three 485 MPa (70 ksi) yield strength acicular ferrite line pipe steels. Deformation behavior, ductility, strength, strain hardening rate, strain rate sensitivity, and fracture behavior were characterized at room temperature and in the temperature range of 200--350 °C, the potential operating range for steels used in oil production by the steam assisted gravity drainage process. Elevated temperature tensile testing was conducted on commercially produced as-received plates at engineering strain rates of 1.67 x 10 -4, 8.33 x 10-4, and 1.67 x 10-3 s-1. The acicular ferrite (X70) line pipe steels were also tested at elevated temperatures after aging at 200, 275, and 350 °C for 100 h under a tensile load of 419 MPa. The presence of serrated yielding depended on temperature and strain rate, and the upper bound of the temperature range where serrated yielding was observed was independent of microstructure between the ferrite-pearlite (X52) steel and the X70 steels. Serrated yielding was observed at intermediate temperatures and continuous plastic deformation was observed at room temperature and high temperatures. All steels exhibited a minimum in ductility as a function of temperature at testing conditions where serrated yielding was observed. At the higher temperatures (>275 °C) the X52 steel exhibited an increase in ductility with an increase in temperature and the X70 steels exhibited a maximum in ductility as a function of temperature. All steels exhibited a maximum in flow strength and average strain hardening rate as a function of temperature. The X52 steel exhibited maxima in flow strength and average strain hardening rate at lower temperatures than observed for the X70 steels. For all steels, the temperature where the maximum in both flow

  12. Association of elevated ambient temperature with death from cocaine overdose.

    Science.gov (United States)

    Auger, Nathalie; Bilodeau-Bertrand, Marianne; Labesse, Maud Emmanuelle; Kosatsky, Tom

    2017-09-01

    Ecologic data suggest that elevated outdoor temperature is correlated with mortality rates from cocaine overdose. Using non-aggregated death records, we studied the association of hot temperatures with risk of death from cocaine overdose. We carried out a case-crossover study of all deaths from cocaine or other drug overdose between the months of May and September, from 2000 through 2013 in Quebec, Canada. We used conditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) for the association between maximum outdoor temperature and death from cocaine or other drug overdose. The main outcome measure was death from cocaine overdose as a function of maximum temperature the day of death and the days immediately preceding death. There were 316 deaths from cocaine overdose and 446 from other drug overdoses during the study. Elevated temperature the preceding week was associated with the likelihood of death from cocaine but not other drug overdose. Compared with 20°C, a maximum weekly temperature of 30°C was associated with an OR of 2.07 for death from cocaine overdose (95% CI 1.15-3.73), but an OR of 1.03 for other drug overdoses (95% CI 0.60-1.75). Associations for cocaine overdose were present with maximum daily temperature the day of and each of the three days preceding death. Elevated ambient temperature is associated with the risk of death from cocaine overdose. Public health practitioners and drug users should be aware of the added risk of mortality when cocaine is used during hot days. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Stability of lithium niobate on irradiation at elevated temperature

    International Nuclear Information System (INIS)

    Primak, W.; Gavin, A.P.; Anderson, T.T.; Monahan, E.

    1977-01-01

    In contrast to results obtained for neutron irradiation in a thermal reactor near room temperature, lithium niobate plates irradiated in the Experimental Breeder Reactor II (EBR-II) did not become metamict. This is attributed to the elevated temperature of the EBR-II. Ion bombardment experiments indicate that to avoid disordering of lithium niobate on irradiation, its temperature should be maintained above 673 K. Evidence for ionic conductivity was found at 873 K, indicating that it would be inadvisable to permit the temperature to rise that high, particularly with voltage across the plate. In reactor application as a microphone transducer, it is tentatively recommended that the lithium niobate be maintained in the middle of this temperature range for a major portion of reactor operating time

  14. Thermal Behavior of Cylindrical Buckling Restrained Braces at Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Elnaz Talebi

    2014-01-01

    Full Text Available The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core’s surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system.

  15. Thermal behavior of cylindrical buckling restrained braces at elevated temperatures.

    Science.gov (United States)

    Talebi, Elnaz; Tahir, Mahmood Md; Zahmatkesh, Farshad; Yasreen, Airil; Mirza, Jahangir

    2014-01-01

    The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system.

  16. Flow stress, subgrain size, and subgrain stability at elevated temperature

    International Nuclear Information System (INIS)

    Sherby, O.D.; Klundt, R.H.; Miller, A.K.

    1977-01-01

    Well defined subgrain boundaries dominate the microstructural changes occurring during plastic flow of polycrystalline metals at elevated temperature. The quantitative influence of subgrain size on elevated-temperature plastic flow is considered. Based on the results of tests under constant-stress and constant-structure conditions, and equation is developed which predicts the creep rate as a function of subgrain size, stress, diffusion coefficient, and elastic modulus. In general, the subgrain size is a unique function of the current modulus-compensated flow stress, but if fine subgrains can be introduced and stabilized, large increases in creep strength may result. The applicability of the phenomenological relation developed to the behavior of dispersion-strengthened materials (where the second-phase particles may predetermine the effective subgrain size) is discussed. When subgrain effects are included, it is shown that the creep rate is less dependent on stacking fault energy than has been previously thought

  17. Fatigue crack propagation under elastic plastic medium at elevated temperature

    International Nuclear Information System (INIS)

    Asada, Y.; Yuuki, R.; Sakon, T.; Sunamoto, D.; Tokimasa, K.; Makino, Y.; Kitagawa, M; Shingai, K.

    1980-01-01

    The purposes of the present study are to establish the testing method to obtain compatible data on the low cycle fatigue crack propagation at elevated temperature, and to investigate the parameter controlling the crack propagation rate. In the present study, the preliminary experiments have been carried out on low cycle fatigue crack propagation behaviour in type 304 stainless steel in air at 550 0 C, using two types of specimen with a through thickness notch. Both strain controlled and stress controlled fatigue tests have been done under a fully reversed strain or stress cycling. The data obtained are correlated with some fracture mechanics parameters and are discussed with the appropriate parameter for evaluating the low cycle fatigue crack propagation behaviour at elevated temperature. (author)

  18. The tensile behavior of GH3535 superalloy at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Han, F.F.; Zhou, B.M.; Huang, H.F.; Leng, B.; Lu, Y.L. [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China); Dong, J.S. [Superalloy Division, Institute of Metal Research, Chinese Academy of Sciences (China); Li, Z.J., E-mail: lizhijun@sinap.ac.cn [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China); Zhou, X.T. [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China)

    2016-10-01

    The tensile behavior of GH3535 alloy has been investigated at strain rates of 8.33 × 10{sup −5}/s{sup −1}–8.33 × 10{sup −3}/s{sup −1}, in the temperature range of 25–800 °C. The results showed that the ultimate tensile strength was decreased with increasing temperature and increased with rising strain rate, whereas the yield strength kept almost a constant value at the temperature range from 550 to 800 °C in all strain rates test. The formation of M{sub 12}C carbides at the grain boundary during the tension process played an important role in increasing the yield strength of the alloy at elevated temperatures. But inhomogeneous deformation at 650 °C resulted in the minimum ductility of the alloy. Additionally, various types of serrations were noticed on the stress-strain curves for the alloy tested in the temperature range of 500–800 °C. Normal Portevin-Le Chatelier (PLC) effect and positive strain rate sensitivity were observed in this alloy. Type A and A + B serrations were presented to stress-strain curves at temperatures below 650 °C, whereas type C serration was noticed when the temperature rose above 650 °C. The analysis suggested that the interactions between substitutional solutes migration and mobile dislocations were the main reason for the serrated flow behavior in this alloy. - Highlights: • The tensile behavior of GH3535 alloy at elevated temperature was studied. • The yield strength anomaly was observed in the temperature range from 550 to 800 °C. • The formation of M{sub 12}C improves the grain boundary strength to a certain extent. • Inhomogeneous deformation at 650 °C results in the ductility loss of the alloy. • The interaction between solute atoms and dislocations results in the PLC effect.

  19. PCPV instrumentation and measurement techniques at elevated temperatures

    International Nuclear Information System (INIS)

    Zemann, H.

    1978-11-01

    Strain measurement within the structural concrete of the prototype Prestressed Concrete Pressure Vessel have been performed during a one year operation at elevated temperatures up to 120 0 C. Laboratory investigations on the properties of the gauges and the concrete mix are applied to separate the different contributions to the strain data. A decrease of creep and loss of prestress and the arise of stable conditions is observed. (author)

  20. Corrosion resistant coatings suitable for elevated temperature application

    Science.gov (United States)

    Chan, Kwai S [San Antonio, TX; Cheruvu, Narayana Sastry [San Antonio, TX; Liang, Wuwei [Austin, TX

    2012-07-31

    The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

  1. Elevations in core and muscle temperature impairs repeated sprint performance

    DEFF Research Database (Denmark)

    Drust, B.; Rasmussen, P.; Mohr, Magni

    2005-01-01

    on a cycle ergometer in normal (approximately 20 degrees C, control) and hot (40 degrees C, hyperthermia) environments. RESULTS: Completion of the intermittent protocol in the heat elevated core and muscle temperatures (39.5 +/- 0.2 degrees C; 40.2 +/- 0.4 degrees C), heart rate (178 +/- 11 beats min(-1...... metabolic fatigue agents and we, therefore, suggest that it may relate to the influence of high core temperature on the function of the central nervous system.......)), rating of perceived exertion (RPE) (18 +/- 1) and noradrenaline (38.9 +/- 13.2 micromol l(-1)) (all P

  2. Thermodynamic and structural characteristics of cement minerals at elevated temperature

    International Nuclear Information System (INIS)

    Bruton, C.J.; Meike, A.; Viani, B.E.; Martin, S.; Phillips, B.L.

    1994-05-01

    We have instituted an experimental and including program designed to elucidate the structural and thermodynamic response of cement minerals to elevated temperature. Components of the program involve: (a) synthesis of hydrated Ca-silicates; (b) structural analysis of cement phases induced by heating and dehydration/rehydration; (c) mechanistic and thermodynamic descriptions of the hydration/dehydration behavior of hydrated Ca-silicates as a function of temperature, pressure and relative humidity; (d) study of naturally occurring hydrated Ca-silicates; and (e) measurements of thermodynamic data for hydrated Ca-silicates

  3. Properties of Free-Machining Aluminum Alloys at Elevated Temperatures

    Science.gov (United States)

    Faltus, Jiří; Karlík, Miroslav; Haušild, Petr

    In areas close to the cutting tool the workpieces being dry machined could be heated up to 350°C and they may be impact loaded. Therefore it is of interest to study mechanical properties of corresponding materials at elevated temperatures. Free-machining alloys of Al-Cu and Al-Mg-Si systems containing Pb, Bi and Sn additions (AA2011, AA2111B, AA6262, and AA6023) were subjected to Charpy U notch impact test at the temperatures ranging from 20 to 350°C. The tested alloys show a sharp drop in notch impact strength KU at different temperatures. This drop of KU is caused by liquid metal embrittlement due to the melting of low-melting point dispersed phases which is documented by differential scanning calorimetry. Fracture surfaces of the specimens were observed using a scanning electron microscope. At room temperature, the fractures of all studied alloys exhibited similar ductile dimple fracture micromorphology, at elevated temperatures, numerous secondary intergranular cracks were observed.

  4. Elevated temperature ductility of types 304 and 316 stainless steel

    International Nuclear Information System (INIS)

    Sikka, V.K.

    1978-01-01

    Austenitic stainless steel types 304 and 316 are known for their high ductility and toughness. However, the present study shows that certain combinations of strain rate and test temperature can result in a significant loss in elevated-temperature ductility. Such a phenomenon is referred to as ductility minimum. The strain rate, below which ductility loss is initiated, decreases with decrease in test temperature. Besides strain rate and temperature, the ductility minimum was also affected by nitrogen content and thermal aging conditions. Thermal aging at 649 0 C was observed to eliminate the ductility minimum at 649 0 C in both types 304 and 316 stainless steel. Such an aging treatment resulted in a higher ductility than the unaged value. Aging at 593 0 C still resulted in some loss in ductility. Current results suggest that ductility-minimum conditions for stainless steel should be considered in design, thermal aging data analysis, and while studying the effects of chemical composition

  5. Microchip Electrophoresis at Elevated Temperatures and High Separation Field Strengths

    Science.gov (United States)

    Mitra, Indranil; Marczak, Steven P.; Jacobson, Stephen C.

    2014-01-01

    We report free-solution microchip electrophoresis performed at elevated temperatures and high separation field strengths. We used microfluidic devices with 11-cm long separation channels to conduct separations at temperatures between 22 (ambient) and 45 °C and field strengths from 100 to 1000 V/cm. To evaluate separation performance, N-glycans were used as a model system and labeled with 8-aminopyrene-1,3,6-trisulfonic acid to impart charge for electrophoresis and render them fluorescent. Typically, increased diffusivity at higher temperatures leads to increased axial dispersion and poor separation performance; however, we demonstrate that sufficiently high separation field strengths can be used to offset the impact of increased diffusivity in order to maintain separation efficiency. Efficiencies for these free-solution separations are the same at temperatures of 25, 35, and 45 °C with separation field strengths ≥500 V/cm. PMID:24114979

  6. Behavior of HPC with Fly Ash after Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Huai-Shuai Shang

    2013-01-01

    Full Text Available For use in fire resistance calculations, the relevant thermal properties of high-performance concrete (HPC with fly ash were determined through an experimental study. These properties included compressive strength, cubic compressive strength, cleavage strength, flexural strength, and the ultrasonic velocity at various temperatures (20, 100, 200, 300, 400 and 500∘C for high-performance concrete. The effect of temperature on compressive strength, cubic compressive strength, cleavage strength, flexural strength, and the ultrasonic velocity of the high-performance concrete with fly ash was discussed according to the experimental results. The change of surface characteristics with the temperature was observed. It can serve as a reference for the maintenance, design, and the life prediction of high-performance concrete engineering, such as high-rise building, subjected to elevated temperatures.

  7. Analysis of the austenitic stainless steel's r-value behavior at elevated temperatures

    OpenAIRE

    Dušan Arsić; Milan Djordjević; Srbislav Aleksandrović; Vukić Lazić; Ruzica R. Nikolic; Branislav Hadzima

    2015-01-01

    An analysis of the anisotropy properties of austenitic steel AISI 304 (X5CrNi18-10) at elevated temperatures is presented in this paper. Considerations of the anisotropy problems are presented in the theoretical part of the paper, as well as the procedure for determination of the normal anisotropy coefficient. The experimental part of the paper describes the plan, methodology and equipment for testing of material's normal anisotropy and mechanical characteristics. The objective of conducting ...

  8. Elevated temperature alters carbon cycling in a model microbial community

    Science.gov (United States)

    Mosier, A.; Li, Z.; Thomas, B. C.; Hettich, R. L.; Pan, C.; Banfield, J. F.

    2013-12-01

    Earth's climate is regulated by biogeochemical carbon exchanges between the land, oceans and atmosphere that are chiefly driven by microorganisms. Microbial communities are therefore indispensible to the study of carbon cycling and its impacts on the global climate system. In spite of the critical role of microbial communities in carbon cycling processes, microbial activity is currently minimally represented or altogether absent from most Earth System Models. Method development and hypothesis-driven experimentation on tractable model ecosystems of reduced complexity, as presented here, are essential for building molecularly resolved, benchmarked carbon-climate models. Here, we use chemoautotropic acid mine drainage biofilms as a model community to determine how elevated temperature, a key parameter of global climate change, regulates the flow of carbon through microbial-based ecosystems. This study represents the first community proteomics analysis using tandem mass tags (TMT), which enable accurate, precise, and reproducible quantification of proteins. We compare protein expression levels of biofilms growing over a narrow temperature range expected to occur with predicted climate changes. We show that elevated temperature leads to up-regulation of proteins involved in amino acid metabolism and protein modification, and down-regulation of proteins involved in growth and reproduction. Closely related bacterial genotypes differ in their response to temperature: Elevated temperature represses carbon fixation by two Leptospirillum genotypes, whereas carbon fixation is significantly up-regulated at higher temperature by a third closely related genotypic group. Leptospirillum group III bacteria are more susceptible to viral stress at elevated temperature, which may lead to greater carbon turnover in the microbial food web through the release of viral lysate. Overall, this proteogenomics approach revealed the effects of climate change on carbon cycling pathways and other

  9. Zinc sacrificial anode behavior at elevated temperatures in sodium chloride and tap water environments

    International Nuclear Information System (INIS)

    Othman, Othman Mohsen

    2005-01-01

    Zinc sacrificial anode coupled to mild steel was tested in sodium chloride and tap water environments at elevated temperatures. The anode failed to protect the mild steel specimens in tap water environment at all temperatures specified for this study. This was partly due to the high resistivity of the medium. The temperature factor did not help to activate the anode in water tap medium. In sodium chloride environment the anode demonstrated good protection for steel cathodes. In tap water environment the anode weight loss was negligible. The zinc anode suffered intergranular corrosion in sodium chloride environment and this was noticed starting at 40 degree centigrade. In tap water environment the zinc anode demonstrated interesting behavior beyond 60 degree centigrade, that could be attributed to the phenomenon of reversal of potential at elevated temperatures. It also showed shallow pitting spots in tap water environment without any sign of intergranular corrosion. Zinc anodes would suffer intergranular corrosion at high temperatures. (author)

  10. Void nucleation at elevated temperatures under cascade-damage irradiation

    International Nuclear Information System (INIS)

    Semenov, A.A.; Woo, C.H.

    2002-01-01

    The effects on void nucleation of fluctuations respectively due to the randomness of point-defect migratory jumps, the random generation of free point defects in discrete packages, and the fluctuating rate of vacancy emission from voids are considered. It was found that effects of the cascade-induced fluctuations are significant only at sufficiently high total sink strength. At lower sink strengths and elevated temperatures, the fluctuation in the rate of vacancy emission is the dominant factor. Application of the present theory to the void nucleation in annealed pure copper neutron-irradiated at elevated temperatures with doses of 10 -4 -10 -2 NRT dpa showed reasonable agreement between theory and experiment. This application also predicts correctly the temporal development of large-scale spatial heterogeneous microstructure during the void nucleation stage. Comparison between calculated and experimental void nucleation rates in neutron-irradiated molybdenum at temperatures where vacancy emission from voids is negligible showed reasonable agreement as well. It was clearly demonstrated that the athermal shrinkage of relatively large voids experimentally observable in molybdenum at such temperatures may be easily explained in the framework of the present theory

  11. Steel fiber reinforced concrete subjected to elevated cyclic temperatures

    International Nuclear Information System (INIS)

    Yousif, R. A.; Rasheed, H. M.; Muhammad, H. A.

    1997-01-01

    The results from a series of tests on steel fiber reinforced concrete at elevated cyclic temperature are presented. The residual compressive strength and ultimate splitting tensile strength were nadir's on specimen ts with no fibers and with 0.5% and 1% plain steel fibers over a temperature range of 300-700 C. concrete was subjected to one, two or three cycles of heating and cooling. In general the exposure to temperature decreased the strength of concrete, although the number of heating cycles seems only to have a secondary effect. The results also show that the steel fiber reinforced concrete performs better than plain concrete. Two equations were suggested to predict the strength of concrete and the results show good agreement with the experimental values. . (authors). 10 refs., 1 tabs. 3 figs

  12. Microstructural design of magnesium alloys for elevated temperature performance

    Science.gov (United States)

    Bryan, Zachary Lee

    Magnesium alloys are promising for automotive and aerospace applications requiring lightweight structural metals due to their high specific strength. Weight reductions through material substitution significantly improve fuel efficiency and reduce greenhouse gas emissions. Challenges to widespread integration of Mg alloys primarily result from their limited ductility and elevated temperature strength. This research presents a microstructurally-driven systems design approach to Mg alloy development for elevated temperature applications. The alloy properties that were targeted included creep resistance, elevated temperature strength, room temperature ductility, and material cost. To enable microstructural predictions during the design process, computational thermodynamics was utilized with a newly developed atomic mobility database for HCP-Mg. The mobilities for Mg self-diffusion, as well as Al, Ag, Sn, and Zn solute diffusion in HCP-Mg were optimized from available diffusion literature using DICTRA. The optimized mobility database was then validated using experimental diffusion couples. To limit dislocation creep mechanisms in the first design iteration, a microstructure consisting of Al solutes in solid solution and a fine dispersion of Mg2Sn precipitates was targeted. The development of strength and diffusion models informed by thermodynamic predictions of phase equilibria led to the selection of an optimum Mg-1.9at%Sn-1.5at%Al (TA) alloy for elevated temperature performance. This alloy was cast, solution treated based upon DICTRA homogenization simulations, and then aged. While the tensile and creep properties were competitive with conventional Mg alloys, the TA mechanical performance was ultimately limited because of abnormal grain growth that occurred during solution treatment and the basal Mg2Sn particle morphology. For the second design iteration, insoluble Mg2Si intermetallic particles were added to the TA alloy to provide enhanced grain boundary pinning

  13. Elevated temperature crack growth in advanced powder metallurgy aluminum alloys

    Science.gov (United States)

    Porr, William C., Jr.; Gangloff, Richard P.

    1990-01-01

    Rapidly solidified Al-Fe-V-Si powder metallurgy alloy FVS0812 is among the most promising of the elevated temperature aluminum alloys developed in recent years. The ultra fine grain size and high volume fraction of thermally stable dispersoids enable the alloy to maintain tensile properties at elevated temperatures. In contrast, this alloy displays complex and potentially deleterious damage tolerant and time dependent fracture behavior that varies with temperature. J-Integral fracture mechanics were used to determine fracture toughness (K sub IC) and crack growth resistance (tearing modulus, T) of extruded FVS0812 as a function of temperature. The alloy exhibits high fracture properties at room temperature when tested in the LT orientation, due to extensive delamination of prior ribbon particle boundaries perpendicular to the crack front. Delamination results in a loss of through thickness constraint along the crack front, raising the critical stress intensity necessary for precrack initiation. The fracture toughness and tensile ductility of this alloy decrease with increasing temperature, with minima observed at 200 C. This behavior results from minima in the intrinsic toughness of the material, due to dynamic strain aging, and in the extent of prior particle boundary delaminations. At 200 C FVS0812 fails at K levels that are insufficient to cause through thickness delamination. As temperature increases beyond the minimum, strain aging is reduced and delamination returns. For the TL orientation, K (sub IC) decreased and T increased slightly with increasing temperature from 25 to 316 C. Fracture in the TL orientation is governed by prior particle boundary toughness; increased strain localization at these boundaries may result in lower toughness with increasing temperature. Preliminary results demonstrate a complex effect of loading rate on K (sub IC) and T at 175 C, and indicate that the combined effects of time dependent deformation, environment, and strain aging

  14. Dynamic Uniaxial Compression of HSLA-65 Steel at Elevated Temperatures

    Science.gov (United States)

    Dike, Shweta; Wang, Tianxue; Zuanetti, Bryan; Prakash, Vikas

    2017-12-01

    In the present study, the dynamic response of a high-strength, low alloy Grade 65 (HSLA-65) steel, used by the United States Navy for ship hull construction, is investigated under dynamic uniaxial compression at temperatures ranging from room temperature to 1000 °C using a novel elevated temperature split-Hopkinson pressure bar. These experiments are designed to probe the dynamic response of HSLA-65 steel in its single α-ferrite phase, mixed α + γ-austenite phase, and the single γ-austenite phase, as a function of temperature. The investigation is conducted at two different average strain rates—1450 and 2100/s. The experimental results indicate that at test temperatures in the range from room temperature to lower than 600 °C, i.e. prior to the development of the mixed α + γ phase, a net softening in flow strength is observed at all levels of plastic strain with increase in test temperatures. As the test temperatures are increased, the rate of this strain softening with temperature is observed to decrease, and at 600 °C the trend reverses itself resulting in an increase in flow stress at all strains tested. This increase in flow stress is understood be due to dynamic strain aging, where solute atoms play a distinctive role in hindering dislocation motion. At 800 °C, a (sharp) drop in the flow stress, equivalent to one-half of its value at room temperature, is observed. As the test temperature are increased to 900 and 1000 °C, further drop in flow stress are observed at all plastic strain levels. In addition, strain hardening in flow stress is observed at all test temperatures up to 600 °C; beyond 800 °C the rate of strain hardening is observed to decrease, with strain softening becoming dominant at temperatures of 900 °C and higher. Moreover, comparing the high strain rate stress versus strain data gathered on HSLA 65 in the current investigation with those available in the literature at quasi-static strain rates, strain-rate hardening can be

  15. Leaf physiological responses of mature Norway Spruce trees exposed to elevated carbon dioxide and temperature

    Science.gov (United States)

    Lamba, Shubhangi; Uddling, Johan; Räntfors, Mats; Hall, Marianne; Wallin, Göran

    2014-05-01

    Leaf photosynthesis, respiration and stomatal conductance exert strong control over the exchange of carbon, water and energy between the terrestrial biosphere and the atmosphere. As such, leaf physiological responses to rising atmospheric CO2 concentration ([CO2]) and temperature have important implications for the global carbon cycle and rate of ongoing global warming, as well as for local and regional hydrology and evaporative cooling. It is therefore critical to improve the understanding of plant physiological responses to elevated [CO2] and temperature, in particular for boreal and tropical ecosystems. In order to do so, we examined physiological responses of mature boreal Norway spruce trees (ca 40-years old) exposed to elevated [CO2] and temperature inside whole-tree chambers at Flakaliden research site, Northern Sweden. The trees were exposed to a factorial combination of two levels of [CO2] (ambient and doubled) and temperature (ambient and +2.8 degree C in summer and +5.6 degree C in winter). Three replicates in each of the four treatments were used. It was found that photosynthesis was increased considerably in elevated [CO2], but was not affected by the warming treatment. The maximum rate of photosynthetic carboxylation was reduced in the combined elevated [CO2] and elevated temperature treatment, but not in single factor treatments. Elevated [CO2] also strongly increased the base rate of respiration and to a lesser extent reduced the temperature sensitivity (Q10 value) of respiration; responses which may be important for the carbon balance of these trees which have a large proportion of shaded foliage. Stomatal conductance at a given VPD was reduced by elevated temperature treatment, to a degree that mostly offset the higher vapour pressure deficit in warmed air with respect to transpiration. Elevated [CO2] did not affect stomatal conductance, and thus increased the ratio of leaf internal to external [CO2]. These results indicate that the large elevated

  16. Rules for the analysis of mechanical structures at elevated temperatures

    International Nuclear Information System (INIS)

    Jakubowicz, H.; Petrequin, P.; Schaller, K.

    1979-01-01

    This paper describes how the experience gained by the CEA (French Atomic Energy Commission) in design, construction and operation of pool type LMFBR, as well as in research an development, is used to establish rules for the analysis of mechanical structures at elevated temperatures. These rules are written by different working groups and approved by a committee named RAMSES. The working methods of the RAMSES committee are described. Some of the approved recommendations are presented. The ongoing work and futur topics are also described

  17. Effects of elevated CO2 and temperature on seed quality

    DEFF Research Database (Denmark)

    Hampton, John G; Boelt, Birte; Rolston, M P

    2013-01-01

    production on three seed quality components: seed mass, germination and seed vigour. In response to elevated CO2, seed mass has been reported to both increase and decrease in C3 plants, but not change in C4 plants. Increases are greater in legumes than non-legumes, and there is considerable variation among...... species. Seed mass increases may result in a decrease of seed nitrogen (N) concentration in non-legumes. Increasing temperature may decrease seed mass because of an accelerated growth rate and reduced seed filling duration, but lower seed mass does not necessarily reduce seed germination or vigour. Like...

  18. Elevated temperature transmission Kikuchi diffraction in the SEM

    DEFF Research Database (Denmark)

    Fanta, Alice Bastos; Todeschini, Matteo; Burrows, Andrew

    2018-01-01

    heating associated with this system enables reliable TKD measurements at elevated temperatures without notable disturbance from infrared radiation. The dewetting of an Au thin film into Au nanoparticles upon heating is followed with orientation mapping in a temperature range between 20 °C and 900 °C....... The local thickness variation associated with the dewetting is observed qualitatively by observing the intensity of the transmitted beam, which decreases as the film thickness increases locally. The results of this study reveal that TKD is a well suited technique to study thin-film stability and solid state...... dewetting. Moreover, the outcome of this methodological study provides a baseline for further in-situ crystallographic studies of electron transparent samples in the SEM....

  19. Effects of Si on microstructure and phase transformation at elevated temperatures in ferritic white cast irons

    Energy Technology Data Exchange (ETDEWEB)

    Wiengmoon, A., E-mail: ampornw@nu.ac.th [Department of Physics, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Pearce, J.T.H. [Panyapiwat Institute of Management, Nonthaburi 11120 (Thailand); Nusen, S.; Chairuangsri, T. [Department of Industrial Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2016-10-15

    The effects of Si on microstructure and phase transformation at elevated temperature of ferritic 31wt.%Cr-1.1wt.%C white cast irons with up to 3wt.%Si have been studied. Applications of these irons include parts requiring heat resistance at elevated temperature. The irons were produced by sand casting. The microstructure in as-cast condition and after being subjected to high temperature (700 to 1000 °C) was investigated by light microscopy, X-ray diffraction, and electron microscopy. The results revealed that the as-cast microstructure consisted mainly of primary ferrite dendrites and eutectic (ferrite + M{sub 7}C{sub 3}). Si promotes M{sub 7}C{sub 3}-to-M{sub 23}C{sub 6} transformation in the irons subjected to transformation at elevated temperature, but no sigma phase was found. The extent of M{sub 7}C{sub 3}-to-M{sub 23}C{sub 6} transformation increases proportional to the increasing transformation temperature, holding time and Si content in the irons. For the iron with 1.0wt.%Si content after holding at elevated temperatures, martensite was also found, which could be attributed to carbon accretion effects in eutectic ferrite. Si was incorporated in M{sub 23}C{sub 6} such that M{sub 23}C{sub 6} containing Si can show darker contrast under SEM-BEI as compared to M{sub 7}C{sub 3}; this is the opposite to what has been observed for the cases of typical M{sub 23}C{sub 6} and M{sub 23}C{sub 6} containing Mo or W. The results obtained are important to understand the change in properties of ferritic, high chromium irons containing Si subjected to elevated temperature.

  20. Rotating disk electrode system for elevated pressures and temperatures.

    Science.gov (United States)

    Fleige, M J; Wiberg, G K H; Arenz, M

    2015-06-01

    We describe the development and test of an elevated pressure and temperature rotating disk electrode (RDE) system that allows measurements under well-defined mass transport conditions. As demonstrated for the oxygen reduction reaction on polycrystalline platinum (Pt) in 0.5M H2SO4, the setup can easily be operated in a pressure range of 1-101 bar oxygen, and temperature of 140 °C. Under such conditions, diffusion limited current densities increase by almost two orders of magnitude as compared to conventional RDE setups allowing, for example, fuel cell catalyst studies under more realistic conditions. Levich plots demonstrate that the mass transport is indeed well-defined, i.e., at low electrode potentials, the measured current densities are fully diffusion controlled, while at higher potentials, a mixed kinetic-diffusion controlled regime is observed. Therefore, the setup opens up a new field for RDE investigations under temperature and current density conditions relevant for low and high temperature proton exchange membrane fuel cells.

  1. Rotating disk electrode system for elevated pressures and temperatures

    International Nuclear Information System (INIS)

    Fleige, M. J.; Wiberg, G. K. H.; Arenz, M.

    2015-01-01

    We describe the development and test of an elevated pressure and temperature rotating disk electrode (RDE) system that allows measurements under well-defined mass transport conditions. As demonstrated for the oxygen reduction reaction on polycrystalline platinum (Pt) in 0.5M H 2 SO 4 , the setup can easily be operated in a pressure range of 1–101 bar oxygen, and temperature of 140 °C. Under such conditions, diffusion limited current densities increase by almost two orders of magnitude as compared to conventional RDE setups allowing, for example, fuel cell catalyst studies under more realistic conditions. Levich plots demonstrate that the mass transport is indeed well-defined, i.e., at low electrode potentials, the measured current densities are fully diffusion controlled, while at higher potentials, a mixed kinetic-diffusion controlled regime is observed. Therefore, the setup opens up a new field for RDE investigations under temperature and current density conditions relevant for low and high temperature proton exchange membrane fuel cells

  2. Rotating disk electrode system for elevated pressures and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Fleige, M. J.; Wiberg, G. K. H.; Arenz, M. [Department of Chemistry and Nano-Science Center, University of Copenhagen, Universitetsparken 5, 2100 Ø Copenhagen (Denmark)

    2015-06-15

    We describe the development and test of an elevated pressure and temperature rotating disk electrode (RDE) system that allows measurements under well-defined mass transport conditions. As demonstrated for the oxygen reduction reaction on polycrystalline platinum (Pt) in 0.5M H{sub 2}SO{sub 4}, the setup can easily be operated in a pressure range of 1–101 bar oxygen, and temperature of 140 °C. Under such conditions, diffusion limited current densities increase by almost two orders of magnitude as compared to conventional RDE setups allowing, for example, fuel cell catalyst studies under more realistic conditions. Levich plots demonstrate that the mass transport is indeed well-defined, i.e., at low electrode potentials, the measured current densities are fully diffusion controlled, while at higher potentials, a mixed kinetic-diffusion controlled regime is observed. Therefore, the setup opens up a new field for RDE investigations under temperature and current density conditions relevant for low and high temperature proton exchange membrane fuel cells.

  3. Rotating disk electrode system for elevated pressures and temperatures

    Science.gov (United States)

    Fleige, M. J.; Wiberg, G. K. H.; Arenz, M.

    2015-06-01

    We describe the development and test of an elevated pressure and temperature rotating disk electrode (RDE) system that allows measurements under well-defined mass transport conditions. As demonstrated for the oxygen reduction reaction on polycrystalline platinum (Pt) in 0.5M H2SO4, the setup can easily be operated in a pressure range of 1-101 bar oxygen, and temperature of 140 °C. Under such conditions, diffusion limited current densities increase by almost two orders of magnitude as compared to conventional RDE setups allowing, for example, fuel cell catalyst studies under more realistic conditions. Levich plots demonstrate that the mass transport is indeed well-defined, i.e., at low electrode potentials, the measured current densities are fully diffusion controlled, while at higher potentials, a mixed kinetic-diffusion controlled regime is observed. Therefore, the setup opens up a new field for RDE investigations under temperature and current density conditions relevant for low and high temperature proton exchange membrane fuel cells.

  4. LCF behavior of Zr-4 alloy at elevated temperature

    International Nuclear Information System (INIS)

    Ye Yuming; Cai Lixun

    2006-01-01

    A series of strain fatigue tests were carried out on small bugle-like slice-specimens of Zr-4 alloy at room temperature and 400 degree C. According to Elastic and Plastic Finite Element Analysis and assumption of local damage equivalence, a strain conversion equation was given to transform the transverse strain of the specimen to the axial strain. Based on the test results of the alloy and the strain conversion equation, fatigue life estimation equations of Zr-4alloy, or M-C (Manson-Coffin) models, were obtained. The results showed that, Zr-4 alloy had obvious cyclic hardening character during high amplitude strain at different temperatures, but showed reverse character during low amplitude strain. Elevated temperature lowered seriously the fatigue life of Zr-4 alloys, ann as the increasing of amplitude strain, temperature effect impaired gradually. Analysis showed that the prediction life by using M-C model based on the traditional strain conversion equation was quite conservative when axial strain amplitude was less than 5000 micro-strain. (authors)

  5. Drought-induced weakening of growth-temperature associations in high-elevation Iberian pines

    Science.gov (United States)

    Diego Galván, J.; Büntgen, Ulf; Ginzler, Christian; Grudd, Håkan; Gutiérrez, Emilia; Labuhn, Inga; Julio Camarero, J.

    2015-01-01

    The growth/climate relationship of theoretically temperature-controlled high-elevation forests has been demonstrated to weaken over recent decades. This is likely due to new tree growth limiting factors, such as an increasing drought risk for ecosystem functioning and productivity across the Mediterranean Basin. In addition, declining tree growth sensitivity to spring temperature may emerge in response to increasing drought stress. Here, we evaluate these ideas by assessing the growth/climate sensitivity of 1500 tree-ring width (TRW) and 102 maximum density (MXD) measurement series from 711 and 74 Pinus uncinata trees, respectively, sampled at 28 high-elevation forest sites across the Pyrenees and two relict populations of the Iberian System. Different dendroclimatological standardization and split period approaches were used to assess the high- to low-frequency behavior of 20th century tree growth in response to temperature means, precipitation totals and drought indices. Long-term variations in TRW track summer temperatures until about 1970 but diverge afterwards, whereas MXD captures the recent temperature increase in the low-frequency domain fairly well. On the other hand summer drought has increasingly driven TRW along the 20th century. Our results suggest fading temperature sensitivity of Iberian high-elevation P. uncinata forest growth, and reveal the importance of summer drought that is becoming the emergent limiting factor of tree ring width formation in many parts of the Mediterranean Basin.

  6. Void growth and coalescence in metals deformed at elevated temperature

    DEFF Research Database (Denmark)

    Klöcker, H.; Tvergaard, Viggo

    2000-01-01

    For metals deformed at elevated temperatures the growth of voids to coalescence is studied numerically. The voids are assumed to be present from the beginning of deformation, and the rate of deformation considered is so high that void growth is dominated by power law creep of the material, without...... any noticeable effect of surface diffusion. Axisymmetric unit cell model computations are used to study void growth in a material containing a periodic array of voids, and the onset of the coalescence process is defined as the stage where plastic flow localizes in the ligaments between neighbouring...... voids. The focus of the study is on various relatively high stress triaxialties. In order to represent the results in terms of a porous ductile material model a set of constitutive relations are used, which have been proposed for void growth in a material undergoing power law creep....

  7. Low cycle fatigue testing in flowing sodium at elevated temperatures

    International Nuclear Information System (INIS)

    Flagella, P.N.; Kahrs, J.R.

    1976-01-01

    The paper describes equipment developed to obtain low cycle strain-controlled fatigue data in flowing sodium at elevated temperatures. Operation and interaction of the major components of the system are discussed, including the calibration technique using remote strain measurement and control. Confirmation of in-air results using the special technique is demonstrated, with data presented for Type 316 stainless steel tested in high purity flowing sodium at 593 0 C. The fatigue life of the material in sodium is essentially the same as that obtained in air for delta epsilon/sub t/= 1 percent. On the other hand, sodium pre-exposure at 650 0 C for 5000 hours increased the fatigue life in-sodium by a factor of two, and sodium pre-exposure at 718 0 C for 5000 hours increased the fatigue life in-sodium by a factor of three

  8. Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials

    Science.gov (United States)

    Keith, Theo G.

    2005-01-01

    The purpose of this report is to provide a final report for the period of 12/1/03 through 11/30/04 for NASA Cooperative Agreement NCC3-776, entitled "Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials." During this final period, major efforts were focused on both the determination of mechanical properties of advanced ceramic materials and the development of mechanical test methodologies under several different programs of the NASA-Glenn. The important research activities made during this period are: 1. Mechanical properties evaluation of two gas-turbine grade silicon nitrides. 2) Mechanical testing for fuel-cell seal materials. 3) Mechanical properties evaluation of thermal barrier coatings and CFCCs and 4) Foreign object damage (FOD) testing.

  9. Expected changes in future temperature extremes and their elevation dependency over the Yellow River source region

    Directory of Open Access Journals (Sweden)

    Y. Hu

    2013-07-01

    Full Text Available Using the Statistical DownScaling Model (SDSM and the outputs from two global climate models, we investigate possible changes in mean and extreme temperature indices and their elevation dependency over the Yellow River source region for the two future periods 2046–2065 and 2081–2100 under the IPCC SRES A2, A1B and B1 emission scenarios. Changes in interannual variability of mean and extreme temperature indices are also analyzed. The validation results show that SDSM performs better in reproducing the maximum temperature-related indices than the minimum temperature-related indices. The projections show that by the middle and end of the 21st century all parts of the study region may experience increases in both mean and extreme temperature in all seasons, along with an increase in the frequency of hot days and warm nights and with a decrease in frost days. By the end of the 21st century, interannual variability increases in all seasons for the frequency of hot days and warm nights and in spring for frost days while it decreases for frost days in summer. Autumn demonstrates pronounced elevation-dependent changes in which around six out of eight indices show significant increasing changes with elevation.

  10. Elevated temperature and high pressure large helium gas loop

    International Nuclear Information System (INIS)

    Sakasai, Minoru; Midoriyama, Shigeru; Miyata, Toyohiko; Nakase, Tsuyoshi; Izaki, Makoto

    1979-01-01

    The development of high temperature gas-cooled reactors especially aiming at the multi-purpose utilization of nuclear heat energy is carried out actively in Japan and West Germany. In Japan, the experimental HTGR of 50 MWt and 1000 deg C outlet temperature is being developed by Japan Atomic Energy Research Institute and others since 1969, and the development of direct iron-making technology utilizing high temperature reducing gas was started in 1973 as the large project of Ministry of Internalional Trade and Industry. Kawasaki Heavy Industries, Ltd., Has taken part in these development projects, and has developed many softwares for nuclear heat design, system design and safety design of nuclear reactor system and heat utilization system. In hardwares also, efforts have been exerted to develop the technologies of design and manufacture of high temperature machinery and equipments. The high temperature, high pressure, large helium gas loop is under construction in the technical research institute of the company, and it is expected to be completed in December, 1979. The tests planned are that of proving the dynamic performances of the loop and its machinery and equipments and the verification of analysis codes. The loop is composed of the main circulation system, the objects of testing, the helium gas purifying system, the helium supplying and evacuating system, instruments and others. (Kako, I.)

  11. Effect of elevated temperature on the mechanical strength of HEPA filters

    International Nuclear Information System (INIS)

    Elfawal, M.M.; Eladham, K.A.; Hammed, F.H.; Abdrabbo, M.F.

    1993-01-01

    The effect of elevated temperature on the mechanical strength of HEPA filters was studied in order to evaluate and improve their performance under high temperature conditions. As part of this study the mechanical strength of HEPA filter medium which is the limiting factor in terms of the filter strength was experimentally studied at elevated temperature up to 400 degree C, and thermal exposure times ranged from 2 min to 4 h. The failure pressures of HEPA filter units after long exposure to 250 degree C were also investigated. The test results show that the medium strength decreases with increase in temperature challenge and thermal exposure time due to burnout of the organic binder used to improve the strength and flexibility of the medium. The test results also show that the tensile strength of the conventional filter medium drops to about 40 % of the value at room temperature after exposure to 250 degree C for 6 h; therefore, the continuous exposure of the conventional filter medium to this temperature is critical. The average failure differential pressures of all commercial tested filters were found to lie between 9 and 18 kPa at ambient temperature and between 6 and 11 kPa after thermal challenge at 250 degree C for 100 h. It was found that swelling and capture of the ends of individual pleats has led to filter failure.3 fig., 2 tab

  12. Creep of Posidonia Shale at Elevated Pressure and Temperature

    Science.gov (United States)

    Rybacki, E.; Herrmann, J.; Wirth, R.; Dresen, G.

    2017-12-01

    The economic production of gas and oil from shales requires repeated hydraulic fracturing operations to stimulate these tight reservoir rocks. Besides simple depletion, the often observed decay of production rate with time may arise from creep-induced fracture closure. We examined experimentally the creep behavior of an immature carbonate-rich Posidonia shale, subjected to constant stress conditions at temperatures between 50 and 200 °C and confining pressures of 50-200 MPa, simulating elevated in situ depth conditions. Samples showed transient creep in the semibrittle regime with high deformation rates at high differential stress, high temperature and low confinement. Strain was mainly accommodated by deformation of the weak organic matter and phyllosilicates and by pore space reduction. The primary decelerating creep phase observed at relatively low stress can be described by an empirical power law relation between strain and time, where the fitted parameters vary with temperature, pressure and stress. Our results suggest that healing of hydraulic fractures at low stresses by creep-induced proppant embedment is unlikely within a creep period of several years. At higher differential stress, as may be expected in situ at contact areas due to stress concentrations, the shale showed secondary creep, followed by tertiary creep until failure. In this regime, microcrack propagation and coalescence may be assisted by stress corrosion. Secondary creep rates were also described by a power law, predicting faster fracture closure rates than for primary creep, likely contributing to production rate decline. Comparison of our data with published primary creep data on other shales suggests that the long-term creep behavior of shales can be correlated with their brittleness estimated from composition. Low creep strain is supported by a high fraction of strong minerals that can build up a load-bearing framework.

  13. Analysis of the austenitic stainless steel's r-value behavior at elevated temperatures

    Directory of Open Access Journals (Sweden)

    Dušan Arsić

    2015-05-01

    Full Text Available An analysis of the anisotropy properties of austenitic steel AISI 304 (X5CrNi18-10 at elevated temperatures is presented in this paper. Considerations of the anisotropy problems are presented in the theoretical part of the paper, as well as the procedure for determination of the normal anisotropy coefficient. The experimental part of the paper describes the plan, methodology and equipment for testing of material's normal anisotropy and mechanical characteristics. The objective of conducting the experiments was to investigate influence of temperature on normal anisotropy, as well as on the mechanical properties of the considered material. The normal anisotropy was monitored by the coefficient – the so-called "r-value". Besides that, the tensile strength, yield stress and elongation at break were monitored, also. The tests were done on the 0.7 mm thick sheet metal within the temperature range 20 to 700°C.

  14. Physical mechanisms related to the degradation of LPCVD tungsten contacts at elevated temperatures

    International Nuclear Information System (INIS)

    Shenai, K.; Lewis, N.; Smith, G.A.; McConnell, M.D.; Burrell, M.

    1990-01-01

    The thermal stability of LPCVD (low pressure chemical vapor deposition) tungsten contacts to n-type silicon is studied at elevated temperatures in excess of 650 degrees C. The process variants studied include silicon doping, tungsten thickness, and post tungsten deposition dielectric stress temperatures. Detailed measurements of Kelvin contact resistance were made at room temperature as well as at elevated temperatures up to 165 degrees C. The tungsten contact resistance degradation at elevated stress temperatures is correlated with worm hole formation in silicon and the formation and diffusion of tungsten silicide. Extensive analytical measurements were used to characterize the material transformation at elevated stress temperatures to understand the physical mechanisms causing contact degradation

  15. Selective solar absorber emittance measurement at elevated temperature

    Science.gov (United States)

    Giraud, Philémon; Braillon, Julien; Raccurt, Olivier

    2017-06-01

    Durability of solar components for CSP (Concentrated Solar Power Plant) technologies is a key point to lower cost and ensure their large deployment. These technologies concentrated the solar radiation by means of mirrors on a receiver tube where it is collected as thermal energy. The absorbers are submitted to strong environmental constraints and the degradation of their optical properties (emittance and solar absorbance) have a direct impact on performance. The characterization of a material in such condition is complicated and requires advanced apparatuses, and different measurement methods exist for the determination of the two quantities of relevance regarding an absorber, which are its emittance and its solar absorbance. The objective is to develop new optical equipment for measure the emittance of this solar absorber at elevated temperature. In this paper, we present an optical bench developed for emittance measurement on absorbers is conditions of use. Results will be shown, with a discussion of some factors of influence over this measurement and how to control them.

  16. Creep testing of nodular iron at ambient and elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Martinsson, Aasa; Andersson-Oestling, Henrik C.M.; Seitisleam, Facredin; Wu, Rui; Sandstroem, Rolf (Swerea KIMAB AB, Stockholm (Sweden))

    2010-12-15

    The creep strain at room temperature, 100 and 125 deg C has been investigated for the ferritic nodular cast iron insert intended for use as the load-bearing part of canisters for long term disposal of spent nuclear fuel. The microstructure consisted of ferrite, graphite nodules of different sizes, compacted graphite and pearlite. Creep tests have been performed for up to 41,000 h. The specimens were cut out from material taken from two genuine inserts, I30 and I55. After creep testing, the specimens from the 100 deg C tests were hardness tested and a metallographic examination was performed. Creep strains at all temperatures appear to be logarithmic, and accumulation of creep strain diminishes with time. The time dependence of the creep strain is consistent to the W-model for primary creep. During the loading plastic strains up to 1% appeared. The maximum recorded creep strain after the loading phase was 0.025%. This makes the creep strains technically insignificant. Acoustic emission recordings during the loading of the room temperature tests showed no sounds or other evidence of microcracking during the loading phase. There is no evidence that the hardness or the graphite microstructure changed during the creep tests

  17. Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature

    International Nuclear Information System (INIS)

    Park, Jingee; Lee, Jongshin; You, Bongsun; Choi, Seogou; Kim, Youngsuk

    2007-01-01

    Using lightweight materials is the emerging need in order to reduce the vehicle's energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine-grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in automotive and electronic industry it is necessary to assure database for sheet metal formability and plastic yielding properties in order to optimize its usage. Especially, plastic yielding criterion is a critical property to predict plastic deformation of sheet metal parts in optimizing process using CAE simulation. Von-Mises yield criterion generally well predicts plastic deformation of steel sheets and Hill'1979 yield criterion predicts plastic deformation of aluminum sheets. In this study, using biaxial tensile test machine yield loci of AZ31 magnesium alloy sheet were obtained at elevated temperature. The yield loci ensured experimentally were compared with the theoretical predictions based on the Von-Mises, Hill, Logan-Hosford, and Barlat model

  18. Ratchetting behavior of type 304 stainless steel at room and elevated temperatures

    International Nuclear Information System (INIS)

    Ruggles, M.; Krempl, E.

    1988-01-01

    The zero-to-tension ratchetting behavior was investigated under uniaxial loading at room temperature and at 550, 600 and 650/degree/ C. In History I the maximum stress level of ratchetting was equal to the stress reached in a tensile test at one percent strain. For History II the maximum stress level was established as the stress reached after a 2100 s relaxation at one percent strain. Significant ratchetting was observed for History I at room temperature but not at the elevated temperatures. The accumulated ratchet strain increases with decreasing stress rate. Independent of the stress rates used insignificant ratchet strain was observed at room temperature for History II. This observation is explained in the context of the viscoplasticity theory based on overstress by the exhaustion of the viscous contribution to the stress during relaxation. The viscous part of the stress is the driving force for the ratchetting in History I. Strain aging is presumably responsible for the lack of short-time inelastic deformation resulting in a nearly rate-independent behavior at the elevated temperatures. 26 refs., 7 figs., 1 tab

  19. The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review.

    Energy Technology Data Exchange (ETDEWEB)

    Naus, Dan J [ORNL

    2006-03-01

    The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

  20. The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review

    International Nuclear Information System (INIS)

    Naus, Dan J.

    2006-01-01

    The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

  1. Arrangement of experiments for simulating the effects of elevated temperatures and elevated CO2 levels on field-sown crops in Finland

    Directory of Open Access Journals (Sweden)

    Kaija Hakala

    1996-01-01

    Full Text Available The experimental plants: spring wheat, winterwheat, spring barley, meadow fescue, potato, strawberry and black currant were sown or planted directly in the field, part of which was covered by an automatically controlled greenhouse to elevate the temperature by 3°C. The temperature of the other part of the field (open field was not elevated, but the field was covered with the same plastic film as the greenhouse to achieve radiation and rainfall conditions comparable to those in the greenhouse. To elevate the CO2 concentrations, four open top chambers (OTC were built for the greenhouse, and four for the open field. Two of these, both in the greenhouse and in the open field, were supplied with pure CO2 to elevate their CO2 level to 700 ppm. The temperatures inside the greenhouse followed accurately the desired level. The relative humidity was somewhat higher in the greenhouse and in the OTC:s than in the open field, especially after the modifications in the ventilation of the greenhouse and in the OTC:s in 1994. Because the OTC:s were large (3 m in diameter, the temperatures inside them differed very little from the surrounding air temperature. The short-term variation in the CO2 concentrations in the OTC:s with elevated CO2 was, however, quite high. The control of the CO2 concentrations improved each year from 1992 to 1994, as the CO2 supplying system was modified. The effects of the experimental conditions on plant growth and phenology are discussed.

  2. Arrangement of experiments for simulating the effects of elevated temperatures and elevated CO2 levels on field-sown crops in Finland

    Directory of Open Access Journals (Sweden)

    K. HAKALA

    2008-12-01

    Full Text Available The experimental plants: spring wheat, winter wheat, spring barley, meadow fescue, potato, strawberry and black currant were sown or planted directly in the field, part of which was covered by an automatically controlled greenhouse to elevate the temperature by 3°C. The temperature of the other part of the field (open field was not elevated, but the field was covered with the same plastic film as the greenhouse to achieve radiation and rainfall conditions comparable to those in the greenhouse. To elevate the CO2 concentrations, four open top chambers (OTC were built for the greenhouse, and four for the open field. Two of these, both in the greenhouse and in the open field, were supplied with pure CO2 to elevate their CO2 level to 700 ppm. The temperatures inside the greenhouse followed accurately the desired level. The relative humidity was somewhat higher in the greenhouse and in the OTC:s than in the open field, especially after the modifications in the ventilation of the greenhouse and in the OTC:s in 1994. Because the OTC:s were large (3 m in diameter, the temperatures inside them differed very little from the surrounding air temperature. The short-term variation in the CO2 concentrations in the OTC:s with elevated CO2 was, however, quite high. The control of the CO2 concentrations improved each year from 1992 to 1994, as the CO2 supplying system was modified. The effects of the experimental conditions on plant growth and phenology are discussed.;

  3. Modeling Silicate Weathering for Elevated CO2 and Temperature

    Science.gov (United States)

    Bolton, E. W.

    2016-12-01

    A reactive transport model (RTM) is used to assess CO2 drawdown by silicate weathering over a wide range of temperature, pCO2, and infiltration rates for basalts and granites. Although RTM's have been used extensively to model weathering of basalts and granites for present-day conditions, we extend such modeling to higher CO2 that could have existed during the Archean and Proterozoic. We also consider a wide range of surface temperatures and infiltration rates. We consider several model basalt and granite compositions. We normally impose CO2 in equilibrium with the various atmospheric ranges modeled and CO2 is delivered to the weathering zone by aqueous transport. We also consider models with fixed CO2 (aq) throughout the weathering zone as could occur in soils with partial water saturation or with plant respiration, which can strongly influence pH and mineral dissolution rates. For the modeling, we use Kinflow: a model developed at Yale that includes mineral dissolution and precipitation under kinetic control, aqueous speciation, surface erosion, dynamic porosity, permeability, and mineral surface areas via sub-grid-scale grain models, and exchange of volatiles at the surface. Most of the modeling is done in 1D, but some comparisons to 2D domains with heterogeneous permeability are made. We find that when CO2 is fixed only at the surface, the pH tends toward higher values for basalts than granites, in large part due to the presence of more divalent than monovalent cations in the primary minerals, tending to decrease rates of mineral dissolution. Weathering rates increase (as expected) with increasing CO2 and temperature. This modeling is done with the support of the Virtual Planetary Laboratory.

  4. Microstructure and tensile properties of tungsten at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Tielong [Laboratory for Nuclear Materials, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Dai, Yong, E-mail: yong.dai@psi.ch [Laboratory for Nuclear Materials, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Lee, Yongjoong [European Spallation Source, Tunavägen 24, 223 63 Lund (Sweden)

    2016-01-15

    In order to support the development of the 5 MW spallation target for the European Spallation Source, the effect of fabrication process on microstructure, ductile-to-brittle transition temperature (DBTT), tensile and fracture behaviour of powder-metallurgy pure tungsten materials has been investigated. A hot-rolled (HR) tungsten piece of 12 mm thickness and a hot-forged (HF) piece of about 80 mm thickness were used to simulate the thin and thick blocks in the target. The two tungsten pieces were characterized with metallography analysis, hardness measurement and tensile testing. The HR piece exhibits an anisotropic grain structure with an average size of about 330 × 140 × 40 μm in rolling, long transverse and short transverse (thickness) directions. The HF piece possesses a bimodal grain structure with about 310 × 170 × 70 μm grain size in deformed part and about 25 μm sized grains remained from sintering process. Hardness (HV0.2) of the HR piece is slightly greater than that of the HF one. The ductility of the HR tungsten specimens is greater than that of the HF tungsten. For the HF tungsten piece, specimens with small grains in gauge section manifest lower ductility but higher strength. The DBTT evaluated from the tensile results is 250–300 °C for the HR tungsten and about 350 °C for the HF tungsten. - Highlights: • This work was conducted to support the development of the 5 MW spallation target for the European Spallation Source. • The effect of fabrication process on microstructure, ductile-to-brittle transition temperature and tensile behaviour was studied with hot-rolled and hot-forged tungsten. • The tungsten materials were characterized with metallography analysis, hardness measurement and tensile test in a temperature range of 25–500 °C. • The results indicate that the HR tungsten has better mechanical properties in terms of greater ductility and lower ductile-to-brittle transition temperature.

  5. Characterization of elevated temperature properties of heat exchanger and steam generator alloys

    International Nuclear Information System (INIS)

    Wright, J.K.; Carroll, L.J.; Cabet, C.; Lillo, T.M.; Benz, J.K.; Simpson, J.A.; Lloyd, W.R.; Chapman, J.A.; Wright, R.N.

    2012-01-01

    The Next Generation Nuclear Plant project is considering Alloy 800H and Alloy 617 for steam generator and intermediate heat exchangers. It is envisioned that a steam generator would operate with reactor outlet temperatures from 750 to 800 °C, while an intermediate heat exchanger for primary to secondary helium would operate up to an outlet temperature of 950 °C. Although both alloys are of interest due in part to their technical maturity, a number of specific properties require further characterization for design of nuclear components. Strain rate sensitivity of both alloys has been characterized and is found to be significant above 600 °C. Both alloys also exhibit dynamic strain aging, characterized by serrated flow, over a wide range of temperatures and strain rates. High temperature tensile testing of Alloy 617 and Alloy 800H has been conducted over a range of temperatures. Dynamic strain aging is a concern for these materials since it is observed to result in reduced ductility for many solid solution alloys. Creep, fatigue, and creep–fatigue properties of Alloy 617 have been measured as well, with the goal of determining the influence of the temperature, strain rate and atmosphere on the creep–fatigue life of Alloy 617. Elevated temperature properties and implications for codification of the alloys will be described.

  6. Elevated exhaust temperature, zoned, electrically-heated particulate matter filter

    Science.gov (United States)

    Gonze, Eugene V [Pinckney, MI; Bhatia, Garima [Bangalore, IN

    2012-04-17

    A system includes an electrical heater and a particulate matter (PM) filter that is arranged one of adjacent to and in contact with the electrical heater. A control module selectively increases an exhaust gas temperature of an engine to a first temperature and that initiates regeneration of the PM filter using the electrical heater while the exhaust gas temperature is above the first temperature. The first temperature is greater than a maximum exhaust gas temperature at the PM filter during non-regeneration operation and is less than an oxidation temperature of the PM.

  7. Tree and forest water use under elevated CO2 and temperature in Scandinavian boreal forest

    Science.gov (United States)

    Berg Hasper, Thomas; Wallin, Göran; Lamba, Shubhangi; Sigurdsson, Bjarni D.; Laudon, Hjalmar; Medhurst, Jane L.; Räntfors, Mats; Linder, Sune; Uddling, Johan

    2014-05-01

    According to experimental studies and models, rising atmospheric carbon dioxide concentration ([CO2]) and temperature have the potential to affect stomatal conductance and, consequently, tree and forest transpiration. This effect has in turn the capacity to influence the terrestrial energy and water balance, including affecting of the magnitude of river runoff. Furthermore, forest productivity is currently water-limited in southern Scandinavia and in a near future, under the projected climatic change, this limitation may become a reality in the central and northern parts of Scandinavia. In this study we examine the water-use responses in 12 40-year old native boreal Norway spruce (Picea abies (L.) Karst.) trees exposed to a factorial combination of two levels of [CO2] (ambient and doubled) and temperature (ambient and +2.8 °C in summer / +5.6 °C in winter), as well as of entire boreal forests to temporal variation in [CO2], temperature and precipitation over the past 50 years in central and northern Sweden. The controlled factorial CO2 and temperature whole-tree chamber experiment at Flakaliden study site demonstrated that Norway spruce trees lacked elevated [CO2]-induced water savings at guard cell, shoot, and tree levels in the years of measurements. Experimentally, elevated temperature did not result in increased shoot or tree water use as stomatal closure fully cancelled the effect of higher vapour pressure deficit in warmed air environment. Consistent with these results, large scale river runoff data and evapotranspiration estimates from large forested watersheds in central Sweden supported lack of elevated CO2-mediated water savings, and rather suggested that the increasing evapotranspiration trend found in this study was primarily linked to increasing precipitation, rising temperature and more efficient forest management. The results from the whole-tree chamber experiment and boreal forested watersheds have important implications for more accurate

  8. Grasslands feeling the heat: The effects of elevated temperatures on a subtropical grassland

    Directory of Open Access Journals (Sweden)

    Rowan D. Buhrmann

    2016-12-01

    Conclusions: OTCs can simulate realistic increases of air temperature in subtropical grasslands. Graminoids and shrubs appear to benefit from elevated temperatures whilst forbs decrease in abundance, possibly through competition and/or direct physiological effects.

  9. Problems to be solved about inelastic behaviour of materials and inelastic analysis of structures at elevated temperature

    International Nuclear Information System (INIS)

    Ledermann, P.; Escatha, Y. d'.

    1981-01-01

    At elevated temperature, ASME CODE CASE N 47 demands, in its design and analysis part to demonstrate that none of eight damages, related to the monotonic and cyclic inelastic behaviour of the material and structure, will happen during the whole life of the reactor. However this demonstration, for strain limits and creep fatigue failure, using a purely elastic analysis as in the ASME CODE Section III, is usually impossible. Inelastic analysis is then necessary. We review some of the research work (theorical and experimental) which is being done to qualify methods for an inelastic analysis of structures at elevated temperature [fr

  10. Optimization Study of PEMFC stack at elevated temperature

    African Journals Online (AJOL)

    UPUser

    structures improves the PEM fuel cell system performance at higher temperature of operation and optimal aspect ... theoretical voltage at which a fuel cell can operate [4]. ... distribution. ... water loss in the cell until a critical temperature is.

  11. Thermal diffusivity of felsic to mafic granulites at elevated temperatures

    Science.gov (United States)

    Ray, Labani; Förster, H.-J.; Schilling, F. R.; Förster, A.

    2006-11-01

    The thermal diffusivity of felsic and intermediate granulites (charnockites, enderbites), mafic granulites, and amphibolite-facies gneisses has been measured up to temperatures of 550 °C using a transient technique. The rock samples are from the Archean and Pan-African terranes of the Southern Indian Granulite Province. Thermal diffusivity at room temperature ( DRT) for different rock types ranges between 1.2 and 2.2 mm 2 s - 1 . For most of the rocks, the effect of radiative heat transfer is observed at temperatures above 450 °C. However, for few enderbites and mafic granulites, radiative heat transfer is negligible up to 550 °C. In the temperature range of conductive heat transfer, i.e., between 20 ° and 450 °C, thermal diffusivity decreases between 35% and 45% with increasing temperature. The temperature dependence of the thermal diffusivity is directly correlated with the thermal diffusivity at room temperature, i.e., the higher the thermal diffusivity at room temperature, DRT, the greater is its temperature dependence. In this temperature range i.e., between 20 and 450 °C, thermal diffusivity can be expressed as D = 0.7 mm 2 s -1 + 144 K ( DRT - 0.7 mm 2 s -1 ) / ( T - 150 K), where T is the absolute temperature in Kelvin. At higher temperatures, an additional radiative contribution is observed according to CT3, where C varies from 10 - 9 to 10 - 10 depending on intrinsic rock properties (opacity, absorption behavior, grain size, grain boundary, etc). An equation is presented that describes the temperature and pressure dependence thermal diffusivity of rocks based only on the room-temperature thermal diffusivity. Room-temperature thermal diffusivity and its temperature dependence are mainly dependent on the major mineralogy of the rock. Because granulites are important components of the middle and lower continental crust, the results of this study provide important constraints in quantifying more accurately the thermal state of the deeper continental

  12. Process Simulation of Aluminium Sheet Metal Deep Drawing at Elevated Temperatures

    International Nuclear Information System (INIS)

    Winklhofer, Johannes; Trattnig, Gernot; Lind, Christoph; Sommitsch, Christof; Feuerhuber, Hannes

    2010-01-01

    Lightweight design is essential for an economic and environmentally friendly vehicle. Aluminium sheet metal is well known for its ability to improve the strength to weight ratio of lightweight structures. One disadvantage of aluminium is that it is less formable than steel. Therefore complex part geometries can only be realized by expensive multi-step production processes. One method for overcoming this disadvantage is deep drawing at elevated temperatures. In this way the formability of aluminium sheet metal can be improved significantly, and the number of necessary production steps can thereby be reduced. This paper introduces deep drawing of aluminium sheet metal at elevated temperatures, a corresponding simulation method, a characteristic process and its optimization. The temperature and strain rate dependent material properties of a 5xxx series alloy and their modelling are discussed. A three dimensional thermomechanically coupled finite element deep drawing simulation model and its validation are presented. Based on the validated simulation model an optimised process strategy regarding formability, time and cost is introduced.

  13. The effects of prolonged exposure to elevated temperatures and elevated CO2 levels on the growth, yield and dry matter partitioning of field-sown meadow fescue

    Directory of Open Access Journals (Sweden)

    Kaija Hakala

    1996-05-01

    Full Text Available Field-sown meadow fescue (Festuca pratensis, cv. Kalevi stands were exposed to elevated temperatures (+3°C and elevated CO2, (700 ppm levels in two experiments conducted in 1992-1993 (experiment 1 and in 1994-1995 (experiment 2. Total aboveground yield was, on average, 38% higher at elevated than at ambient temperatures. At ambient temperatures elevated CO2 increased the number of tillers by 63% in 1992, 24% in 1993, 90% in 1994 and 14% in 1995. At elevated temperatures, the increase in tiller number in elevated CO2 was seen only in the first growing seasons after sowing. The total yield in a growing season was about 10% higher in elevated CO2 in experiment 1. In experiment 2 the yield was more than 20% higher in elevated CO2 at elevated temperatures, whereas at ambient temperatures the rise in CO2 level had no effect on the yield; the root biomass, however, increased by more than 30%. In elevated CO2 at ambient temperatures the root biomass also increased in experiment I, but at elevated temperatures there was no consistent change. The soluble carbohydrate content of above-ground biomass was 5-48% higher in elevated CO2 at most of the measuring times during the growing season, but the nitrogen content did not show a clear decrease. The reasons for the lack of a marked increase in biomass in elevated CO2 despite a 40-60% increase in photosynthesis are discussed.

  14. Low cycle fatigue strength of some austenitic stainless steels at room temperature and elevated temperatures

    International Nuclear Information System (INIS)

    Type 304, 316, and 316L stainless steels were tested from room temperature to 650 0 C using two kinds of bending test specimens. Particularly, Type 304 was tested at several cyclic rates and 550 0 and 650 0 C, and the effect of cyclic rate on its fatigue strength was investigated. Test results are summarized as follows: (1) The bending fatigue strength at room temperature test shows good agreement with the axial fatigue one, (2) Manson--Coffin's fatigue equation can be applied to the results, (3) the ratio of crack initiation to failure life becomes larger at higher stress level, and (4) the relation between crack propagation life and total strain range or elastic strain range are linear in log-log scale. This relation also agrees with the equations which were derived from some crack propagation laws. It was also observed at the elevated temperature test: (1) The reduction of fatigue strength is not noticeable below 500 0 C, but it is noted at higher temperature. (2) The cycle rate does not affect on fatigue strength in faster cyclic rate than 20 cpm and below 100,000 cycles life range. (3) Type 316 stainless steel shows better fatigue property than type 304 and 316L stainless steels. 30 figures

  15. Radionuclide solubilities at elevated temperatures. A literature study

    International Nuclear Information System (INIS)

    Carlsson, T.; Vuorinen, U.

    1997-07-01

    This literature study contains experimental data and modelling data collected in order to illustrate how temperature affects radionuclide solubilities under conditions similar to those expected in the vicinity of a planned repository for spent nuclear fuel. The elements considered were Ni, Se, Zr, Tc, Pd, Sn, Ra, Th, Pa, U, Np, Pu and Am. The temperatures of main interest are restricted to the interval between room temperature and 100 deg C. The study showed that the literature on radionuclide solubility at temperatures above room temperature is scarce. Therefore, also work that refers to conditions slightly varying from the expected repository conditions has been considered. A minor modelling exercise was done in this study in order to show the effect of temperature on the solubilities of Ni, Np and U under various conditions. The results from the literature survey and our modelling demonstrate the complexity of groundwater systems and the difficulty in finding simple and general relationships between temperature and radionuclide solubilities. Often an increase in temperature (below 100 deg C) leads to a reduction of the radionuclide solubility or leaves it roughly unchanged. However, examples are also found where the rise in temperature increases the radionuclide solubility by several orders of magnitude. (orig.)

  16. Radionuclide solubilities at elevated temperatures. A literature study

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, T.; Vuorinen, U. [Technical Research Centre of Finland, Espoo (Finland)

    1997-07-01

    This literature study contains experimental data and modelling data collected in order to illustrate how temperature affects radionuclide solubilities under conditions similar to those expected in the vicinity of a planned repository for spent nuclear fuel. The elements considered were Ni, Se, Zr, Tc, Pd, Sn, Ra, Th, Pa, U, Np, Pu and Am. The temperatures of main interest are restricted to the interval between room temperature and 100 deg C. The study showed that the literature on radionuclide solubility at temperatures above room temperature is scarce. Therefore, also work that refers to conditions slightly varying from the expected repository conditions has been considered. A minor modelling exercise was done in this study in order to show the effect of temperature on the solubilities of Ni, Np and U under various conditions. The results from the literature survey and our modelling demonstrate the complexity of groundwater systems and the difficulty in finding simple and general relationships between temperature and radionuclide solubilities. Often an increase in temperature (below 100 deg C) leads to a reduction of the radionuclide solubility or leaves it roughly unchanged. However, examples are also found where the rise in temperature increases the radionuclide solubility by several orders of magnitude. (orig.). 54 refs.

  17. Effects of Elevated Ambient Temperature on Reproductive Outcomes and Offspring Growth Depend on Exposure Time

    Directory of Open Access Journals (Sweden)

    Huda Yahia Hamid

    2012-01-01

    Full Text Available Reproductive performance has been shown to be greatly affected by changes in environmental factors, such as temperature. However, it is also crucial to identify the particular stage of pregnancy that is most adversely affected by elevated ambient temperature. The aims of this study were to determine the effect on reproductive outcomes of exposure to elevated ambient temperature during different stages of pregnancy and to determine the effect of prenatal heat stress on offspring growth. Sixty pregnant rats were used in this study. The rats were divided equally into four groups as group 1 (control, group 2 (exposed to elevated temperature following implantation, group 3 (exposed to elevated temperature during pre- and periimplantation, and group 4 (exposed to elevated temperature during pre- and periimplantation and following implantation. Groups 3 and 4 had prolonged gestation periods, reduced litter sizes, and male-biased sex ratios. Moreover, the growth patterns of group 3 and 4 pups were adversely affected by prenatal exposure to elevated temperature. The differences between group 1 and group 3 and between group 1 and group 4 were highly significant. However, no significant differences were observed between groups 1 and 2 in the gestation length, sex ratios, and growth patterns. Thus, it can be concluded that exposure to elevated ambient temperature during pre- and periimplantation has stronger adverse effects on reproductive outcomes and offspring growth than postimplantation exposure.

  18. Mechanical and Microstructural Evaluations of Lightweight Aggregate Geopolymer Concrete before and after Exposed to Elevated Temperatures.

    Science.gov (United States)

    Abdulkareem, Omar A; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Ismail, Khairul Nizar; Binhussain, Mohammed

    2013-10-09

    This paper presents the mechanical and microstructural characteristics of a lightweight aggregate geopolymer concrete (LWAGC) synthesized by the alkali-activation of a fly ash source (FA) before and after being exposed to elevated temperatures, ranging from 100 to 800 °C. The results show that the LWAGC unexposed to the elevated temperatures possesses a good strength-to-weight ratio compared with other LWAGCs available in the published literature. The unexposed LWAGC also shows an excellent strength development versus aging times, up to 365 days. For the exposed LWAGC to the elevated temperatures of 100 to 800 °C, the results illustrate that the concretes gain compressive strength after being exposed to elevated temperatures of 100, 200 and 300 °C. Afterward, the strength of the LWAGC started to deteriorate and decrease after being exposed to elevated temperatures of 400 °C, and up to 800 °C. Based on the mechanical strength results of the exposed LWAGCs to elevated temperatures of 100 °C to 800 °C, the relationship between the exposure temperature and the obtained residual compressive strength is statistically analyzed and achieved. In addition, the microstructure investigation of the unexposed LWAGC shows a good bonding between aggregate and mortar at the interface transition zone (ITZ). However, this bonding is subjected to deterioration as the LWAGC is exposed to elevated temperatures of 400, 600 and 800 °C by increasing the microcrack content and swelling of the unreacted silicates.

  19. Inference of domain structure at elevated temperature in fine ...

    African Journals Online (AJOL)

    The thermal variation of the number of domains (nd) for Fe7S8 particles (within the size range 1-30 mm and between 20 and 300°C), has been inferred from the room temperature analytic expression between nd and particle size (L), the temperature dependences of the anisotropy energy constant (K) and the spontaneous ...

  20. Spring photosynthetic recovery of boreal Norway spruce under conditions of elevated [CO(2)] and air temperature.

    Science.gov (United States)

    Wallin, Göran; Hall, Marianne; Slaney, Michelle; Räntfors, Mats; Medhurst, Jane; Linder, Sune

    2013-11-01

    Accumulated carbon uptake, apparent quantum yield (AQY) and light-saturated net CO2 assimilation (Asat) were used to assess the responses of photosynthesis to environmental conditions during spring for three consecutive years. Whole-tree chambers were used to expose 40-year-old field-grown Norway spruce trees in northern Sweden to an elevated atmospheric CO2 concentration, [CO2], of 700 μmol CO2 mol(-1) (CE) and an air temperature (T) between 2.8 and 5.6 °C above ambient T (TE), during summer and winter. Net shoot CO2 exchange (Anet) was measured continuously on 1-year-old shoots and was used to calculate the accumulated carbon uptake and daily Asat and AQY. The accumulated carbon uptake, from 1 March to 30 June, was stimulated by 33, 44 and 61% when trees were exposed to CE, TE, and CE and TE combined, respectively. Air temperature strongly influenced the timing and extent of photosynthetic recovery expressed as AQY and Asat during the spring. Under elevated T (TE), the recovery of AQY and Asat commenced ∼10 days earlier and the activity of these parameters was significantly higher throughout the recovery period. In the absence of frost events, the photosynthetic recovery period was less than a week. However, frost events during spring slowed recovery so that full recovery could take up to 60 days to complete. Elevated [CO2] stimulated AQY and Asat on average by ∼10 and ∼50%, respectively, throughout the recovery period, but had minimal or no effect on the onset and length of the photosynthetic recovery period during the spring. However, AQY, Asat and Anet all recovered at significantly higher T (average +2.2 °C) in TE than in TA, possibly caused by acclimation or by shorter days and lower light levels during the early part of the recovery in TE compared with TA. The results suggest that predicted future climate changes will cause prominent stimulation of photosynthetic CO2 uptake in boreal Norway spruce forest during spring, mainly caused by elevated T

  1. Experimental Investigation of a Mechanical Vapour Compression Chiller at Elevated Chilled Water Temperatures

    KAUST Repository

    Thu, Kyaw

    2017-05-18

    The performance of a Mechanical Vapour Compression (MVC) chiller is experimentally investigated under operating conditions suitable for sensible cooling. With the emergence of the energy efficient dehumidification systems, it is possible to decouple the latent load from the MVC chillers which can be operated at higher chilled water temperature for handling sensible cooling load. In this article, the performance of the chiller is evaluated at the elevated chilled water outlet temperatures (7 – 17° C) at various coolant temperatures (28 – 32° C) and flow rates (ΔT = 4 and 5° C) for both full- and part-load conditions. Keeping the performance at the AHRI standard as the baseline condition, the efficacy of the chiller in terms of compression ratio, cooling capacity and COP at aforementioned conditions is quantified experimentally. It is observed that for each one-degree Celsius increase in the chilled water temperature, the COP of the chiller improves by about 3.5% whilst the cooling capacity improvement is about 4%. For operation at 17° C chilled water outlet temperature, the improvements in COP and cooling capacity are between 37 – 40% and 40 – 45%, respectively, compared to the performance at the AHRI standards. The performance of the MVC chiller at the abovementioned operation conditions is mapped on the chiller performance characteristic chart.

  2. Experimental Investigation of a Mechanical Vapour Compression Chiller at Elevated Chilled Water Temperatures

    KAUST Repository

    Thu, Kyaw; Saththasivam, Jayaprakash; Saha, Bidyut Baran; Chua, Kian Jon; Srinivasa Murthy, S.; Ng, Kim Choon

    2017-01-01

    The performance of a Mechanical Vapour Compression (MVC) chiller is experimentally investigated under operating conditions suitable for sensible cooling. With the emergence of the energy efficient dehumidification systems, it is possible to decouple the latent load from the MVC chillers which can be operated at higher chilled water temperature for handling sensible cooling load. In this article, the performance of the chiller is evaluated at the elevated chilled water outlet temperatures (7 – 17° C) at various coolant temperatures (28 – 32° C) and flow rates (ΔT = 4 and 5° C) for both full- and part-load conditions. Keeping the performance at the AHRI standard as the baseline condition, the efficacy of the chiller in terms of compression ratio, cooling capacity and COP at aforementioned conditions is quantified experimentally. It is observed that for each one-degree Celsius increase in the chilled water temperature, the COP of the chiller improves by about 3.5% whilst the cooling capacity improvement is about 4%. For operation at 17° C chilled water outlet temperature, the improvements in COP and cooling capacity are between 37 – 40% and 40 – 45%, respectively, compared to the performance at the AHRI standards. The performance of the MVC chiller at the abovementioned operation conditions is mapped on the chiller performance characteristic chart.

  3. EFFECT OF ELEVATED TEMPERATURE ON COMPRESSIVE STRENGTH OF FIBER REINFORCED CONCRETE

    OpenAIRE

    Prashant shinkar*, Prof. Deepak kakade, Dr.A.P.Wadekar

    2017-01-01

    This paper deals with the mechanical properties of concrete with steel fibers subjected to temperatures up to 500°C. Now a day concrete are being used extensively in the construction that might be subjected to elevated temperatures. The behavior of concrete structures at elevated temperatures is of significant importance in predicting the safety of structures in response to certain accidents or particular service conditions. Concrete mixes of M 50 have been designed along with steel fibers fr...

  4. Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine.

    Science.gov (United States)

    Chang, Christine Y; Fréchette, Emmanuelle; Unda, Faride; Mansfield, Shawn D; Ensminger, Ingo

    2016-10-01

    Rising global temperature and CO 2 levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO 2 , affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L -1 ) or elevated (800 μmol mol -1 ) CO 2 , and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO 2 (LTAC), elevated temperature/ambient CO 2 (ETAC), or elevated temperature/elevated CO 2 (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus Our findings suggest that exposure to elevated temperature and CO 2 during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO 2 also impaired freezing tolerance. However, unless the frequency and timing of extreme low-temperature

  5. Interactive effect of elevated CO2 and temperature on coral physiology

    Science.gov (United States)

    Grottoli, A. G.; Cai, W.; Warner, M.; Melman, T.; Schoepf, V.; Baumann, J.; Matsui, Y.; Pettay, D. T.; Hoadley, K.; Xu, H.; Wang, Y.; Li, Q.; Hu, X.

    2011-12-01

    Increases in ocean acidification and temperature threaten coral reefs globally. However, the interactive effect of both lower pH and higher temperature on coral physiology and growth are poorly understood. Here, we present preliminary findings from a replicated controlled experiment where four species of corals (Acorpora millepora, Pocillopora damicornis, Montipora monasteriata, Turbinaria reniformis) were reared under the following six treatments for three weeks: 1) 400ppm CO2 and ambient temperature, 2) 400ppm CO2 and elevated temperature, 3) 650ppm CO2 and ambient temperature, 4) 650ppm CO2 and elevated temperature, 5) 800ppm CO2 and ambient temperature, 6) 800ppm CO2 and elevated temperature. Initial findings of photophysiological health (Fv/Fm), calcification rates (as measured by both buoyant weight and the total alkalinity methods), and energy reserves will be presented.

  6. Elevated temperature tensile properties of borated 304 stainless steel

    International Nuclear Information System (INIS)

    Stephens, J.J.; Sorenson, K.B.; McConnell, P.

    1993-01-01

    This paper presents a comparison of the tensile properties of Powder Metallurgy (PM) 'Grade A' material with that of the conventional IM 'Grade B' material for two selected Types (i.e., boron contents) as defined by the ASTM A887 specification: Types 304B5 and 304B7. Tensile properties have been generated for these materials at temperatures ranging from room temperature to 400degC (752degF). The data at higher temperatures are required for ASME Code Case purposes, since the use temperature of a basket under 'worst case' cask conditions may be as high as 343degC (650degF), due to self-heating by the activated fuel elements. We will also discuss the current status of efforts aimed at obtaining an ASME Boiler and Pressure Vessel Code Case for selected grades of borated stainless steel covered by the ASTM A887 specification. (J.P.N.)

  7. Effects of elevated ambient temperature on embryo implantation in rats

    African Journals Online (AJOL)

    Yomi

    2012-03-22

    Mar 22, 2012 ... ambient temperature leads to a delayed implantation and reduced number of implantation sites in. Sprague ... rates decrease after exposure to stress. One of the ..... implantation initiation time, support the previous findings.

  8. Behavior of HPC with Fly Ash after Elevated Temperature

    OpenAIRE

    Shang, Huai-Shuai; Yi, Ting-Hua

    2013-01-01

    For use in fire resistance calculations, the relevant thermal properties of high-performance concrete (HPC) with fly ash were determined through an experimental study. These properties included compressive strength, cubic compressive strength, cleavage strength, flexural strength, and the ultrasonic velocity at various temperatures (20, 100, 200, 300, 400 and 500∘C) for high-performance concrete. The effect of temperature on compressive strength, cubic compressive strength, cleavage strength,...

  9. Uranyl(VI) luminescence spectroscopy at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Steudtner, Robin; Franzen, Carola; Brendler, Vinzenz [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Surface Processes; Haubitz, Toni [Brandenburg Univ. of Technology, Cottbus-Senftenberg (Germany)

    2016-07-01

    We studied the influence of temperature and ionic strength on the luminescence characteristics (band position, decay time and intensity) of the free uranyl ion (UO{sub 2}{sup 2+}) in acidic aqueous solution. Under the chosen conditions an increasing temperature reduced both intensity and luminescence decay time of the UO{sub 2}{sup 2+} luminescence, but the individual U(VI) emission bands did not change.

  10. The reaction of OH with H at elevated temperatures

    DEFF Research Database (Denmark)

    Lundström, T.; Christensen, H.; Sehested, K.

    2002-01-01

    The temperature dependence of the rate constant for the reaction between OH radicals and H atoms has been determined in Ar-saturated solutions at pH 2. The reaction was studied in the temperature range 5-233degreesC. The rate constants at 20degreesC and 200degreesC are 9.3 x 10(9) and 3.3 x 10...

  11. Elevated temperature creep behavior of Inconel alloy 625

    International Nuclear Information System (INIS)

    Purohit, A.; Burke, W.F.

    1984-07-01

    Inconel 625 in the solution-annealed condition has been selected as the clad material for the fuel and control rod housing assemblies of the Upgraded Transient Reactor Test Facility (TREAT Upgrade or TU). The clad is expected to be subjected to temperatures up to about 1100 0 C. Creep behavior for the temperature range of 800 0 C to 1100 0 C of Inconel alloy 625, in four distinct heat treated conditions, was experimentally evaluated

  12. Surface alloying in Sn/Au(111) at elevated temperature

    Science.gov (United States)

    Sadhukhan, Pampa; Singh, Vipin Kumar; Rai, Abhishek; Bhattacharya, Kuntala; Barman, Sudipta Roy

    2018-04-01

    On the basis of x-ray photoelectron spectroscopy, we show that when Sn is deposited on Au(111) single crystal surface at a substrate temperature TS=373 K, surface alloying occurs with the formation of AuSn phase. The evolution of the surface structure and the surface morphology has been studied by low energy electron diffraction and scanning tunneling microscopy, respectively as a function of Sn coverage and substrate temperatures.

  13. Elevated body temperature in ischemic stroke associated with neurological improvement.

    Science.gov (United States)

    Khanevski, A N; Naess, H; Thomassen, L; Waje-Andreassen, U; Nacu, A; Kvistad, C E

    2017-11-01

    Some studies suggest that high body temperature within the first few hours of ischemic stroke onset is associated with improved outcome. We hypothesized an association between high body temperature on admission and detectable improvement within 6-9 hours of stroke onset. Consecutive ischemic stroke patients with NIHSS scores obtained within 3 hours and in the interval 6-9 hours after stroke onset were included. Body temperature was measured on admission. A total of 315 patients with ischemic stroke were included. Median NIHSS score on admission was 6. Linear regression showed that NIHSS score 6-9 hours after stroke onset was inversely associated with body temperature on admission after adjusting for confounders including NIHSS score body temperature and neurological improvement within few hours after admission. This finding may be limited to patients with documented proximal middle cerebral artery occlusion on admission and suggests a beneficial effect of higher body temperature on clot lysis within the first three hours. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  14. Evaluation Of Liner Back-pressure Due To Concrete Pore Pressure At Elevated Temperatures

    International Nuclear Information System (INIS)

    James, R.J.; Rashid, Y.R.; Liu, A.S.; Gou, B.

    2006-01-01

    GE's latest evolution of the boiling water reactor, the ESBWR, has innovative passive design features that reduce the number and complexity of active systems, which in turn provide economic advantages while also increasing safety. These passive systems used for emergency cooling also mean that the primary containment system will experience elevated temperatures with longer durations than conventional plants in the event of design basis accidents. During a Loss of Coolant Accident (LOCA), the drywell in the primary containment structure for the ESBWR will be exposed to saturated steam conditions for up to 72 hours following the accident. A containment spray system may be activated that sprays the drywell area with water to condense the steam as part of the recovery operations. The liner back-pressure will build up gradually over the 72 hours as the concrete temperatures increase, and a sudden cool down could cause excessive differential pressure on the liner to develop. For this analysis, it is assumed that the containment spray is activated at the end of the 72-hour period. A back-pressure, acting between the liner and the concrete wall of the containment, can occur as a result of elevated temperatures in the concrete causing steam and saturated vapor pressures to develop from the free water remaining in the pores of the concrete. Additional pore pressure also develops under the elevated temperatures from the non-condensable gases trapped in the concrete pores during the concrete curing process. Any buildup of this pore pressure next to the liner, in excess of the drywell internal pressure, will act to push the liner away from the concrete with a potential for tearing at the liner anchorages. This paper describes the methods and analyses used to quantify this liner back-pressure so that appropriate measures are included in the design of the liner and anchorage system. A pore pressure model is developed that calculates the pressure distribution across the concrete

  15. Elevated temperature study of Nd-Fe-B--based magnets with cobalt and dysprosium additions

    International Nuclear Information System (INIS)

    Gauder, D.R.; Froning, M.H.; White, R.J.; Ray, A.E.

    1988-01-01

    This paper discusses the elevated temperature performance of Nd-Fe-B magnets containing 0--15 wt. % cobalt substitutions for iron and 0--10 wt. % dysprosium substitutions for neodymium. Test samples were prepared using conventional powder metallurgy techniques. Elevated temperature hysteresis loop and open-circuit measurements were performed on the samples to investigate irreversible losses and long term aging losses at 150 0 C. Magnets with high amounts of both cobalt and dysprosium exhibited lower losses of coercivity and magnetization. Dysprosium had more influence on the elevated temperature performance of the material than did cobalt

  16. Elevated temperature stress strain behavior of beryllium powder product

    International Nuclear Information System (INIS)

    Abeln, S.P.; Field, R.; Mataya, M.C.

    1995-01-01

    Several grades of beryllium powder product were tested under isothermal conditions in compression over a temperature range of room temperature to 1000 C and a strain rate range from 0.001 s -1 to 1 s -1 . Samples were compressed to a total strain of 1 (64% reduction in height). It is shown that all the grades are strain rate sensitive and that strain rate sensitivity increases with temperature. Yield points were exhibited by some grades up to a temperature of 500 C, and appeared to be primarily dependent on prior thermal history which determined the availability of mobile dislocations. Serrated flow in the form of stress drops was seen in all the materials tested and was most pronounced at 500 C. The appearance and magnitude of the stress drops were dependent on accumulated strain, strain rate, sample orientation, and composition. The flow stress and shape of the flow curves differed significantly from grade to grade due to variations in alloy content, the size and distribution of BeO particles, aging precipitates, and grain size. The ductile-brittle transition temperature (DBTT) was determined for each grade of material and shown to be dependent on composition and thermal treatment. Structure/property relationships are discussed using processing history, microscopy (light and transmission), and property data

  17. Low cycle fatigue behavior of Sanicro25 steel at room and at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Polák, Jaroslav, E-mail: polak@ipm.cz [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); CEITEC, Institute of Physics of Materials Academy of Sciences of the Czech Republic, Žižkova 22, Brno (Czech Republic); Petráš, Roman; Heczko, Milan; Kuběna, Ivo [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); Kruml, Tomáš [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); CEITEC, Institute of Physics of Materials Academy of Sciences of the Czech Republic, Žižkova 22, Brno (Czech Republic); Chai, Guocai [Sandvik Materials Technology, SE-811 81 Sandviken (Sweden); Linköping University, Engineering Materials, SE-581 83 Linköping (Sweden)

    2014-10-06

    Austenitic heat resistant Sanicro 25 steel developed for high temperature applications in power generation industry has been subjected to strain controlled low cycle fatigue tests at ambient and at elevated temperature in a wide interval of strain amplitudes. Fatigue hardening/softening curves, cyclic stress–strain curves and fatigue life curves were evaluated at room temperature and at 700 °C. The internal dislocation structures of the material at room and at elevated temperature were studied using transmission electron microscopy. High resolution surface observations and FIB cuts revealed early damage at room temperature in the form of persistent slip bands and at elevated temperature as oxidized grain boundary cracks. Dislocation arrangement study and surface observations were used to identify the cyclic slip localization and to discuss the fatigue softening/hardening behavior and the temperature dependence of the fatigue life.

  18. Behavior of reinforcement SCC beams under elevated temperatures

    Science.gov (United States)

    Fathi, Hamoon; Farhang, Kianoosh

    2015-09-01

    This experimental study focuses on the behavior of heated reinforced concrete beams. Four types of concrete mixtures were used for the tested self-compacting concrete beams. A total of 72 reinforced concrete beams and 72 standard cylindrical specimens were tested. The compressive strength under uniaxial loading at 23 °C ranged from 30 to 45 MPa. The specimens were exposed to different temperatures. The test parameters of interest were the compressive strength and the temperature of the specimens. The effect of changes in the parameters was examined so as to control the behavior of the tested concrete and that of the reinforced concrete beam. The results indicated that flexibility and compressive strength of the reinforced concrete beams decreased at higher temperatures. Furthermore, heating beyond 400 °C produced greater variations in the structural behavior of the materials in both the cylindrical samples and the reinforced concrete beams.

  19. Technology for Elevated Temperature Tests of Structural Panels

    Science.gov (United States)

    Thornton, E. A.

    1999-01-01

    A technique for full-field measurement of surface temperature and in-plane strain using a single grid imaging technique was demonstrated on a sample subjected to thermally-induced strain. The technique is based on digital imaging of a sample marked by an alternating line array of La2O2S:Eu(+3) thermographic phosphor and chromium illuminated by a UV lamp. Digital images of this array in unstrained and strained states were processed using a modified spin filter. Normal strain distribution was determined by combining unstrained and strained grid images using a single grid digital moire technique. Temperature distribution was determined by ratioing images of phosphor intensity at two wavelengths. Combined strain and temperature measurements demonstrated on the thermally heated sample were DELTA-epsilon = +/- 250 microepsilon and DELTA-T = +/- 5 K respectively with a spatial resolution of 0.8 mm.

  20. Design considerations for CRBRP heat transport system piping operating at elevated temperatures

    International Nuclear Information System (INIS)

    Pollono, L.P.; Mello, R.M.

    1979-01-01

    The heat transport system sodium piping for the Clinch River Breeder Reactor Plant (CRBRP) within the reactor containment building must withstand high temperatures for long periods of time. Each phase of the mechanical design process of the piping system is influenced by elevated temperature considerations which include material thermal creep effects, ratchetting caused by rapid temperature transients and stress relaxation, and material degradation effects. The structural design philosophy taken to design the CRBRP piping operating in a high temperature environment is described. The resulting design of the heat transport system piping is presented along with a discussion of special features that resulted from the elevated temperature considerations

  1. Liquid oxygen liquid acquisition device bubble point tests with high pressure lox at elevated temperatures

    Science.gov (United States)

    Jurns, J. M.; Hartwig, J. W.

    2012-04-01

    When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth's gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMDs) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. The present work reports on testing with liquid oxygen (LOX) at elevated pressures (and thus temperatures) (maximum pressure 1724 kPa and maximum temperature 122 K) as part of NASA's continuing cryogenic LAD development program. These tests evaluate LAD performance for LOX stored in higher pressure vessels that may be used in propellant systems using pressure fed engines. Test data shows a significant drop in LAD bubble point values at higher liquid temperatures, consistent with lower liquid surface tension at those temperatures. Test data also indicates that there are no first order effects of helium solubility in LOX on LAD bubble point prediction. Test results here extend the range of data for LOX fluid conditions, and provide insight into factors affecting predicting LAD bubble point pressures.

  2. Tensile Strength of Finger Joints at Elevated Temperatures

    DEFF Research Database (Denmark)

    Nielsen, Peter C.; Olesen, Frits Bolonius

    A series of test s aimed a t establishing the effect of temperature upon the tensile strength parallel-to-grain of finger jointed laminae for glulam has been conducted in the Fire Research Laboratory at Aalborg University Centre. The objective of this report is to present the background...

  3. Elevated temperature axial and torsional fatigue behavior of Haynes 188

    Science.gov (United States)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1992-06-01

    The results of high-temperature axial and torsional low-cycle fatigue experiments performed on Haynes 188, a wrought cobalt-base superalloy, are reported. Fatigue tests were performed at 760 C in air on thin-walled tubular specimens at various ranges under strain control. Data are also presented for coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. The data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME boiler and pressure vessel code), Manson-Halford, Modified Multiaxiality Factor (proposed here), Modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The Modified Multiaxiality Factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.

  4. Whey protein concentrate storage at elevated temperature and humidity

    Science.gov (United States)

    Dairy processors are finding new export markets for whey protein concentrate (WPC), a byproduct of cheesemaking, but they need to know if full-sized bags of this powder will withstand high temperature and relative humidity (RH) levels during unrefrigerated storage under tropical conditions. To answ...

  5. Isopiestic studies of aqueous solutions at elevated temperatures

    International Nuclear Information System (INIS)

    Holmes, H.F.; Mesmer, R.E.

    1981-01-01

    Isopiestic measurements have been made for LiCl(aq) and CsCl(aq) over the temperature range 382.96 to 473.61 K. NcCl(aq) served as the reference electrolyte for the calculation of osmotic coefficients and the molalities ranged from about 0.6 to 6 mol kg -1 , for NaCl(aq). An ion-interaction model gave an excellent fit to the experimental osmotic coefficients with a standard error of fit ranging from 0.0004 to 0.0016 in the osmotic coefficient. Parameters obtained from the fit were used to calculate the activity coefficients. The osmotic and activity coefficients both decreased with increasing temperature over this temperature range. LiCl(aq) is somewhat unusual among the alkali-metal chlorides in that the osmotic (and activity) coefficient is much more dependent on molality at the higher molalities and there is no maximum between 273.15 and 373.15 K in the osmotic coefficient as a function of temperature. For both LiCl(aq) and CsCl(aq) there is an excellent correlation between the isopiestic results and the vapor pressures of Lindsay and Liu. Existing electrochemical results between 283.15 and 343.15 K are consistent with the calculated activity coefficients for CsCl(aq). (author)

  6. Effects of Elevated Temperature on Concrete with Recycled Coarse Aggregates

    Science.gov (United States)

    Salau, M. A.; Oseafiana, O. J.; Oyegoke, T. O.

    2015-11-01

    This paper discusses the effects of heating temperatures of 200°C, 400°C and 600°C each for 2 hours at a heating rate of 2.5°C/min on concrete with the content of Natural Coarse Aggregates (NCA) partially replaced with Recycled Coarse Aggregates (RCA), obtained from demolished building in the ratio of 0%, 15% and 30%.There was an initial drop in strength from 100°C to 200°C which is suspected to be due to the relatively weak interfacial bond between the RCA and the hardened paste within the concrete matrix;a gradual increase in strength continued from 200°C to 450°C and steady drop occurred again as it approached 600°C.With replacement proportion of 0%, 15% and 30% of NCA and exposure to peak temperature of 600°C, a relative concrete strength of 23.6MPa, 25.3MPa and 22.2MPa respectively can be achieved for 28 days curing age. Furthermore, RAC with 15% NCA replacement when exposed to optimum temperature of 450°C yielded high compressive strength comparable to that of control specimen (normal concrete). In addition, for all concrete samples only slight surface hairline cracks were noticed as the temperature approached 400°C. Thus, the RAC demonstrated behavior just like normal concrete and may be considered fit for structural use.

  7. Effects of seawater components on radiolysis of water at elevated temperature

    International Nuclear Information System (INIS)

    Wada, Yoichi; Tachibana, Masahiko; Ishida, Kazushige; Ota, Nobuyuki; Shigenaka, Naoto; Inagaki, Hiromitsu; Noda, Hiroshi

    2014-01-01

    Effects of seawater components on radiolysis of water at elevated temperature have been studied with a radiolysis model in order to evaluate influence on integrity of materials used in an ABWR. In 2011, seawater flowed into a wide part of the nuclear power plant system of the Hamaoka Nuclear Power Station Reactor No. 5 owned by Chubu Electric Power Co., Inc. after condenser tubes broke during the plant shutdown operation. The reactor water temperature was 250°C and its maximum Cl − concentration was ca. 450 ppm when seawater was mixed with reactor water. In order to clarify effects of the sea water components on radiolysis of water at elevated temperature, a radiolysis model calculation was conducted with Hitachi's radiolysis analysis code 'SIMFONY'. For the calculation, the temperature range was set from 50 to 250°C with 50°C increments and the gamma dose rate was set at 60 Gys −1 to see the effect of gamma irradiation from fuels under shutdown conditions. Concentrations of radiolytic species were calculated for 10 5 s. Dilution ratio of seawater was changed to see the effects of concentration of seawater components. Reaction rate constants of the Cl − , Br − , HCO 3 − , and SO 4 2− systems were considered. The main radiolytic species were predicted to be hydrogen and oxygen. Hydrogen peroxide of low concentration was produced in seawater-mixed water at elevated temperatures. Compared with these main products, concentrations of radiolytic products originating from chloride ion and other seawater components were found to be rather low. The dominant product among them was ClO 3 − and its concentration was found to be below 0.01ppm at 10 5 s. Then, during the plant shutdown operation, the harmful influence from radiolytic species originating from seawater components on integrity of fuel materials must be smaller than that of chloride ion which is the main ionic species in seawater. (author)

  8. The effect of long-term impact of elevated temperature on changes in the microstructure of inconel 740H alloy

    Directory of Open Access Journals (Sweden)

    M. Sroka

    2017-01-01

    Full Text Available This paper presents the results of investigations on microstructure changes after the long-term impact of temperature. The microstructure investigations were carried out by light microscopy and scanning electron microscopy. The qualitative and quantitative identification of the existing precipitates was carried out using X-ray phase composition analysis. The effect of elevated temperature on precipitation processes of test material were described. The obtained results of investigations form part of the material characteristics of new-generation alloys, which can be indirectly associated with the stability of functional properties under the simultaneous effect of high temperature and stress.

  9. Analysis and evaluation system for elevated temperature design of pressure vessels

    International Nuclear Information System (INIS)

    Hayakawa, Teiji; Sayawaki, Masaaki; Nishitani, Masahiro; Mii, Tatsuo; Murasawa, Kanji

    1977-01-01

    In pressure vessel technology, intensive efforts have recently been made to develop the elevated temperature design methods. Much of the impetus of these efforts has been provided mainly by the results of the Liquid Metal Fast Breeder Reactor (LMFBR) and more recently, of the High Temperature Gas-cooled Reactor (HTGR) Programs. The pressure vessels and associated components in these new type nuclear power plants must operate for long periods at elevated temperature where creep effects are significant and then must be designed by rigorous analysis for high reliability and safety. To carry out such an elevated temperature designing, numbers of highly developed analysis and evaluation techniques, which are so complicated as to be impossible by manual work, are indispensable. Under these circumstances, the authors have made the following approaches in the study: (1) Study into basic concepts and the associated techniques in elevated temperature design. (2) Systematization (Analysis System) of the procedure for loads and stress analyses. (3) Development of post-processor, ''POST-1592'', for strength evaluation based on ASME Code Case 1592-7. By linking the POST-1592 together with the Analysis System, an analysis and evaluation system is developed for an elevated temperature design of pressure vessels. Consequently, designing of elevated temperature vessels by detailed analysis and evaluation has easily and effectively become feasible by applying this software system. (auth.)

  10. Elevated-temperature (6000F), manual contact ultrasonic examination

    International Nuclear Information System (INIS)

    Donnelly, C.W.

    1981-01-01

    Manual contact ultrasonic examination at temperatures above 250 0 F has not been successful in providing meaningful results. Sensitivity of standard transducers degrades rapidly at 250 0 F and above. It has been demonstrated that by using standard transducers and commercially available wedges and couplants in combination with a couplant/cooler system, manual contact ultrasonic examination can be performed at 600 0 F for an essentially 100% duty cycle in conformance to the sensitivity requirement of the ASME B and PV Code

  11. Performance of proton exchange membrane fuel cells at elevated temperature

    International Nuclear Information System (INIS)

    Shyu, Jin-Cherng; Hsueh, Kan-Lin; Tsau, Fanghei

    2011-01-01

    Highlights: → At 1 atm, cell has best performance (∼1300 mA/cm at 0.6 V) at 100 deg. C and RH = 100%. → The A value in Eq. increased with increases in the back pressure and RH. →R i dramatically decreased at back pressure of 1 atm. → At each RH, R i decreased and then increased as cell temperature increased at 1 atm. - Abstract: The polarization curves of a single PEMFC having a Nafion membrane fed with H 2 /O 2 with relative humidity (RH) of 35%, 70% and 100% were measured at cell temperatures ranging from 65 deg. C to 120 deg. C at back pressures of 0 atm and 1 atm, respectively. Measured results showed that the best cell performance at 0.6 V operated within 65-120 deg. C at zero back pressure was 1000 mA cm -2 at 65 deg. C and RH = 100%, while the best cell performance at 1 atm back pressure was 1300 mA cm -2 at 100 deg. C and RH = 100%. Based on the analysis of impedance data measured at anode and cathode humidification temperatures of 90 deg. C and cell temperature of 100 deg. C at back pressures of 0 and 1 atm (90-100p0 and 90-100p1), it could be found that the membrane resistance was reduced and the catalyst became more active as the back pressure increases. The present results showed that increasing back pressure was able to dramatically improve cell performance and the effect of the back pressure surpassed that of humidification in the internal resistance of cell.

  12. Analysis of coupled transport phenomena in concrete at elevated temperatures

    OpenAIRE

    Beneš, Michal; Štefan, Radek; Zeman, Jan

    2010-01-01

    In this paper, we study a non-linear numerical scheme arising from the implicit time discretization of the Ba\\v{z}ant-Thonguthai model for hygro-thermal behavior of concrete at high temperatures. Existence and uniqueness of the time-discrete solution in two dimensions is established using the theory of pseudomonotone operators in Banach spaces. Next, the spatial discretization is accomplished by the conforming finite element method. An illustrative numerical example shows that the numerical m...

  13. Elevated transition temperature in Ge doped VO2 thin films

    Science.gov (United States)

    Krammer, Anna; Magrez, Arnaud; Vitale, Wolfgang A.; Mocny, Piotr; Jeanneret, Patrick; Guibert, Edouard; Whitlow, Harry J.; Ionescu, Adrian M.; Schüler, Andreas

    2017-07-01

    Thermochromic GexV1-xO2+y thin films have been deposited on Si (100) substrates by means of reactive magnetron sputtering. The films were then characterized by Rutherford backscattering spectrometry (RBS), four-point probe electrical resistivity measurements, X-ray diffraction, and atomic force microscopy. From the temperature dependent resistivity measurements, the effect of Ge doping on the semiconductor-to-metal phase transition in vanadium oxide thin films was investigated. The transition temperature was shown to increase significantly upon Ge doping (˜95 °C), while the hysteresis width and resistivity contrast gradually decreased. The precise Ge concentration and the film thickness have been determined by RBS. The crystallinity of phase-pure VO2 monoclinic films was confirmed by XRD. These findings make the use of vanadium dioxide thin films in solar and electronic device applications—where higher critical temperatures than 68 °C of pristine VO2 are needed—a viable and promising solution.

  14. Fuel retention under elevated wall temperature in KSTAR with a carbon wall

    Science.gov (United States)

    Cao, B.; Hong, S. H.

    2018-03-01

    The fuel retention during KSTAR discharges with elevated wall temperature (150 °C) has been studied by using the method of global particle balance. The results show that the elevated wall temperature could reduce the dynamic retention via implantation and absorption, especially for the short pulse shots with large injected fuel particles. There is no signature changing of long-term retention, which related to co-deposition, under elevated wall temperature. For soft-landing shots (normal shots), the exhausted fuel particles during discharges is larger with elevated wall temperature than without, but the exhausted particles after discharges within 90 s looks similar. The outgassing particles because of disruption could be exhausted within 15 s.

  15. Element size and other restrictions in finite-element modeling of reinforced concrete at elevated temperatures

    DEFF Research Database (Denmark)

    Carstensen, Josephine Voigt; Jomaas, Grunde; Pankaj, Pankaj

    2013-01-01

    to extend this approach for RC at elevated temperatures. Prior to the extension, the approach is investigated for associated modeling issues and a set of limits of application are formulated. The available models of the behavior of plain concrete at elevated temperatures were used to derive inherent......One of the accepted approaches for postpeak finite-element modeling of RC comprises combining plain concrete, reinforcement, and interaction behaviors. In these, the postpeak strain-softening behavior of plain concrete is incorporated by the use of fracture energy concepts. This study attempts...... fracture energy variation with temperature. It is found that the currently used tensile elevated temperature model assumes that the fracture energy decays with temperature. The existing models in compression also show significant decay of fracture energy at higher temperatures (>400°) and a considerable...

  16. Effect of methyl mercaptophos in different combinations with elevated atmospheric temperature and ultraviolet radiation

    International Nuclear Information System (INIS)

    Gabovich, R.D.; Murashko, V.A.

    1975-01-01

    Rats were exposed to methyl mercaptophos (I) vapor combined with various doses of uv irradiation at 22deg or 37deg. Changes in the levels of serum alkaline phosphatase, hepatic and serum cholinestrerase, adrenal ascorbic acid, and other parameters indicated that the animals' resistance to the effects of I was decreased by: a) low uv irradiation, b) elevated temperature, or c) combined elevated temperature and excessive uv irradiation

  17. Microstructure and elevated-temperature erosion-oxidation behaviour of aluminized 9Cr-1Mo Steel

    OpenAIRE

    Huttunen, E.; Honkanen, M.; Tsipas, Sophia Alexandra; Omar, H.; Tsipas, D.

    2012-01-01

    Degradation of materials by a combination of erosive wear and atmospheric oxidation at elevated temperatures constitutes a problem in some power generation processes, such as fluidized-bed combustion. In this work, 9Cr-1Mo steel, a common tube material in combustion chambers, is coated by a pack cementation method from an Al-containing pack in order to improve the resistance to erosion-oxidation at elevated temperatures. The resulting coating is studied in terms of microstructure and microhar...

  18. Electrolysis test of different composite membranes at elevated temperatures

    DEFF Research Database (Denmark)

    Hansen, Martin Kalmar

    temperatures, phosphoric acid (H3PO4)[1] and zirconium phosphate (ZrP)[2] were introduced. These composite membranes were tested in an electrolysis setup. A typical electrolysis test was performed at 130°C with a galvanostatic load. Polarization curves were recorded under stationary conditions. Testing...... night at 150°C in a zirconium phosphate saturated 85wt% phosphoric acid solution. Different thicknesses of membranes were tested and as expected, the performance increased when the thickness of the membranes decreased. Furthermore composite membranes only treated with phosphoric acid or only treated...

  19. Radiolysis of phenol in aqueous solution at elevated temperatures

    International Nuclear Information System (INIS)

    Miyazaki, Toyoaki; Katsumura, Yosuke; Lin Mingzhang; Muroya, Yusa; Kudo, Hisaaki; Taguchi, Mitsumasa; Asano, Masaharu; Yoshida, Masaru

    2006-01-01

    γ-Radiolysis and pulse radiolysis of phenol in aqueous solution up to supercritical condition have been carried out. G-values of phenol consumption and product formation have been determined. While dihydroxybenzenes were major products at room temperature, multi-ring compounds and benzene were formed above 300 deg. C. This indicates reaction mechanism was changed above 300 deg. C, where phenoxyl radical plays a predominant role. This is supported by the observation of phenoxyl radical in pulse radiolysis. In supercritical water, the G-values increased with decrease of density

  20. Isopiestic studies of aqueous solutions at elevated temperatures

    International Nuclear Information System (INIS)

    Holmes, H.F.; Mesmer, R.E.

    1981-01-01

    Isopiestic measurements have been made on SrCl 2 (aq) and BaCl 2 (aq) over the temperature range 382.96 to 473.61 K with NaCl(aq) as the reference solution for the calculation of osmotic coefficients. The molalities corresponded to NaCl(aq) molalities ranging from 0.6 to 6.5 mol kg -1 . An ion-interaction model was fitted to the osmotic coefficients of SrCl 2 (aq) and BaCl 2 (aq) with a standard deviation of fit (in the osmotic coefficient) ranging from 0.0007 to 0.0048. Parameters derived from the fit were used to calculate the activity coefficients. The osmotic and activity coefficients decrease with increasing temperature and become less dependent on molality. Previous isopiestic results between 318 and 394 K agree with the present study. Activity coefficients from electrochemical measurements between 283.15 and 343.15 K are not consistent with the isopiestic results. (author)

  1. Intrapartum Temperature Elevation, Epidural Use, and Adverse Outcome in Term Infants

    Science.gov (United States)

    Wyshak, Grace; Ringer, Steven A.; Johnson, Lise C.; Rivkin, Michael J.; Lieberman, Ellice

    2012-01-01

    OBJECTIVES: To examine the association of intrapartum temperature elevation with adverse neonatal outcome among low-risk women receiving epidural analgesia and evaluate the association of epidural with adverse neonatal outcome without temperature elevation. METHODS: We studied all low-risk nulliparous women with singleton pregnancies ≥37 weeks delivering at our hospital during 2000, excluding pregnancies where infants had documented sepsis, meningitis, or a major congenital anomaly. Neonatal outcomes were compared between women receiving (n = 1538) and not receiving epidural analgesia (n = 363) in the absence of intrapartum temperature elevation (≤99.5°F) and according to the level of intrapartum temperature elevation within the group receiving epidural (n = 2784). Logistic regression was used to evaluate neonatal outcome while controlling for confounders. RESULTS: Maternal temperature >100.4°F developed during labor in 19.2% (535/2784) of women receiving epidural compared with 2.4% (10/425) not receiving epidural. In the absence of intrapartum temperature elevation (≤99.5°F), no significant differences were observed in adverse neonatal outcomes between women receiving and not receiving epidural. Among women receiving epidural, a significant linear trend was observed between maximum maternal temperature and all neonatal outcomes examined including hypotonia, assisted ventilation, 1- and 5-min Apgar scores 101°F had a two- to sixfold increased risk of all adverse outcomes examined. CONCLUSIONS: The proportion of infants experiencing adverse outcomes increased with the degree of epidural-related maternal temperature elevation. Epidural use without temperature elevation was not associated with any of the adverse outcomes we studied. PMID:22291120

  2. Analysis of elevated temperature cyclic deformation of austenitic stainless steels

    International Nuclear Information System (INIS)

    Rohde, R.W.; Swearengen, J.C.

    1977-01-01

    The stress relaxation behavior of 304 and 316 stainless steels during cyclic deformation at 538 and 650 0 C with various hold times and strain amplitudes has been analyzed in terms of a power-law equation of state which includes internal stress and drag stress as structure variables. At 650 0 C the internal sress in 304 appears to be zero and microstructural recovery plays an important role in the kinetics of stress relaxation. For deformation at 538 0 C, the internal stress in 304 is nonzero and microstructural recovery appears minimal. In 316 tested at 650 0 C the internal stress is zero and again recovery is important. However, the kinetics of recovery differ from those measured in 304. These observations are explained physically in terms of strain and temperature-induced recovery of the structural variables, and provide insights into the procedures for calculating accumulated ''creep'' damage in reactor components

  3. Carbothermal Reduction of Quartz and Carbon Pellets at Elevated Temperatures

    Science.gov (United States)

    Li, Fei; Tangstad, Merete; Ringdalen, Eli

    2018-02-01

    In this study, the carbothermal reduction of pellets composed of quartz and carbon at temperatures between 1898 K and 1948 K (1625 °C and 1675 °C) are investigated. The main product from this reaction is silicon carbide (SiC). The reduction of quartz with carbon black, charcoal, coke, coal, and pre-heated coal in the pellet were compared to investigate the different carbon resources used in silicon production. Charcoal and coke have high SiO reactivity, while carbon black and coal (pre-heated coal) have low SiO reactivity. Charcoal and carbon black show better matching between quartz/carbon reactivity and SiO reactivity, and will lose less SiO gas than coke and pre-heated coal. Coal has a high volatile content and is thus not recommended as a raw material for the pellets.

  4. Measurement of local void fraction at elevated temperature and pressure

    International Nuclear Information System (INIS)

    Duncan, D.; Trabold, T.A.

    1993-03-01

    Significant advances have recently been made in analytical and computational methods for the prediction of local thermal-hydraulic conditions in gas/liquid two-phase flows. There is, however, a need for extensive experimental data, for the dual purposes of constitutive relation development and code qualification. There is especially true of systems involving complicated geometries and/or extreme flow conditions for which little, if any, applicable information exists in the open literature. For the tests described in the present paper, a novel electrical probe has been applied to measure the void fraction in atmospheric pressure air/water flows, and steam/water mixtures at high temperature and pressure. The data acquired in the latter experiments are compared with the results of a one-dimensional two-fluid computational analysis

  5. Solute strengthening effects for 316 stainless steel at elevated temperature

    International Nuclear Information System (INIS)

    Park, Nam Ju; Lee, Sang Mae

    1986-01-01

    The inelastic behavior of 316 stainless steel is studied in order to investigate the solute strengthening effects. The Arrhenius-type rate equation with inclusion of the Voce-type evolution phenomenon is extended by addition of solute strengthening term to the isotropic work hardening effect. Changing of strain rate and temperature during the tension tests, we found that the strong work hardening for the inelastic of 316 stainless steel resulted from the vacancy-interstitial pair mechanism. Thus, the calculated results using the extended constitutive equations including solute effect due to the vacancy-interstitial pair mechanism were found to be in good agreement with the stress-strain curves obtained from the tension tests. (Author)

  6. Carbothermal Reduction of Quartz and Carbon Pellets at Elevated Temperatures

    Science.gov (United States)

    Li, Fei; Tangstad, Merete; Ringdalen, Eli

    2018-06-01

    In this study, the carbothermal reduction of pellets composed of quartz and carbon at temperatures between 1898 K and 1948 K (1625 °C and 1675 °C) are investigated. The main product from this reaction is silicon carbide (SiC). The reduction of quartz with carbon black, charcoal, coke, coal, and pre-heated coal in the pellet were compared to investigate the different carbon resources used in silicon production. Charcoal and coke have high SiO reactivity, while carbon black and coal (pre-heated coal) have low SiO reactivity. Charcoal and carbon black show better matching between quartz/carbon reactivity and SiO reactivity, and will lose less SiO gas than coke and pre-heated coal. Coal has a high volatile content and is thus not recommended as a raw material for the pellets.

  7. Recycling temperature elevation device and temperature control method for control rod driving system

    International Nuclear Information System (INIS)

    Okamura, Hajime.

    1996-01-01

    The present invention concerns a device for and a method of controlling a recycling temperature control device for control rod drives (CRD) of a nuclear power plant, which can prevent occurrence of cavitation and keep the amount of cooling water to be transferred to a water source transfer pipeline thereby improving maintenanciability, operationability and reliability. Namely, a supply pipeline supplies cooling water required for the control rod drives from a water source. A CRD pump elevates the pressure of the cooling water. A recycling pipeline is branched from the downstream of the CRD pump of the supply pipeline and connected to the supply pipeline at the upstream of the CRD pump. A first pressure element and a restricting valve disposed at the upstream thereof are connected to the upstream of the CRD pump and the water source transfer pipeline. The water source transfer pipeline is branched from the recycling pipeline and connected to the water source. A second pressure element is disposed to a recycling pipeline at the downstream of the branched point from the water source transfer pipeline. (I.S.)

  8. Elevated temperature design of KALIMER reactor internals accounting for creep and stress-rupture effects

    International Nuclear Information System (INIS)

    Koo, Gyeong Hoi; Yoo, Bong

    2000-01-01

    In most LMFBR (Liquid Metal Fast Breed Reactor) design, the operating temperature is very high and the time-dependent creep and stress-rupture effects become so important in reactor structural design. Therefore, unlike with conventional PWR, the normal operating conditions can be basically dominant design loading because the hold time at elevated temperature condition is so long and enough to result in severe total creep ratcheting strains during total service lifetime. In this paper, elevated temperature design of the conceptually designed baffle annulus regions of KALIMER (Korea Advanced Liquid Metal Reactor) reactor internal structures is carried out for normal operating conditions which have the operating temperature 530 deg. C and the total service lifetime of 30 years. For the elevated temperature design of reactor internal structures, the ASME Code Case N-201-4 is used. Using this code, the time-dependent stress limits, the accumulated total inelastic strain during service lifetime, and the creep-fatigue damages are evaluated with the calculation results by the elastic analysis under conservative assumptions. The application procedures of elevated temperature design of the reactor internal structures using ASME code case N-201-4 with the elastic analysis method are described step by step in detail. This paper will be useful guide for actual application of elevated temperature design of various reactor types accounting for creep and stress-rupture effects. (author)

  9. Temperature elevation in the fetus from electromagnetic exposure during magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, Satoru; Ito, Koichi [Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Saito, Kazuyuki; Takahashi, Masaharu [Research Center for Frontier Medical Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)], E-mail: kikuchi@graduate.chiba-u.jp

    2010-04-21

    This study computationally assessed the temperature elevations due to electromagnetic wave energy deposition during magnetic resonance imaging in non-pregnant and pregnant woman models. We used a thermal model with thermoregulatory response of the human body for our calculations. We also considered the effect of blood temperature variation on body core temperature. In a thermal equilibrium state, the temperature elevations in the intrinsic tissues of the woman and fetal tissues were 0.85 and 0.61 deg. C, respectively, at a whole-body averaged specific absorption rate of 2.0 W kg{sup -1}, which is the restriction value of the International Electrotechnical Commission for the normal operating mode. As predicted, these values are below the temperature elevation of 1.5 deg. C that is expected to be teratogenic. However, these values exceeded the recommended temperature elevation limit of 0.5 deg. C by the International Commission on Non-Ionizing Radiation Protection. We also assessed the irradiation time required for a temperature elevation of 0.5 deg. C at the aforementioned specific absorption rate. As a result, the calculated irradiation time was 40 min.

  10. Temperature elevation in the fetus from electromagnetic exposure during magnetic resonance imaging

    International Nuclear Information System (INIS)

    Kikuchi, Satoru; Ito, Koichi; Saito, Kazuyuki; Takahashi, Masaharu

    2010-01-01

    This study computationally assessed the temperature elevations due to electromagnetic wave energy deposition during magnetic resonance imaging in non-pregnant and pregnant woman models. We used a thermal model with thermoregulatory response of the human body for our calculations. We also considered the effect of blood temperature variation on body core temperature. In a thermal equilibrium state, the temperature elevations in the intrinsic tissues of the woman and fetal tissues were 0.85 and 0.61 deg. C, respectively, at a whole-body averaged specific absorption rate of 2.0 W kg -1 , which is the restriction value of the International Electrotechnical Commission for the normal operating mode. As predicted, these values are below the temperature elevation of 1.5 deg. C that is expected to be teratogenic. However, these values exceeded the recommended temperature elevation limit of 0.5 deg. C by the International Commission on Non-Ionizing Radiation Protection. We also assessed the irradiation time required for a temperature elevation of 0.5 deg. C at the aforementioned specific absorption rate. As a result, the calculated irradiation time was 40 min.

  11. Standard Test Method for Normal Spectral Emittance at Elevated Temperatures

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1972-01-01

    1.1 This test method describes a highly accurate technique for measuring the normal spectral emittance of electrically conducting materials or materials with electrically conducting substrates, in the temperature range from 600 to 1400 K, and at wavelengths from 1 to 35 μm. 1.2 The test method requires expensive equipment and rather elaborate precautions, but produces data that are accurate to within a few percent. It is suitable for research laboratories where the highest precision and accuracy are desired, but is not recommended for routine production or acceptance testing. However, because of its high accuracy this test method can be used as a referee method to be applied to production and acceptance testing in cases of dispute. 1.3 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this stan...

  12. Response of ferritic steels to nonsteady loading at elevated temperatures

    International Nuclear Information System (INIS)

    Swindeman, R.W.

    1984-01-01

    High-temperature operating experience is lacking in pressure vessel materials that have strength levels above 586 MPa. Because of their tendency toward strain softening, we have been concerned about their behavior under nonsteady loading. Testing was undertaken to explore the extent of softening produced by monotonic and cyclic strains. The specific materials included bainitic 2 1/4Cr-1Mo steel, a micro-alloyed version of 2 1/4Cr-1Mo steel, a micro-alloyed version of 2 1/4Cr-1Mo steel containing vanadium, titanium, and boron, and a martensitic 9Cr-1Mo-V-Nb steel. Tests included tensile, creep, variable stress creep, relaxation, strain cycling, stress cycling, and non-isothermal creep ratchetting experiments. We found that these steels had very low uniform elongation and exhibited small strains to the onset of tertiary creep compared to annealed 2 1/4Cr-1Mo steel. Repeated relaxation test data also indicated a limited capacity for strain hardening. Reversal strains produced softening. The degree of softening increased with increased initial strength level. We concluded that the high strength bainitic and martensitic steels should perform well when used under conditions where severe cyclic operation does not occur

  13. Elevated temperature and CO{sub 2} concentration effects on xylem anatomy of Scots pine

    Energy Technology Data Exchange (ETDEWEB)

    Kilpelainen, A.; Gerendiain, A.Z.; Luostarinen, K.; Peltola, H.; Kellomaki, S. [Joensuu Univ., Joensuu (Finland). Faculty of Forestry

    2007-09-15

    The effects of carbon dioxide (CO{sub 2}) concentrations and elevated temperatures on the xylem anatomy of 20-year old Scots pine trees were investigated. The experiment was conducted in 16 chambers containing 4 trees each with a factorial combination of both ambient and elevated CO{sub 2} concentrations and 2 different temperature regimes. CO{sub 2} concentrations were doubled with a corresponding increase of between 2 and 6 degrees C according to each season over a period of 6 years. The study showed that elevated CO{sub 2} concentrations increased the ring width in 4 of the 6 analyzed treatment years. Earlywood width increased during the first 2 years of the experiment, while latewood width increased during the third year of the study. The study also showed that the tracheid walls in both the latewood and earlywood samples were thicker when either temperature levels or CO{sub 2} levels were increased. It was noted that combined CO{sub 2} and temperature elevations resulted in thinner tracheid walls. However, latewood tracheid lumen diameters were larger in all CO{sub 2} and temperature treatments than trees grown in ambient conditions. It was concluded that xylem anatomy was impacted more by increases in temperature than by elevated CO{sub 2} concentrations. 48 refs., 2 tabs., 6 figs.

  14. Qualification of diesel generator exhaust carbon steel piping to intermitted elevated temperatures

    International Nuclear Information System (INIS)

    Ratiu, M.D.; Moisidis, N.T.

    1996-01-01

    The diesel generator exhaust piping, usually made up of carbon steel piping (e.g., ASME SA-106, SA-53), is subjected to successive short time exposures at elevated temperatures up to 1,000 F (538 C). A typical design of this piping, without consideration for creep-fatigue cumulative damage, is at least incomplete, if not inappropriate. Also, a design for creep-fatigue, usually employed for long-term exposure to elevated temperatures, would be too conservative and will impose replacement of the carbon steel piping with heat-resistant CrMo alloy piping. The existing ASME standard procedures do not explicitly provide acceptance criteria for the design qualification to withstand these intermittent exposures to elevated temperatures. The serviceability qualification proposed is based on the evaluation of equivalent full temperature cycles which are presumed/expected to be experienced by the exhaust piping during the design operating life of the diesel engine. The proposed serviceability analysis consists of: (a) determination of the permissible stress at elevated temperatures, and (b) estimation of creep-fatigue damage for the total expected cycles of elevated temperature exposures following the procedure provided in ASME Code Cases N-253-6 and N-47-28

  15. Elevated temperature and CO2 concentration effects on xylem anatomy of Scots pine

    International Nuclear Information System (INIS)

    Kilpelainen, A.; Gerendiain, A.Z.; Luostarinen, K.; Peltola, H.; Kellomaki, S.

    2007-01-01

    The effects of carbon dioxide (CO 2 ) concentrations and elevated temperatures on the xylem anatomy of 20-year old Scots pine trees were investigated. The experiment was conducted in 16 chambers containing 4 trees each with a factorial combination of both ambient and elevated CO 2 concentrations and 2 different temperature regimes. CO 2 concentrations were doubled with a corresponding increase of between 2 and 6 degrees C according to each season over a period of 6 years. The study showed that elevated CO 2 concentrations increased the ring width in 4 of the 6 analyzed treatment years. Earlywood width increased during the first 2 years of the experiment, while latewood width increased during the third year of the study. The study also showed that the tracheid walls in both the latewood and earlywood samples were thicker when either temperature levels or CO 2 levels were increased. It was noted that combined CO 2 and temperature elevations resulted in thinner tracheid walls. However, latewood tracheid lumen diameters were larger in all CO 2 and temperature treatments than trees grown in ambient conditions. It was concluded that xylem anatomy was impacted more by increases in temperature than by elevated CO 2 concentrations. 48 refs., 2 tabs., 6 figs

  16. Pressure drop in packed beds of spherical particles at ambient and elevated air temperatures

    Directory of Open Access Journals (Sweden)

    Pešić Radojica

    2015-01-01

    Full Text Available The aim of this work was the experimental investigation of the particle friction factor for air flow through packed bed of particles at ambient and elevated temperatures. The experiments were performed by measuring the pressure drop across the packed bed, heated to the desired temperature by hot air. Glass spherical particles of seven different diameters were used. The temperature range of the air flowing through the packed bed was from 20ºC to 350ºC and the bed voidages were from 0.3574 to 0.4303. The obtained results were correlated using a number of available literature correlations. The overall best fit of all of the experimental data was obtained using Ergun [1] equation, with mean absolute deviation of 10.90%. Ergun`s equation gave somewhat better results in correlating the data at ambient temperature with mean absolute deviation of 9.77%, while correlation of the data at elevated temperatures gave mean absolute deviation of 12.38%. The vast majority of the correlations used gave better results when applied to ambient temperature data than to the data at elevated temperatures. Based on the results obtained, Ergun [1] equation is proposed for friction factor calculation both at ambient and at elevated temperatures. [Projekat Ministarstva nauke Republike Srbije, br. ON172022

  17. Tensile behaviour of radiata pine with different moisture contents at elevated temperatures

    DEFF Research Database (Denmark)

    Pearson, Hamish; Gabbitas, Brian; Ormarsson, Sigurdur

    2012-01-01

    that moisture and temperature can play a significant role in reducing stress during drying, regardless of the drying time. Properties of wood, such as tensile elastic information at elevated temperatures, are important for mechanical design, distortion modelling and understanding the fundamental behaviour...

  18. Measurements of fatigue crack length at elevated temperature by D. C. electrical potential method

    International Nuclear Information System (INIS)

    Matsumoto, Masakatsu; Yamauchi, Isamu; Kodaira, Tsuneo

    1982-07-01

    The direct current (d.c.) electrical potential method was used to automatically and continuously measure the crack length in cyclic crack growth test at elevated temperature. This report describes some results concerning the calibration curves, i.e. the relation between electrical potential change and amount of crack extention, using SUS 304 and 2 1/4Cr-1Mo steels. It can be concluded that the measurements of fatigue crack length is possible even at elevated temperature as well as at room temperature with the equivalent accuracy. (author)

  19. Effects of elevated environmental temperature combined with radiation on the organism

    Energy Technology Data Exchange (ETDEWEB)

    Tsapkov, M M

    1981-01-01

    Literature data concerning the combined effects of ionizing radiation and elevated temperatures on the physiological functions of laboratory animals is reviewed. The data demonstrate effects of combined exposures on the cardiovascular system, impairments in the enzymatic activity of various tissues and the inactivation of chromosomal repair processes following radiation damage. The degree of radiation damage depends both on the radiation dose and the duration of the temperature factor, although elevated temperatures accelerate the elimination of radioactive substances from the body. A need for further experimental data for the evaluation of human working conditions and radiation safety is expressed.

  20. The altitudinal temperature lapse rates applied to high elevation rockfalls studies in the Western European Alps

    Science.gov (United States)

    Nigrelli, Guido; Fratianni, Simona; Zampollo, Arianna; Turconi, Laura; Chiarle, Marta

    2018-02-01

    Temperature is one of the most important aspects of mountain climates. The relationships between air temperature and rockfalls at high-elevation sites are very important to know, but are also very difficult to study. In relation to this, a reliable method to estimate air temperatures at high-elevation sites is to apply the altitudinal temperature lapse rates (ATLR). The aims of this work are to quantify the values and the variability of the hourly ATLR and to apply this to estimated temperatures at high-elevation sites for rockfalls studies. To calculate ATLR prior the rockfalls, we used data acquired from two automatic weather stations that are located at an elevation above 2500 m. The sensors/instruments of these two stations are reliable because subjected to an accurate control and calibration once for year and the raw data have passed two automatic quality controls. Our study has yielded the following main results: (i) hourly ATLR increases slightly with increasing altitude, (ii) it is possible to estimate temperature at high-elevation sites with a good level of accuracy using ATLR, and (iii) temperature plays an important role on slope failures that occur at high-elevation sites and its importance is much more evident if the values oscillate around 0 °C with an amplitude of ±5 °C during the previous time-period. For these studies, it is not enough to improve the knowledge on air temperature, but it is necessary to develop an integrated knowledge of the thermal conditions of different materials involved in these processes (rock, debris, ice, water). Moreover, this integrated knowledge must be acquired by means of sensors and acquisition chains with known metrological traceability and uncertainty of measurements.

  1. Elevated [CO2] does not ameliorate the negative effects of elevated temperature on drought-induced mortality in Eucalyptus radiata seedlings.

    Science.gov (United States)

    Duan, Honglang; Duursma, Remko A; Huang, Guomin; Smith, Renee A; Choat, Brendan; O'Grady, Anthony P; Tissue, David T

    2014-07-01

    It has been reported that elevated temperature accelerates the time-to-mortality in plants exposed to prolonged drought, while elevated [CO(2)] acts as a mitigating factor because it can reduce stomatal conductance and thereby reduce water loss. We examined the interactive effects of elevated [CO(2)] and temperature on the inter-dependent carbon and hydraulic characteristics associated with drought-induced mortality in Eucalyptus radiata seedlings grown in two [CO(2)] (400 and 640 μL L(-1)) and two temperature (ambient and ambient +4 °C) treatments. Seedlings were exposed to two controlled drying and rewatering cycles, and then water was withheld until plants died. The extent of xylem cavitation was assessed as loss of stem hydraulic conductivity. Elevated temperature triggered more rapid mortality than ambient temperature through hydraulic failure, and was associated with larger water use, increased drought sensitivities of gas exchange traits and earlier occurrence of xylem cavitation. Elevated [CO(2)] had a negligible effect on seedling response to drought, and did not ameliorate the negative effects of elevated temperature on drought. Our findings suggest that elevated temperature and consequent higher vapour pressure deficit, but not elevated [CO(2)], may be the primary contributors to drought-induced seedling mortality under future climates. © 2013 John Wiley & Sons Ltd.

  2. Ecological studies of neritic phytoplankton of Southern California: seasonal variations, associations, and responses to temperature elevations

    International Nuclear Information System (INIS)

    Briand, F.J.P.

    1974-01-01

    The first part of this study investigates the seasonal variations and associations of the nearshore phytoplankton communities at Seal Beach, Orange County, California. A total of 90 species was recorded in samples taken weekly from June 1972 to May 1973. On a yearly basis, the two dominant algal groups were diatoms (46 species) and dinoflagellates (36 species), accounting respectively for 64.1 percent and 30.4 percent of the total cell number, and for 20.2 percent and 79.2 percent of the total cell volume. The species diversity index (H') remained relatively stable during the year, showing no distinct seasonal pattern. The major group, composed mainly of dinoflagellates, was correlated with warm water conditions at Seal Beach. At this location, two electric power plants use sea-water for cooling purposes at the rate of six million l/min, which subjects the planktonic organisms entrained in the condenser systems to appreciable temperature increases. This problem is general in southern California, where 14 coastal power plants draw presently no less than 20 billion l/day from the ocean. The large quantities of marine phytoplankton passing through the cooling systems of the two power plants studied were found greatly reduced in numbers (41.7 percent) and in volume (33.7 percent). There was no apparent reduction in phytoplankton stocks when the intake water was cooler than 15 0 C. Species diversity (H') in the effluent was consistently lower than in the influent. Temperature elevations up to 10 0 C increased the gross primary productivity by 37 percent when intake water temperatures were 19 0 C or cooler, and reduced productivity by 22 percent when ambient water temperatures were warmer than 21.5 0 C. Since heating was consistently less damaging when applied to relatively cold water, use by coastal power plants of deep sea-water for cooling is strongly advocated. (U.S.)

  3. Elevated temperature affects development, survivorship, and settlement of the elkhorn coral, Acropora palmata (Lamarck 1816).

    Science.gov (United States)

    Randall, Carly J; Szmant, Alina M

    2009-12-01

    Elevated seawater temperatures during the late summer have the potential to negatively affect the development and survivorship of the larvae of reef corals that are reproductive during that time of year. Acropora palmata, a major Caribbean hermatype, reproduces annually during August and September. A. palmata populations have severely declined over the past three decades, and recovery will require high recruitment rates. Such recruitment will be limited if larval supply is reduced by elevated temperatures. The effects of elevated temperatures on development, survival, and larval settlement of A. palmata were investigated by culturing newly fertilized eggs at temperatures ranging from 27.5 to 31.5 degrees C. Development was accelerated and the percentage of developmental abnormalities increased at higher temperatures. Embryo mortality peaked during gastrulation, indicating that this complex developmental process is particularly sensitive to elevated temperatures. Larvae cultured at 30 and 31.5 degrees C experienced as much as an 8-fold decrease in survivorship compared to those at 28 degrees C. Additionally, settlement was 62% at 28 degrees C compared to 37% at 31.5 degrees C. These results indicate that embryos and larvae of A. palmata will be negatively affected as sea surface temperatures continue to warm, likely reducing recruitment and the recovery potential of A. palmata on Caribbean reefs.

  4. Radio frequency-induced temperature elevations in the human head considering small anatomical structures

    International Nuclear Information System (INIS)

    Schmid, G.; Ueberbacher, R.; Samaras, T.

    2007-01-01

    In order to enable a detailed numerical radio frequency (RF) dosimetry and the computations of RF-induced temperature elevations, high-resolution (0.1 mm) numerical models of the human eye, the inner ear organs and the pineal gland were developed and inserted into a commercially available head model. As radiation sources, generic models of handsets at 400, 900 and 1850 MHz operating in close proximity to the head were considered. The results, obtained by finite-difference time domain-based computations, showed a highly heterogeneous specific absorption rate (SAR) distribution and SAR-peaks inside the inner ear structures; however, the corresponding RF-induced temperature elevations were well below 0.1 deg. C, when considering typical output power values of hand-held devices. In case of frontal exposure, with the radiation sources ∼2.5 cm in front of the closed eye, maximum temperature elevations in the eye in the range of ∼0.2-0.6 deg. C were found for typical device output powers. A reduction in tissue perfusion mainly affected the maximum RF-induced temperature elevation of tissues deep inside the head. Similarly, worst-case considerations regarding pulsed irradiation affected temperature elevations in deep tissue significantly more than in superficial tissues. (authors)

  5. Evaluation test of high temperature strain gages used in a stethoscope for OGL-1 components in an elevated temperature service

    International Nuclear Information System (INIS)

    Sato, Toshimi; Tanaka, Isao; Komori, Yoshihiro; Suzuki; Toshiaki.

    1982-01-01

    The stethoscope for OGL-1 components in a elevated temperature service (SOCETS) is a measuring system of evaluation integrity of structures for high temperature pipings during operations of Japan Material Testing Reactor. This paper is described about the results on fundamental performance on high temperature strain gages. From their test results that have been based on correlation of temperature-timestrain factors, it became clear that two weldable strain gages and a capacitance strain gage were available for strain measurements of OGL-1 components. (author)

  6. Evaluation test of high temperature strain gages used in a stethoscope for OGL-1 components in an elevated temperature service

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Toshimi (Kyowa Electronic Inst. Co. Ltd. (Japan)); Tanaka, Isao; Komori, Yoshihiro; Suzuki; Toshiaki

    1982-08-01

    The stethoscope for OGL-1 components in a elevated temperature service (SOCETS) is a measuring system of evaluation integrity of structures for high temperature pipings during operations of Japan Material Testing Reactor. This paper is described about the results on fundamental performance on high temperature strain gages. From their test results that have been based on correlation of temperature-timestrain factors, it became clear that two weldable strain gages and a capacitance strain gage were available for strain measurements of OGL-1 components.

  7. Effects of drilling parameters in numerical simulation to the bone temperature elevation

    Science.gov (United States)

    Akhbar, Mohd Faizal Ali; Malik, Mukhtar; Yusoff, Ahmad Razlan

    2018-04-01

    Drilling into the bone can produce significant amount of heat which can cause bone necrosis. Understanding the drilling parameters influence to the heat generation is necessary to prevent thermal necrosis to the bone. The aim of this study is to investigate the influence of drilling parameters on bone temperature elevation. Drilling simulations of various combinations of drill bit diameter, rotational speed and feed rate were performed using finite element software DEFORM-3D. Full-factorial design of experiments (DOE) and two way analysis of variance (ANOVA) were utilised to examine the effect of drilling parameters and their interaction influence on the bone temperature. The maximum bone temperature elevation of 58% was demonstrated within the range in this study. Feed rate was found to be the main parameter to influence the bone temperature elevation during the drilling process followed by drill diameter and rotational speed. The interaction between drill bit diameter and feed rate was found to be significantly influence the bone temperature. It is discovered that the use of low rotational speed, small drill bit diameter and high feed rate are able to minimize the elevation of bone temperature for safer surgical operations.

  8. Design rule for fatigue of welded joints in elevated-temperature nuclear components

    International Nuclear Information System (INIS)

    O'Connor, D.G.; Corum, J.M.

    1986-01-01

    Elevated-temperature weldment fatigue failures have occurred in several operating liquid-metal reactor plants. Yet, ASME Code Case N-47, which governs the design of such plants in the United States, does not currently address the Code Subgroup on Elevated Temperature Design recently proposed a fatigue strength reduction factor for austenitic and ferritic steel weldments. The factor is based on a variety of weld metal and weldment fatigue data generated in the United States, Europe, and Japan. This paper describes the factor and its bases, and it presents the results of confirmatory fatigue tests conducted at Oak Ridge National Laboratory on 316 stainless steel tubes with axial and circumferential welds of 16-8-2 filler metal. These test results confirm the suitability of the design factor, and they support the premise that the metallurgical notch effect produced by yield strength variations across a weldment is largely responsible for the observed elevated-temperature fatigue strength reduction

  9. Class 2 piping rules in elevated temperature applications compared with Class 1 prescriptions for LMFBRs

    International Nuclear Information System (INIS)

    Capello, R.; Stretti, G.; Cesari, F.G.

    1989-01-01

    An LMFBR plant has many piping systems subjected to elevated temperature (> 427 o C) which, depending on their function and safety criteria, are classified as of quality level 1 or 2. The design of class 1 and class 2 piping for elevated temperatures is performed in accordance with ASME CCN-47 and CCN-253 respectively. This paper discusses what level of knowledge and analysis is necessary, to apply the rules of class 2 (CCN-253) rather than those of class 1 (CCN-47) for the design analysis of piping systems. From the designer viewpoint the burden of verification is much greater in class 1 than in class 2. This paper also examines the reliability of class 2 rules for elevated temperature when used to obtain structural results and justify the design of class 1 systems. In fact it can be shown that in some cases it is possible to design class 1 piping systems using class 2 rules. (author)

  10. Microstructure-based multiscale modeling of elevated temperature deformation in aluminum alloys

    International Nuclear Information System (INIS)

    Krajewski, Paul E.; Hector, Louis G.; Du Ningning; Bower, Allan F.

    2010-01-01

    A multiscale model for predicting elevated temperature deformation in Al-Mg alloys is presented. Constitutive models are generated from a theoretical methodology and used to investigate the effects of grain size on formability. Flow data are computed with a polycrystalline, microstructure-based model which accounts for grain boundary sliding, stress-induced diffusion, and dislocation creep. Favorable agreement is found between the computed flow data and elevated temperature tensile measurements. A creep constitutive model is then fit to the computed flow data and used in finite-element simulations of two simple gas pressure forming processes, where favorable results are observed. These results are fully consistent with gas pressure forming experiments, and suggest a greater role for constitutive models, derived largely from theoretical methodologies, in the design of Al alloys with enhanced elevated temperature formability. The methodology detailed herein provides a framework for incorporation of results from atomistic-scale models of dislocation creep and diffusion.

  11. Combination treatment of elevated UVB radiation, CO2 and temperature has little effect on silver birch (Betula pendula) growth and phytochemistry.

    Science.gov (United States)

    Lavola, Anu; Nybakken, Line; Rousi, Matti; Pusenius, Jyrki; Petrelius, Mari; Kellomäki, Seppo; Julkunen-Tiitto, Riitta

    2013-12-01

    Elevations of carbon dioxide, temperature and ultraviolet-B (UBV) radiation in the growth environment may have a high impact on the accumulation of carbon in plants, and the different factors may work in opposite directions or induce additive effects. To detect the changes in the growth and phytochemistry of silver birch (Betula pendula) seedlings, six genotypes were exposed to combinations of ambient or elevated levels of CO2 , temperature and UVB radiation in top-closed chambers for 7 weeks. The genotypes were relatively similar in their responses, and no significant interactive effects of three-level climate factors on the measured parameters were observed. Elevated UVB had no effect on growth, nor did it alter plant responses to CO2 and/or temperature in combined treatments. Growth in all plant parts increased under elevated CO2 , and height and stem biomass increased under elevated temperature. Increased carbon distribution to biomass did not reduce its allocation to phytochemicals: condensed tannins, most flavonols and phenolic acids accumulated under elevated CO2 and elevated UVB, but this effect disappeared under elevated temperature. Leaf nitrogen content decreased under elevated CO2 . We conclude that, as a result of high genetic variability in phytochemicals, B. pendula seedlings have potential to adapt to the tested environmental changes. The induction in protective flavonoids under UVB radiation together with the positive impact of elevated CO2 and temperature mitigates possible UVB stress effects, and thus atmospheric CO2 concentration and temperature are the climate change factors that will dictate the establishment and success of birch at higher altitudes in the future. © 2013 Scandinavian Plant Physiology Society.

  12. In Situ Elevated Temperature Testing of Fly Ash Based Geopolymer Composites

    Science.gov (United States)

    Vickers, Les; Pan, Zhu; Tao, Zhong; van Riessen, Arie

    2016-01-01

    In situ elevated temperature investigations using fly ash based geopolymers filled with alumina aggregate were undertaken. Compressive strength and short term creep tests were carried out to determine the onset temperature of viscous flow. Fire testing using the standard cellulose curve was performed. Applying a load to the specimen as the temperature increased reduced the temperature at which viscous flow occurred (compared to test methods with no applied stress). Compressive strength increased at the elevated temperature and is attributed to viscous flow and sintering forming a more compact microstructure. The addition of alumina aggregate and reduction of water content reduced the thermal conductivity. This led to the earlier onset and shorter dehydration plateau duration times. However, crack formation was reduced and is attributed to smaller thermal gradients across the fire test specimen. PMID:28773568

  13. Study on cord/rubber interface at elevated temperatures by H-pull test method

    Science.gov (United States)

    Jamshidi, M.; Afshar, F.; Mohammadi, N.; Pourmahdian, S.

    2005-08-01

    Cords are used as reinforcing materials in rubber compounds. To increase cord/rubber interfacial adhesion, they are coated by an adhesive (usually based on resorcinol-formaldehyde-latex). These composites are used in many sectors such as tire and belt industries. Cord/rubber adhesion strength is an important aspect to determine the durability of system. Due to temperature increase during running tires, the adhesion energy becomes different from initial one. To study cord/rubber interface at elevated temperatures, H-adhesion test method was used. H-pull test is a simple method for adhesion evaluation at ambient temperature, so it is usually used for material quality control. In this research, cord/rubber systems were vulcanized at different temperatures and H-adhesion of samples were evaluated at elevated temperatures. Also cord/rubber interface was studied by ATR analyze to determine interfacial interactions kind.

  14. Optimization of tribological behaviour on Al- coconut shell ash composite at elevated temperature

    Science.gov (United States)

    Siva Sankara Raju, R.; Panigrahi, M. K.; Ganguly, R. I.; Srinivasa Rao, G.

    2018-02-01

    In this study, determine the tribological behaviour of composite at elevated temperature i.e. 50 - 150 °C. The aluminium matrix composite (AMC) are prepared with compo casting route by volume of reinforcement of coconut shell ash (CSA) such as 5, 10 and 15%. Mechanical properties of composite has enhances with increasing volume of CSA. This study details to optimization of wear behaviour of composite at elevated temperatures. The influencing parameters such as temperature, sliding velocity and sliding distance are considered. The outcome response is wear rate (mm3/m) and coefficient of friction. The experiments are designed based on Taguchi [L9] array. All the experiments are considered as constant load of 10N. Analysis of variance (ANOVA) revealed that temperature is highest influencing factor followed by sliding velocity and sliding distance. Similarly, sliding velocity is most influencing factor followed by temperature and distance on coefficient of friction (COF). Finally, corroborates analytical and regression equation values by confirmation test.

  15. In Situ Elevated Temperature Testing of Fly Ash Based Geopolymer Composites

    Directory of Open Access Journals (Sweden)

    Les Vickers

    2016-06-01

    Full Text Available In situ elevated temperature investigations using fly ash based geopolymers filled with alumina aggregate were undertaken. Compressive strength and short term creep tests were carried out to determine the onset temperature of viscous flow. Fire testing using the standard cellulose curve was performed. Applying a load to the specimen as the temperature increased reduced the temperature at which viscous flow occurred (compared to test methods with no applied stress. Compressive strength increased at the elevated temperature and is attributed to viscous flow and sintering forming a more compact microstructure. The addition of alumina aggregate and reduction of water content reduced the thermal conductivity. This led to the earlier onset and shorter dehydration plateau duration times. However, crack formation was reduced and is attributed to smaller thermal gradients across the fire test specimen.

  16. Additive pressures of elevated sea surface temperatures and herbicides on symbiont-bearing foraminifera.

    Directory of Open Access Journals (Sweden)

    Joost W van Dam

    Full Text Available Elevated ocean temperatures and agrochemical pollution individually threaten inshore coral reefs, but these pressures are likely to occur simultaneously. Experiments were conducted to evaluate the combined effects of elevated temperature and the photosystem II (PSII inhibiting herbicide diuron on several types of symbiotic algae (diatom, dinoflagellate or rhodophyte of benthic foraminifera in hospite. Diuron was shown to evoke a direct effect on photosynthetic efficiency (reduced effective PSII quantum yield ΔF/F'(m, while elevated temperatures (>30 °C, only 2 °C above current average summer temperatures were observed to impact photosynthesis more indirectly by causing reductions in maximum PSII quantum yield (F(v/F(m, interpreted as photodamage. Additionally, elevated temperatures were shown to cause bleaching through loss of chlorophyll a in foraminifera hosting either diatoms or dinoflagellates. A significant linear correlation was found between reduced F(v/F(m and loss of chlorophyll a. In most cases, symbionts within foraminifera proved more sensitive to thermal stress in the presence of diuron (≥ 1 µg L(-1. The mixture toxicity model of Independent Action (IA described the combined effects of temperature and diuron on the photosystem of species hosting diatoms or dinoflagellates convincingly and in agreement with probabilistic statistics, so a response additive joint action can be assumed. We thus demonstrate that improving water quality can improve resilience of symbiotic phototrophs to projected increases in ocean temperatures. As IA described the observed combined effects from elevated temperature and diuron stress it may therefore be employed for prediction of untested mixtures and for assessing the efficacy of management measures.

  17. Additive pressures of elevated sea surface temperatures and herbicides on symbiont-bearing foraminifera.

    Science.gov (United States)

    van Dam, Joost W; Negri, Andrew P; Mueller, Jochen F; Altenburger, Rolf; Uthicke, Sven

    2012-01-01

    Elevated ocean temperatures and agrochemical pollution individually threaten inshore coral reefs, but these pressures are likely to occur simultaneously. Experiments were conducted to evaluate the combined effects of elevated temperature and the photosystem II (PSII) inhibiting herbicide diuron on several types of symbiotic algae (diatom, dinoflagellate or rhodophyte) of benthic foraminifera in hospite. Diuron was shown to evoke a direct effect on photosynthetic efficiency (reduced effective PSII quantum yield ΔF/F'(m)), while elevated temperatures (>30 °C, only 2 °C above current average summer temperatures) were observed to impact photosynthesis more indirectly by causing reductions in maximum PSII quantum yield (F(v)/F(m)), interpreted as photodamage. Additionally, elevated temperatures were shown to cause bleaching through loss of chlorophyll a in foraminifera hosting either diatoms or dinoflagellates. A significant linear correlation was found between reduced F(v)/F(m) and loss of chlorophyll a. In most cases, symbionts within foraminifera proved more sensitive to thermal stress in the presence of diuron (≥ 1 µg L(-1)). The mixture toxicity model of Independent Action (IA) described the combined effects of temperature and diuron on the photosystem of species hosting diatoms or dinoflagellates convincingly and in agreement with probabilistic statistics, so a response additive joint action can be assumed. We thus demonstrate that improving water quality can improve resilience of symbiotic phototrophs to projected increases in ocean temperatures. As IA described the observed combined effects from elevated temperature and diuron stress it may therefore be employed for prediction of untested mixtures and for assessing the efficacy of management measures.

  18. Study on Strengthening and Toughening Mechanisms of Aluminum Alloy 2618-Ti at Elevated Temperature

    Science.gov (United States)

    Kun, Ma; Tingting, Liu; Ya, Liu; Xuping, Su; Jianhua, Wang

    2018-01-01

    The tensile properties of the alloy 2618 and 2618-Ti were tested using a tensile testing machine. The morphologies of the fracture of tensile samples were observed using scanning electron microscopy. The strengthening and toughening mechanisms of alloy 2618-Ti at elevated temperature were systematically investigated based on the analyses of experimental results. The results showed that the tensile strength of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 250 and 300 °C. But the elongation of alloy 2618-Ti is much higher than that of alloy 2618 at the temperature range of 200 and 300 °C. The equal-strength temperature of intragranular and grain boundary of alloy 2618-Ti is about 235 °C. When the temperature is lower than 235 °C, the strengthening of alloy 2618-Ti is ascribed to the strengthening effect of fine grains and dispersed Al3Ti/Al18Mg3Ti2 phase. When the temperature is higher than 235 °C, the strengthening effect of alloy 2618-Ti is mainly attributed to the load transfer of Al3Ti and Al18Mg3Ti2 particles. The toughening of alloy 2618-Ti at elevated temperature is mainly ascribed to the fine grain microstructure, excellent combination between matrix and dispersed Al3Ti/Al18Mg3Ti2 particles as well as the recrystallization of the alloy at elevated temperature.

  19. EFFECTS OF ELEVATED CO2 AND TEMPERATURE ON SOIL CARBON DENSITY FRACTIONS IN A DOUGLAS FIR MESOCOSM STUDY

    Science.gov (United States)

    We conducted a 4-year full-factorial study of the effects of elevated atmospheric CO2 and temperature on Douglas fir seedlings growing in reconstructed native forest soils in mesocosms. The elevated CO2 treatment was ambient CO2 plus 200 ppm CO2. The elevated temperature treatm...

  20. Requirements on the mechanical design of reactor systems operating at elevated temperature

    International Nuclear Information System (INIS)

    Schulz, H.; Glahn, M.

    1979-01-01

    The paper presents the contemporary status of the requirements on the mechanical design and analysis developed during the licensing procedure of reactor systems operating at elevated temperature. General requirements for the design at elevated temperature are reviewed. The main proposal is to point out some limit strain criteria which are not included in present design guidelines and codes. The developed strain criteria are used to limit the component deformations in case of power excursions like the Bethe-Tait accident. It is also applicable for loads arising from other faulted conditions. (orig.)

  1. Creep Behavior of High-Strength Concrete Subjected to Elevated Temperatures

    OpenAIRE

    Minho Yoon; Gyuyong Kim; Youngsun Kim; Taegyu Lee; Gyeongcheol Choe; Euichul Hwang; Jeongsoo Nam

    2017-01-01

    Strain is generated in concrete subjected to elevated temperatures owing to the influence of factors such as thermal expansion and design load. Such strains resulting from elevated temperatures and load can significantly influence the stability of a structure during and after a fire. In addition, the lower the water-to-binder (W?B) ratio and the smaller the quantity of aggregates in high-strength concrete, the more likely it is for unstable strain to occur. Hence, in this study, the compressi...

  2. Degradation chemistry of N719 and Z-907 dyes at elevated temperatures

    DEFF Research Database (Denmark)

    Lund, Torben; Nguyen, Hoang Thai; Phuong, Nguyen Tuyet

    2009-01-01

    Degradation chemistry of N719 and Z-907 dyes at elevated temperatures.   Torben Lunda, Phuong Tuyet Nguyena and Hoang Thai Nguyenb aDepartment of Science, Systems and Models, Roskilde University, DK-4000, Denmark bDepartment of Chemistry, University of Sciences, HoChiMinh City, Vietnam......      The popular dye sensitized solar cell dyes N719 and Z-907 are in general accepted to be very stable under solar cell conditions below 45 ºC.1 The dyes, however, may undergo thiocyanate ligand substitution reactions with the DSC solvent and additive molecules at elevated temperatures (80-100 º...

  3. Fatigue of a 3D Orthogonal Non-crimp Woven Polymer Matrix Composite at Elevated Temperature

    Science.gov (United States)

    Wilkinson, M. P.; Ruggles-Wrenn, M. B.

    2017-12-01

    Tension-tension fatigue behavior of two polymer matrix composites (PMCs) was studied at elevated temperature. The two PMCs consist of the NRPE polyimide matrix reinforced with carbon fibers, but have different fiber architectures: the 3D PMC is a singly-ply non-crimp 3D orthogonal weave composite and the 2D PMC, a laminated composite reinforced with 15 plies of an eight harness satin weave (8HSW) fabric. In order to assess the performance and suitability of the two composites for use in aerospace components designed to contain high-temperature environments, mechanical tests were performed under temperature conditions simulating the actual operating conditions. In all elevated temperature tests performed in this work, one side of the test specimen was at 329 °C while the other side was open to ambient laboratory air. The tensile stress-strain behavior of the two composites was investigated and the tensile properties measured for both on-axis (0/90) and off-axis (±45) fiber orientations. Elevated temperature had little effect on the on-axis tensile properties of the two composites. The off-axis tensile strength of both PMCs decreased slightly at elevated temperature. Tension-tension fatigue tests were conducted at elevated temperature at a frequency of 1.0 Hz with a ratio of minimum stress to maximum stress of R = 0.05. Fatigue run-out was defined as 2 × 105 cycles. Both strain accumulation and modulus evolution during cycling were analyzed for each fatigue test. The laminated 2D PMC exhibited better fatigue resistance than the 3D composite. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Post-test examination under optical microscope revealed severe delamination in the laminated 2D PMC. The non-crimp 3D orthogonal weave composite offered improved delamination resistance.

  4. Study on low cycle fatigue behavior of two titanium alloy materials with elevated temperature effects

    International Nuclear Information System (INIS)

    Cai Lixun; Sun Yafang; Wang Li; Huang Shuzhen

    2000-01-01

    A serial of tensional and low cycle fatigue tests for two titanium alloy materials:T42NG and T225NG under room temperature and 350 degree C elevated temperature are carried out. Based on the test results, four monotonic constitutive relationships between stress and strain and four relationships between life Nf and strain amplitude controlled are given. By three ratio λ σ , λ Δσ and λ Nf of the materials related to the elevated temperature, systematical investigations about the influence of the elevated temperature on monotonic tensional intensity, cyclic intensity and fatigue life are performed. According to the important rule opened out that it exists a linearity relationship between the ratio λ Nf and strain amplitude Δε/2, the author present a λ-M-C model for predicting the fatigue life of a exponential material under R= -1 and an elevated temperature. To get the λ-M-C model, the authors give available discussion about the method simplified test and regression. The authors know from test results that T42NG steel has better fatigue and tensional behaviors than those of T225NG steel

  5. Acetone photophysics at 282 nm excitation at elevated pressure and temperature. II: Fluorescence modeling

    Science.gov (United States)

    Hartwig, Jason; Raju, Mandhapati; Sung, Chih-Jen

    2017-07-01

    This is the second in a series of two papers that presents an updated fluorescence model and compares with the new experimental data reported in the first paper, as well as the available literature data, to extend the range of acetone photophysics to elevated pressure and temperature conditions. This work elucidates the complete acetone photophysical model in terms of each and every competing radiative and non-radiative rate. The acetone fluorescence model is then thoroughly examined and optimized based on disparity with recently conducted elevated pressure and temperature photophysical calibration experiments. The current work offers insight into the competition between non-radiative and vibrational energy decay rates at elevated temperature and pressure and proposes a global optimization of model parameters from the photophysical model developed by Thurber (Acetone Laser-Induced Fluorescence for Temperature and Multiparameter Imaging in Gaseous Flows. PhD thesis, Stanford University Mechanical Engineering Department, 1999). The collisional constants of proportionality, which govern vibrational relaxation, are shown to be temperature dependent at elevated pressures. A new oxygen quenching rate is proposed which takes into account collisions with oxygen as well as the oxygen-assisted intersystem crossing component. Additionally, global trends in ketone photophysics are presented and discussed.

  6. Effects of elevated temperature on protein breakdown in muscles from septic rats

    International Nuclear Information System (INIS)

    Hall-Angeras, M.A.; Angeras, U.H.; Hasselgren, P.O.; Fischer, J.E.

    1990-01-01

    Elevated temperature has been proposed to contribute to accelerated muscle protein degradation during fever and sepsis. The present study examined the effect of increased temperature in vitro on protein turnover in skeletal muscles from septic and control rats. Sepsis was induced by cecal ligation and puncture (CLP); control rats were sham operated. After 16 h, the extensor digitorum longus (EDL) and soleus (SOL) muscles were incubated at 37 or 40 degrees C. Protein synthesis was determined by measuring incorporation of [14C]phenylalanine into protein. Total and myofibrillar protein breakdown was assessed from release of tyrosine and 3-methylhistidine (3-MH), respectively. Total protein breakdown was increased at 40 degrees C by 15% in EDL and by 29% in SOL from control rats, whereas 3-MH release was not affected. In muscles from septic rats, total and myofibrillar protein breakdown was increased by 22 and 30%, respectively, at 40 degrees C in EDL but was not altered in SOL. Protein synthesis was unaffected by high temperature both in septic and nonseptic muscles. The present results suggest that high temperature is not the primary mechanism of increased muscle protein breakdown in sepsis because the typical response to sepsis, i.e., a predominant increase in myofibrillar protein breakdown, was not induced by elevated temperature in normal muscle. It is possible, however, that increased temperature may potentiate protein breakdown that is already stimulated by sepsis because elevated temperature increased both total and myofibrillar protein breakdown in EDL from septic rats

  7. Improved Mechanical Properties of Various Fabric-Reinforced Geocomposite at Elevated Temperature

    Science.gov (United States)

    Samal, Sneha; Phan Thanh, Nhan; Petríková, Iva; Marvalová, Bohadana

    2015-07-01

    This article signifies the improved performance of the various types of fabric reinforcement of geopolymer as a function of physical, thermal, mechanical, and heat-resistant properties at elevated temperatures. Geopolymer mixed with designed Si:Al ratios of 15.6 were synthesized using three different types of fabric reinforcement such as carbon, E-glass, and basalt fibers. Heat testing was conducted on 3-mm-thick panels with 15 × 90 mm surface exposure region. The strength of carbon-based geocomposite increased toward a higher temperature. The basalt-reinforced geocomposite strength decreased due to the catastrophic failure in matrix region. The poor bridging effect and dissolution of fabric was observed in the E-glass-reinforced geocomposite. At an elevated temperature, fiber bridging was observed in carbon fabric-reinforced geopolymer matrix. Among all the fabrics, carbon proved to be suitable candidate for the high-temperature applications in thermal barrier coatings and fire-resistant panels.

  8. Effect of hydrogen on the integrity of aluminium–oxide interface at elevated temperatures

    KAUST Repository

    Li, Meng; Xie, De-Gang; Ma, Evan; Li, Ju; Zhang, Xixiang; Shan, Zhi-Wei

    2017-01-01

    Hydrogen can facilitate the detachment of protective oxide layer off metals and alloys. The degradation is usually exacerbated at elevated temperatures in many industrial applications; however, its origin remains poorly understood. Here by heating hydrogenated aluminium inside an environmental transmission electron microscope, we show that hydrogen exposure of just a few minutes can greatly degrade the high temperature integrity of metal–oxide interface. Moreover, there exists a critical temperature of ∼150 °C, above which the growth of cavities at the metal–oxide interface reverses to shrinkage, followed by the formation of a few giant cavities. Vacancy supersaturation, activation of a long-range diffusion pathway along the detached interface and the dissociation of hydrogen-vacancy complexes are critical factors affecting this behaviour. These results enrich the understanding of hydrogen-induced interfacial failure at elevated temperatures.

  9. Elastic Modulus of Foamcrete in Compression and Bending at Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Md Azree Othuman Mydin

    2012-09-01

    Full Text Available This paper will presents the experimental results that have been performed to examine and characterize the mechanical properties of foamcrete at elevated temperatures. Foamcrete of 650 and 1000 kg/m 3 density were cast and tested under compression and bending. The tests were done at room temperature, 100, 200, 300, 400, 500, and 600°C. The results of this study consistently demonstrated that the loss in stiffness for cement based material like foamcrete at elevated temperatures occurs predominantly after about 95°C, regardless of density. This indicates that the primary mechanism causing stiffness degradation is microcracking, which occurs as water expands and evaporates from the porous body. As expected, reducing the density of LFC reduces its strength and stiffness. However, for LFC of different densities, the normalised strength-temperature and stiffnesstemperature relationships are very similar.

  10. Concrete for PCRVs: strength of concrete under triaxial loading and creep at elevated temperatures

    International Nuclear Information System (INIS)

    Linse, D.; Aschl, H.; Stoeckl, S.

    1975-01-01

    To provide detailed information for the calculation of prestressed concrete reactor vessels, investigations of the behaviour of concrete under multiaxial loading and on creep at elevated temperatures were made at the Institut fuer Massivbau of the Technical University of Munich. The strength of concrete under triaxial compression is dependent on the stress ratio. The less the stresses differ from hydrostatic compression the more strength increases. Triaxial compression increases very much the deformability of concrete. Plastic deformations of +-10% and more (all stresses compression, but not equal, strains compression or tension) are possible without large cracks. The creep deformations are considerably dependent on the temperature. Creep at 80 0 C is about three to four times higher than at 20 0 C. The Poisson's ratio of creep at elevated temperature seems to be bigger than at normal temperatures at a rate of loading of 35% and 50% of the ultimate strength. (Auth.)

  11. Effect of hydrogen on the integrity of aluminium–oxide interface at elevated temperatures

    KAUST Repository

    Li, Meng

    2017-02-20

    Hydrogen can facilitate the detachment of protective oxide layer off metals and alloys. The degradation is usually exacerbated at elevated temperatures in many industrial applications; however, its origin remains poorly understood. Here by heating hydrogenated aluminium inside an environmental transmission electron microscope, we show that hydrogen exposure of just a few minutes can greatly degrade the high temperature integrity of metal–oxide interface. Moreover, there exists a critical temperature of ∼150 °C, above which the growth of cavities at the metal–oxide interface reverses to shrinkage, followed by the formation of a few giant cavities. Vacancy supersaturation, activation of a long-range diffusion pathway along the detached interface and the dissociation of hydrogen-vacancy complexes are critical factors affecting this behaviour. These results enrich the understanding of hydrogen-induced interfacial failure at elevated temperatures.

  12. "Ultra"-Fast Fracture Strength of Advanced Structural Ceramic Materials Studied at Elevated Temperatures

    Science.gov (United States)

    Choi, Sung R.; Gyekenyesi, John P.

    1999-01-01

    The accurate determination of inert strength is important in reliable life prediction of structural ceramic components. At ambient temperature, the inert strength of a brittle material is typically regarded as free of the effects of slow crack growth due to stress corrosion. Therefore, the inert strength can be determined either by eliminating active species, especially moisture, with an appropriate inert medium, or by using a very high test rate. However, at elevated temperatures, the concept or definition of the inert strength of brittle ceramic materials is not clear, since temperature itself is a degrading environment, resulting in strength degradation through slow crack growth and/or creep. Since the mechanism to control strength is rate-dependent viscous flow, the only conceivable way to determine the inert strength at elevated temperatures is to utilize a very fast test rate that either minimizes the time for or eliminates slow crack growth. Few experimental studies have measured the elevated-temperature, inert (or "ultra"-fast fracture) strength of advanced ceramics. At the NASA Lewis Research Center, an experimental study was initiated to better understand the "ultra"-fast fracture strength behavior of advanced ceramics at elevated temperatures. Fourteen advanced ceramics - one alumina, eleven silicon nitrides, and two silicon carbides - have been tested using constant stress-rate (dynamic fatigue) testing in flexure with a series of stress rates including the "ultra"-fast stress rate of 33 000 MPa/sec with digitally controlled test frames. The results for these 14 advanced ceramics indicate that, notwithstanding possible changes in flaw populations as well as flaw configurations because of elevated temperatures, the strength at 33 000 MPa/sec approached the room-temperature strength or reached a higher value than that determined at the conventional test rate of 30 MPa/sec. On the basis of the experimental data, it can be stated that the elevated-temperature

  13. Design of Cold-Formed Steel Screw Connections with Gypsum Sheathing at Ambient and Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Wei Chen

    2016-09-01

    Full Text Available Load-bearing cold-formed steel (CFS walls sheathed with double layers of gypsum plasterboard on both sides have demonstrated good fire resistance and attracted increasing interest for use in mid-rise CFS structures. As the main connection method, screw connections between CFS and gypsum sheathing play an important role in both the structural design and fire resistance of this wall system. However, studies on the mechanical behavior of screw connections with double-layer gypsum sheathing are still limited. In this study, 200 monotonic tests of screw connections with single- or double-layer gypsum sheathing at both ambient and elevated temperatures were conducted. The failure of screw connections with double-layer gypsum sheathing in shear was different from that of single-layer gypsum sheathing connections at ambient temperature, and it could be described as the breaking of the loaded sheathing edge combined with significant screw tilting and the loaded sheathing edge flexing fracture. However, the screw tilting and flexing fracture of the loaded sheathing edge gradually disappear at elevated temperatures. In addition, the influence of the loaded edge distance, double-layer sheathing and elevated temperatures is discussed in detail with clear conclusions. A unified design formula for the shear strength of screw connections with gypsum sheathing is proposed for ambient and elevated temperatures with adequate accuracy. A simplified load–displacement model with the post-peak branch is developed to evaluate the load–displacement response of screw connections with gypsum sheathing at ambient and elevated temperatures.

  14. Elastic and strength properties of Hanford concrete mixes at room and elevated temperatures

    International Nuclear Information System (INIS)

    Abrams, M.S.; Gillen, M.; Campbell, D.H.

    1979-03-01

    The effects of long-term exposure to elevated temperatures on the physical properties of concrete mixes used in Hanford radioactive waste storage tanks were determined. Temperature had a significant effect on the elastic modulus of concretes. Poisson's ratio determined by the sonic method remained relatively constant. The splitting tensile strength increased rapidly up to 190 days of age. Then strength decreased to about 350 days and either leveled off or increased from that point on. Compressive strength data were erratic

  15. Drought-induced weakening of growth-temperature associations in high-elevation Iberian pines

    Czech Academy of Sciences Publication Activity Database

    Diego Galvan, J.; Büntgen, Ulf; Ginzler, Ch.; Grudd, H.; Gutierrez, E.; Labuhn, I.; Julio Camarero, J.

    2015-01-01

    Roč. 124, JAN (2015), s. 95-106 ISSN 0921-8181 Institutional support: RVO:67179843 Keywords : tree-ring chronologies * regional curve standardization * pinus-uncinata * european alps * spatial variability * summer temperatures * divergence problem * spanish pyrenees * fagus-sylvatica * large-scale * Climate change * Drought * Growth response * High-elevation forest * Pyrenees * Summer temperature Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.548, year: 2015

  16. The Impact of Elevated Temperatures on Continental Carbon Cycling in the Paleogene

    Science.gov (United States)

    Pancost, R. D.; Handley, L.; Taylor, K. W.; Collinson, M. E.; Weijers, J.; Talbot, H. M.; Hollis, C. J.; Grogan, D. S.; Whiteside, J. H.

    2010-12-01

    Recent climate and biogeochemical modelling suggests that methane flux from wetlands and soils was greater during past greenhouse climates, due to a combination of higher continental temperatures, an enhanced hydrological cycle, and elevated primary production. Here, we examine continental environments in the Paleogene using a range of biomarker proxies (complemented by palaeobotanical approaches), including air temperatures derived from the distribution of soil bacterial glycerol dialkyl glycerol tetraethers (the MBT/CBT proxy), as well as evidence from wetland and lacustrine settings for enhanced methane cycling. Previously published and new MBT/CBT records parallel sea surface temperature records, suggesting elevated continental temperatures during the Eocene even at mid- to high latitudes (New Zealand, 20-28°C; the Arctic, 17°C; across the Sierra Nevada, 15-25°C; and SE England, 20-30°C). Such temperatures are broadly consistent with paleobotanical records and would have directly led to increased methane production via the metabolic impact of temperature on rates of methanogenesis. To test this, we have determined the distributions and carbon isotopic compositions of archaeal ether lipids and bacterial hopanoids in thermally immature Eocene lignites. In particular, the Cobham lignite, deposited in SE England and spanning the PETM, is characterised by markedly higher concentrations of both methanogen and methanotroph biomarkers compared to modern and Holocene temperate peats. Elevated temperatures, by fostering either stratification and/or decreased oxygen solubility, could have also led to enhanced methane production in Paleogene lakes. Both the Messel Shale (Germany) and Green River Formation, specifically the Parachute Creek oil shale horizons (Utah and Wyoming), are characterised by strongly reducing conditions (including euxinic conditions in the latter), as well as abundant methanogen and methanotroph biomarkers. Such results confirm model predictions

  17. Elevated CO2 and temperature increase soil C losses from a soybean-maize ecosystem.

    Science.gov (United States)

    Black, Christopher K; Davis, Sarah C; Hudiburg, Tara W; Bernacchi, Carl J; DeLucia, Evan H

    2017-01-01

    Warming temperatures and increasing CO 2 are likely to have large effects on the amount of carbon stored in soil, but predictions of these effects are poorly constrained. We elevated temperature (canopy: +2.8 °C; soil growing season: +1.8 °C; soil fallow: +2.3 °C) for 3 years within the 9th-11th years of an elevated CO 2 (+200 ppm) experiment on a maize-soybean agroecosystem, measured respiration by roots and soil microbes, and then used a process-based ecosystem model (DayCent) to simulate the decadal effects of warming and CO 2 enrichment on soil C. Both heating and elevated CO 2 increased respiration from soil microbes by ~20%, but heating reduced respiration from roots and rhizosphere by ~25%. The effects were additive, with no heat × CO 2 interactions. Particulate organic matter and total soil C declined over time in all treatments and were lower in elevated CO 2 plots than in ambient plots, but did not differ between heat treatments. We speculate that these declines indicate a priming effect, with increased C inputs under elevated CO 2 fueling a loss of old soil carbon. Model simulations of heated plots agreed with our observations and predicted loss of ~15% of soil organic C after 100 years of heating, but simulations of elevated CO 2 failed to predict the observed C losses and instead predicted a ~4% gain in soil organic C under any heating conditions. Despite model uncertainty, our empirical results suggest that combined, elevated CO 2 and temperature will lead to long-term declines in the amount of carbon stored in agricultural soils. © 2016 John Wiley & Sons Ltd.

  18. Visualizing Stress and Temperature Distribution During Elevated Temperature Deformation of IN-617 Using Nanomechanical Raman Spectroscopy

    Science.gov (United States)

    Zhang, Yang; Wang, Hao; Tomar, Vikas

    2018-04-01

    This work presents direct measurements of stress and temperature distribution during the mesoscale microstructural deformation of Inconel-617 (IN-617) during 3-point bending tests as a function of temperature. A novel nanomechanical Raman spectroscopy (NMRS)-based measurement platform was designed for simultaneous in situ temperature and stress mapping as a function of microstructure during deformation. The temperature distribution was found to be directly correlated to stress distribution for the analyzed microstructures. Stress concentration locations are shown to be directly related to higher heat conduction and result in microstructural hot spots with significant local temperature variation.

  19. ELEVATED CO2 AND ELEVATED TEMPERATURE HAVE NO EFFECT ON DOUGLAS-FIR FINE-ROOT DYNAMICS IN NITROGEN-POOR SOIL

    Science.gov (United States)

    Here, we investigate fine-root production, mortality and standing crop of Douglas-fir (Pseudotsuga menziesii) seedlings exposed to elevated atmospheric CO2 and elevated air temperature. We hypothesized that these treatments would increase fine-root production, but that mortality ...

  20. IN-VITRO PREDEGRADATION AT ELEVATED-TEMPERATURES OF POLY(LACTIDE)

    NARCIS (Netherlands)

    BERGSMA, JE; ROZEMA, FR; BOS, RRM; BOERING, G; JOZIASSE, CAP; PENNINGS, AJ

    1995-01-01

    In this study in vitro predegradation at elevated temperatures, used to obtain an increased degradation rate, was investigated. The in vitro degradation was followed by mass loss, molecular weight loss and changes in thermal properties. Two biodegradable polymers, the homopolymer PLLA and a

  1. A Review of the Effects of Elevated Temperature on Concrete Materials and Structures

    International Nuclear Information System (INIS)

    Naus, D.J.; Graves, H.L. III

    2006-01-01

    Concrete's properties are more complex than those of most materials because not only is concrete a composite material whose constituents have different properties, but its properties depend upon moisture and porosity. Exposure of concrete to elevated temperature affects its mechanical and physical properties. Elements could distort and displace, and, under certain conditions, the concrete surfaces could spall due to the buildup of steam pressure. Because thermally-induced dimensional changes, loss of structural integrity, and release of moisture and gases resulting from the migration of free water could adversely affect plant operations and safety, a complete understanding of the behavior of concrete under long-term elevated-temperature exposure as well as both during and after a thermal excursion resulting from a postulated design-basis accident condition is essential for reliable design evaluations and assessments of nuclear power plant structures. As the properties of concrete change with respect to time and the environment to which it is exposed, an assessment of the effects of concrete aging is also important in performing safety evaluations. The effects of elevated temperature on Portland cement concretes and constituent materials are summarized, design codes and standards identified, and considerations for elevated temperature service noted. (authors)

  2. Determination of the potentiostatic stability of PEMFC electro catalysts at elevated temperatures

    NARCIS (Netherlands)

    Dam, V.A.T.; Jayasayee, K.; Bruijn, de F.A.

    2009-01-01

    The electrochemical stability of platinum on carbon catalyst (Hispec TM 4000, Johnson Matthey) has been investigated predominantly at constant potentials ranging from 0.95 to 1.25 V at elevated temperatures. By combining a quartz crystal microbalance (QCM) with electrochemical techniques, dynamic

  3. Physical and chemical changes in whey protein concentrate stored at elevated temperature and humidity

    Science.gov (United States)

    The chemistry of whey protein concentrate (WPC) under adverse storage conditions was monitored to provide information on shelf life in hot, humid areas. WPC34 (34.9 g protein/100 g) and WPC80 (76.8 g protein/100 g) were stored for up to 18 mo under ambient conditions and at elevated temperature and...

  4. Effects of elevated water temperature on physiological responses in adult freshwater mussels

    Science.gov (United States)

    Ganser, Alissa M.; Newton, Teresa J.; Haro, Roger J.

    2015-01-01

    Freshwater mussels (order Unionoida) face multiple environmental stressors, which pose serious conservation challenges to this diverse assemblage of aquatic invertebrates. Of these stressors, elevated water temperature from global climate change and other anthropogenic sources may be the most ubiquitous and could be placing many mussel populations dangerously close to their thermal maxima.

  5. Elevated temperature mechanical properties of a rapidly solidified A1-Fe-V-Si alloy

    International Nuclear Information System (INIS)

    Mitra, S.

    1992-01-01

    Dispersion strengthened Al alloys based on the Al-Fe-V-Si quartenary system have recently been developed using rapid solidification techniques. Rapid solidification techniques which resulted in the above mentioned alloys have also been used to manufacture another commercial alloy, FVS 1212, with 37 volume % of dispersoid. The alloy has shown excellent resistance to coarsening at high temperatures and to creep deformation. Elevated temperature exposure of FVS 1212, for times up to 100 hours, resulted in a significant loss in room temperature mechanical properties only beyond 500 degrees C while 1000 hours at 425 degrees C did not result in any degradation of mechanical but no detailed study of the tensile behavior of FVS 1212 at slow strain rates and elevated temperatures has been reported to date. This paper reports that the present study was undertaken to investigate the tensile behavior of FVS 1212 from room temperature to 400 degrees C at strain rates of 6.56 x 10 - 5/sec and 6.56 x 10 -6 /sec. The study focussed on dynamic strain aging effects and strain hardening behavior, while the effect of strain rate on the flow behavior at elevated temperatures was also evaluated

  6. Burst pressure of super duplex stainless steel pipes subject to combined axial tension, internal pressure and elevated temperature

    International Nuclear Information System (INIS)

    Lasebikan, B.A.; Akisanya, A.R.

    2014-01-01

    The burst pressure of super duplex stainless steel pipe is measured under combined internal pressure, external axial tension and elevated temperature up to 160 °C. The experimental results are compared with existing burst pressure prediction models. Existing models are found to provide reasonable estimate of the burst pressure at room temperature but significantly over estimate the burst pressure at elevated temperature. Increasing externally applied axial stress and elevated temperature reduces the pressure capacity. - Highlights: • The burst pressure of super duplex steel is measured under combined loading. • Effect of elevated temperature on burst pressure is determined. • Burst pressure decreases with increasing temperature. • Existing models are reliable at room temperature. • Burst strength at elevated temperature is lower than predictions

  7. GWAS of Barley Phenotypes Established Under Future Climate Conditions of Elevated Temperature, CO2, O3 and Elevated Temperature and CO2 Combined

    DEFF Research Database (Denmark)

    Ingvordsen, Cathrine Heinz; Backes, G.; Lyngkjær, M. F.

    2015-01-01

    Climate change is likely to decrease crop yields worldwide. Developing climate resilient cultivars is one way to combat this production scarcity, however, little is known of crop response to future climate conditions and in particular the variability within crops.In Scandinavia, barley is widely...... cultivated, but yields have stagnated since the start of this century. In this study we cultivated 138 spring barley accessions in a climate phytotron under four treatments mimicking forecasted levels of temperature, carbon dioxide concentration ([CO2]) and ozone ([O3]) at the end of the 21st century1...... yield, grain protein concentration, grain protein harvested, number of grains, number of ears, aboveground vegetative biomass and harvest index. In addition, stability of the production was calculated over the applied treatments for the assessed parameters.In the climate scenario of elevated temperature...

  8. Creep of Sylramic-iBN Fiber Tows at Elevated Temperature in Air and in Silicic Acid-Saturated Steam

    Science.gov (United States)

    2015-06-01

    CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM ...protection in the United States. AFIT-ENY-15-J-46 CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM ...DISTRIBUTION UNLIMITED. AFIT-ENY-15-J-46 CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM

  9. High-fluence hyperthermal ion irradiation of gallium nitride surfaces at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Finzel, A.; Gerlach, J.W., E-mail: juergen.gerlach@iom-leipzig.de; Lorbeer, J.; Frost, F.; Rauschenbach, B.

    2014-10-30

    Highlights: • Irradiation of gallium nitride films with hyperthermal nitrogen ions. • Surface roughening at elevated sample temperatures was observed. • No thermal decomposition of gallium nitride films during irradiation. • Asymmetric surface diffusion processes cause local roughening. - Abstract: Wurtzitic GaN films deposited on 6H-SiC(0001) substrates by ion-beam assisted molecular-beam epitaxy were irradiated with hyperthermal nitrogen ions with different fluences at different substrate temperatures. In situ observations with reflection high energy electron diffraction showed that during the irradiation process the surface structure of the GaN films changed from two dimensional to three dimensional at elevated temperatures, but not at room temperature. Atomic force microscopy revealed an enhancement of nanometric holes and canyons upon the ion irradiation at higher temperatures. The roughness of the irradiated and heated GaN films was clearly increased by the ion irradiation in accordance with x-ray reflectivity measurements. A sole thermal decomposition of the films at the chosen temperatures could be excluded. The results are discussed taking into account temperature dependent sputtering and surface uphill adatom diffusion as a function of temperature.

  10. The elevated temperature and thermal shock fracture toughnesses of nuclear pressure vessel steel

    International Nuclear Information System (INIS)

    Hirano, Kazumi; Kobayashi, Hideo; Nakazawa, Hajime; Nara, Atsushi.

    1979-01-01

    Thermal shock experiments were conducted on nuclear pressure vessel steel A533 Grade B Class 1. Elastic-plastic fracture toughness tests were carried out within the same high temperature range of the thermal shock experiment and the relation between stretched zone width, SZW and J-integral was clarified. An elastic-plastic thermal shock fracture toughness value. J sub(tsc) was evaluated from a critical value of stretched zone width, SZW sub(tsc) at the initiation of thermal shock fracture by using the relation between SZW and J. The J sub(tsc) value was compared with elastic-plastic fracture toughness values, J sub( ic), and the difference between the J sub(tsc) and J sub( ic) values was discussed. The results obtained are summarized as follows; (1) The relation between SZW and J before the initiation of stable crack growth in fracture toughness test at a high temperature can be expressed by the following equation regardless of test temperature, SZW = 95(J/E), where E is Young's modulus. (2) Elevated temperature fracture toughness values ranging from room temperature to 400 0 C are nearly constant regardless of test temperature. It is confirmed that upper shelf fracture toughness exists. (3) Thermal shock fracture toughness is smaller than elevated temperature fracture toughness within the same high temperature range of thermal shock experiment. (author)

  11. The Mechanical Behavior of a 25Cr Super Duplex Stainless Steel at Elevated Temperature

    Science.gov (United States)

    Lasebikan, B. A.; Akisanya, A. R.; Deans, W. F.

    2013-02-01

    Super duplex stainless steel (SDSS) is a candidate material for production tubing in oil and gas wells and subsea pipelines used to transport corrosive hydrocarbon fluids. The suitability of this material for high temperature applications is examined in this article. The uniaxial tensile properties are determined for a 25Cr SDSS over a range of temperature relevant to high pressure-high temperature oil and gas wells. It is shown that there is a significant effect of temperature on the uniaxial tensile properties. Elevated temperature was shown to reduce the Young's modulus and increase the strain hardening index; temperature effects on these two parameters are usually neglected in the design of subsea pipelines and oil well tubulars, and this could lead to wrong predictions of the collapse pressure. The manufacturing process of the super duplex tubular did not lead to significant anisotropy in the hardness and the ultimate tensile and uniaxial yield strengths.

  12. The Coupling of Treeline Elevation and Temperature is Mediated by Non-Thermal Factors on the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Yafeng Wang

    2017-04-01

    Full Text Available Little is known about the relationships between treeline elevation and climate at regional and local scales. It is compelling to fill this research gap with data from the Tibetan Plateau where some of the highest alpine treelines in the world are found. This research question partially results from the lack of in situ temperature data at treeline sites. Herein, treeline variables (e.g., elevation, topography, tree species and temperature data were collected from published investigations performed during this decade on the Tibetan Plateau. Temperature conditions near treeline sites were estimated using global databases and these estimates were corrected by using in situ air temperature measurements. Correlation analyses and generalized linear models were used to evaluate the effects of different variables on treeline elevation including thermal (growing-season air temperatures and non-thermal (latitude, longitude, elevation, tree species, precipitation, radiation factors. The commonality analysis model was applied to explore how several variables (July mean temperature, elevation of mountain peak, latitude were related to treeline elevation. July mean temperature was the most significant predictor of treeline elevation, explaining 55% of the variance in treeline elevation across the Tibetan Plateau, whereas latitude, tree species, and mountain elevation (mass-elevation effect explained 30% of the variance in treeline elevation. After considering the multicollinearity among predictors, July mean temperature (largely due to the influence of minimum temperature still showed the strongest association with treeline elevation. We conclude that the coupling of treeline elevation and July temperature at a regional scale is modulated by non-thermal factors probably acting at local scales. Our results contribute towards explaining the decoupling between climate warming and treeline dynamics.

  13. Creep Behavior of High-Strength Concrete Subjected to Elevated Temperatures.

    Science.gov (United States)

    Yoon, Minho; Kim, Gyuyong; Kim, Youngsun; Lee, Taegyu; Choe, Gyeongcheol; Hwang, Euichul; Nam, Jeongsoo

    2017-07-11

    Strain is generated in concrete subjected to elevated temperatures owing to the influence of factors such as thermal expansion and design load. Such strains resulting from elevated temperatures and load can significantly influence the stability of a structure during and after a fire. In addition, the lower the water-to-binder (W-B) ratio and the smaller the quantity of aggregates in high-strength concrete, the more likely it is for unstable strain to occur. Hence, in this study, the compressive strength, elastic modulus, and creep behavior were evaluated at target temperatures of 100, 200, 300, 500, and 800 °C for high-strength concretes with W-B ratios of 30%, 26%, and 23%. The loading conditions were set as non-loading and 0.33f cu . It was found that as the compressive strength of the concrete increased, the mechanical characteristics deteriorated and transient creep increased. Furthermore, when the point at which creep strain occurred at elevated temperatures after the occurrence of transient creep was considered, greater shrinkage strain occurred as the compressive strength of the concrete increased. At a heating temperature of 800 °C, the 80 and 100 MPa test specimens showed creep failure within a shrinkage strain range similar to the strain at the maximum load.

  14. Creep Behavior of High-Strength Concrete Subjected to Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Minho Yoon

    2017-07-01

    Full Text Available Strain is generated in concrete subjected to elevated temperatures owing to the influence of factors such as thermal expansion and design load. Such strains resulting from elevated temperatures and load can significantly influence the stability of a structure during and after a fire. In addition, the lower the water-to-binder (W–B ratio and the smaller the quantity of aggregates in high-strength concrete, the more likely it is for unstable strain to occur. Hence, in this study, the compressive strength, elastic modulus, and creep behavior were evaluated at target temperatures of 100, 200, 300, 500, and 800 °C for high-strength concretes with W–B ratios of 30%, 26%, and 23%. The loading conditions were set as non-loading and 0.33fcu. It was found that as the compressive strength of the concrete increased, the mechanical characteristics deteriorated and transient creep increased. Furthermore, when the point at which creep strain occurred at elevated temperatures after the occurrence of transient creep was considered, greater shrinkage strain occurred as the compressive strength of the concrete increased. At a heating temperature of 800 °C, the 80 and 100 MPa test specimens showed creep failure within a shrinkage strain range similar to the strain at the maximum load.

  15. Proteomic responses to elevated ocean temperature in ovaries of the ascidian Ciona intestinalis

    Directory of Open Access Journals (Sweden)

    Chelsea E. Lopez

    2017-07-01

    Full Text Available Ciona intestinalis, a common sea squirt, exhibits lower reproductive success at the upper extreme of the water temperatures it experiences in coastal New England. In order to understand the changes in protein expression associated with elevated temperatures, and possible response to global temperature change, we reared C. intestinalis from embryos to adults at 18°C (a temperature at which they reproduce normally at our collection site in Rhode Island and 22°C (the upper end of the local temperature range. We then dissected ovaries from animals at each temperature, extracted protein, and measured proteomic levels using shotgun mass spectrometry (LC-MS/MS. 1532 proteins were detected at a 1% false discovery rate present in both temperature groups by our LC-MS/MS method. 62 of those proteins are considered up- or down-regulated according to our statistical criteria. Principal component analysis shows a clear distinction in protein expression pattern between the control (18°C group and high temperature (22°C group. Similar to previous studies, cytoskeletal and chaperone proteins are upregulated in the high temperature group. Unexpectedly, we find evidence that proteolysis is downregulated at the higher temperature. We propose a working model for the high temperature response in C. intestinalis ovaries whereby increased temperature induces upregulation of signal transduction pathways involving PTPN11 and CrkL, and activating coordinated changes in the proteome especially in large lipid transport proteins, cellular stress responses, cytoskeleton, and downregulation of energy metabolism.

  16. Effects of elevated temperature postharvest on color aspect, physiochemical characteristics, and aroma components of pineapple fruits.

    Science.gov (United States)

    Liu, Chuanhe; Liu, Yan

    2014-12-01

    In this work, 2 separate experiments were performed to describe the influence of elevated temperature treatments postharvest on the color, physiochemical characteristics and aroma components of pineapple fruits during low-temperature seasons. The L* (lightness) values of the skin and pulp of pineapple fruits were decreased. The a* (greenness-redness) and b* (blueness-yellowness) values of the skin and pulp were all markedly increased. The elevated temperature significantly increased the contents of total soluble solids (TSS) and slightly affected contents of vitamin C (nonsignificant). Titratable acidity (TA) of pineapple fruits were notably decreased, whereas the values of TSS/TA of pineapple fruits were significantly increased. The firmness of the pineapple fruits decreased and more esters and alkenes were identified. The total relative contents of esters were increased, and the total relative contents of alkenes were decreased. © 2014 Institute of Food Technologists®

  17. Temperature elevation in the eye of anatomically based human head models for plane-wave exposures

    International Nuclear Information System (INIS)

    Hirata, A; Watanabe, S; Fujiwara, O; Kojima, M; Sasaki, K; Shiozawa, T

    2007-01-01

    This study investigated the temperature elevation in the eye of anatomically based human head models for plane-wave exposures. The finite-difference time-domain method is used for analyzing electromagnetic absorption and temperature elevation. The eyes in the anatomic models have average dimensions and weight. Computational results show that the ratio of maximum temperature in the lens to the eye-average SAR (named 'heating factor for the lens') is almost uniform (0.112-0.147 deg. C kg W -1 ) in the frequency region below 3 GHz. Above 3 GHz, this ratio increases gradually with an increase of frequency, which is attributed to the penetration depth of an electromagnetic wave. Particular attention is paid to the difference in the heating factor for the lens between this study and earlier works. Considering causes clarified in this study, compensated heating factors in all these studies are found to be in good agreement

  18. Towards the standardization of time--temperature parameter usage in elevated temperature data analysis

    International Nuclear Information System (INIS)

    Goldhoff, R.M.

    1975-01-01

    Work devoted to establishment of recommended practices for correlating and extrapolating relevant data on creep-rupture properties of materials at high temperatures is described. An analysis of the time-temperature parameter is included along with descriptions of analysis and evaluation methods. Results of application of the methods are compared

  19. Shape of isolated domains in lithium tantalate single crystals at elevated temperatures

    International Nuclear Information System (INIS)

    Shur, V. Ya.; Akhmatkhanov, A. R.; Baturin, I. S.; Chezganov, D. S.; Lobov, A. I.; Smirnov, M. M.

    2013-01-01

    The shape of isolated domains has been investigated in congruent lithium tantalate (CLT) single crystals at elevated temperatures and analyzed in terms of kinetic approach. The obtained temperature dependence of the growing domain shape in CLT including circular shape at temperatures above 190 °C has been attributed to increase of relative input of isotropic ionic conductivity. The observed nonstop wall motion and independent domain growth after merging in CLT as opposed to stoichiometric lithium tantalate have been attributed to difference in wall orientation. The computer simulation has confirmed applicability of the kinetic approach to the domain shape explanation

  20. Guidelines for the structural design of experimental multi-purpose VHTR at the elevated temperature services

    International Nuclear Information System (INIS)

    Nomura, Sueo; Uga, Takeo; Miyamoto, Yoshiaki; Muto, Yasushi; Ikushima, Takeshi

    1976-02-01

    The guidelines are presented for structural design of the experimental multi-purpose VHTR(Very High Temperature Reactor) at the elevated temperature services. Covered are features of the VHTR structural design, specifications, safety design, seismic design, failure modes to be considered, stress criteria for various load combinations and the mechanical properties of the materials. The guidelines were prepared by referring to safety criteria of high-temperature gas cooled reactors, ASME Boiler and Pressure Vessel code, Section III, case 1592 and the domestic seismic design guide of nuclear power facilities. (auth.)

  1. Extended exposure to elevated temperature affects escape response behaviour in coral reef fishes

    Directory of Open Access Journals (Sweden)

    Donald T. Warren

    2017-08-01

    Full Text Available The threat of predation, and the prey’s response, are important drivers of community dynamics. Yet environmental temperature can have a significant effect on predation avoidance techniques such as fast-start performance observed in marine fishes. While it is known that temperature increases can influence performance and behaviour in the short-term, little is known about how species respond to extended exposure during development. We produced a startle response in two species of damselfish, the lemon damsel Pomacentrus moluccensis, and the Ambon damselfish Pomacentrus amboinensis, by the repeated use of a drop stimulus. We show that the length of thermal exposure of juveniles to elevated temperature significantly affects this escape responses. Short-term (4d exposure to warmer temperature affected directionality and responsiveness for both species. After long-term (90d exposure, only P. moluccensis showed beneficial plasticity, with directionality returning to control levels. Responsiveness also decreased in both species, possibly to compensate for higher temperatures. There was no effect of temperature or length of exposure on latency to react, maximum swimming speed, or escape distance suggesting that the physical ability to escape was maintained. Evidence suggests that elevated temperature may impact some fish species through its effect on the behavioural responses while under threat rather than having a direct influence on their physical ability to perform an effective escape response.

  2. Characterization of the magnetic properties of NdFeB thick films exposed to elevated temperatures

    Science.gov (United States)

    Fujiwara, Ryogen; Devillers, Thibaut; Givord, Dominique; Dempsey, Nora M.

    2018-05-01

    Hard magnetic films used in magnetic micro-systems may be exposed to elevated temperatures during film and system fabrication and also during use of the micro-system. In this work, we studied the influence of temperature on the magnetic properties of 10 μm thick out-of-plane textured NdFeB films fabricated by high rate triode sputtering. Out-of-plane hysteresis loops were measured in the range 300K - 650K to establish the temperature dependence of coercivity, magnetization at 7 T and remanent magnetization. Thermal demagnetization was measured and magnetization losses were recorded from 350K in films heated under zero or low (-0.1 T) external field and from 325 K for films heated under an external field of -0.5 T. The effect of thermal cycling under zero field on the remanent magnetization was also studied and it was found that cycling between room temperature and 323 K did not lead to any significant loss in remanence at room temperature, while a 4% drop is recorded when the sample is cycled between RT and 343K. Measurement of hysteresis loops at room temperature following exposure to elevated temperatures reveals that while remanent magnetisation is practically recovered in all cases, irreversible losses in coercivity occur (6.7 % following heating to 650K, and 1.3 % following heating to 343K). The relevance of these results is discussed in terms of system fabrication and use.

  3. Part-load performance of a high temperature Kalina cycle

    International Nuclear Information System (INIS)

    Modi, Anish; Andreasen, Jesper Graa; Kærn, Martin Ryhl; Haglind, Fredrik

    2015-01-01

    Highlights: • Detailed algorithm to solve high temperature Kalina cycle in part load. • A central receiver concentrating solar power plant with direct vapour generation considered as case study. • Part-load performance curves and fitted equations presented. - Abstract: The Kalina cycle has recently seen increased interest as an alternative to the conventional steam Rankine cycle. The cycle has been studied for use with both low and high temperature applications such as geothermal power plants, ocean thermal energy conversion, waste heat recovery, gas turbine bottoming cycle, and solar power plants. The high temperature cycle layouts are inherently more complex than the low temperature layouts due to the presence of a distillation-condensation subsystem, three pressure levels, and several heat exchangers. This paper presents a detailed approach to solve the Kalina cycle in part-load operating conditions for high temperature (a turbine inlet temperature of 500 °C) and high pressure (100 bar) applications. A central receiver concentrating solar power plant with direct vapour generation is considered as a case study where the part-load conditions are simulated by changing the solar heat input to the receiver. Compared with the steam Rankine cycle, the Kalina cycle has an additional degree of freedom in terms of the ammonia mass fraction which can be varied in order to maximize the part-load efficiency of the cycle. The results include the part-load curves for various turbine inlet ammonia mass fractions and the fitted equations for these curves.

  4. Determining noncondensible gas fractions at elevated temperatures and pressures using wet and dry bulb temperature measurements

    International Nuclear Information System (INIS)

    Griffith, P.; Bowman, J.

    1987-01-01

    The work reported in this note was undertaken to provide a method of determining the noncondensible gas fractions in a steam-gas mixture such as might be found in large reactor safety experiment like LOFT. In essence, the method used involves measuring the wet and dry bulb temperatures and using an algorithm, in place of the psychometric chart, to determine the partial pressure of the noncondensible gas in the mixture. In accomplishing this, the authors did the following: (1) extended the use of wet and dry-bulb temperature readings to determine mixture composition up to a temperature of 589 K and a pressure of 4.13 x 10 6 Pa. (2) developed an algorithm to reduce the data (3) found which materials would survive those temperatures

  5. The likely impact of elevated [CO2], nitrogen deposition, increased temperature and management on carbon sequestration in temperate and boreal forest ecosystems: a literature review

    Science.gov (United States)

    Riitta Hyvönen; Göran I. Ågren; Sune Linder; Tryggve Persson; M. Francesca Cotrufo; Alf Ekblad; Michael Freeman; Achim Grelle; Ivan A. Janssens; Paul G. Jarvis; Seppo Kellomäki; Anders Lindroth; Denis Loustau; Tomas Lundmark; Richard J. Norby; Ram Oren; Kim Pilegaard; Michael G. Ryan; Bjarni D. Sigurdsson; Monika Strömgren; Marcel van Oijen; Göran Wallin

    2007-01-01

    Temperate and boreal forest ecosystems contain a large part of the carbon stored on land, in the form of both biomass and soil organic matter. Increasing atmospheric [CO2], increasing temperature, elevated nitrogen deposition and intensified management will change this C store. Well documented single-factor responses of net primary production are: higher photosynthetic...

  6. Effect of Elevated Temperature on the Residual Properties of Quartzite, Granite and Basalt Aggregate Concrete

    Science.gov (United States)

    Masood, A.; Shariq, M.; Alam, M. Masroor; Ahmad, T.; Beg, A.

    2018-05-01

    In the present study, experimental investigations have been carried out to determine the effect of elevated temperature on the residual properties of quartzite, granite and basalt aggregate concrete mixes. Ultrasonic pulse velocity and unstressed residual compressive strength tests on cube specimens have been conducted at ambient and after single heating-cooling cycle of elevated temperature ranging from 200 to 600 °C. The relationship between ultrasonic pulse velocity and residual compressive strength of all concrete mixes have been developed. Scanning electron microscopy was also carried out to study micro structure of quartzite, granite and basalt aggregate concrete subjected to single heating-cooling cycle of elevated temperature. The results show that the residual compressive strength of quartzite aggregate concrete has been found higher than granite and basalt aggregate concrete at ambient and at all temperatures. It has also been found that the loss of strength in concrete is due to the development of micro-cracks result in failure of cement matrix and coarse aggregate bond. Further, the basalt aggregate concrete has been observed lower strength due to low affinity with Portland cements ascribed to its ferro-magnesium rich mineral composition.

  7. Experimental Evaluation of Cermet Turbine Stator Blades for Use at Elevated Gas Temperatures

    Science.gov (United States)

    Chiarito, Patrick T.; Johnston, James R.

    1959-01-01

    The suitability of cermets for turbine stator blades of a modified turbojet engine was determined at an average turbine-inlet-gas temperature of 2000 F. Such an increase in temperature would yield a premium in thrust from a service engine. Because the cermet blades require no cooling, all the available compressor bleed air could be used to cool a turbine made from conventional ductile alloys. Cermet blades were first run in 100-hour endurance tests at normal gas temperatures in order to evaluate two methods for mounting them. The elevated gas-temperature test was then run using the method of support considered best for high-temperature operation. After 52 hours at 2000 F, one of the group of four cermet blades fractured probably because of end loads resulting from thermal distortion of the spacer band of the nozzle diaphragm. Improved design of a service engine would preclude this cause of premature failure.

  8. Room and elevated temperature Mechanical Behavior of 9-12% Cr Steels

    Energy Technology Data Exchange (ETDEWEB)

    Dogan, Omer N.; Hawk, Jeffrey A.; Schrems, Karol K.

    2005-02-01

    The mechanical properties of medium Cr steels used in fossil fired power plants are very good because of their excellent high temperature microstructural stability. However, as the desire to increase the operating temperature (>650C) of the plant goes up, the need for steels that maintain their strength at these temperatures also increases. The mechanical properties of three medium Cr steels (0.08C-(9-12)Cr-1.2Ni-0.7Mo-3.0Cu-3.0Co-0.5Ti) were investigated through hardness, hot hardness and tensile measurements. The strength of the 9-12%Cr steels at room temperature after long-term isothermal aging (750C; 1000 hours) compares favorably with that of other power plant steels (e.g., P91). In addition, the elevated temperature strength and hot hardness also behave similarly. The mechanical behavior will be discussed in terms of the strength, elongation and tensile fracture characteristics.

  9. Fundamental studies of ceramic/metal interfacial reactions at elevated temperatures.

    Energy Technology Data Exchange (ETDEWEB)

    McDeavitt, S. M.; Billings, G. W.; Indacochea, J. E.

    2000-12-14

    This work characterizes the interfaces resulting from exposing oxide and non-oxide ceramic substrates to zirconium metal and stainless steel-zirconium containing alloys. The ceramic/metal systems together were preheated at about 600 C and then the temperatures were increased to the test maximum temperature, which exceeded 1800 C, in an atmosphere of high purity argon. Metal samples were placed onto ceramic substrates, and the system was heated to elevated temperatures past the melting point of the metallic specimen. After a short stay at the peak temperature, the system was cooled to room temperature and examined. The chemical changes across the interface and other microstructural developments were analyzed with energy dispersive spectroscopy (EDS). This paper reports on the condition of the interfaces in the different systems studied and describes possible mechanisms influencing the microstructure.

  10. Estimation methods of deformational behaviours of RC beams under the unrestrained condition at elevated temperatures

    International Nuclear Information System (INIS)

    Kanezu, Tsutomu; Nakano, Takehiro; Endo, Tatsumi

    1986-01-01

    The estimation methods of free deformations of reinforced concrete (RC) beams at elevated temperatures are investigated based on the concepts of ACI's and CEB/FIP's formulas, which are well used to estimate the flexural deformations of RC beams at normal temperature. Conclusions derived from the study are as follows. 1. Features of free deformations of RC beams. (i) The ratios of the average compressive strains on the top fiber of RC beams to the calculated ones at the cracked section show the inclinations that the ratios once drop after cracking and then remain constant according to temperature rises. (ii) Average compressive strains might be estimated by the average of the calculated strains at the perfect bond section and the cracked section of RC beam. (iii) The ratios of the average tensile strains on the level of reinforcements to the calculated ones at the cracked section are inclined to approach the value of 1.0 monotonically according to temperature rises. The changes of the average tensile strains are caused by the deterioration of bond strength and cracking due to the increase of the differences of expansive strains between reinforcement and concrete. 2. Estimation methods of free deformations of RC beams. (i) In order to estimate the free deformations of RC beams at elevated temperatures, the basic concepts of ACI's and CEB/FIP's formulas are adopted, which are well used to estimate the M-φ relations of RC beams at normal temperature. (ii) It was confirmed that the suggested formulas are able to estimate the free deformations of RC beams, that is, the longitudinal deformation and the curvature, at elevated temperatures. (author)

  11. Solvated electrons at elevated temperatures in different alcohols: Temperature and molecular structure effects

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Yu [Department of Nuclear Engineering and Management, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Lin, Mingzhang [Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1195 (Japan); Katsumura, Yosuke, E-mail: katsu@n.t.u-tokyo.ac.j [Department of Nuclear Engineering and Management, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Nuclear Professional School, Graduate School of Engineering, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188 (Japan); Fu, Haiying; Muroya, Yusa [Nuclear Professional School, Graduate School of Engineering, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188 (Japan)

    2010-12-15

    The absorption spectra of solvated electrons in pentanol, hexanol and octanol are measured from 22 to 200, 22 to 175 and 50 to150 {sup o}C, respectively, at a fixed pressure of 15 MPa, using nanosecond pulse radiolysis technique. The results show that the peak positions of the absorption spectra have a red-shift (shift to longer wavelengths) as temperature increases, similar to water and other alcohols. Including the above mentioned data, a compilation of currently available experimental data on the energy of absorption maximum (E{sub max}) of solvated electrons changed with temperature in monohydric alcohols, diols and triol is presented. E{sub max} of solvated electron is larger in those alcohols that have more OH groups at all the temperatures. The molecular structure effect, including OH numbers, OH position and carbon chain length, is investigated. For the primary alcohols with same OH group number and position, the temperature coefficient increases with increase in chain length. For the alcohols with same chain length and OH numbers, temperature coefficient is larger for the symmetric alcohols than the asymmetric ones.

  12. Daphnia fed algal food grown at elevated temperature have reduced fitness

    Directory of Open Access Journals (Sweden)

    Anna B. Sikora

    2014-05-01

    Full Text Available Lake water temperature is negatively correlated with fatty acids content and P:C ratio in green algae. Hence, elevated temperature may indirectly reduce the fitness of Daphnia due to induced decrease in algal food quality. The aim of this study was to test the hypotheses that quality of algal food decreases with increasing temperature of its culture and that large-bodied Daphnia are more vulnerable to the temperature-related deterioration of algal food quality than small-bodied ones. Laboratory life-table experiments were performed at 20°C with large-bodied D. pulicaria and small-bodied D. cucullata fed with the green alga Scenedesmus obliquus, that had been grown at temperatures of 16, 24 or 32°C. The somatic growth rates of both species decreased significantly with increasing algal culture temperature and this effect was more pronounced in D. pulicaria than in D. cucullata. In the former species, age at first reproduction significantly increased and clutch size significantly decreased with increasing temperature of algae growth, while no significant changes in these two parameters were observed in the latter species. The proportion of egg-bearing females decreased with increasing algal culture temperature in both species. The results of this study support the notion that the quality of algal food decreases with increasing water temperature and also suggest that small-bodied Daphnia species might be less vulnerable to temperature-related decreases in algal food quality than large-bodied ones.

  13. Growth response and acclimation of CO2 exchange characteristics to elevated temperatures in tropical tree seedlings.

    Science.gov (United States)

    Cheesman, Alexander W; Winter, Klaus

    2013-09-01

    Predictions of how tropical forests will respond to future climate change are constrained by the paucity of data on the performance of tropical species under elevated growth temperatures. In particular, little is known about the potential of tropical species to acclimate physiologically to future increases in temperature. Seedlings of 10 neo-tropical tree species from different functional groups were cultivated in controlled-environment chambers under four day/night temperature regimes between 30/22 °C and 39/31 °C. Under well-watered conditions, all species showed optimal growth at temperatures above those currently found in their native range. While non-pioneer species experienced catastrophic failure or a substantially reduced growth rate under the highest temperature regime employed (i.e. daily average of 35 °C), growth in three lowland pioneers showed only a marginal reduction. In a subsequent experiment, three species (Ficus insipida, Ormosia macrocalyx, and Ochroma pyramidale) were cultivated at two temperatures determined as sub- and superoptimal for growth, but which resulted in similar biomass accumulation despite a 6°C difference in growth temperature. Through reciprocal transfer and temperature adjustment, the role of thermal acclimation in photosynthesis and respiration was investigated. Acclimation potential varied among species, with two distinct patterns of respiration acclimation identified. The study highlights the role of both inherent temperature tolerance and thermal acclimation in determining the ability of tropical tree species to cope with enhanced temperatures.

  14. Measurement of mechanical properties of metallic glass at elevated temperature using sonic resonance method

    Science.gov (United States)

    Kaluvan, Suresh; Zhang, Haifeng; Mridha, Sanghita; Mukherjee, Sundeep

    2017-04-01

    Bulk metallic glasses are fully amorphous multi-component alloys with homogeneous and isotropic structure down to the atomic scale. Some attractive attributes of bulk metallic glasses include high strength and hardness as well as excellent corrosion and wear resistance. However, there are few reports and limited understanding of their mechanical properties at elevated temperatures. We used a nondestructive sonic resonance method to measure the Young's modulus and Shear modulus of a bulk metallic glass, Zr41.2Ti13.8Cu12.5Ni10Be22.5, at elevated temperatures. The measurement system was designed using a laser displacement sensor to detect the sonic vibration produced by a speaker on the specimen in high-temperature furnace. The OMICRON Bode-100 Vector Network Analyzer was used to sweep the frequency and its output was connected to the speaker which vibrated the material in its flexural mode and torsional modes. A Polytec OFV-505 laser vibrometer sensor was used to capture the vibration of the material at various frequencies. The flexural and torsional mode frequency shift due to the temperature variation was used to determine the Young's modulus and Shear modulus. The temperature range of measurement was from 50°C to 350°C. The Young's modulus was found to reduce from 100GPa to 94GPa for the 300°C temperature span. Similarly, the Shear modulus decreased from 38.5GPa at 50°C to 36GPa at 350°C.

  15. Study on the shear transfer of reinforced concrete at elevated temperature

    International Nuclear Information System (INIS)

    Ishida, Hiroaki; Kanazu, Tsutomu

    1989-01-01

    Reinforced concrete structures in nuclear power stations, such as a containment vessel and structural members supporting a reactor vessel, are designed assuming that they may be subjected to elevated temperature. In the design code, it is specified that the temperature of concrete must not exceed the limitation, and thermal effect shall be taken into account. In this study, the shearing test using Mattock type specimens was performed to investigate into the shear behavior of the reinforced concrete subjected to elevated temperature. The test parameters studied in this program were the reinforcement ratio in a shear plane, the compressive stress normal to a shear plane and temperature. The maximum shearing load of the specimens heated to 200 degC was about 10-20 % lower than that at normal temperature, but nearly equal to that of the specimens heated to 100 degC. The equation for evaluating the shearing strength ratio was proposed. The cracking width and slip at maximum shearing load increased as temperature rose. Up to 200 degC, the same relation existed between interface shear transfer rigidity and cracking width. (K.I.)

  16. Temperature development and sterilization of red pine poles during CCA treatment, elevated temperature fixation and drying

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, P.; Albright, M.; Srinivasan, U.; Ung, A. [New Brunswick Univ., Fredericton, NB (Canada). Wood Science and Technology Centre

    2002-07-01

    The application of chromated copper arsenate (CCA) treatment and fixation and drying under the conditions of the study to large red pine poles left for an air seasoning period of 10 months in Quebec, Canada progressively reduced the number of micro-organisms present. A large number of microfungi isolations were effected before the treatment from the sapwood and heartwood of all poles and wood decay fungi on 8 selected poles from the 20 test poles. They originated from the sapwood zone. A reduction of approximately 50 per cent in the number of microfungi isolated from the sapwood was noted after the CCA treatment. In the case of 9 of 30 poles, basidiomycetes were isolated after treatment primarily from the untreated heartwood. There were a few instances where basidiomycetes were isolated from unpenetrated sapwood (wet pockets). Temperatures of 55 to 60 degrees Celsius were achieved under moderate temperature fixation schedules (20 hours) for approximately 5 hours at full sapwood depth. Only by the end of the schedule was a temperature of 55 degrees celsius achieved at the centre of the poles. Most of the microfungi were eliminated by this temperature regime. Trichoderma was eliminated, and only one isolation of basidiomycetes was left from the heartwood of one pole. Temperatures of 55 to 60 degrees Celsius were achieved in the wood core for 9 to 10 days during kiln drying. No basidiomycete isolations remained after this exposure. In several of the poles, there was evidence of Paecilomyces variotii, a thermo-tolerant species and a number of species of Penicillium moulds. It was concluded that there was a negligible probability of decay fungi surviving the sequence of processes as described, given the effectiveness of the fixation exposure and the higher wood temperatures sustained for longer periods. 16 refs., 5 tabs., 2 figs.

  17. FDTD computation of temperature elevation in the elderly for far-field RF exposures

    International Nuclear Information System (INIS)

    Nomura, Tomoki; Laakso, Ilkka; Hirata, Akimasa

    2014-01-01

    Core temperature elevation and perspiration in younger and older adults is investigated for plane-wave exposure at whole-body averaged specific absorption rate of 0.4 W kg -1 . Numeric Japanese male model is considered together with a thermo-regulatory response formula proposed in the authors' previous study. The frequencies considered were at 65 MHz and 2 GHz where the total power absorption in humans becomes maximal for the allowable power density prescribed in the international guidelines. From the computational results used here, the core temperature elevation in the older adult model was larger than that in the younger one at both frequencies. The reason for this difference is attributable to the difference of sweating, which is originated from the difference in the threshold activating the sweating and the decline in sweating in the legs. (authors)

  18. Influence of a Cyclic Events Configuration on a Elevated Temperature Structural Integrity

    International Nuclear Information System (INIS)

    Park, Chang-Gyu; Koo, Gyeong-Hoi; Lee, Jae-Han

    2008-01-01

    A nuclear power plant generally undergoes the various types of operating events for a plant life time. The cyclic events for a life time may bring about a structural failure such as fatigue damage. The structures of the LMR(Liquid Metal Reactor) operated in a elevated temperature environment are seriously affected by a thermal deformation and strain. Therefore, the thermal transient condition is a key factor for ensuring the structural integrity for the LMR reactor structures. Since it is not easy to consider the entire operating events at the preliminary or conceptual design stage, the LMR structural integrity is evaluated with representative duty cycle events. In this study, the influence of the elevated temperature structural integrity evaluation per the combination and sequence of the duty cycle events is investigated

  19. Evaluation of weldment creep and fatigue strength-reduction factors for elevated-temperature design

    International Nuclear Information System (INIS)

    Corum, J.M.

    1989-01-01

    New explicit weldment strength criteria in the form of creep and fatigue strength-reduction factors were recently introduced into the American Society of Mechanical Engineers Code Case N-47, which governs the design of elevated-temperature nuclear plants components in the United States. This paper provides some of the background and logic for these factors and their use, and it describes the results of a series of long-term, confirmatory, creep-rupture and fatigue tests of simple welded structures. The structures (welded plates and tubes) were made of 316 stainless steel base metal and 16-8-2 weld filler metal. Overall, the results provide further substantiation of the validity of the strength-reduction factor approach for ensuring adequate life in elevated-temperature nuclear component weldments. 16 refs., 7 figs

  20. Equilibrium moisture content of radiata pine at elevated temperature and pressure reveals measurement challenges

    DEFF Research Database (Denmark)

    Pearson, Hamish; Gabbitas, Brian; Ormarsson, Sigurdur

    2012-01-01

    moisture contents were attributed to condensation of liquid water on the specimen with subsequent evaporation at a rate that was too slow for the moisture content to reach equilibrium before it was measured. Reliable EMC data at elevated temperatures require (1) tight process control of experimental......Relatively few studies have been performed on the equilibrium moisture content (EMC) of wood under conditions of elevated temperature and pressure. Eight studies indicated that EMC near saturation decreased between 100 and 150 °C, whilst five studies indicated that EMC increased. The aim...... of this study was to identify the likely source of the disagreement using radiata pine (Pinus radiata D. Don) sapwood which was conditioned to a moisture content of around 3 % and then exposed for 1 h at 150 °C and relative humidities of either 50, 70 or 90 %. Mean values of EMC, obtained through in situ...

  1. FDTD computation of temperature elevation in the elderly for far-field RF exposures.

    Science.gov (United States)

    Nomura, Tomoki; Laakso, Ilkka; Hirata, Akimasa

    2014-03-01

    Core temperature elevation and perspiration in younger and older adults is investigated for plane-wave exposure at whole-body averaged specific absorption rate of 0.4 W kg(-1). Numeric Japanese male model is considered together with a thermoregulatory response formula proposed in the authors' previous study. The frequencies considered were at 65 MHz and 2 GHz where the total power absorption in humans becomes maximal for the allowable power density prescribed in the international guidelines. From the computational results used here, the core temperature elevation in the older adult model was larger than that in the younger one at both frequencies. The reason for this difference is attributable to the difference of sweating, which is originated from the difference in the threshold activating the sweating and the decline in sweating in the legs.

  2. Nonlinear structural analysis methods and their application to elevated temperature design: A US perspective

    International Nuclear Information System (INIS)

    Dhalla, A.K.

    1989-01-01

    Technological advances over the last two decades have been assimilated into the routine design of Liquid Metal Reactor (LMR) structural components operating at elevated temperatures. The mature elevated temperature design technology is based upon: (a) an extensive material data base, (b) recent advances in nonlinear computational methods, and (c) conservative design criteria based upon past successful and reliable operating experiences with petrochemical and nonnuclear power plants. This survey paper provides a US perspective on the role of nonlinear analysis methods used in the design of LMR plants. The simplified and detailed nonlinear analysis methods and the level of computational effort required to qualify structural components for safe and reliable long-term operation are discussed. The paper also illustrates how a detailed nonlinear analysis can be used to resolve technical licensing issues, to understand complex nonlinear structural behavior, to identify predominant failure modes, and to guide future experimental programs

  3. Stress-controlled inelastic behavior of modified 9 Cr-1 Mo steel at elevated temperatures

    International Nuclear Information System (INIS)

    Taguchi, Kosei.

    1989-01-01

    Interest in the ferritic steels of higher chromium concentration has increased recently because of an economical combination of mechanical and corrosion properties at elevated temperatures. A modified 9 Cr-1 Mo ferritic steel, developed in the United States, has been expected as an alternative structural material for fast breeder reactor components, in which Type 304 stainless steel or 2.25 Cr-1 Mo steel is currently used. For application of this material to the structural components, a lot of work has been done to develop evaluation methods for the deformation behavior and strength properties. The authors have studied the inelastic behavior and the creep-fatigue properties of modified 9 Cr-1 Mo steel at elevated temperatures, and proposed a constitutive equation and a creep-fatigue damage equation based on the overstress concept. In this paper, the applicability is discussed of the constitutive equation to stress-controlled inelastic behavior, such as creep strain hardening and stress cycling

  4. Interrelationship betwen material strength and component design under elevated temperature for FBR

    International Nuclear Information System (INIS)

    Nakagawa, Y.

    Structural design under elevated temperature for fast breeder reactor plant is very troublesome compared to that of for lower temperature. This difficulty can be mainly discussed from two different stand points. One is design and design code, another is material strength. Components in FBR are operated under creep regime and time dependent creep behaviour should be elevated properly. This means the number and combinations of design code and material strength are significantly large and makes these systems very complicated. Material selection is, in no words, not an easy job. This should be done by not only material development but also component design stand point. With valuable experience of construction and research on FBR, a lot of information on component design and material behaviour is available. And it is a time to choose the ''best material'' from the entire stand points of component construction. (author)

  5. Elevation of liquidus temperature in a gel-derived Na2O-SiO2 glass

    Science.gov (United States)

    Weinberg, M. C.; Neilson, G. F.

    1983-01-01

    The liquidus temperatures of a 19 wt% soda-silica glass prepared by gel and conventional techniques were determined. X-ray diffraction measurements of the glasses which were heat-treated at several temperatures were used to experimentally determine the liquidus temperatures. It was found that the gel-derived glass has an elevated liquidus. This result is discussed in relation to the previous discovery that the immiscibility temperature of this gel-derived glass is elevated

  6. Elevated temperature erosion studies on some materials for high temperature applications

    International Nuclear Information System (INIS)

    Zhou Jianren.

    1991-01-01

    The surface degradation of materials due to high temperature erosion or combined erosion corrosion is a serious problem in many industrial and aeronautical applications. As such, it has become an important design consideration in many situations. The materials investigated in the present studies are stainless steels, Ti-6Al-4V, alumina ceramics, with and without silicate glassy phase, and zirconia. These are some of the potential materials for use in the high temperature erosive-corrosive environments. The erosion or erosion-corrosion experiments were performed in a high temperature sand-blast type of test rig. The variables studied included the temperature, material composition, heat treatment condition, impingement velocity and angle, erodent concentration, etc. The morphological features of the eroded or eroded-corroded surfaces, substrate deformation, and oxide characteristics were studied by optical and scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, thermogravimetric analysis. The scratch test, single ball impact, and indentation tests were used to understand the behavior of oxide film in particle impacts. Based on these studies, the understanding of the mechanisms involved in the mechanical or combined mechanical and chemical actions in erosion was developed

  7. Development of fatigue crack propagation models for engineering applications at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Tomkins, B.

    1975-05-01

    The value of modelling the fatigue crack propagation process is discussed and current models are examined in the light of increasing knowledge of crack tip deformation. Elevated temperature fatigue is examined in detail as an area in which models could contribute significantly to engineering design. A model is developed which examines the role of time-dependent creep cavitation on the failure process in an interactive creep-fatigue situation. (auth)

  8. An advanced straight tube heat exchanger in which a fluid flows at variable and elevated temperatures

    International Nuclear Information System (INIS)

    Mauget, C.; Benoit, G.; Stalport, G.

    1993-01-01

    Straight tube heat exchangers are used as steam generators in nuclear reactors such as in fast neutron nuclear power plants; elevated and highly variable temperatures induce very high thermal expansion constraints in these long straight tubes. In order to avoid the expansion problems, an expansion bellow is disposed between the heat exchanger and the collector tubular plate in such a way that the bundle differential expansions may be absorbed

  9. The response of three dominant Arctic copepod species to elevated CO2 concentrations and water temperatures

    OpenAIRE

    Hildebrandt, Nicole

    2014-01-01

    Ocean acidification (OA) and ocean warming are threatening marine life. Within the framework of the research project BIOACID, this thesis aims to provide a comprehensive overview on the sensitivity of the dominant Arctic calanoid copepod species Calanus finmarchicus, C. glacialis and C. hyperboreus to elevated pCO2 and temperatures. Controlled laboratory experiments have shown that subadult and adult Calanus life stages are rather robust to the direct effects of OA during both active and rest...

  10. Bending Strength of EN AC-44200 – Al2O3 Composites at Elevated Temperatures

    OpenAIRE

    Kurzawa A.; Kaczmar J. W.

    2017-01-01

    The paper presents results of bend tests at elevated temperatures of aluminium alloy EN AC-44200 (AlSi12) based composite materials reinforced with aluminium oxide particles. The examined materials were manufactured by squeeze casting. Preforms made of Al2O3 particles, with volumetric fraction 10, 20, 30 and 40 vol.% of particles joined with sodium silicate bridges were used as reinforcement. The preforms were characterised by open porosity ensuring proper infiltration with the EN AC-44200 (A...

  11. Simplified methods and application to preliminary design of piping for elevated temperature service

    International Nuclear Information System (INIS)

    Severud, L.K.

    1975-01-01

    A number of simplified stress analysis methods and procedures that have been used on the FFTF project for preliminary design of piping operating at elevated temperatures are described. The rationale and considerations involved in developing the procedures and preliminary design guidelines are given. Applications of the simplified methods to a few FFTF pipelines are described and the success of these guidelines are measured by means of comparisons to pipeline designs that have had detailed Code type stress analyses. (U.S.)

  12. Compressive behavior of steel fiber reinforced recycled aggregate concrete after exposure to elevated temperatures

    OpenAIRE

    Chen, G. M.; He, Y. H.; Yang, H.; Chen, J. F.; Guo, Y.C.

    2014-01-01

    For sustainability considerations, the use of recycled aggregate in concrete has attracted many interests in the research community. One of the main concerns for using such concrete in buildings is its spalling in fire. This may be alleviated by adding steel fibers to form steel fiber reinforced recycled aggregate concrete (SFRAC). This paper presents an experimental investigation into the compressive properties of SFRAC cylinders after exposure to elevated temperatures, including the compres...

  13. Noise and optimum filtering in spectrometers with semiconductor detectors operating at elevated temperature

    International Nuclear Information System (INIS)

    Dabrowski, W.; Korbel, K.

    1983-01-01

    The importance of the excess noise in the semiconductor detectors operating at the elevated temperature is discussed. Under the assumption of a conventional CR-RC type filtration the variancy of the noise output is determined. The new term ''second noise-corner time constant'' was proposed. The expression for relative signal-to-noise ratio as the dependence on the noise as well as circuits time constants was derived. It was also presented in a graphical form. 12 refs., 6 figs. (author)

  14. A simplified approach for evaluating secondary stresses in elevated temperature design

    International Nuclear Information System (INIS)

    Becht, C.

    1983-01-01

    Control of secondary stresses is important for long-term reliability of components, particularly at elevated temperatures where substantial creep damage can occur and result in cracking. When secondary stresses are considered in the design of elevated temperature components, these are often addressed by the criteria contained in Nuclear Code Case N-47 for use with elastic or inelastic analysis. The elastic rules are very conservative as they bound a large range of complex phenomena; because of this conservatism, only components in relatively mild services can be designed in accordance with these rules. The inelastic rules, although more accurate, require complex and costly nonlinear analysis. Elevated temperature shakedown is a recognized phenomenon that has been considered in developing Code rules and simplified methods. This paper develops and examines the implications of using a criteria which specifically limits stresses to the shakedown regime. Creep, fatigue, and strain accumulation are considered. The effect of elastic follow-up on the conservatism of the criteria is quantified by means of a simplified method. The level of conservatism is found to fall between the elastic and inelastic rules of N-47 and, in fact, the incentives for performing complex inelastic analyses appear to be low except in the low cycle regime. The criteria has immediate applicability to non-code components such as vessel internals in the chemical, petroleum, and synfuels industry. It is suggested that such a criteria be considered in future code rule development

  15. On the capability of austenitic steel to withstand cyclic deformations during service at elevated temperatures

    International Nuclear Information System (INIS)

    Etienne, C.F.; Dortland, W.; Zeedijk, H.B.

    1975-01-01

    Safe design for structures with steels for elevated temperatures necessitates screening these materials on the basis of objective criteria for ductility, besides screening them on elevated temperature strength. Because creep and fatigue damage may occur during operation, the ductility of a steel after a long operation time is more important than the ductility in the as delivered condition. This paper describes results of an investigation into the ductility of some austenitic Cr-Ni-steels. In order to determine the capability of the steels to withstand cyclic plastic deformation in the aged condition, various ageing treatments were applied before determining the ductility in low-cycle fatigue testing. Correlating the ductility with the sizes of the carbide precipitates made it possible to predict the ductility behaviour during long service times. This led to the conclusion that for an austenitic steel with a high thermal stability (17.5 per cent Cr-11 per cent Ni) the ductility can decrease considerably during service at elevated temperature. Nevertheless it is expected that the remaining ductility of such steels in aged condition will be amply sufficient to withstand the cyclic deformations that occur during normal service. (author)

  16. Capability of austenitic steel to withstand cyclic deformations during service at elevated temperatures

    International Nuclear Information System (INIS)

    Etienne, C.F.; Dortland, W.; Zeedijk, H.B.

    1975-01-01

    Safe design for structures with steels for elevated temperatures necessitates screening these materials on the basis of objective criteria for ductility, besides screening them on elevated temperature strength. Because creep and fatigue damage may occur during operation, the ductility of a steel after a long operation time is more important than the ductility in the as delivered condition. Results of an investigation into the ductility of austenitic Cr--Ni-steels are described. In order to determine the capability of the steels to withstand cyclic plastic deformations in the aged condition, various aging treatments were applied before determining the ductility in low-cycle fatigue testing. Correlating the ductility with the sizes of the carbide precipitates made it possible to predict the ductility behavior during long service times. This led to the conclusion that for an austenitic steel with a high thermal stability (17.5 percent Cr--11 percent Ni) the ductility can decrease considerably during service at elevated temperature. Nevertheless it is expected that the remaining ductility of such steels in aged condition will be amply sufficient to withstand the cyclic deformations that occur during normal service

  17. Radiation chemistry of aqueous solutions of hydrazine at elevated temperatures: Pt. 2. Solutions containing oxygen

    International Nuclear Information System (INIS)

    Buxton, G.V.; Stuart, C.R.

    1997-01-01

    Here, we investigate the effects of oxygen on the radiation chemistry of hydrazine at elevated temperatures. The chemistry of this system is important to reactor coolant chemistry, particularly under start-up conditions when hydrazine is added to suppress corrosion which would otherwise be caused by the ingress of oxygen. The radiation chemistry of aqueous solutions of hydrazine has been investigated previously in the presence of oxygen by Ershov et al., but only at room temperature. In those experiments, both steady-state γ-radiolysis and pulse radiolysis were used to deduce the mechanism of decomposition of hydrazine in the presence of oxygen. (author)

  18. Note: A method for minimizing oxide formation during elevated temperature nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, I. C.; Hodge, A. M., E-mail: ahodge@usc.edu [Department of Aerospace and Mechanical Engineering, University of Southern California, 3650 McClintock Avenue OHE430, Los Angeles, California 90089 (United States); Garcia-Sanchez, E. [Department of Aerospace and Mechanical Engineering, University of Southern California, 3650 McClintock Avenue OHE430, Los Angeles, California 90089 (United States); Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, Av. Universidad S/N, San Nicolás de los Garza, NL 66450 (Mexico)

    2014-09-15

    A standardized method to protect metallic samples and minimize oxide formation during elevated-temperature nanoindentation was adapted to a commercial instrument. Nanoindentation was performed on Al (100), Cu (100), and W (100) single crystals submerged in vacuum oil at 200 °C, while the surface morphology and oxidation was carefully monitored using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results were compared to room temperature and 200 °C nanoindentation tests performed without oil, in order to evaluate the feasibility of using the oil as a protective medium. Extensive surface characterization demonstrated that this methodology is effective for nanoscale testing.

  19. Synergistic effect of elevated temperature, pCO2 and nutrients on marine biofilm

    Digital Repository Service at National Institute of Oceanography (India)

    Baragi, L.V.; Anil, A.C.

    the respiration and in turn metabolic and energy cost of bacteria (Del Giorgio et al., 1999; Siu et al., 2014). This highlights the significant influence of nutrients on the response of bacteria to ocean acidification. Elevated temperature, irrespective of p...., Thyrhaug, R., Grossart, H.-P., 2008. Coupling of heterotrophic bacteria to phytoplankton bloom development at different pCO2 levels: a mesocosm study. Biogeosciences 5, 1007-1022. Apple, J.K., Del Giorgio, P., Kemp, W.M., 2006. Temperature regulation...

  20. Experimental and numerical investigation of formability for austenitic stainless steel 316 at elevated temperatures

    Directory of Open Access Journals (Sweden)

    Syed Mujahed Hussaini

    2014-01-01

    Full Text Available Sheet metal forming at elevated temperature is not much used in industries but it is going to be a very important process in the future. The present work is aimed to investigate the formability of austenitic stainless steel 316 at elevated temperatures. Limiting drawing ratio and thickness of the drawn cup are the indicators of formability in deep drawing. In the present investigation circular blanks are deep drawn at room temperature, 150 °C and 300 °C using a 20 ton hydraulic press coupled with a furnace. Finite element simulations are carried out using Dynaform with LS-Dyna solver. Simulations and experimental results show an increase in the limiting drawing ration as the temperature increases and a decrease in the thickness of the drawn cup without any fracture. An artificial neural network model is developed for the prediction of the cup thickness at different locations. Based on the input variables, such as distance from the center of the cup, temperature and LDR, a back propagation neural network model to predict the thickness as output was develop. The comparison between these sets of results indicates the reliability of the predictions. It was found that there is a good agreement between the experimental and predicted values.

  1. Residual Tensile Strength and Bond Properties of GFRP Bars after Exposure to Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Devon S. Ellis

    2018-02-01

    Full Text Available The use of fiber reinforced polymer (FRP bars in reinforced concrete members enhances corrosion resistance when compared to traditional steel reinforcing bars. Although there is ample research available on the behavior of FRP bars and concrete members reinforced with FRP bars under elevated temperatures (due to fire, there is little published information available on their post-fire residual load capacity. This paper reports residual tensile strength, modulus of elasticity, and bond strength (to concrete of glass fiber reinforced polymer (GFRP bars after exposure to elevated temperatures of up to 400 °C and subsequent cooling to an ambient temperature. The results showed that the residual strength generally decreases with increasing temperature exposure. However, as much as 83% of the original tensile strength and 27% of the original bond strength was retained after the specimens were heated to 400 °C and then cooled to ambient temperature. The residual bond strength is a critical parameter in post-fire strength assessments of GFRP-reinforced concrete members.

  2. Elevated service water temperature systems analysis for a nuclear power plant

    International Nuclear Information System (INIS)

    Lewis, T.; Hurt, W.

    1992-01-01

    This paper describes analyses performed to support the evaluation of the effects of elevated Service Water (SW) temperatures on the operation of a Pressurized Water Reactor. The purpose of the analyses is to provide justification of continued plant operation with SW temperatures up to 5 degrees F (3 degrees C) above the original temperature design limit. The study involved evaluation of the following major components or plant transients: Containment Design Basis Accident (DBA), Emergency Diesel Generator (EDG), Plant Cooldown, Engineered Safety Feature (ESF) Room Coolers, Engineered Safety Feature Pumps, and Assessment for Impact on Normal Operation. The principal objective was related to raising the design maximum temperature of the SW system from 95 degrees F (35 degrees C) to 100 degrees F (38 degrees C). since the Service Water system is safety related, an serves a plant during both normal and design basis conditions, a wide variety of components must be analyzed under various operating modes. The evaluation of systems and components affected by elevated SW temperature is presented, along with conclusions

  3. Residual Tensile Strength and Bond Properties of GFRP Bars after Exposure to Elevated Temperatures.

    Science.gov (United States)

    Ellis, Devon S; Tabatabai, Habib; Nabizadeh, Azam

    2018-02-27

    The use of fiber reinforced polymer (FRP) bars in reinforced concrete members enhances corrosion resistance when compared to traditional steel reinforcing bars. Although there is ample research available on the behavior of FRP bars and concrete members reinforced with FRP bars under elevated temperatures (due to fire), there is little published information available on their post-fire residual load capacity. This paper reports residual tensile strength, modulus of elasticity, and bond strength (to concrete) of glass fiber reinforced polymer (GFRP) bars after exposure to elevated temperatures of up to 400 °C and subsequent cooling to an ambient temperature. The results showed that the residual strength generally decreases with increasing temperature exposure. However, as much as 83% of the original tensile strength and 27% of the original bond strength was retained after the specimens were heated to 400 °C and then cooled to ambient temperature. The residual bond strength is a critical parameter in post-fire strength assessments of GFRP-reinforced concrete members.

  4. Elevated temperatures and bleaching on a high latitude coral reef: the 1988 Bermuda event

    Science.gov (United States)

    Cook, Clayton B.; Logan, Alan; Ward, Jack; Luckhurst, Brian; Berg, Carl J.

    1990-03-01

    Sea temperatures were normal in Bermuda during 1987, when Bermuda escaped the episodes of coral bleaching which were prevalent throughout the Caribbean region. Survey transecs in 1988 on 4 6 m reefs located on the rim margin and on a lagoonal patch reef revealed bleaching only of zoanthids between May and July. Transect and tow surveys in August and September revealed bleaching of several coral species; Millepora alcicornis on rim reefs was the most extensively affected. The frequency of bleaching in this species, Montastrea annularis and perhaps Diploria labyrinthiformis was significantly higher on outer reefs than on inshore reefs. This bleaching period coincided with the longest period of elevated sea temperatures in Bermuda in 38 years (28.9 30.9°C inshore, >28° offshore). By December, when temperatures had returned to normal, bleaching of seleractinians continued, but bleaching of M. alcicornis on the outer reefs was greatly reduced. Our observations suggest that corals which normally experience wide temperature ranges are less sensitive to thermal stress, and that high-latitude reef corals are sensitive to elevated temperatures which are within the normal thermal range of corals at lower latitudes.

  5. The tunnel sealing experiment: The construction and performance of full scale clay and concrete bulkheads at elevated pressure and temperature

    International Nuclear Information System (INIS)

    Martino, J.B.; Dixon, D.A.; Vignal, B.; Fujita, T.

    2006-01-01

    Concepts for deep geologic disposal of radioactive waste, as proposed by many international organizations, include bulkheads or plugs in the shaft, or at the entrances to disposal rooms, or both. The seals are primarily to prevent groundwater transport of radioisotopes along underground openings but also provide a measure of security by restricting tunnel access. The safety of the respective disposal systems relies on the combined performance of the natural barriers (host rock) and engineered barriers (the waste form, the waste container, the buffer barrier, the room, tunnel and shaft backfill and sealing materials). To understand the functionality of these systems it is important to study them in whole or in part at full scale. One such study was the Tunnel Sealing Experiment (TSX), a full-scale tunnel seal component study. The TSX showed it is possible to construct tunnel seals that limit axial flow under high hydraulic gradient and elevated temperature. The clay and concrete bulkheads had seepage rates of 1 mL/min and 10 mL/min at ambient temperature. Elevated temperatures caused a further decrease in seepage past the concrete bulkhead to approximately 2-3 mL/min. (author)

  6. Current Status of the Elevated Temperature Structure Design Codes for VHTR

    International Nuclear Information System (INIS)

    Kim, Jong-Bum; Kim, Seok-Hoon; Park, Keun-Bae; Lee, Won-Jae

    2006-01-01

    An elevated temperature structure design and analysis is one of the key issues in the VHTR (Very High Temperature Reactor) project to achieve an economic production of hydrogen which will be an essential energy source for the near future. Since the operating temperature of a VHTR is above 850 .deg. C, the existing code and standards are insufficient for a high temperature structure design. Thus the issues concerning a material selection and behaviors are being studied for the main structural components of a VHTR in leading countries such as US, France, UK, and Japan. In this study, the current status of the ASME code, French RCC-MR, UK R5, and Japanese code were investigated and the necessary R and D items were discussed

  7. High-rate capability of lithium-ion batteries after storing at elevated temperature

    International Nuclear Information System (INIS)

    Wu, Mao-Sung; Chiang, Pin-Chi Julia

    2007-01-01

    High-rate performances of a lithium-ion battery after storage at elevated temperature are investigated electrochemically by means of three-electrode system. The high-rate capability is decreased significantly after high-temperature storage. A 3 C discharge capacities after room-temperature storage and 60 o C storage are 650 and 20 mAh, respectively. Lithium-ion diffusion in lithium cobalt oxide cathode limits the battery's capacity and the results show that storage temperature changes this diffusion behavior. Transmission electron microscopy (TEM) images show that many defects are directly observed in the cathode after storage compared with the fresh cathode; the structural defects block the diffusion within the particles. Electrochemical impedance and polarization curve indicate that mass-transfer (diffusion) dominates the discharge capacity during high-rate discharge

  8. Fatigue crack growth in ferritic steels as influence by elevated temperature and environment

    International Nuclear Information System (INIS)

    Nakamura, H.; Minakawa, K.; Murali, K.; Mc Evily, A.J.

    1987-01-01

    Fatigue crack growth studies have been carried out at room temperature and at 538 deg C in air as well as in vacuum in order to assess the influence of both temperature and environment on the growth process. The materials investigated were 2 1/4Cr-1Mo steel, a modified 9Cr-1Mo steel and a 9Cr-2Mo steel, as well as weldments of the 9Cr-2Mo steel. Crack opening levels were determined for all test conditions. The R-dependency of the crack growth rate could be accounted for by crack closure, both at room and elevated temperature. Closure in air at 538 deg C was due to oxidation, whereas at room temperature closure was due to microstructurally related roughness and the influence of oxygen. (Author)

  9. The interactive effects of elevated CO2, temperature and N supply on rice yield

    International Nuclear Information System (INIS)

    Baysa, Marieta C.; Tremmel, David C.; Reynolds, James F.; Rivero, Gilda C.; Tabbada, Reynaldo A.

    2001-01-01

    Rice (Oryza sativa L. cv. IR 72)was grown in growth chambers under combinations of two CO 2 (375 and 750 μL L -1 ), temperature(29/21 and 34/26 degrees centigrade day/night) and N (40 and 80 mg L -1 ) regimes from sowing until grain maturity. Panicle production was significantly enhanced by elevated CO 2 with more pronounced effects at high temperature and N. CO 2 -enriched plants grown at high temperatures had lower harvest indices due to reductions in the number of grains per panicle and grain mass. Any potential benefit of increased atmospheric CO 2 on rice grain yield and grain N content under optimal N supply may therefore be dampened by higher temperatures associated with possible future global warming conditions. (Author)

  10. Instrumentation enabling study of plant physiological response to elevated night temperature

    Directory of Open Access Journals (Sweden)

    Tarpley Lee

    2009-06-01

    Full Text Available Abstract Background Global climate warming can affect functioning of crops and plants in the natural environment. In order to study the effects of global warming, a method for applying a controlled heating treatment to plant canopies in the open field or in the greenhouse is needed that can accept either square wave application of elevated temperature or a complex prescribed diurnal or seasonal temperature regime. The current options are limited in their accuracy, precision, reliability, mobility or cost and scalability. Results The described system uses overhead infrared heaters that are relatively inexpensive and are accurate and precise in rapidly controlling the temperature. Remote computer-based data acquisition and control via the internet provides the ability to use complex temperature regimes and real-time monitoring. Due to its easy mobility, the heating system can randomly be allotted in the open field or in the greenhouse within the experimental setup. The apparatus has been successfully applied to study the response of rice to high night temperatures. Air temperatures were maintained within the set points ± 0.5°C. The incorporation of the combination of air-situated thermocouples, autotuned proportional integrative derivative temperature controllers and phase angled fired silicon controlled rectifier power controllers provides very fast proportional heating action (i.e. 9 ms time base, which avoids prolonged or intense heating of the plant material. Conclusion The described infrared heating system meets the utilitarian requirements of a heating system for plant physiology studies in that the elevated temperature can be accurately, precisely, and reliably controlled with minimal perturbation of other environmental factors.

  11. Control of surface temperature of an aluminum alloy billet by air flow during a heating process at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Young [KITECH, Cheonan (Korea, Republic of); Park, Joon Hong [Dong-A University, Busan (Korea, Republic of)

    2016-06-15

    The procedure of semi-solid forming is composed of heating a billet, forming, compression holding and ejecting step. There are several methods to heat a billet during semi-solid forming process such as electric heating and induction heating. Usually in semi-solid forming process, induction heating has been adopted to achieve more uniform temperature of semi-solid material. Although induction heating is better method than any others, however, there is still difference of temperature between internal part and surface part of semi-solid material. Worse yet, in case of high liquid fraction of semi-solid material, liquid of the billet will flow down though solid of the billet still remains, which is very difficult to handle. In the present study, induction heating of the billet during thixoforging process with forced surface cooling has been performed to obtain more uniform distribution of temperature, microstructure and shape of the billet. Distribution of temperature of the billets was measured and compared with that of conventional distribution of temperature. Microscopic and macroscopic aspects of the billets were discussed according to location of the measuring points. By this new induction heating method, not only temperature distributions over the whole billet become uniform, but also control of temperature distribution between inside and outside part of the billet is possible as user's experimental intentions,.

  12. Phase distribution and microstructural changes of self-compacting cement paste at elevated temperature

    International Nuclear Information System (INIS)

    Ye, G.; Liu, X.; De Schutter, G.; Taerwe, L.; Vandevelde, P.

    2007-01-01

    Self-compacting concrete, as a new smart building material with various advanced properties, has been used for a wide range of structures and infrastructures. However little investigation have been reported on the properties of Self-compacting when it is exposed to elevated temperatures. Previous experiments on fire test have shown the differences between high performance concrete and traditional concrete at elevated temperature. This difference is largely depending on the microstructural properties of concrete matrix, i.e. the cement paste, especially on the porosity, pore size distribution and the connectivity of pores in cement pastes. In this contribution, the investigations are focused on the cement paste. The phase distribution and microstructural changes of self-compacting cement paste at elevated temperatures are examined by mercury intrusion porosimetry and scanning electron microscopy. The chemical decomposition of self-compacting cement paste at different temperatures is determined by thermogravimetric analysis. The experimental results of self-compacting cement paste are compared with those of high performance cement paste and traditional cement paste. It was found that self-compacting cement paste shows a higher change of the total porosity in comparison with high performance cement paste. When the temperature is higher than 700 deg. C, a dramatic loss of mass was observed in the self-compacting cement paste samples with addition of limestone filler. This implies that the SCC made by this type of self-compacting cement paste will probably show larger damage once exposed to fire. Investigation has shown that 0.5 kg/m 3 of Polypropylene fibers in the self-compacting cement paste can avoid the damage efficiently

  13. Europium sorption on zirconia at elevated temperatures: experimental study and modeling

    International Nuclear Information System (INIS)

    Eglizaud, N.; Catalette, H.

    2005-01-01

    Full text of publication follows: Direct disposal of spent nuclear fuel in deep underground repository is being considered by several countries. The waste package maintains an elevated temperature for thousands of years. As sorption is one of the main phenomenon limiting the dispersion of radionuclides in the environment, it has to be studied at elevated temperatures. Zirconia is an oxide produced by cladding oxidation which is suspected in the near field of a nuclear repository. It then could possibly be in contact with waste elements as Europium (III), the sorption of which is therefore studied on zirconia. Experiments were performed by the batch method at a solid/liquid ratio of 10 g.L-1. The sorption edges were recorded in the pH-range from 2 to 10 at 2.10 -5 mol.L -1 Eu(NO 3 ) 3 (I = 0.1 mol.L -1 KNO 3 ). An over-pressure device in an autoclave with an incorporated filtering system allowed the experiments, carbonate free, at 25 deg. C, 50 deg. C, 80 deg. C, 120 deg. C and 150 deg. C and in situ pH measurements. Filtrates were analyzed by the ICP-AES method. Sorption isotherms show an increase in the sorption phenomenon when the temperature raises. The half sorption pH decreases from 7 at 25 deg. C to 3,6 at 150 deg. C. The distribution coefficients that were obtained at elevated temperatures enriched the databases of integrated performance assessment codes. Raw data were modeled with the surface complexation theory using the double layer model (DLM). Several possible surface complexes were examined and discussed, taking into account aqueous hydrolyzed and precipitated species of Europium. A good agreement between experimental values and modeled isotherms was found at all studied temperatures. Results were consistent with a bidentate complex formed by Europium (III) on the zirconia surface. Associated formation constants were then determined with the geochemical computer code CHESS. (authors)

  14. A French guideline for defect assessment at elevated temperature and leak before break analysis

    Energy Technology Data Exchange (ETDEWEB)

    Drubay, B.; Chapuliot, St.; Lacire, M.H.; Marie, St. [CEA Saclay, Lab. d' Ingegrite des Structures et Normalisation, LISN, 91 - Gif sur Yvette (France); Deschanels, H. [FRAMATOME/Novatome, 69 - Lyon (France); Cambefort, P. [Electricite de France (EDF/SEPTEN), 69 - Lyon (France)

    2001-07-01

    A large program is performed in France in order to develop, for the design and operating FBR (fast breeder reactor) plants, defect assessment procedures and Leak-Before-Break methods (L.B.B.). The main objective of this A16 guide is to propose analytical solutions at elevated temperature coherent with those proposed at low temperature by the RSE-M. The main items developed in this A16 guide for laboratory specimen, plates, pipes and elbows are the following: evaluation of ductile crack initiation and crack propagation based on the J parameter and material characteristics as J{sub R}-{delta}a curve or J{sub i}/G{sub fr}. Algorithms to evaluate the maximum endurable load under increasing load for through wall cracks or surface cracks are also proposed; determination of fatigue or creep-fatigue crack initiation based on the {sigma} approach calculating stress and strain at a characteristic distance d from the crack tip; evaluation of fatigue crack growth based on da/dN-{delta}K{sub eff} relationship with a {delta}K{sub eff} derived from a simplified estimation of {delta}J for the cyclic load; evaluation of creep-fatigue crack growth adding the fatigue crack growth and the creep crack growth during the hold time derived from a simplified evaluation of C{sup *}; Leak-Before-Break procedure. The fracture mechanic parameters determined in the A16 guide (K{sub 1}, J, C{sup *}) are derived from handbooks and formula in accordance with those proposed in the RSE-M document for in service inspection. Those are: the K{sub I} handbook for a large panel of surface and through-wall defect in plates, pipes and elbows; elastic stress and reference stress formula; analytical Js and Cs{sup *} formulations for mechanical and through thickness thermal load. The main part of the formula and assessment methodologies proposed in the A16 guide are included in a software, called MJSAM, developed under the MS Windows environment in support of the document. This allows a simple application of

  15. A French guideline for defect assessment at elevated temperature and leak before break analysis

    International Nuclear Information System (INIS)

    Drubay, B.; Chapuliot, St.; Lacire, M.H.; Marie, St.; Deschanels, H.; Cambefort, P.

    2001-01-01

    A large program is performed in France in order to develop, for the design and operating FBR (fast breeder reactor) plants, defect assessment procedures and Leak-Before-Break methods (L.B.B.). The main objective of this A16 guide is to propose analytical solutions at elevated temperature coherent with those proposed at low temperature by the RSE-M. The main items developed in this A16 guide for laboratory specimen, plates, pipes and elbows are the following: evaluation of ductile crack initiation and crack propagation based on the J parameter and material characteristics as J R -Δa curve or J i /G fr . Algorithms to evaluate the maximum endurable load under increasing load for through wall cracks or surface cracks are also proposed; determination of fatigue or creep-fatigue crack initiation based on the σ approach calculating stress and strain at a characteristic distance d from the crack tip; evaluation of fatigue crack growth based on da/dN-ΔK eff relationship with a ΔK eff derived from a simplified estimation of ΔJ for the cyclic load; evaluation of creep-fatigue crack growth adding the fatigue crack growth and the creep crack growth during the hold time derived from a simplified evaluation of C * ; Leak-Before-Break procedure. The fracture mechanic parameters determined in the A16 guide (K 1 , J, C * ) are derived from handbooks and formula in accordance with those proposed in the RSE-M document for in service inspection. Those are: the K I handbook for a large panel of surface and through-wall defect in plates, pipes and elbows; elastic stress and reference stress formula; analytical Js and Cs * formulations for mechanical and through thickness thermal load. The main part of the formula and assessment methodologies proposed in the A16 guide are included in a software, called MJSAM, developed under the MS Windows environment in support of the document. This allows a simple application of the analysis proposed in the document. (authors)

  16. Elevated CO2 reduced floret death in wheat under warmer average temperatures and terminal drought.

    Directory of Open Access Journals (Sweden)

    Eduardo eDias de Oliveira

    2015-11-01

    Full Text Available Elevated CO2 often increases grain yield in wheat by enhancing grain number per ear, which can result from an increase in the potential number of florets or a reduction in the death of developed florets. The hypotheses that elevated CO2 reduces floret death rather than increases floret development, and that grain size in a genotype with more grains per unit area is limited by the rate of grain filling, were tested in a pair of sister lines contrasting in tillering capacity (restricted- vs free-tillering. The hypotheses were tested under elevated CO2, combined with +3 C above ambient temperature and terminal drought, using specialized field tunnel houses. Elevated CO2 increased net leaf photosynthetic rates and likely the availability of carbon assimilates, which significantly reduced the rates of floret death and increased the potential number of grains at anthesis in both sister lines by an average of 42%. The restricted-tillering line had faster grain-filling rates than the free-tillering line because the free-tillering line had more grains to fill. Furthermore, grain-filling rates were faster under elevated CO2 and +3 C above ambient. Terminal drought reduced grain yield in both lines by 19%. Elevated CO2 alone increased the potential number of grains, but a trade-off in yield components limited grain yield in the free-tillering line. This emphasizes the need for breeding cultivars with a greater potential number of florets, since this was not affected by the predicted future climate variables.

  17. Elevated CO2 Reduced Floret Death in Wheat Under Warmer Average Temperatures and Terminal Drought

    Science.gov (United States)

    Dias de Oliveira, Eduardo; Palta, Jairo A.; Bramley, Helen; Stefanova, Katia; Siddique, Kadambot H. M.

    2015-01-01

    Elevated CO2 often increases grain yield in wheat by enhancing grain number per ear, which can result from an increase in the potential number of florets or a reduction in the death of developed florets. The hypotheses that elevated CO2 reduces floret death rather than increases floret development, and that grain size in a genotype with more grains per unit area is limited by the rate of grain filling, were tested in a pair of sister lines contrasting in tillering capacity (restricted- vs. free-tillering). The hypotheses were tested under elevated CO2, combined with +3°C above ambient temperature and terminal drought, using specialized field tunnel houses. Elevated CO2 increased net leaf photosynthetic rates and likely the availability of carbon assimilates, which significantly reduced the rates of floret death and increased the potential number of grains at anthesis in both sister lines by an average of 42%. The restricted-tillering line had faster grain-filling rates than the free-tillering line because the free-tillering line had more grains to fill. Furthermore, grain-filling rates were faster under elevated CO2 and +3°C above ambient. Terminal drought reduced grain yield in both lines by 19%. Elevated CO2 alone increased the potential number of grains, but a trade-off in yield components limited grain yield in the free-tillering line. This emphasizes the need for breeding cultivars with a greater potential number of florets, since this was not affected by the predicted future climate variables. PMID:26635837

  18. OSL at elevated temperatures: Towards the simultaneous thermal and optical stimulation

    International Nuclear Information System (INIS)

    Polymeris, George S.

    2015-01-01

    In routine OSL dating measurements, a preheat procedure at high temperatures is used to empty the shallow traps. Thus no contribution from shallow traps was expected as each OSL measurement is subsequently performed at moderately high temperatures, around 110–125 °C. The present work attempts to consider the OSL measurements performed at elevated temperatures without any previous preheat as a case of simultaneous thermal and optical stimulation of the same trap. Towards this direction, a set of proposed equations is derived for all three different cases of optical stimulation modes, namely CW-OSL, LM-OSL as well as PS-LM-OSL. According to these equations, indicative features of thermally activated OSL processes are expected, such as the steepening of CW-OSL decay curves as either stimulation temperature or intensity increases, as well as the shifting of the stimulation time of the maximum intensity for both LM-OSL and PS-LM-OSL curves towards shorter times with increasing temperatures. Experimentally, specific measurement sequences after varying stimulation temperature and/or intensity were applied in order to estimate the values of associated trap parameters, such as activation energy and photo-ionization cross-section. Experimental OSL data from a milky natural quartz sample stand in good agreement of these theoretical considerations in the case of 110 °C TL peak and the intense OSL component C 2 monitored at RT. - Highlights: • OSL at elevated temperatures without preheat results from two simultaneous stimulation modes. • Equations were derived assuming of linear superposition of two stimulation modes. • Data for 110 °C TL peak and OSL C 2 at RT stand in agreement with these equations. • Results verify the linear superposition of the two stimulation modes

  19. Thermophysical properties of multi-wall carbon nanotube bundles at elevated temperatures up to 830 K

    International Nuclear Information System (INIS)

    Wang, Xinwei; Wang, Jianmei; Huang, Xiaopeng; Eres, Gyula

    2011-01-01

    In this paper we discuss the results of thermal transport measurements in multi-wall carbon nanotube (MWCNT) bundles at elevated temperatures. A novel generalized electrothermal technique (GET) was developed for measuring the thermal diffusivity ( ) and conductivity (k) of MWCNT bundles. The results show that the feeding current has a negligible effect on the thermal properties. The measured k is larger than the reported values for unaligned bundles, and is comparable to that of typical aligned arrays. Compared with experimental and theoretical data for individual CNTs, k of the MWCNT bundles is two to three orders of magnitude lower, suggesting that the thermal transport in CNT bundles is dominated by the thermal contact resistance of tube-to-tube junctions. The effective density for the two MWCNT bundles, which is difficult to measure using other techniques, was determined to be 116 kg/m3 and 234 kg/m3, respectively. The temperature dependences of and k at temperatures up to 830 K was obtained. slightly decreases with temperature while k exhibits a small increase with temperature up to 500 K and then decreases. For the first time, the behavior of specific heat cp(T) for CNTs above room temperature was determined. The specific heat is close to graphite at 300-400 K but is lower than that for graphite above 400 K, indicating that the behavior of phonons in MWCNT bundles is dominated by boundary scattering rather than by the three-phonon Umklapp process. The length of the mean curvature between two adjacent tube contact points in these bundles is estimated to be on the order of micrometer to millimeter. The analysis of the radiation heat loss suggests that it needs to be considered when measuring the thermophysical properties of micro/nano wires of high aspect ratios at elevated temperatures, especially for individual CNTs due to their extremely small diameter.

  20. Development and evaluation of a HEPA filter for increased strength and resistance to elevated temperature

    International Nuclear Information System (INIS)

    Gilbert, H.; Bergman, W.; Fretthold, J.K.

    1992-01-01

    We have developed an improved HEPA filter for increased strength and resistance to elevated temperature to improve the reliability of HEPA filters under accident conditions. The improvements to the HEPA filter consist of a silicone rubber sealant and a new HEPA medium reinforced with a glass cloth. Several prototype filters were built and evaluated for temperature and pressure resistance and resistance to rough handling. The temperature resistance test consisted of exposing the HEPA filter to 1,000 scan at 700 degrees F for five minutes. The pressure resistance test consisted of exposing the HEPA filter to a differential pressure of 10 in. w.g. using a water saturated air flow at 95 degrees F. For the rough handling test, we used a vibrating machine designated the Q110. DOP filter efficiency tests were performed before and after each of the environmental tests. In addition to following the standard practice of using a separate new filter for each environmental test, we also subjected the same filter to the elevated temperature test followed by the pressure resistance test. The efficiency test results show that the improved HEPA filter is significantly better than the standard HEPA filter

  1. Development and evaluation of a HEPA filter for increased strength and resistance to elevated temperature

    International Nuclear Information System (INIS)

    Gilbert, H.; Bergman, W.; Fretthold, J.K.

    1993-01-01

    We have completed a preliminary study of an improved HEPA filter for increased strength and resistance to elevated temperature to improve the reliability of the standard deep pleated HEPA filter under accident conditions. The improvements to the HEPA filter consist of a silicone rubber sealant and a new HEPA medium reinforced with a glass cloth. Three prototype filters were built and evaluated for temperature and pressure resistance and resistance to rough handling. The temperature resistance test consisted of exposing the HEPA filter to 1,000 scan (1,700 m 3 /hr) at 700 degrees F (371 degrees C) for five minutes.The pressure resistance test consisted of exposing the HEPA filter to a differential pressure of 10 in. w.g. (2.5 kPa) using a water saturated air flow at 95 degrees F (35 degrees C). For the rough handling test, we used a vibrating machine designated the Q110. DOP filter efficiency tests were performed before and after each of the environmental tests. In addition to following the standard practice of using a separate new filter for each environmental test, we also subjected the same filter to the elevated temperature test followed by the pressure resistance test. The efficiency test results show that the improved HEPA filter is significantly better than the standard HEPA filter. Further studies are recommended to evaluate the improved HEPA filter and to assess its performance under more severe accident conditions

  2. A New Experimental Design to Study the Kinetics of Solid Dissolution into Liquids at Elevated Temperature

    Science.gov (United States)

    Wang, Huijun; White, Jesse F.; Sichen, Du

    2018-04-01

    A new method was developed to study the dissolution of a solid cylinder in a liquid under forced convection at elevated temperature. In the new design, a rotating cylinder was placed concentrically in a crucible fabricated by boring four holes into a blank material for creating an internal volume with a quatrefoil profile. A strong flow in the radial direction in the liquid was created, which was evidently shown by computational fluid dynamic (CFD) calculations and experiments at both room temperature and elevated temperature. The new setup was able to freeze the sample as it was at experimental temperature, particularly the interface between the solid and the liquid. This freezing was necessary to obtain reliable information for understanding the reaction mechanism. This was exemplified by the study of dissolution of a refractory in liquid slag. The absence of flow in the radial direction in the traditional setup using a symmetrical cylinder was also discussed. The differences in the findings by past investigators using the symmetrical cylinder are most likely due to the extent of misalignment of the cylinder in the containment vessel.

  3. Effect of elevated temperature on the tensile strength of Napier/glass-epoxy hybrid reinforced composites

    Science.gov (United States)

    Ridzuan, M. J. M.; Majid, M. S. Abdul; Afendi, M.; Firdaus, A. Z. Ahmad; Azduwin, K.

    2017-11-01

    The effects of elevated temperature on the tensile strength of Napier/glass-epoxy hybrid reinforced composites and its morphology of fractured surfaces are discussed. Napier/glass-epoxy hybrid reinforced composites were fabricated by using vacuum infusion method by arranging Napier fibres in between sheets of woven glass fibres. Napier and glass fibres were laminated with estimated volume ratios were 24 and 6 vol. %, respectively. The epoxy resin was used as matrix estimated to 70 vol. %. Specimens were tested to failure under tension at a cross-head speed of 1 mm/min using Universal Testing Machine (Instron) with a load cell 100 kN at four different temperatures of RT, 40°C, 60°C and 80°C. The morphology of fractured surface of hybrid composites was investigated by field emission scanning electron microscopy. The result shows reduction in tensile strength at elevated temperatures. The increase in the temperature activates the process of diffusion, and generates critical stresses which cause the damage at first-ply or at the centre of the hybrid plate, as a result lower the tensile strength. The observation of FESEM images indicates that the fracture mode is of evolution of localized damage, from fibre/matrix debonding, matric cracking, delamination and fibre breakage.

  4. Mechanical Properties of T650-35/AFR-PE-4 at Elevated Temperatures for Lightweight Aeroshell Designs

    Science.gov (United States)

    Whitley, Karen S.; Collins, TImothy J.

    2006-01-01

    Considerable efforts have been underway to develop multidisciplinary technologies for aeroshell structures that will significantly increase the allowable working temperature for the aeroshell components, and enable the system to operate at higher temperatures while sustaining performance and durability. As part of these efforts, high temperature polymer matrix composites and fabrication technologies are being developed for the primary load bearing structure (heat shield) of the spacecraft. New high-temperature resins and composite material manufacturing techniques are available that have the potential to significantly improve current aeroshell design. In order to qualify a polymer matrix composite (PMC) material as a candidate aeroshell structural material, its performance must be evaluated under realistic environments. Thus, verification testing of lightweight PMC's at aeroshell entry temperatures is needed to ensure that they will perform successfully in high-temperature environments. Towards this end, a test program was developed to characterize the mechanical properties of two candidate material systems, T650-35/AFR-PE-4 and T650-35/RP46. The two candidate high-temperature polyimide resins, AFR-PE-4 and RP46, were developed at the Air Force Research Laboratory and NASA Langley Research Center, respectively. This paper presents experimental methods, strength, and stiffness data of the T650-35/AFR-PE-4 material as a function of elevated temperatures. The properties determined during the research test program herein, included tensile strength, tensile stiffness, Poisson s ratio, compressive strength, compressive stiffness, shear modulus, and shear strength. Unidirectional laminates, a cross-ply laminate and two eight-harness satin (8HS)-weave laminates (4-ply and 10-ply) were tested according to ASTM standard methods at room and elevated temperatures (23, 316, and 343 C). All of the relevant test methods and data reduction schemes are outlined along with

  5. Elastic properties of Sr- and Mg-doped lanthanum gallate at elevated temperature

    Science.gov (United States)

    Okamura, T.; Shimizu, S.; Mogi, M.; Tanimura, M.; Furuya, K.; Munakata, F.

    The elastic moduli, i.e., Young's modulus, shear modulus and Poisson's ratio, of a sintered La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ bulk have been experimentally determined in the temperature range from room temperature to 1373 K using a resonance technique. Anomalous elastic properties were observed over a wide temperature range from 473 to 1173 K. In the results for internal friction and in X-ray diffraction measurements at elevated temperature, two varieties of structural changes were seen in La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ in the examined temperature range. The results agreed with the findings of a previous crystallographic study of the same composition system by Slater et al. In addition, the temperature range in which a successive structural change occurred in La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ was the same as that exhibiting the anomalous elastic properties. Taking all the results together, it can be inferred that the successive structural change in the significant temperature range is responsible for the elastic property anomaly of La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ.

  6. Characteristics of ocular temperature elevations after exposure to quasi- and millimeter waves (18-40 GHz)

    Science.gov (United States)

    Kojima, Masami; Suzuki, Yukihisa; Tsai, Cheng-Yu; Sasaki, Kensuke; Wake, Kanako; Watanabe, Soichi; Taki, Masao; Kamimura, Yoshitsugu; Hirata, Akimasa; Sasaki, Kazuyuki; Sasaki, Hiroshi

    2015-04-01

    In order to investigate changes in ocular temperature in rabbit eyes exposed to different frequencies (18 to 40 GHz) of quasi-millimeter waves, and millimeter waves (MMW). Pigmented rabbits were anesthetized with both general and topical anesthesia, and thermometer probes (0.5 mm in diameter) were inserted into their cornea (stroma), lens (nucleus) and vitreous (center of vitreous). The eyes were exposed unilaterally to 200 mW/cm2 by horn antenna for 3 min at 18, 22 and 26.5 GHz using a K band exposure system or 26.5, 35 and 40 GHz using a Ka band exposure system. Changes in temperature of the cornea, lens and vitreous were measured with a fluoroptic thermometer. Since the ocular temperatures after exposure to 26.5 GHz generated by the K band and Ka band systems were similar, we assumed that experimental data from these 2 exposure systems were comparable. The highest ocular temperature was induced by 40 GHz MMW, followed by 35 GHz. The 26.5 and 22 GHz corneal temperatures were almost the same. The lowest temperature was recorded at 18 GHz. The elevation in ocular temperature in response to exposure to 200 mW/cm2 MMW is dependent on MMW frequency. MMW exposure induced heat is conveyed not only to the cornea but also the crystalline lens.

  7. Real-Time Prediction of Temperature Elevation During Robotic Bone Drilling Using the Torque Signal.

    Science.gov (United States)

    Feldmann, Arne; Gavaghan, Kate; Stebinger, Manuel; Williamson, Tom; Weber, Stefan; Zysset, Philippe

    2017-09-01

    Bone drilling is a surgical procedure commonly required in many surgical fields, particularly orthopedics, dentistry and head and neck surgeries. While the long-term effects of thermal bone necrosis are unknown, the thermal damage to nerves in spinal or otolaryngological surgeries might lead to partial paralysis. Previous models to predict the temperature elevation have been suggested, but were not validated or have the disadvantages of computation time and complexity which does not allow real time predictions. Within this study, an analytical temperature prediction model is proposed which uses the torque signal of the drilling process to model the heat production of the drill bit. A simple Green's disk source function is used to solve the three dimensional heat equation along the drilling axis. Additionally, an extensive experimental study was carried out to validate the model. A custom CNC-setup with a load cell and a thermal camera was used to measure the axial drilling torque and force as well as temperature elevations. Bones with different sets of bone volume fraction were drilled with two drill bits ([Formula: see text]1.8 mm and [Formula: see text]2.5 mm) and repeated eight times. The model was calibrated with 5 of 40 measurements and successfully validated with the rest of the data ([Formula: see text]C). It was also found that the temperature elevation can be predicted using only the torque signal of the drilling process. In the future, the model could be used to monitor and control the drilling process of surgeries close to vulnerable structures.

  8. Effect of Elevated Temperature on Mechanical Assets of Metakaolin Base Steel Fiber Reinforced Concrete

    Science.gov (United States)

    Vijay Anand, M.; Ibrahim, Azmi; Patil, Anand A.; Muthu, K. U.

    2017-06-01

    The fact of vast usage of concrete leads to important problems regarding its design and preparation of eco-friendly to obtain an economic cost of the product on varieties of time periods. Conventional ordinary Portland concrete may not able to meet its functional requisites as it found inconsistency in high temperature. The exposing of concrete structure to elevated temperature may be in case of rocket launching space ships, nuclear power plants. In this experiment, to enhance the high temperature resistance, pozzolanic materials and steel fibres are added to preserve the strength characteristics of concrete structure. In this analysis, the pozzolanic admixture MK is used as partial replacement of cementatious materials. The volume fraction of steel fibre is varied 0.25%, 0.5%, 0.75% and 1% by preserving MK as stationary for 10% replacement of cement. The strength parameters of concrete such as compressive strength, split tensile strength and flexural strength are studied.

  9. Study of tertiary creep instability in several elevated-temperature structural materials

    International Nuclear Information System (INIS)

    Booker, M.K.; Sikka, V.K.

    1978-01-01

    Data for a number of common elevated temperature structural materials have been analyzed to yield mathematical predictions for the time and strain to tertiary creep at various rupture lives and temperatures. Materials examined include types 304 and 316 stainless steel, 2 1/4 Cr-1 Mo steel, alloy 800H, alloy 718, Hastelloy alloy X, and ERNiCr--3 weld metal. Data were typically examined over a range of creep temperatures for rupture lives ranging from less than 100 to greater than 10,000 hours. Within a given material, trends in these quantities can be consistently described, but it is difficult to directly relate the onset of tertiary creep to failure-inducing instabilities. A series of discontinued tests for alloy 718 at 649 and 620 0 C showed that the material fails by intergranular cracking but that no significant intergranular cracking occurs until well after the onset of tertiary creep

  10. Preparation and Dynamic Mechanical Properties at Elevated Temperatures of a Tungsten/Glass Composite

    Science.gov (United States)

    Gao, Chong; Wang, Yingchun; Ma, Xueya; Liu, Keyi; Wang, Yubing; Li, Shukui; Cheng, Xingwang

    2018-03-01

    Experiments were conducted to prepare a borosilicate glass matrix composite containing 50 vol.% tungsten and examine its dynamic compressive behavior at elevated temperatures in the range of 450-775 °C. The results show that the homogenous microstructure of the tungsten/glass composite with relative density of 97% can be obtained by hot-pressing sintering at 800 °C for 1 h under pressure of 30 MPa. Dynamic compressive testing was carried out by a separate Hopkinson pressure bar system with a synchronous device. The results show that the peak stress decreases and the composite transforms from brittle to ductile in nature with testing temperature increasing from 450 to 750 °C. The brittle-ductile transition temperature is about 500 °C. Over 775 °C, the composite loses load-bearing capacity totally because of the excessive softening of the glass phase. In addition, the deformation and failure mechanism were analyzed.

  11. Development of elevated temperature fatigue design information for type 316 stainless steel

    International Nuclear Information System (INIS)

    Jaske, C.E.; Mindlin, H.; Perrin, J.S.

    1975-01-01

    To develop material properties information for use in elevated-temperature fatigue design, an extensive study of the fatigue and stress-strain behaviour of Type 316 stainless steel was conducted at temperatures from 21 to 649 0 C. Fatigue life and cyclic stress-strain curves were developed. Creep-fatigue interaction was evaluated by conducting strain hold-time tests at 566 and 649 0 C. Hold periods at peak tensile strain produced a large reduction in cyclic life. It was found that both a linear damage rule and the strain-partitioning method could be used to assess cumulative creep and fatigue damage. Aging for 1000 h at test temperature before testing caused only small or no changes in continuous cycling fatigue resistance at 566 and 649 0 C and in tension hold-time fatigue resistance at 566 0 C. This aging produced a significant increase in tension hold-time fatigue resistance at 649 0 C. (author)

  12. Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine[OPEN

    Science.gov (United States)

    2016-01-01

    Rising global temperature and CO2 levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO2, affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L−1) or elevated (800 μmol mol−1) CO2, and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO2 (LTAC), elevated temperature/ambient CO2 (ETAC), or elevated temperature/elevated CO2 (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus. Our findings suggest that exposure to elevated temperature and CO2 during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO2 also impaired freezing tolerance. However, unless the frequency and timing of extreme low-temperature

  13. Al based ultra-fine eutectic with high room temperature plasticity and elevated temperature strength

    Energy Technology Data Exchange (ETDEWEB)

    Tiwary, C.S., E-mail: cst311@gmail.com [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, Karnataka (India); Kashyap, S. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, Karnataka (India); Kim, D.H. [Center for Non-Crystalline Materials, Department of Metallurgical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Chattopadhyay, K. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, Karnataka (India)

    2015-07-15

    Developments of aluminum alloys that can retain strength at and above 250 °C present a significant challenge. In this paper we report an ultrafine scale Al–Fe–Ni eutectic alloy with less than 3.5 at% transition metals that exhibits room temperature ultimate tensile strength of ~400 MPa with a tensile ductility of 6–8%. The yield stress under compression at 300 °C was found to be 150 MPa. We attribute it to the refinement of the microstructure that is achieved by suction casting in copper mold. The characterization using scanning and transmission electron microscopy (SEM and TEM) reveals an unique composite structure that contains the Al–Al{sub 3}Ni rod eutectic with spacing of ~90 nm enveloped by a lamellar eutectic of Al–Al{sub 9}FeNi (~140 nm). Observation of subsurface deformation under Vickers indentation using bonded interface technique reveals the presence of extensive shear banding during deformation that is responsible for the origin of ductility. The dislocation configuration in Al–Al{sub 3}Ni eutectic colony indicates accommodation of plasticity in α-Al with dislocation accumulation at the α-Al/Al{sub 3}Ni interface boundaries. In contrast the dislocation activities in the intermetallic lamellae are limited and contain set of planner dislocations across the plates. We present a detailed analysis of the fracture surface to rationalize the origin of the high strength and ductility in this class of potentially promising cast alloy.

  14. Bending Strength of EN AC-44200 – Al2O3 Composites at Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Kurzawa A.

    2017-03-01

    Full Text Available The paper presents results of bend tests at elevated temperatures of aluminium alloy EN AC-44200 (AlSi12 based composite materials reinforced with aluminium oxide particles. The examined materials were manufactured by squeeze casting. Preforms made of Al2O3 particles, with volumetric fraction 10, 20, 30 and 40 vol.% of particles joined with sodium silicate bridges were used as reinforcement. The preforms were characterised by open porosity ensuring proper infiltration with the EN AC-44200 (AlSi12 liquid alloy. The largest bending strength was found for the materials containing 40 vol.% of reinforcing ceramic particles, tested at ambient temperature. At increased test temperature, bending strength Rg of composites decreased in average by 30 to 50 MPa per 100°C of temperature increase. Temperature increase did not significantly affect cracking of the materials. Cracks propagated mainly along the interfaces particle/matrix, with no effect of the particles falling-out from fracture surfaces. Direction of cracking can be affected by a small number of agglomerations of particles or of non-reacted binder. In the composites, the particles strongly restrict plastic deformation of the alloy, which leads to creation of brittle fractures. At elevated temperatures, however mainly at 200 and 300°C, larger numbers of broken, fragmented particles was observed in the vicinity of cracks. Fragmentation of particles occurred mainly at tensioned side of the bended specimens, in the materials with smaller fraction of Al2O3 reinforcement, i.e. 10 and 20 vol.%.

  15. Plant Pathogenic Microbial Communication Affected by Elevated Temperature in Pectobacterium carotovorum subsp. carotovorum.

    Science.gov (United States)

    Saha, N D; Chaudhary, A; Singh, S D; Singh, D; Walia, S; Das, T K

    2015-11-01

    Gram-negative plant pathogenic bacteria regulate specific gene expression in a population density-dependent manner by sensing level of Acyl-Homoserine Lactone (HSL) molecules which they produce and liberate to the environment, called Quorum Sensing (QS). The production of virulence factors (extracellular enzyme viz. cellulase, pectinase, etc.) in Pectobacterium carotovorum subsp. carotovorum (Pcc) is under strong regulation of QS. The QS signal molecule, N-(3-oxohexanoyl)-L-Homoserine Lactone (OHHL) was found as the central regulatory system for the virulence factor production in Pcc and is also under strict regulation of external environmental temperature. Under seven different incubation temperatures (24, 26, 28, 30, 33, 35, and 37 °C) in laboratory condition, highest amount of OHHL (804 violacein unit) and highest (79 %) Disease Severity Index (DSI) were measured at 33 °C. The OHHL production kinetics showed accumulation of highest concentration of OHHL at late log phase of the growth but diminution in the concentration occurred during stationary phase onwards to death phase. At higher temperature (35 and 37 °C) exposure, OHHL was not at detectable range. The effect of temperature on virulence factor production is the concomitant effect of HSL production and degradation which justifies less disease severity index in cross-inoculated tomato fruits incubated at 35 and 37 °C. The nondetection of the OHHL in the elevated temperature may because of degradation as these signal molecules are quite sensitive and prone to get degraded under different physical factors. This result provides the rationale behind the highest disease severity up to certain elevated temperature and leaves opportunities for investigation on mutation, co-evolution of superior plant pathogen with more stable HSL signals-mediated pathogenesis under global warming context.

  16. A microscopic investigation of failure mechanisms in a triaxially braided polyimide composite at room and elevated temperatures

    International Nuclear Information System (INIS)

    Montesano, John; Fawaz, Zouheir; Poon, Cheung; Behdinan, Kamran

    2014-01-01

    Highlights: • Experimental investigation on a unique braided polyimide composite material. • Tensile static and fatigue tests at both room temperature and elevated temperature. • Tests reveal that elevated temperature causes a reduction in microscopic damage. • Temperature-dependent damage development caused a reduction in fatigue life. • A fundamental understanding of the novel material behavior was achieved. - Abstract: An experimental investigation is conducted on a unique triaxially braided polyimide composite material in order to track the development of microscopic damage leading to failure. Tensile static and fatigue tests are conducted at both room and elevated temperatures. Edge replication and scanning electron microscopy are employed to track damage development and to identify failure mechanisms, respectively. Static tests reveal that although the elevated temperature environment does not significantly alter the mechanical properties of the composite, its influence on the development of microscopic damage development is notable. The dominant damage mechanism of braider yarn cracking is mitigated at elevated temperatures as a direct result of resin softening, which is also the case for the fatigue test specimens. The result of the temperature-dependent microscopic damage development is a reduction in the fatigue lives at elevated temperatures. This study yielded an improved understanding of microscopic damage mechanisms and local deformation behavior for an advanced composite material, which is valuable for designers

  17. Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress

    Science.gov (United States)

    Jia, Xia; Zhao, Yonghua; Wang, Wenke; He, Yunhua

    2015-09-01

    The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and L-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings.

  18. OSMOTIC COEFFICIENTS, SOLUBILITIES, AND DELIQUESCENCE RELATIONS IN MIXED AQUEOUS SALT SOLUTIONS AT ELEVATED TEMPERATURE

    International Nuclear Information System (INIS)

    M.S. Gruszkiewicz; D.A. Palmer

    2006-01-01

    While thermodynamic properties of pure aqueous electrolytes are relatively well known at ambient temperature, there are far fewer data for binary systems extending to elevated temperatures and high concentrations. There is no general theoretically sound basis for prediction of the temperature dependence of ionic activities, and consequently temperature extrapolations based on ambient temperature data and empirical equations are uncertain and require empirical verification. Thermodynamic properties of mixed brines in a wide range of concentrations would enhance the understanding and precise modeling of the effects of deliquescence of initially dry solids in humid air in geological environments and in modeling the composition of waters during heating, cooling, evaporation or condensation processes. These conditions are of interest in the analysis of waters on metal surfaces at the proposed radioactive waste repository at Yucca Mountain, Nevada. The results obtained in this project will be useful for modeling the long-term evolution of the chemical environment, and this in turn is useful for the analysis of the corrosion of waste packages. In particular, there are few reliable experimental data available on the relationship between relative humidity and composition that reveals the eutonic points of the mixtures and the mixture deliquescence RH. The deliquescence RH for multicomponent mixtures is lower than that of pure component or binary solutions, but is not easy to predict quantitatively since the solutions are highly nonideal. In this work we used the ORNL low-temperature and high-temperature isopiestic facilities, capable of precise measurements of vapor pressure between ambient temperature and 250 C for determination of not only osmotic coefficients, but also solubilities and deliquescence points of aqueous mixed solutions in a range of temperatures. In addition to standard solutions of CaCl 2 , LiCl, and NaCl used as references, precise direct

  19. Temperature elevation by HIFU in ex vivo porcine muscle: MRI measurement and simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Solovchuk, Maxim A., E-mail: solovchuk@gmail.com [Center for Advanced Study in Theoretical Sciences (CASTS), National Taiwan University, Taipei 10617, Taiwan (China); Hwang, San Chao; Chang, Hsu [Medical Engineering Research Division, National Health Research Institute, Miaoli 35053, Taiwan (China); Thiriet, Marc [Sorbonne Universités, UPMC Univ Paris 06, UMR 7598, Laboratoire Jacques-Louis Lions, F-75005, Paris (France); Sheu, Tony W. H., E-mail: twhsheu@ntu.edu.tw [Department of Engineering Science and Ocean Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, Republic of China and Center for Advanced Study in Theoretical Sciences (CASTS), National Taiwan University, Taipei 10617, Taiwan (China)

    2014-05-15

    Purpose: High-intensity focused ultrasound is a rapidly developing medical technology with a large number of potential clinical applications. Computational model can play a pivotal role in the planning and optimization of the treatment based on the patient's image. Nonlinear propagation effects can significantly affect the temperature elevation and should be taken into account. In order to investigate the importance of nonlinear propagation effects, nonlinear Westervelt equation was solved. Weak nonlinear propagation effects were studied. The purpose of this study was to investigate the correlation between the predicted and measured temperature elevations and lesion in a porcine muscle. Methods: The investigated single-element transducer has a focal length of 12 cm, an aperture of 8 cm, and frequency of 1.08 MHz. Porcine muscle was heated for 30 s by focused ultrasound transducer with an acoustic power in the range of 24–56 W. The theoretical model consists of nonlinear Westervelt equation with relaxation effects being taken into account and Pennes bioheat equation. Results: Excellent agreement between the measured and simulated temperature rises was found. For peak temperatures above 85–90 °C “preboiling” or cavitation activity appears and lesion distortion starts, causing small discrepancy between the measured and simulated temperature rises. From the measurements and simulations, it was shown that distortion of the lesion was caused by the “preboiling” activity. Conclusions: The present study demonstrated that for peak temperatures below 85–90 °C numerical simulation results are in excellent agreement with the experimental data in three dimensions. Both temperature rise and lesion size can be well predicted. Due to nonlinear effect the temperature in the focal region can be increased compared with the linear case. The current magnetic resonance imaging (MRI) resolution is not sufficient. Due to the inevitable averaging the measured

  20. Low-cyclic fatigue behavior of modified 9Cr–1Mo steel at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Guguloth, Krishna; Sivaprasad, S. [CSIR-National Metallurgical laboratory, Material Science and Technology Division, Jamshedpur 831007 (India); Chakrabarti, D. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Tarafder, S. [CSIR-National Metallurgical laboratory, Material Science and Technology Division, Jamshedpur 831007 (India)

    2014-05-01

    The low-cycle fatigue behavior of indigenously developed modified 9Cr–1Mo steel has been evaluated using a constant strain rate (1×10{sup −3} s{sup −1}) at ambient temperature (25 °C) and at elevated temperatures (500–600 °C) over the strain amplitudes varying between ±0.7% and ±1.2%. Cyclic stress response showed a gradual softening regime that ended in a stress plateau until complete failure of the specimens. The estimated fatigue life decreased with the increase in test temperature. The effect of temperature on fatigue life was more pronounced at lower strain amplitudes. The cyclic deformation behavior at different temperatures has been analyzed from hysteresis loop and also in view of the changes taking place in dislocation structure and dislocation–precipitation interaction. Evaluation of low-cycle fatigue properties of modified 9Cr–1Mo steel over a range of test temperature can help in designing components for in-core applications in fast breeder reactors and in super heaters for nuclear power plants.

  1. Air and ground temperatures along elevation and continentality gradients in Southern Norway

    Science.gov (United States)

    Farbrot, Herman; Hipp, Tobias; Etzelmüller, Bernd; Humlum, Ole; Isaksen, Ketil; Strand Ødegârd, Rune

    2010-05-01

    The modern southern boundary for Scandinavian permafrost is located in the mountains of Southern Norway. Permafrost and seasonal frost are considered key components of the cryosphere, and the climate-permafrost relation has acquired added importance with the increasing awareness and concern of rising air temperatures. The three-year research project CRYOLINK ("Permafrost and seasonal frost in southern Norway") aims at improving knowledge on past and present ground temperatures, seasonal frost, and distribution of mountain permafrost in Southern Norway by addressing the fundamental problem of heat transfer between the atmosphere and the ground surface. Hence, several shallow boreholes have been drilled, and a monitoring program to measure air and ground temperatures was started August 2008. The borehole areas (Juvvass, Jetta and Tron) are situated along a west-east transect and, hence, a continentality gradient, and each area provides boreholes at different elevations. Here we present the first year of air and ground temperatures from these sites and discuss the influence of air temperature and ground surface charcteristics (snow conditions, sediments/bedrock, vegetation) on ground temperatures.

  2. In-situ Elevated Temperature Mechanical Performance of MWCNT/epoxy Nanocomposite

    Directory of Open Access Journals (Sweden)

    Bhanu Pratap Singh

    2017-03-01

    Full Text Available The present investigation has been focused on the effects of multi-walled carbon nanotube (MWCNT addition on the mechanical performance of epoxy under different in-service elevated temperature environments. Room temperature flexural test results revealed that addition of 0.1 wt. % MWCNT into epoxy resin resulted in modulus and strength enhancement of 21 % and 9 % respectively. With increase in service temperature, significant decrement in both modulus and strength was noticed for both materials (neat epoxy and MWCNT/epoxy nanocomposite, but the rate of degradation was found to be quite drastic for the nanocomposite. At 90 °C temperature, the CNT/epoxy nanocomposite exhibited inferior modulus and strength, which are 41 % and 59 % lower than neat epoxy respectively. The variation trend in elastic modulus with temperature obtained from both flexural testing and DMA for both these materials was also analyzed. It was found that addition of 0.1 % CNT in the epoxy reduced the glass transition temperature by about 16°C.

  3. Pourbaix Diagrams at Elevated Temperatures A Study of Zinc and Tin

    Science.gov (United States)

    Palazhchenko, Olga

    Metals in industrial settings such as power plants are often subjected to high temperature and pressure aqueous environments, where failure to control corrosion compromises worker and environment safety. For instance, zircaloy (1.2-1.7 wt.% Sn) fuel rods are exposed to aqueous 250-310 °C coolant in CANDU reactors. The Pourbaix (EH-pH) diagram is a plot of electrochemical potential versus pH, which shows the domains of various metal species and by inference, corrosion susceptibility. Elevated temperature data for tin +II and tin +IV species were obtained using solid-aqueous phase equilibria with the respective oxides, in a batch vessel with in-situ pH measurement. Solubilities, determined via spectroscopic techniques, were used to calculate equilibrium constants and the Gibbs energies of Sn complexes for E-pH diagram construction. The SnOH3+ and Sn(OH )-5 species were incorporated, for the first time, into the 298.15 K and 358.15 K diagrams, with novel Go values determined at 358.15 K. Key words: Pourbaix diagrams, EH-pH, elevated temperatures, solubility, equilibrium, metal oxides, hydrolysis, redox potential, pH, thermochemical data, tin, zinc, zircaloy, corrosion, passivity.

  4. Measurements of Young's and shear moduli of rail steel at elevated temperatures.

    Science.gov (United States)

    Bao, Yuanye; Zhang, Haifeng; Ahmadi, Mehdi; Karim, Md Afzalul; Felix Wu, H

    2014-03-01

    The design and modelling of the buckling effect of Continuous Welded Rail (CWR) requires accurate material constants, especially at elevated temperatures. However, such material constants have rarely been found in literature. In this article, the Young's moduli and shear moduli of rail steel at elevated temperatures are determined by a new sonic resonance method developed in our group. A network analyser is used to excite a sample hanged inside a furnace through a simple tweeter type speaker. The vibration signal is picked up by a Polytec OFV-5000 Laser Vibrometer and then transferred back to the network analyser. Resonance frequencies in both the flexural and torsional modes are measured, and the Young's moduli and shear moduli are determined through the measured resonant frequencies. To validate the measured elastic constants, the measurements have been repeated by using the classic sonic resonance method. The comparisons of obtained moduli from the two methods show an excellent consistency of the results. In addition, the material elastic constants measured are validated by an ultrasound test based on a pulse-echo method and compared with previous published results at room temperature. The measured material data provides an invaluable reference for the design of CWR to avoid detrimental buckling failure. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Comparison of elevated temperature design codes of ASME Subsection NH and RCC-MRx

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeong-Yeon, E-mail: hylee@kaeri.re.kr

    2016-11-15

    Highlights: • Comparison of elevated temperature design (ETD) codes was made. • Material properties and evaluation procedures were compared. • Two heat-resistant materials of Grade 91 steel and austenitic stainless steel 316 are the target materials in the present study. • Application of the ETD codes to Generation IV reactor components and a comparison of the conservatism was conducted. - Abstract: The elevated temperature design (ETD) codes are used for the design evaluation of Generation IV (Gen IV) reactor systems such as sodium-cooled fast reactor (SFR), lead-cooled fast reactor (LFR), and very high temperature reactor (VHTR). In the present study, ETD code comparisons were made in terms of the material properties and design evaluation procedures for the recent versions of the two major ETD codes, ASME Section III Subsection NH and RCC-MRx. Conservatism in the design evaluation procedures was quantified and compared based on the evaluation results for SFR components as per the two ETD codes. The target materials are austenitic stainless steel 316 and Mod.9Cr-1Mo steel, which are the major two materials in a Gen IV SFR. The differences in the design evaluation procedures as well as the material properties in the two ETD codes are highlighted.

  6. Microstructure and elevated-temperature erosion-oxidation behaviour of aluminized 9Cr-1Mo Steel

    Science.gov (United States)

    Huttunen-Saarivirta, E.; Honkanen, M.; Tsipas, S. A.; Omar, H.; Tsipas, D.

    2012-10-01

    Degradation of materials by a combination of erosive wear and atmospheric oxidation at elevated temperatures constitutes a problem in some power generation processes, such as fluidized-bed combustion. In this work, 9Cr-1Mo steel, a common tube material in combustion chambers, is coated by a pack cementation method from an Al-containing pack in order to improve the resistance to erosion-oxidation at elevated temperatures. The resulting coating is studied in terms of microstructure and microhardness and tested for its resistance against impacts by sand particles in air at temperatures of 550-700 °C under several conditions, with thickness changes and appearance of the exposed surfaces being studied. The coating was found to contain several phases and layers, the outermost of which was essentially Al-rich and contained e.g., small AlN precipitates. The microhardness values for such coating ranged from 950 to 1100 HV20g. The coating provided the substrate with increased protection particularly against normal particle impacts, as manifested by smaller thickness losses for coated specimens as compared to uncoated counterparts. However, much of the coating was lost under all test conditions, despite the fact that particle debris formed a homogeneous layer on the surface. These results are described and discussed in this paper.

  7. Resilience of the prokaryotic microbial community of Acropora digitifera to elevated temperature.

    Science.gov (United States)

    Gajigan, Andrian P; Diaz, Leomir A; Conaco, Cecilia

    2017-08-01

    The coral is a holobiont formed by the close interaction between the coral animal and a diverse community of microorganisms, including dinoflagellates, bacteria, archaea, fungi, and viruses. The prokaryotic symbionts of corals are important for host fitness but are also highly sensitive to changes in the environment. In this study, we used 16S ribosomal RNA (rRNA) sequencing to examine the response of the microbial community associated with the coral, Acropora digitifera, to elevated temperature. The A. digitifera microbial community is dominated by operational taxonomic unit (OTUs) affiliated with classes Alphaproteobacteria and Gammaproteobacteria. The prokaryotic community in the coral tissue is distinct from that of the mucus and the surrounding seawater. Remarkably, the overall microbial community structure of A. digitifera remained stable for 10 days of continuous exptosure at 32°C compared to corals maintained at 27°C. However, the elevated temperature regime resulted in a decrease in the abundance of OTUs affiliated with certain groups of bacteria, such as order Rhodobacterales. On the other hand, some OTUs affiliated with the orders Alteromonadales, Vibrionales, and Flavobacteriales, which are often associated with diseased and stressed corals, increased in abundance. Thus, while the A. digitifera bacterial community structure appears resilient to higher temperature, prolonged exposure and intensified stress results in changes in the abundance of specific microbial community members that may affect the overall metabolic state and health of the coral holobiont. © 2017 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

  8. Investigation of impact toughness of a Ni-based superalloy at elevated temperature

    International Nuclear Information System (INIS)

    Yang, Y.H.; Yu, J.J.; Sun, X.F.; Jin, T.; Guan, H.R.; Hu, Z.Q.

    2012-01-01

    Highlights: ► The samples show highest impact toughness at 600 °C. ► The impact toughness of samples impact at 760 °C drops sharply. ► The voids nucleation and growth are fracture mechanism at elevated temperature. ► The decrease in strength of grain boundaries causes reduction in impact toughness. -- Abstract: The impact toughness of M951 alloy is investigated in temperature range between 20 °C and 800 °C. The results show that the impact toughness of samples impacted at 600 °C shows highest impact toughness value, the impact toughness value drops sharply when the samples impacted at 760 °C. In addition samples impacted at 800 °C show the higher impact toughness than that of samples impact at 760 °C. The scanning electron microscope observations show that cracks initiate at carbides particles due to high stress concentration, which leads to low impact toughness value at 20 °C. The dimples which can absorb more energy are formed during the impact at 600 °C. The samples impacted at 760 °C show lowest impact toughness. Additionally, the dimples nucleation, growth and coalescence are the major fracture mechanism at elevated temperature.

  9. The response of rice (Oryza sativa L. to elevated night temperature with application of Pyraclostobin

    Directory of Open Access Journals (Sweden)

    T.Y. Wahjanto

    2016-07-01

    Full Text Available Rice productivity is having a problem related with climate change phenomenon, mainly the global warming. The rising of temperature in some country threat the rice production. The increasing of temperature is a major limiting factor that affects yield through the growth and development of rice plant. This study was aimed to examine the response of rice (Oryza sativa L. to elevated night temperature with the application of Pyraclostobin. A glasshouse experiment that was conducted from March to August 2015 at Brawijaya University Research Station of Jatikerto – Malang, used nested plot design with three replications and two treatments. The first treatments were the night temperature level (normal temperature, increased 2oC, and increased 4oC. The second treatments were the concentration of Pyraclostrobin (0 ppm, 400 ppm and 800 ppm. Results of the study showed that the increase of temperature at night for about 2oC and 4oC, as well as application of Pyraclostrobin, affected growth and yield of rice. Application of Pyraclostrobin by concentrations of 400 ppm and 800 ppm effectively reduced yield loss by increasing night temperature of 2oC, which resulted in 20.20% and 24.93%, respectively, in comparison with the control; while the increase of night temperature by 4oC have resulted 26.86% and 33.33% in comparison with the control. Pyraclostrobin was effective in maintaining percentage of the filled spikelets by the increase of temperature at night for about 2oC and 4oC.

  10. The effects of elevated seawater temperatures on Caribbean gorgonian corals and their algal symbionts, Symbiodinium spp.

    Directory of Open Access Journals (Sweden)

    Tamar L Goulet

    Full Text Available Global climate change not only leads to elevated seawater temperatures but also to episodic anomalously high or low temperatures lasting for several hours to days. Scleractinian corals are detrimentally affected by thermal fluctuations, which often lead to an uncoupling of their mutualism with Symbiodinium spp. (coral bleaching and potentially coral death. Consequently, on many Caribbean reefs scleractinian coral cover has plummeted. Conversely, gorgonian corals persist, with their abundance even increasing. How gorgonians react to thermal anomalies has been investigated utilizing limited parameters of either the gorgonian, Symbiodinium or the combined symbiosis (holobiont. We employed a holistic approach to examine the effect of an experimental five-day elevated temperature episode on parameters of the host, symbiont, and the holobiont in Eunicea tourneforti, E. flexuosa and Pseudoplexaura porosa. These gorgonian corals reacted and coped with 32°C seawater temperatures. Neither Symbiodinium genotypes nor densities differed between the ambient 29.5°C and 32°C. Chlorophyll a and c2 per Symbiodinium cell, however, were lower at 32°C leading to a reduction in chlorophyll content in the branches and an associated reduction in estimated absorbance and increase in the chlorophyll a specific absorption coefficient. The adjustments in the photochemical parameters led to changes in photochemical efficiencies, although these too showed that the gorgonians were coping. For example, the maximum excitation pressure, Qm, was significantly lower at 32°C than at 29.5°C. In addition, although per dry weight the amount of protein and lipids were lower at 32°C, the overall energy content in the tissues did not differ between the temperatures. Antioxidant activity either remained the same or increased following exposure to 32°C further reiterating a response that dealt with the stressor. Taken together, the capability of Caribbean gorgonian corals to modify

  11. Evolution of precipitate in nickel-base alloy 718 irradiated with argon ions at elevated temperature

    International Nuclear Information System (INIS)

    Jin, Shuoxue; Luo, Fengfeng; Ma, Shuli; Chen, Jihong; Li, Tiecheng; Tang, Rui; Guo, Liping

    2013-01-01

    Alloy 718 is a nickel-base superalloy whose strength derives from γ′(Ni 3 (Al,Ti)) and γ″(Ni 3 Nb) precipitates. The evolution of the precipitates in alloy 718 irradiated with argon ions at elevated temperature were examined via transmission electron microscopy. Selected-area electron diffraction indicated superlattice spots disappeared after argon ion irradiation, which showing that the ordered structure of the γ′ and γ″ precipitates became disordered. The size of the precipitates became smaller with the irradiation dose increasing at 290 °C

  12. Broiler incubation. 1. Effect of elevated temperature during late incubation on body weight and organs of chicks.

    Science.gov (United States)

    Leksrisompong, N; Romero-Sanchez, H; Plumstead, P W; Brannan, K E; Brake, J

    2007-12-01

    Three experiments were conducted to investigate the effect of increased egg temperature during the final third of incubation on BW, yolk sac, heart, and digestive organs of broiler chicks at hatching. Egg temperatures were found to be approximately 1.0 to 1.5 degrees C higher than incubator air temperature. Elevated egg temperature (39.5 degrees C) after embryonic day 14 generally accelerated hatching time but decreased the relative weight of the heart in all 3 experiments, whereas BW and relative weights of the gizzard, proventriculus, and small intestines were significantly smaller in 2 of 3 experiments as compared with the control (approximately 38.2 degrees C). Relative weights of the yolk sac or liver were significantly larger due to elevated egg temperature in single experiments only. A striking feature of the chicks that developed at an elevated egg temperature was their white color as compared with the yellow color of chicks from eggs incubated at more normal temperatures.

  13. Structural characteristics and elevated temperature mechanical properties of AJ62 Mg alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kubásek, J., E-mail: Jiri.Kubasek@vscht.cz; Vojtěch, D.; Martínek, M.

    2013-12-15

    Structure and mechanical properties of the novel casting AJ62 (Mg–6Al–2Sr) alloy developed for elevated temperature applications were studied. The AJ62 alloy was compared to commercial casting AZ91 (Mg–9Al–1Zn) and WE43 (Mg–4Y–3RE) alloys. The structure was examined by scanning electron microscopy, x-ray diffraction and energy dispersive spectrometry. Mechanical properties were characterized by Viskers hardness measurements in the as-cast state and after a long-term heat treatment at 250 °C/150 hours. Compressive mechanical tests were also carried out both at room and elevated temperatures. Compressive creep tests were conducted at a temperature of 250 °C and compressive stresses of 60, 100 and 140 MPa. The structure of the AJ62 alloy consisted of primary α-Mg dendrites and interdendritic nework of the Al{sub 4}Sr and massive Al{sub 3}Mg{sub 13}Sr phases. By increasing the cooling rate during solidification from 10 and 120 K/s the average dendrite arm thickness decreased from 18 to 5 μm and the total volume fraction of the interdendritic phases from 20% to 30%. Both factors slightly increased hardness and compressive strength. The room temperature compressive strength and hardness of the alloy solidified at 30 K/s were 298 MPa and 50 HV 5, i.e. similar to those of the as-cast WE43 alloy and lower than those of the AZ91 alloy. At 250 °C the compressive strength of the AJ62 alloy decreased by 50 MPa, whereas those of the AZ91 and WE43 alloys by 100 and 20 MPa, respectively. The creep rate of the AJ62 alloy was higher than that of the WE43 alloy, but significantly lower in comparison with the AZ91 alloy. Different thermal stabilities of the alloys were discussed and related to structural changes during elevated temperature expositions. - Highlights: • Small effect of cooling rate on the compressive strength and hardness of AJ 62 • A bit lower compressive strength of AJ 62 compared to AZ91 at room temperature • Higher resistance of the AJ 62

  14. Creep performance of oxide ceramic fiber materials at elevated temperature in air and in steam

    Science.gov (United States)

    Armani, Clinton J.

    Structural aerospace components that operate in severe conditions, such as extreme temperatures and detrimental environments, require structural materials that have superior long-term mechanical properties and that are thermochemically stable over a broad range of service temperatures and environments. Ceramic matrix composites (CMCs) capable of excellent mechanical performance in harsh environments are prime candidates for such applications. Oxide ceramic materials have been used as constituents in CMCs. However, recent studies have shown that high-temperature mechanical performance of oxide-oxide CMCs deteriorate in a steam-rich environment. The degradation of strength at elevated temperature in steam has been attributed to the environmentally assisted subcritical crack growth in the oxide fibers. Furthermore, oxide-oxide CMCs have shown significant increases in steady-state creep rates in steam. The present research investigated the effects of steam on the high-temperature creep and monotonic tension performance of several oxide ceramic materials. Experimental facilities were designed and configured, and experimental methods were developed to explore the influence of steam on the mechanical behaviors of ceramic fiber tows and of ceramic bulk materials under temperatures in the 1100--1300°C range. The effects of steam on creep behavior of Nextel(TM)610 and Nextel(TM)720 fiber tows were examined. Creep rates at elevated temperatures in air and in steam were obtained for both types of fibers. Relationships between creep rates and applied stresses were modeled and underlying creep mechanisms were identified. For both types of fiber tows, a creep life prediction analysis was performed using linear elastic fracture mechanics and a power-law crack velocity model. These results have not been previously reported and have critical design implications for CMC components operating in steam or near the recommended design limits. Predictions were assessed and validated via

  15. Simulation of spring wheat responses to elevated CO2 and temperature by using CERES-wheat crop model

    Directory of Open Access Journals (Sweden)

    H. LAURILA

    2008-12-01

    Full Text Available The CERES-wheat crop simulation model was used to estimate the changes in phenological development and yield production of spring wheat (Triticum aestivum L., cv. Polkka under different temperature and CO2 growing conditions. The effects of elevated temperature (3-4°C and CO2 concentration (700 ppm as expected for Finland in 2100 were simulated. The model was calibrated for long-day growing conditions in Finland. The CERES-wheat genetic coefficients for cv. Polkka were calibrated by using the MTT Agrifood Research Finland (MTT official variety trial data (1985-1990. Crop phenological development and yield measurements from open-top chamber experiments with ambient and elevated temperature and CO2 treatments were used to validate the model. Simulated mean grain yield under ambient temperature and CO2 conditions was 6.16 t ha-1 for potential growth (4.49 t ha-1 non-potential and 5.47 t ha-1 for the observed average yield (1992-1994 in ambient open-top chamber conditions. The simulated potential grain yield increased under elevated CO2 (700 ppm to 142% (167% non-potential from the simulated reference yield (100%, ambient temperature and CO2 350 ppm. Simulations for current sowing date and elevated temperature (3°C indicate accelerated anthesis and full maturity. According to the model estimations, potential yield decreased on average to 80.4% (76.8% non-potential due to temperature increase from the simulated reference. When modelling the concurrent elevated temperature and CO2 interaction, the increase in grain yield due to elevated CO2 was reduced by the elevated temperature. The combined CO2 and temperature effect increased the grain yield to 106% for potential growth (122% non-potential compared to the reference. Simulating the effects of earlier sowing, the potential grain yield increased under elevated temperature and CO2 conditions to 178% (15 days earlier sowing from 15 May, 700 ppm CO2, 3°C from the reference. Simulation results suggest

  16. Effects of Single and Multifactor Treatments with Elevated Temperature, CO2 and Ozone on Oilseed Rape and Barley

    DEFF Research Database (Denmark)

    Clausen, Sabine Karin; Frenck, Georg; van der Linden, Leon Gareth

    2011-01-01

    We investigated the effect of elevated [CO2], [O3] and temperature on plant productivity and if these climate factors interacted with each other in multifactor treatments. The climate effects were studied in 14 different cultivars/lines of European spring oilseed rape (Brassica napus L.) and spring...... barley (Hordeum vulgare L.). Seven genotypes of each species were cultivated in six single- and multifactor treatments with ambient or elevated CO2 (385 ppm and 700 ppm), O3 (20 ppb and 60 ppb) and temperature (12/19 °C and 17/24 °C). Growth and production parameters were measured. Elevated CO2 increased....... A significantly decreased yield and thousand grain weight was also seen in barley due to elevated O3. The multifactor combination of elevated CO2, O3 and temperature showed a decrease in growth and production in the two species, though not statistically significant for all parameters. This trend suggests...

  17. Microstructures and mechanical properties of Cu-Sn alloy subjected to elevated-temperature heat deformation

    Science.gov (United States)

    Hui, Jun; Feng, Zaixin; Fan, Wenxin; Wang, Pengfei

    2018-04-01

    Cu-Sn alloy was subjected to elevated-temperature isothermal compression with 0.01 s‑1 strain rate and 500 ∼ 700 °C temperature range. The thermal compression curve reflected a competing process of work hardening versus dynamic recovery (DRV) and recrystallization, which exhibited an obvious softening trend. Meanwhile, high-temperature deformation and microstructural features in different regions of the alloy was analyzed through EBSD. The results show that grains grow as the temperature rises, competition among recrystallization, substructural, and deformation regions tends to increase with the increase of temperature, and distribution frequency of recrystallization regions gradually increases and then drops suddenly at 650 °C. At 500 ∼ 550 °C, preferentially oriented texturing phenomenon occurs, low angle boundaries(LABs) are gradually transformed into high angle boundaries (HABs) and the Σ (CSL) boundaries turn gradually into Σ3 boundaries. In tensile test of tin bronze, elongation at break increases slowly, whereas yield strength (YS) and ultimate tensile strength (TS) decrease gradually.

  18. Fracture Characteristics of C/SiC Composites for Rocket Nozzle at Elevated Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Dong Hyun; Lee, Jeong Won; Kim, Jae Hoon [Chungnam Nat’l Univ., Daejeon (Korea, Republic of); Sihn, Ihn Cheol; Lim, Byung Joo [Dai-Yang Industries Co., Daejeon (Korea, Republic of)

    2016-11-15

    In a solid propulsion system, the rocket nozzle is exposed to high temperature combustion gas. Hence, choosing an appropriate material that could demonstrate adequate performance at high temperature is important. As advanced materials, carbon/silicon carbide composites (C/SiC) have been studied with the aim of using them for the rocket nozzle throat. However, when compared with typical structural materials, C/SiC composites are relatively weak in terms of both strength and toughness, owing to their quasi-brittle behavior and oxidation at high temperatures. Therefore, it is important to evaluate the thermal and mechanical properties of this material before using it in this application. This study presents an experimental method to investigate the fracture behavior of C/SiC composite material manufactured using liquid silicon infiltration (LSI) method at elevated temperatures. In particular, the effects of major parameters, such as temperature, loading, oxidation conditions, and fiber direction on strength and fracture characteristics were investigated. Fractography analysis of the fractured specimens was performed using an SEM.

  19. Moisture migration and shrinkage of hardened cement paste at elevated temperatures

    International Nuclear Information System (INIS)

    Numao, Tatsuya; Mihashi, Hirozo.

    1991-01-01

    The drying shrinkage of concrete is caused by the loss of water in the concrete. The moisture diffusion behavior influences the mechanical properties of concrete. When concrete is exposed to high temperature, the rate of moisture migration becomes fast, and moisture gradient is formed. This gradient causes cracks on the concrete surface. Accordingly, it is important to study on the relation between the drying shrinkage and the water diffusion in concrete when its mechanical properties at elevated temperature are discussed. In this paper, the results of the experiment which was carried out by using thin-walled cylinder specimens kept at different temperature and stress are reported. The specimens, the drying shrinkage of concrete and acoustic emission (AE), the thermal expansion of hardened cement paste, the influence that temperature change exerted to the drying shrinkage, and the influence that compressive stress and temperature exerted to water migration are described. The thin-walled cylinder specimens were useful for these experimental studies. (K.I.)

  20. The relationship between gross and net erosion of beryllium at elevated temperature

    International Nuclear Information System (INIS)

    Doerner, R.P.; Jepu, I.; Nishijima, D.; Safi, E.; Bukonte, L.; Lasa, A.; Nordlund, K.; Schwarz-Selinger, T.

    2015-01-01

    Surface temperature is a critical variable governing plasma–material interactions. PISCES-B injects controllable amounts of Be impurities into the plasma to balance, or exceed, the erosion rate of beryllium from samples in un-seeded plasma exposures. At low temperature, an order of magnitude more beryllium, than the beryllium mass loss measured in un-seeded discharges, needs to be seeded into the plasma to achieve no mass loss from a sample. At elevated temperature, no mass loss is achieved when the beryllium-seeding rate equals the mass loss rate in un-seeded discharges. Molecular dynamics simulations show that below 500 K, Be adatoms have difficulty surmounting the Ehrlich–Schwoebel barrier at the edge of a terrace. Above this temperature, an Arrhenius behavior is observed with an activation energy of 0.32 eV. Qualitatively, this indicates that at low surface temperature the deposited atoms may be more easily re-eroded, accounting for the increased seeding needed to balance the erosion

  1. Elevated temperature cyclic deformation of stainless-steel and interaction effects with other modes of deformation

    International Nuclear Information System (INIS)

    Turner, A.P.L.

    1976-01-01

    Since pertinent information concerning the deformation history of a material is stored in its current structure, an attempt has been made to determine the number of state variables necessary to uniquely describe the material's present condition. An experimental program has been carried out to determine the number of state variables which is required to describe the tensile test, cyclic, and creep behavior of 304 stainless steel at elevated temperature. Tests have been conducted at 300 0 C and 560 0 C which correspond to homologous temperatures of 1 / 3 and 1 / 2 , respectively. The experiments consisted of subjecting samples to deformation histories during which the mode of deformation was changed so that two material responses could be measured for the same state of the material. Results strongly suggest that at least two state variables are necessary

  2. Study of the degradation of power generation combustion components at elevated temperature

    International Nuclear Information System (INIS)

    Castrejon, J.; Serna, S.; Wong-Moreno, A.; Fragiel, A.; Lopez-Lopez, D.

    2006-01-01

    Elevated temperature combustion of fuel oil that contains large amounts of vanadium, asphaltenes and mostly sulfur, presents a major challenge for materials selection and design of combustion components for the electric power generation. The combustion system, which consists of air nozzles and air swirlers, plays a key role in the performance of electric power plants. Air nozzles and air swirlers, which were operated for one year in a 350 MW boiler, were analyzed, presenting accelerated degradation. The particular features of corrosion behavior of these components made by stainless steels: 304, 446 and HH, are presented. The results obtained after optical, metallographic, and microprobe analysis revealed that the components flame contact at very high operating temperature promoted all materials degradation mechanisms. Under this scenario, it is very difficult to find a material resistant to such accelerated wastage conditions. So, the solution of the problem must be oriented to re-design and improve the efficiency of the flame contact with these components

  3. Wear Response of Aluminium 6061 Composite Reinforced with Red Mud at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    R. Dabral

    2017-09-01

    Full Text Available The present work is focused on the investigations on dry sliding wear behaviour of aluminium metal matrix composite at room and elevated temperature. Aluminium metal matrix composites reinforced with red mud are prepared by stir casting method. The experiments are planned using Taguchi technique. An orthogonal array, analysis of variance and signal to noise ratio are used to check the influence of wear parameters like temperature, percentage of reinforcement, mesh size, load, sliding distance and sliding speed on dry sliding wear of composites. The optimal testing parameters are found and their values are calculated which are then compared with predicted values. A reasonable agreement is found between predicted and actual values. The model prepared in the present work can be effectively used to predict the specific wear rate of the composites.

  4. Damage behavior in helium-irradiated reduced-activation martensitic steels at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Fengfeng [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Chen, Jihong; Li, Tiecheng; Zheng, Zhongcheng [Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Yao, Z. [Department of Mechanical and Materials Engineering, Queen’s University, Kingston K7L 3N6, ON (Canada); Suo, Jinping [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-12-15

    Dislocation loops induced by helium irradiation at elevated temperatures in reduced-activation martensitic steels were investigated using transmission electron microscopy. Steels were irradiated with 100 keV helium ions to 0.8 dpa between 300 K and 723 K. At irradiation temperatures T{sub irr} ⩽ 573 K, small defects with both Burger vectors b = 1/2〈1 1 1〉 and b = 〈1 0 0〉 were observed, while at T{sub irr} ⩾ 623 K, the microstructure was dominated by large convoluted interstitial dislocation loops with b = 〈1 0 0〉. Only small cavities were found in the steels irradiated at 723 K.

  5. Dynamics of a Circular Mindlin Plate under Mechanical Loading and Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Warminska Anna

    2016-01-01

    Full Text Available Dynamics of a nonlinear circular Midlin plate is studied in the paper. The mathematical model represented by partial differential equations includes nonlinear geometrical terms resulted from large displacements. The plate is subjected to mechanical and thermal loadings. The dynamics of a coupled thermo-mechanical problem is reduced from partial to ordinary differential equations. Considering the first mode reduction and uniformly distributed temperature just a single nonlinear differential equation is obtained. The bifurcation analysis shows that elevated temperature shifts the rezonanse curve and new solutions arise. Depending on initial conditions this may lead to buckling phenomenon and then relatively small oscillations around this state, symmetric periodic oscillations of large amplitude, or irregular oscillations.

  6. Fabrication of wire and flat strips with elevated recrystallization temperature of Mo monocrystals

    International Nuclear Information System (INIS)

    Mikhajlov, S.M.; Nesgovorov, V.V.; Kabakova, L.G.; Korzukhin, V.E.; Savitskij, E.M.; Burkhanov, G.S.; Ottenberg, E.V.

    1977-01-01

    A technique is developed for manufacturing wire and flat strip of elevated recrystallization point from single crystals fo molybdenum with micro-additions of zirconium and titanium by rotary hot forging with subsequent drawing under hydrodynamic friction conditions. Flat strip is manufactured next from a wire annealed at 1300-1400 deg C in hydrogen. Resultant wire and flat strip feature a high recrystallization point and a good shape stability. Tests on their ultimate strength on the range of temperatures between 20 and 1700 deg C have shown that the maximum temperature of the recrystallization onset is that of a wire from Mo single crystals of orientation [110], containing micro-additions of Zr and Ti, whereas loss of strength is at its highest in a wire from non-alloyed single-crystal molybdenum

  7. Study of the degradation of power generation combustion components at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Castrejon, J. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas-UAEM, Av. Universidad 1001, C.P. 62209, Cuernavaca, Mor., Mexico (Mexico); Serna, S. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas-UAEM, Av. Universidad 1001, C.P. 62209, Cuernavaca, Mor., Mexico (Mexico)]. E-mail: aserna@uaem.mx; Wong-Moreno, A. [Instituto Mexicano del Petroleo, Eje Central No. 152, Col. San. Bartolo Atepehuacan, C.P. 07730, Mexico, DF (Mexico); Fragiel, A. [Centro de Ciencias de la Materia Condensada-UNAM, Km 7 Carretera Tijuana-Ensenada, C.P. 22800, Ensenada, Baja California (Mexico); Lopez-Lopez, D. [Instituto Mexicano del Petroleo, Eje Central No. 152, Col. San. Bartolo Atepehuacan, C.P. 07730, Mexico, DF (Mexico)

    2006-01-15

    Elevated temperature combustion of fuel oil that contains large amounts of vanadium, asphaltenes and mostly sulfur, presents a major challenge for materials selection and design of combustion components for the electric power generation. The combustion system, which consists of air nozzles and air swirlers, plays a key role in the performance of electric power plants. Air nozzles and air swirlers, which were operated for one year in a 350 MW boiler, were analyzed, presenting accelerated degradation. The particular features of corrosion behavior of these components made by stainless steels: 304, 446 and HH, are presented. The results obtained after optical, metallographic, and microprobe analysis revealed that the components flame contact at very high operating temperature promoted all materials degradation mechanisms. Under this scenario, it is very difficult to find a material resistant to such accelerated wastage conditions. So, the solution of the problem must be oriented to re-design and improve the efficiency of the flame contact with these components.

  8. Microstructure and mechanical behaviour of an elevated temperature Mg-rare earth based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Bettles, C.J. [ARC Centre of Excellence for Design in Light Metals, Department of Materials Engineering, Monash University, Clayton 3800, Vic. (Australia); CAST CRC, CSIRO Materials Science and Engineering, Private Bag 33, Clayton South MDC, Clayton 3169, Vic. (Australia)], E-mail: colleen.bettles@eng.monash.edu.au; Gibson, M.A. [CAST CRC, CSIRO Materials Science and Engineering, Private Bag 33, Clayton South MDC, Clayton 3169, Vic. (Australia); Zhu, S.M. [CAST CRC, Department of Materials Engineering, Monash University, Clayton 3800, Vic. (Australia)

    2009-04-15

    AM-SC1 is a heat treatable magnesium alloy that has been specifically developed to achieve the elevated temperature strength and creep properties necessary for engine block applications. This paper describes the interrelationship between the microstructure and the mechanical properties of AM-SC1. The compressive and tensile strengths are relatively insensitive to temperature up to and including 450 K and the tensile yield behaviour deviates from a standard Hall-Petch relationship at grain sizes below 200 {mu}m. The microstructural features contributing to the creep resistance are both inter- and intra-granular in nature and are on length scales from nanometers to micrometers. The creep behaviour at 423 K and 450 K is diffusion controlled, with any contribution from the grain boundaries being negligible.

  9. The permeation of hydrogen in a steel at elevated temperature by an electrochemical method

    International Nuclear Information System (INIS)

    Tsubakino, H.; Ando, A.; Yamakawa, K.

    1984-01-01

    An electrochemical permeation method has been widely used to study the transport characteristics of hydrogen in metals, i.e., the content, diffusivity and permeability. This electrochemical measurement technique has the following remarkable features: a good detection limit for the measurement of hydrogen content, a simpler measuring apparatus, suitability for successive measurement of the transport characteristics, and flexibility in variation of experimental conditions. However this method has been restricted to temperatures below 373 K because an aqueous solution has been used as an electrode. In this study, an electrochemical permeation method using molten salts at elevated temperatures (673-773 K) in the range of practical interest for hydrogen attack in steel is presented. The introduction of hydrogen by use of molten salts has been reported but it has been performed at 423473 K and at 553 K

  10. Residual characteristic properties of ternary blended steel fibre reinforced concrete subjected to sustained elevated temperature

    Directory of Open Access Journals (Sweden)

    Sinha Deepa A.

    2013-09-01

    Full Text Available To study the behavior of ternary blended steel fibre reinforced concrete when subjected to 800 Deg.C and 1000 Deg.C for 3 hours. It has been found that the ternary blended steel fibre reinforced concrete containing (FA+GGBFS and (FA+MK offer higher resistance to sustained elevated temperatures upto 800 Deg.C, where as the blend containing (FA+SF does not offer any resistance at this temperature. The study reveals that the blend containing (FA+GGBFS and (FA+MK gives highest resistance at replacement levels of (10+20 and (15+15 respectively at sustained exposure to 800 Deg.C.

  11. Composite polymer membranes for proton exchange membrane fuel cells operating at elevated temperatures and reduced humidities

    Science.gov (United States)

    Zhang, Tao

    Proton Exchange Membrane Fuel Cells (PEMFCs) are the leading candidate in the fuel cell technology due to the high power density, solid electrolyte, and low operational temperature. However, PEMFCs operating in the normal temperature range (60-80°C) face problems including poor carbon monoxide tolerance and heat rejection. The poisoning effect can be significantly relieved by operating the fuel cell at elevated temperature, which also improves the heat rejection and electrochemical kinetics. Low relative humidity (RH) operation is also desirable to simplify the reactant humidification system. However, at elevated temperatures, reduced RH PEMFC performance is seriously impaired due to irreversible water loss from presently employed state-of-the-art polymer membrane, Nafion. This thesis focuses on developing polymer electrolyte membranes with high water retention ability for operation in elevated temperature (110-150°C), reduced humidity (˜50%RH) PEMFCs. One approach is to alter Nafion by adding inorganic particles such as TiO2, SiO2, Zr(HPO 4)2, etc. While the presence of these materials in Nafion has proven beneficial, a reduction or no improvement in the PEMFC performance of Nafion/TiO2 and Nafion/Zr(HPO4)2 membranes is observed with reduced particle sizes or increased particle loadings in Nafion. It is concluded that the PEMFC performance enhancement associated with addition of these inorganic particles was not due to the particle hydrophilicity. Rather, the particle, partially located in the hydrophobic region of the membrane, benefits the cell performance by altering the membrane structure. Water transport properties of some Nafion composite membranes were investigated by NMR methods including pulsed field gradient spin echo diffusion, spin-lattice relaxation, and spectral measurements. Compared to unmodified Nafion, composite membranes materials exhibit longer longitudinal relaxation time constant T1. In addition to the Nafion material, sulfonated styrene

  12. General purpose nonlinear analysis program FINAS for elevated temperature design of FBR components

    International Nuclear Information System (INIS)

    Iwata, K.; Atsumo, H.; Kano, T.; Takeda, H.

    1982-01-01

    This paper presents currently available capabilities of a general purpose finite element nonlinear analysis program FINAS (FBR Inelastic Structural Analysis System) which has been developed at Power Reactor and Nuclear Fuel Development Corporation (PNC) since 1976 to support structural design of fast breeder reactor (FBR) components in Japan. This program is capable of treating inelastic responses of arbitrary complex structures subjected to static and dynamic load histories. Various types of finite element covering rods, beams, pipes, axisymmetric, two and three dimensional solids, plates and shells, are implemented in the program. The thermal elastic-plastic creep analysis is possible for each element type, with primary emphasis on the application to FBR components subjected to sustained or cyclic loads at elevated temperature. The program permits large deformation, buckling, fracture mechanics, and dynamic analyses for some of the element types and provides a number of options for automatic mesh generation and computer graphics. Some examples including elevated temperature effects are shown to demonstrate the accuracy and the efficiency of the program

  13. Coralline algal physiology is more adversely affected by elevated temperature than reduced pH.

    Science.gov (United States)

    Vásquez-Elizondo, Román Manuel; Enríquez, Susana

    2016-01-07

    In this study we analyzed the physiological responses of coralline algae to ocean acidification (OA) and global warming, by exposing algal thalli of three species with contrasting photobiology and growth-form to reduced pH and elevated temperature. The analysis aimed to discern between direct and combined effects, while elucidating the role of light and photosynthesis inhibition in this response. We demonstrate the high sensitivity of coralline algae to photodamage under elevated temperature and its severe consequences on thallus photosynthesis and calcification rates. Moderate levels of light-stress, however, were maintained under reduced pH, resulting in no impact on algal photosynthesis, although moderate adverse effects on calcification rates were still observed. Accordingly, our results support the conclusion that global warming is a stronger threat to algal performance than OA, in particular in highly illuminated habitats such as coral reefs. We provide in this study a quantitative physiological model for the estimation of the impact of thermal-stress on coralline carbonate production, useful to foresee the impact of global warming on coralline contribution to reef carbon budgets, reef cementation, coral recruitment and the maintenance of reef biodiversity. This model, however, cannot yet account for the moderate physiological impact of low pH on coralline calcification.

  14. Material properties of Grade 91 steel at elevated temperature and their comparison with a design code

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyeong Yeon; Kim, Woo Gon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Han Sang; Kim, Yun Jae [Korea Univ., Seoul (Korea, Republic of)

    2013-10-15

    In this study, the material properties of tensile strength, creep properties, and creep crack growth model for Gr.91 steel at elevated temperature were obtained from material tests at KAERI, and the test data were compared with those of the French elevated temperature design code, RCC-MRx. The conservatism of the material properties in the French design code is highlighted. Mod.9Cr-1Mo (ASME Grade 91; Gr.91) steel is widely adopted as candidate material for Generation IV nuclear systems as well as for advanced thermal plants. In a Gen IV sodium-cooled fast reactor of the PGSFR (Prototype Gen IV Sodium-cooled Fast Reactor) being developed by KAERI (Korea Atomic Energy Research Institute), Gr.91 steel is selected as the material for the steam generator, secondary piping, and decay heat exchangers. However, as this material has a relatively shorter history of usage in an actual plant than austenitic stainless steel, there are still many issues to be addressed including the long-term creep rupture life extrapolation and ratcheting behavior with cyclic softening characteristics.

  15. Effect of elevated substrate temperature deposition on the mechanical losses in tantala thin film coatings

    Science.gov (United States)

    Vajente, G.; Birney, R.; Ananyeva, A.; Angelova, S.; Asselin, R.; Baloukas, B.; Bassiri, R.; Billingsley, G.; Fejer, M. M.; Gibson, D.; Godbout, L. J.; Gustafson, E.; Heptonstall, A.; Hough, J.; MacFoy, S.; Markosyan, A.; Martin, I. W.; Martinu, L.; Murray, P. G.; Penn, S.; Roorda, S.; Rowan, S.; Schiettekatte, F.; Shink, R.; Torrie, C.; Vine, D.; Reid, S.; Adhikari, R. X.

    2018-04-01

    Brownian thermal noise in dielectric multilayer coatings limits the sensitivity of current and future interferometric gravitational wave detectors. In this work we explore the possibility of improving the mechanical losses of tantala, often used as the high refractive index material, by depositing it on a substrate held at elevated temperature. Promising results have been previously obtained with this technique when applied to amorphous silicon. We show that depositing tantala on a hot substrate reduced the mechanical losses of the as-deposited coating, but subsequent thermal treatments had a larger impact, as they reduced the losses to levels previously reported in the literature. We also show that the reduction in mechanical loss correlates with increased medium range order in the atomic structure of the coatings using x-ray diffraction and Raman spectroscopy. Finally, a discussion is included on our results, which shows that the elevated temperature deposition of pure tantala coatings does not appear to reduce mechanical loss in a similar way to that reported in the literature for amorphous silicon; and we suggest possible future research directions.

  16. Sliding friction and wear behavior of high entropy alloys at room and elevated temperatures

    Science.gov (United States)

    Kadhim, Dheyaa

    Structure-tribological property relations have been studied for five high entropy alloys (HEAs). Microhardness, room and elevated (100°C and 300°C) temperature sliding friction coefficients and wear rates were determined for five HEAs: Co0.5 Cr Cu0.5 Fe Ni1.5 Al Ti0.4; Co Cr Fe Ni Al0.25 Ti0.75; Ti V Nb Cr Al; Al0.3CoCrFeNi; and Al0.3CuCrFeNi2. Wear surfaces were characterized with scanning electron microscopy and micro-Raman spectroscopy to determine the wear mechanisms and tribochemical phases, respectively. It was determined that the two HEAs Co0.5 Cr Cu0.5 Fe Ni1.5 Al Ti0.4 and Ti V Nb Cr Al exhibit an excellent balance of high hardness, low friction coefficients and wear rates compared to 440C stainless steel, a currently used bearing steel. This was attributed to their more ductile body centered cubic (BCC) solid solution phase along with the formation of tribochemical Cr oxide and Nb oxide phases, respectively, in the wear surfaces. This study provides guidelines for fabricating novel, low-friction, and wear-resistant HEAs for potential use at room and elevated temperatures, which will help reduce energy and material losses in friction and wear applications.

  17. Improving xylitol production at elevated temperature with engineered Kluyveromyces marxianus through over-expressing transporters.

    Science.gov (United States)

    Zhang, Jia; Zhang, Biao; Wang, Dongmei; Gao, Xiaolian; Hong, Jiong

    2015-01-01

    Three transporter genes including Kluyveromyces marxianus aquaglyceroporin gene (KmFPS1), Candida intermedia glucose/xylose facilitator gene (CiGXF1) or glucose/xylose symporter gene (CiGXS1) were over-expressed in K. marxianus YZJ017 to improve xylitol production at elevated temperatures. The xylitol production of YZJ074 that harbored CiGXF1 was improved to 147.62g/L in Erlenmeyer flask at 42°C. In fermenter, 99.29 and 149.60g/L xylitol were produced from 99.55 and 151.91g/L xylose with productivity of 4.14 and 3.40g/L/h respectively at 42°C. Even at 45°C, YZJ074 could produce 101.30g/L xylitol from 101.41g/L xylose with productivity of 2.81g/L/h. Using fed-batch fermentation through repeatedly adding non-sterilized substrate directly, YZJ074 could produce 312.05g/L xylitol which is the highest yield reported to date. The engineered strains YZJ074 which can produce xylitol at elevated temperatures is an excellent foundation for xylitol bioconversion. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Piezoelectric Flexible LCP-PZT Composites for Sensor Applications at Elevated Temperatures

    Science.gov (United States)

    Tolvanen, Jarkko; Hannu, Jari; Juuti, Jari; Jantunen, Heli

    2018-03-01

    In this paper fabrication of piezoelectric ceramic-polymer composites is demonstrated via filament extrusion enabling cost-efficient large-scale production of highly bendable pressure sensors feasible for elevated temperatures. These composites are fabricated by utilizing environmentally resistant and stable liquid crystal polymer matrix with addition of lead zirconate titanate at loading levels of 30 vol%. These composites, of approximately 0.99 mm thick and length of > 50 cm, achieved excellent bendability with minimum bending radius of 6.6 cm. The maximum piezoelectric coefficients d33 and g33 of the composites were > 14 pC/N and > 108 mVm/N at pressure < 10 kPa. In all cases, the piezoelectric charge coefficient (d33) of the composites decreased as a function of pressure. Also, piezoelectric coefficient (d33) further decreased in the case of increased frequency press-release cycle sand pre-stress levels by approximately 37-50%. However, the obtained results provide tools for fabricating novel piezoelectric sensors in highly efficient way for environments with elevated temperatures.

  19. Research on weld cracking of TP321H stainless steel pipeline under elevated temperature

    International Nuclear Information System (INIS)

    Pan, Jian-hua; Fan, Zhi-cao; Zong, Ning-sheng

    2016-01-01

    The failure of pipeline which adopted material type TP321H austenitic stainless steel and occurred cracking after servicing at elevated temperature for less than two years had been investigated. The cracks were appeared repeatedly although they had been repaired for several times. The pipeline stress analysis was conducted to determine stress levels of cracking positions by finite element analysis software ABAQUS. The mechanical properties of base metals and welds including tensile and charpy impact tests were carried out. The test results showed that ductility of welds cut from the serviced pipeline was very poor. The microstructure investigations suggested that it was intergranular crack located in the HAZ near fusion line. It could be determined that it was reheat cracking based on some other works such as metallographic inspection, SEM, X-ray diffraction, etc. Welds analysis results showed that the welding of pipeline had not been in accord with right qualification of welding procedure leading to poor welding quality. The cracking reasons and preventive measures were discussed. Several suggestions were proposed to help extend service lifetime of the stainless steel pipeline under elevated temperature condition. - Highlights: • The pipeline is calculated by finite element analysis software ABAQUS. • Various tests are made, such as mechanical property, SEM, EDS, X-ray diffraction. • It is reheat cracking or stress relief cracking for the pipeline failure. • The stress levels of pipeline should be as low as possible. • The lifetime of pipeline would be shorten obviously due to poor weld quality.

  20. Coralline algal physiology is more adversely affected by elevated temperature than reduced pH

    Science.gov (United States)

    Vásquez-Elizondo, Román Manuel; Enríquez, Susana

    2016-01-01

    In this study we analyzed the physiological responses of coralline algae to ocean acidification (OA) and global warming, by exposing algal thalli of three species with contrasting photobiology and growth-form to reduced pH and elevated temperature. The analysis aimed to discern between direct and combined effects, while elucidating the role of light and photosynthesis inhibition in this response. We demonstrate the high sensitivity of coralline algae to photodamage under elevated temperature and its severe consequences on thallus photosynthesis and calcification rates. Moderate levels of light-stress, however, were maintained under reduced pH, resulting in no impact on algal photosynthesis, although moderate adverse effects on calcification rates were still observed. Accordingly, our results support the conclusion that global warming is a stronger threat to algal performance than OA, in particular in highly illuminated habitats such as coral reefs. We provide in this study a quantitative physiological model for the estimation of the impact of thermal-stress on coralline carbonate production, useful to foresee the impact of global warming on coralline contribution to reef carbon budgets, reef cementation, coral recruitment and the maintenance of reef biodiversity. This model, however, cannot yet account for the moderate physiological impact of low pH on coralline calcification.

  1. Characteristics and mechanism of explosive reactions of Purex solvents with Nitric Acid at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Miyata, Teijiro [Radiation Application Development Association, Tokai, Ibaraki (Japan); Takada, Junichi; Koike, Tadao; Tsukamoto, Michio; Watanabe, Koji [Department of Fuel Cycle Safety Research, Nuclear Safety Research Center, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Ida, Masaaki [JGC PLANTECH CO., LTD (Japan); Nakagiri, Naotaka [JGC Corp., Tokyo (Japan); Nishio, Gunji [Research Organization for Information Science and Technology, Tokai, Ibaraki (Japan)

    2000-03-01

    This investigation was undertaken to make clear the energetic properties and mechanism of explosive decomposition of Purex solvent systems (TBP/n-Dodecane/HNO{sub 3}) by Nitric Acid at elevated temperatures using a calorimetric technique (DSC, ARC) and a chromatographic technique (GC, GC/MS). The measurement of exothermic events of solvent-HNO{sub 3} reactions using DSC with a stainless steel sealed cell showed distinct two peaks with maxima at around 170 and 320degC, respectively. The peak at around 170degC was mainly attributed to the reactions of dealkylation products (n-butyl nitrate) of TBP and the solvent with nitric acid, and the peak at around 320degC was attributed to the exothermic decomposition of nitrated dodecanes formed in the foregoing exothermic reaction of dodecane with nitric acid. By using the data obtained in ARC experiments, activation energies of 123.2 and 152.5 kJ/mol were determined for the exothermic reaction of TBP with nitric acid and for the exothermic pyrolysis of n-butyl nitrate, respectively. Some possible pathways were considered for the explosive decomposition of TBP by nitric acid at elevated temperatures. (author)

  2. Elevated-Temperature Ferritic and Martensitic Steels and Their Application to Future Nuclear Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, RL

    2005-01-31

    In the 1970s, high-chromium (9-12% Cr) ferritic/martensitic steels became candidates for elevated-temperature applications in the core of fast reactors. Steels developed for conventional power plants, such as Sandvik HT9, a nominally Fe-12Cr-1Mo-0.5W-0.5Ni-0.25V-0.2C steel (composition in wt %), were considered in the United States, Europe, and Japan. Now, a new generation of fission reactors is in the planning stage, and ferritic, bainitic, and martensitic steels are again candidates for in-core and out-of-core applications. Since the 1970s, advances have been made in developing steels with 2-12% Cr for conventional power plants that are significant improvements over steels originally considered. This paper will review the development of the new steels to illustrate the advantages they offer for the new reactor concepts. Elevated-temperature mechanical properties will be emphasized. Effects of alloying additions on long-time thermal exposure with and without stress (creep) will be examined. Information on neutron radiation effects will be discussed as it applies to ferritic and martensitic steels.

  3. Shock Response of Commercial Purity Polycrystalline Magnesium Under Uniaxial Strain at Elevated Temperatures

    Science.gov (United States)

    Wang, Tianxue; Zuanetti, Bryan; Prakash, Vikas

    2017-12-01

    In the present paper, results of plate impact experiments designed to investigate the onset of incipient plasticity in commercial purity polycrystalline magnesium (99.9%) under weak uniaxial strain compression and elevated temperatures up to melt are presented. The dynamic stress at yield and post yield of magnesium, as inferred from the measured normal component of the particle velocity histories at the free (rear) surface of the target plate, are observed to decrease progressively with increasing test temperatures in the range from 23 to 500 °C. At (higher) test temperatures in the range 500-610 °C, the rate of decrease of dynamic stress with temperature at yield and post-yield in the sample is observed to weaken. At still higher test temperatures (617 and 630 °C), a dramatic increase in dynamic yield as well as flow stress is observed indicating a change in dominant mechanism of plastic deformation as the sample approaches the melt point of magnesium at strain rates of 105/s. In addition to these measurements at the wavefront, the plateau region of the free surface particle velocity profiles indicates that the longitudinal (plastic) impedance of the magnesium samples decreases continuously as the sample temperatures are increased from room to 610 °C, and then reverses trend (indicating increasing material longitudinal impedance/strength) as the sample temperatures are increased to 617 and 630 °C. Electron back scattered diffraction analysis of the as-received and annealed pre-test magnesium samples reveal grain coarsening as well as grain re-orientation to a different texture during the heating process of the samples.

  4. Climate change (elevated CO{sub 2}, elevated temperature and moderate drought) triggers the antioxidant enzymes' response of grapevine cv. Tempranillo, avoiding oxidative damage

    Energy Technology Data Exchange (ETDEWEB)

    Salazar-Parra, C.; Aguirreolea, J.; Sanchez-Diaz, M.; Irigoyen, J.J.; Morales, F. (Departamento de Biologia Vegetal, Seccion Biologia Vegetal (Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logrono), Facultades de Ciencias y Farmacia, Universidad de Navarra, Pamplona (Spain))

    2012-07-01

    Photosynthetic carbon fixation (A{sub N}) and photosynthetic electron transport rate (ETR) are affected by different environmental stress factors, such as those associated with climate change. Under stress conditions, it can be generated an electron excess that cannot be consumed, which can react with O{sub 2}, producing reactive oxygen species. This work was aimed to evaluate the influence of climate change (elevated CO{sub 2}, elevated temperature and moderate drought) on the antioxidant status of grapevine (Vitis vinifera) cv. Tempranillo leaves, from veraison to ripeness. The lowest ratios between electrons generated (ETR) and consumed (A{sub N} + respiration + photorespiration) were observed in plants treated with elevated CO{sub 2} and elevated temperature. In partially irrigated plants under current ambient conditions, electrons not consumed seemed to be diverted to alternative ways. Oxidative damage to chlorophylls and carotenoids was not observed. However, these plants had increases in thiobarbituric acid reacting substances, an indication of lipid peroxidation. These increases matched well with an early rise of H{sub 2}O{sub 2} and antioxidant enzyme activities, superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and catalase (EC 1.11.1.6). Enzymatic activities were maintained high until ripeness. In conclusion, plants grown under current ambient conditions and moderate drought were less efficient to cope with oxidative damage than well-irrigated plants, and more interestingly, plants grown under moderate drought but treated with elevated CO{sub 2} and elevated temperature were not affected by oxidative damage, mainly because of higher rates of electrons consumed in photosynthetic carbon fixation. (Author)

  5. The Impact of Central and Peripheral Cyclooxygenase Enzyme Inhibition on Exercise-Induced Elevations in Core Body Temperature.

    Science.gov (United States)

    Veltmeijer, Matthijs T W; Veeneman, Dineke; Bongers, Coen C C W; Netea, Mihai G; van der Meer, Jos W; Eijsvogels, Thijs M H; Hopman, Maria T E

    2017-05-01

    Exercise increases core body temperature (T C ) due to metabolic heat production. However, the exercise-induced release of inflammatory cytokines including interleukin-6 (IL-6) may also contribute to the rise in T C by increasing the hypothalamic temperature set point. This study investigated whether the exercise-induced increase in T C is partly caused by an altered hypothalamic temperature set point. Fifteen healthy, active men age 36 ± 14 y were recruited. Subjects performed submaximal treadmill exercise in 3 randomized test conditions: (1) 400 mg ibuprofen and 1000 mg acetaminophen (IBU/APAP), (2) 1000 mg acetaminophen (APAP), and (3) a control condition (CTRL). Acetaminophen and ibuprofen were used to block the effect of IL-6 at a central and peripheral level, respectively. T C , skin temperature, and heart rate were measured continuously during the submaximal exercise tests. Baseline values of T C , skin temperature, and heart rate did not differ across conditions. Serum IL-6 concentrations increased in all 3 conditions. A significantly lower peak T C was observed in IBU/APAP (38.8°C ± 0.4°C) vs CTRL (39.2°C ± 0.5°C, P = .02) but not in APAP (38.9°C ± 0.4°C) vs CTRL. Similarly, a lower ΔT C was observed in IBU/APAP (1.7°C ± 0.3°C) vs CTRL (2.0°C ± 0.5°C, P exercise compared with a CTRL. This observation suggests that a prostaglandin-E2-induced elevated hypothalamic temperature set point may contribute to the exercise-induced rise in T C .

  6. An Indentation Technique for Nanoscale Dynamic Viscoelastic Measurements at Elevated Temperature

    Science.gov (United States)

    Ye, Jiping

    2012-08-01

    Determination of nano/micro-scale viscoelasticity is very important to understand the local rheological behavior and degradation phenomena of multifunctional polymer blend materials. This article reviews research results concerning the development of indentation techniques for making nanoscale dynamic viscoelastic measurements at elevated temperature. In the last decade, we have achieved breakthroughs in noise floor reduction in air and thermal load drift/noise reduction at high temperature before taking on the challenge of nanoscale viscoelastic measurements. A high-temperature indentation technique has been developed that facilitates viscoelastic measurements up to 200 °C in air and 500 °C in a vacuum. During the last year, two viscoelastic measurement methods have been developed by making a breakthrough in suppressing the contact area change at high temperature. One is a sharp-pointed time-dependent nanoindentation technique for microscale application and the other is a spherical time-dependent nanoindentation technique for nanoscale application. In the near future, we expect to lower the thermal load drift and load noise floor even more substantially.

  7. Elevated-Temperature Tests Under Static and Aerodynamic Conditions on Honeycomb-Core Sandwich Panels

    Science.gov (United States)

    Groen, Joseph M.; Johnson, Aldie E., Jr.

    1959-01-01

    Stainless-steel honeycomb-core sandwich panels which differed primarily in skin thicknesses were tested at elevated temperatures under static and aerodynamic conditions. The results of these tests were evaluated to determine the insulating effectiveness and structural integrity of the panels. The static radiant-heating tests were performed in front of a quartz-tube radiant heater at panel skin temperatures up to 1,5000 F. The aerodynamic tests were made in a Mach 1.4 heated blowdown wind tunnel. The tunnel temperature was augmented by additional heat supplied by a radiant heater which raised the panel surface temperature above 8000 F during air flow. Static radiant-heating tests of 2 minutes duration showed that all the panels protected the load-carrying structure about equally well. Thin-skin panels showed an advantage for this short-time test over thick-skin panels from a standpoint of weight against insulation. Permanent inelastic strains in the form of local buckles over each cell of the honeycomb core caused an increase in surface roughness. During the aero- dynamic tests all of the panels survived with little or no damage, and panel flutter did not occur.

  8. The effect of gamma radiation on hardness evolution in high density polyethylene at elevated temperatures

    International Nuclear Information System (INIS)

    Chen, Pei-Yun; Chen, C.C.; Harmon, Julie P.; Lee, Sanboh

    2014-01-01

    This research focuses on characterizing hardness evolution in irradiated high density polyethylene (HDPE) at elevated temperatures. Hardness increases with increasing gamma ray dose, annealing temperature and annealing time. The hardness change is attributed to the variation of defects in microstructure and molecular structure. The kinetics of defects that control the hardness are assumed to follow the first order structure relaxation. The experimental data are in good agreement with the predicted model. The rate constant follows the Arrhenius equation, and the corresponding activation energy decreases with increasing dose. The defects that control hardness in post-annealed HDPE increase with increasing dose and annealing temperature. The structure relaxation of HDPE has a lower energy of mixing in crystalline regions than in amorphous regions. Further, the energy of mixing for defects that influence hardness in HDPE is lower than those observed in polycarbonate (PC), poly(methyl methacrylate) (PMMA) and poly (hydroxyethyl methacrylate) (HEMA). This is due to the fact that polyethylene is a semi-crystalline material, while PC, PMMA and PHEMA are amorphous. - Highlights: • Hardness of HDPE increases with increasing gamma ray dose, annealing time and temperature. • The hardness change arises from defects in microstructure and molecular structure. • Defects affecting hardness follow a kinetics of structure relaxation. • The structure relaxation has a low energy of mixing in crystalline regime

  9. The effect of gamma radiation on hardness evolution in high density polyethylene at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Pei-Yun [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Chen, C.C. [Institute of Nuclear Energy Research, Longtan, Taoyuan 325, Taiwan (China); Harmon, Julie P. [Department of Chemistry, University of South Florida, Tampa, FL 33620 (United States); Lee, Sanboh, E-mail: sblee@mx.nthu.edu.tw [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China)

    2014-08-01

    This research focuses on characterizing hardness evolution in irradiated high density polyethylene (HDPE) at elevated temperatures. Hardness increases with increasing gamma ray dose, annealing temperature and annealing time. The hardness change is attributed to the variation of defects in microstructure and molecular structure. The kinetics of defects that control the hardness are assumed to follow the first order structure relaxation. The experimental data are in good agreement with the predicted model. The rate constant follows the Arrhenius equation, and the corresponding activation energy decreases with increasing dose. The defects that control hardness in post-annealed HDPE increase with increasing dose and annealing temperature. The structure relaxation of HDPE has a lower energy of mixing in crystalline regions than in amorphous regions. Further, the energy of mixing for defects that influence hardness in HDPE is lower than those observed in polycarbonate (PC), poly(methyl methacrylate) (PMMA) and poly (hydroxyethyl methacrylate) (HEMA). This is due to the fact that polyethylene is a semi-crystalline material, while PC, PMMA and PHEMA are amorphous. - Highlights: • Hardness of HDPE increases with increasing gamma ray dose, annealing time and temperature. • The hardness change arises from defects in microstructure and molecular structure. • Defects affecting hardness follow a kinetics of structure relaxation. • The structure relaxation has a low energy of mixing in crystalline regime.

  10. Correlation of hot-microhardness with elevated-temperature tensile properties of low activation ferritic steel

    International Nuclear Information System (INIS)

    Hsu Chenyih

    1986-01-01

    Hot microhardness and elevated temperature tensile tests have been performed on 9Cr-2.5W-0.3V-0.15C(GA3X) low activation ferritic steel at temperatures from 20 0 C to 650 0 C. The uniform elongation of the tensile test correlated well with the ductility parameter of the microhardness test. The hot-microhardness test showed a sensitive response to the softening and changes in ductility of the GA3X steel. The ultimate tensile strength and 0.2% yield strength of this steel correlated well with hot microhardness data at test temperatures up to 400 0 C using Cahoon's expressions σ uts = (H/2.9)(n/0.217) n and σ ys = (H/3)(0.1) n , respectively, where H is the diamond pyramid hardness and n is the strain hardening exponent. A 20-30% underestimate of tensile strengths were obtained using Cahoon's expressions at temperatures above 400 0 C, which is probably attributed to creep deformation and may be improved by selecting a proper loading condition during the hardness test. (orig.)

  11. Facility for studying the effects of elevated carbon dioxide concentration and increased temperature on crops

    Energy Technology Data Exchange (ETDEWEB)

    Lawlor, D.W.; Mitchell, R.A.C.; Franklin, J.; Mitchell, V.J.; Driscoll, S.P.; Delgado, E. (Institute of Arable Crops Research, Harpenden (United Kingdom). Dept. of Biochemistry and Physiology)

    1993-06-01

    The requirements for the experimental study of the effects of global climate change conditions on plants are outlined. A semi-controlled plant growth facility is described which allows the study of elevated CO[sub 2] and temperature, and their interaction on the growth of plants under radiation and temperature conditions similar to the field. During an experiment on winter wheat (cv. Mercia), which ran from December 1990 through to August 1991, the facility maintained mean daytime CO[sub 2] concentrations of 363 and 692 cm[sup 3] m[sup -3] for targets of 350 and 700 cm[sup 3] m[sup 3] respectively. Temperatures were set to follow outside ambient or outside ambient +4[degree]C, and hourly means were within 0.5[degree]C of the target for 92% of the time for target temperatures greater than 6[degree]C. Total photosynthetically active radiation incident on the crop (solar radiation supplemented by artificial light with natural photoperiod) was 2% greater than the total measured outside over the same period.

  12. Indium tin oxide thin film strain gages for use at elevated temperatures

    Science.gov (United States)

    Luo, Qing

    A robust ceramic thin film strain gage based on indium-tin-oxide (ITO) has been developed for static and dynamic strain measurements in advanced propulsion systems at temperatures up to 1400°C. These thin film sensors are ideally suited for in-situ strain measurement in harsh environments such as those encountered in the hot sections of gas turbine engines. A novel self-compensation scheme was developed using thin film platinum resistors placed in series with the active strain element (ITO) to minimize the thermal effect of strain or apparent strain. A mathematical model as well as design rules were developed for the self-compensated circuitry using this approach and close agreement between the model and actual static strain results has been achieved. High frequency dynamic strain tests were performed at temperatures up to 500°C and at frequencies up to 2000Hz to simulate conditions that would be encountered during engine vibration fatigue. The results indicated that the sensors could survive extreme test conditions while maintaining sensitivity. A reversible change in sign of the piezoresistive response from -G to +G was observed in the vicinity of 950°C, suggesting that the change carrier responsible for conduction in the ITO gage had been converted from a net "n-carrier" to a net "p-carrier" semiconductor. Electron spectroscopy for chemical analysis (ESCA) of the ITO films suggested they experienced an interfacial reaction with the Al2O3 substrate at 1400°C. It is likely that oxygen uptake from the substrate is responsible for stabilizing the ITO films to elevated temperatures through the interfacial reaction. Thermo gravimetric analysis of ITO films on alumina at elevated temperatures showed no sublimation of ITO films at temperature up to 1400°C. The surface morphology of ITO films heated to 800, 1200 and 1400°C were also evaluated by atomic force microscopy (AFM). A linear current-voltage (I--V) characteristic indicated that the contact interface

  13. Tribological characteristics of electroless Ni–P–MoS2 composite coatings at elevated temperatures

    International Nuclear Information System (INIS)

    Li Zhen; Wang Jingbo; Lu Jinjun; Meng Junhu

    2013-01-01

    Highlights: ► Uniform Ni–P–MoS 2 composite coatings are deposited by electroless plating. ► Friction coefficient of composite coating decreases with the increase of temperature. ► Formation of lubricious oxide film leads to excellent tribological property. - Abstract: Ni–P–MoS 2 composite coatings were deposited on AISI-1045 steel plate by electroless plating followed by a heat treatment at 300 °C for 2 h. The high-temperature tribological characteristics of the composite coatings were evaluated under dry sliding conditions in a tribometer with ball-on-disk configuration. The effect of the co-deposition of MoS 2 on the friction and wear behaviors of composite coatings at elevated temperature was investigated. Scanning electron microscopy was used to determine the morphology of the worn surface of composite coating. The chemical states of some typical elements on the worn surfaces were determined by X-ray photoelectron spectroscope. The results indicate that friction coefficient of the composite coatings decreases with the increase of test temperature up to 500 °C, and the best tribological properties of Ni–P–MoS 2 composite coatings are achieved at 400 °C. The worn surface of Ni–P–MoS 2 composite coatings are characterized by mild scuffing and deformation. The improvement of tribological properties of the composite coatings was attributed to the formation of the lubricious oxide film composed of oxides of Ni and Mo at high temperatures. With the test temperature increasing to 600 °C, the tribological properties of the composite coating begin to deteriorate due to softening of the coating.

  14. Effects of Elevated Temperature Treatment on Compositions and Tensile Properties of Several Kinds of Basalt Fibers

    Directory of Open Access Journals (Sweden)

    CHEN Jing

    2017-06-01

    Full Text Available Five kinds of domestic basalt fibers were studied for the changes of chemical compositions, physical properties and tensile properties of these fibers before and after 200-800℃ treatment in air atmosphere and in nitrogen atmosphere. These works were done mainly by means of X-ray fluorescence spectrometry and fiber monofilament tensile testing methods in order to understand the elevated temperature resistance of basalt fiber. The experimental results show that the surface of basalt fibers becomes smoother with slightly smaller in diameter and mass reduction at the same time, due to the removal of fiber surface treatment agent after elevated temperature treatment in air atmosphere. Mass fractions of SiO2 and Al2O3 decrease while mass fractions of FeO+Fe2O3, CaO and MgO increase, among which the mass fraction of FeO+Fe2O3 increase the most with the maximum increase of 21%. The monofilament tensile strength of basalt fiber is reduced after 200℃ treatment and the maximum strength retention percentage is 98.3%. The monofilament tensile strength reduces evidently after 400℃ treatment and the maximum strength retention percentage is 64.6%. Moreover, the strength retention percentages of five kinds of basalt fibers are all less than 20% after 800℃ treatment. In addition, the fiber elongation at break decreases with the increase of treating temperature and the elastic modulus increases. Compared with that in air atmosphere, strength retention rate of basalt fiber is higher and tensile properties are more stable in nitrogen atmosphere.

  15. Impact of elevated carbon dioxide concentration and temperature on bud burst and shoot growth of boreal Norway spruce

    International Nuclear Information System (INIS)

    Slaney, M.; Linder, S.

    2007-01-01

    Atmospheric carbon dioxide (CO 2 ) concentrations are predicted to double during the next century, and recent studies have suggested that temperature changes as a result of global warming will be pronounced over the mid and high latitudes of northern continents. The phenology of boreal forests is mainly driven by temperature, and is a reliable indicator of climate change. This article presented the results of a study investigating the effects of elevated carbon dioxide (CO 2 ) and temperature on bud and shoot phenology of mature Norway spruce trees grown in northern Sweden. The trees were grown in whole tree chambers over a period of 3 years and supplied with either ambient or elevated CO 2 at either ambient, or elevated temperatures, which were altered on a monthly time step based on simulations by the Swedish Regional Climate Modelling Program. Temperature elevation ranged between 2.8 and 5.6 degrees C above ambient temperatures, with a CO 2 elevation of 700 μmol per mol. Bud development and shoot extension were monitored from early spring until the termination of elongation growth. Results of the study showed that elevated air temperature hastened both bud development and the initiation and termination of shoot growth by 2 to 3 weeks in each of the study years. It was noted that elevated CO 2 had no significant effect on bud development patterns or on the length of the shoot growth period. Although there was a distinct correlation between temperature sum and shoot elongation, a precise timing of bud burst could not be obtained by using an accumulation of temperature sums. It was concluded that climate warming will results in earlier bud burst in boreal Norway spruce. 59 refs., 3 tabs., 7 figs

  16. Rikkunshito Ameliorates Cancer Cachexia Partly through Elevation of Glucarate in Plasma

    Directory of Open Access Journals (Sweden)

    Katsuya Ohbuchi

    2015-01-01

    Full Text Available Cancer cachexia, which is characterized by decreased food intake, weight loss and systemic inflammation, increases patient’s morbidity and mortality. We previously showed that rikkunshito (RKT, a Japanese traditional herbal medicine (Kampo, ameliorated the symptoms of cancer cachexia through ghrelin signaling-dependent and independent pathways. To investigate other mechanisms of RKT action in cancer cachexia, we performed metabolome analysis of plasma in a rat model bearing the Yoshida AH-130 hepatoma. A total of 110 metabolites were detected in plasma and RKT treatment significantly altered levels of 23 of those metabolites in cachexia model rats. Among them, glucarate, which is known to have anticarcinogenic activity through detoxification of carcinogens via inhibition of β-glucuronidase, was increased in plasma following administration of RKT. In our AH-130 ascites-induced cachexia rat model, administration of glucarate delayed onset of weight loss, improved muscle atrophy, and reduced ascites content. Additionally, glucarate reduced levels of plasma interferon-γ (IFN-γ in tumor-bearing rats and was also found to suppress LPS-induced IFN-γ expression in splenocytes in vitro. These results suggest that glucarate has anti-inflammatory activity via a direct effect on immune host cells and suggest that RKT may also ameliorate inflammation partly through the elevation of glucarate in plasma.

  17. OH-initiated oxidation of benzene - Part II. Influence of elevated NOx concentrations

    DEFF Research Database (Denmark)

    Klotz, B; Volkamer, R; Hurley, MD

    2002-01-01

    The present work represents a continuation of part I of this series of papers, in which we investigated the phenol yields in the OH-initiated oxidation of benzene under conditions of low to moderate concentrations of NOx, to elevated NOx levels. The products of the OH-initiated oxidation of benzene...... concentrations of NOx, the phenol yield increases with increasing O-2 partial pressure. The rate constant of the reaction of hydroxycyclohexadienyl peroxyl radicals with NO was determined to be (1.7 +/- 0.6) x 10(-11) cm(3) molecule(-1) s(-1). This reaction leads to the formation of E, E-2,4-hexadienedial...... as the main identiable product (29 +/- 16. The reaction of the hydroxycyclohexadienyl radical with NO2 gave phenol (5.9 +/- 3.4 and E,E-2,4-hexadienedial (3.4 +/- 1.9, no other products could be identified. The residual FTIR product spectra indicate the formation of unknown nitrates or other nitrogen...

  18. Microfracture behaviour of extruded Mg–Zn–Y alloys containing long-period stacking ordered structure at room and elevated temperatures

    International Nuclear Information System (INIS)

    Mine, Yoji; Yoshimura, Hajime; Matsuda, Mitsuhiro; Takashima, Kazuki; Kawamura, Yoshihito

    2013-01-01

    We studied the fracture behaviour of extruded Mg–Zn–Y alloys at room temperature (RT) and at 523 K using microfracture testing. An Mg 97 Zn 1 Y 2 alloy was used to obtain two-phase specimens consisting of α-Mg and long-period stacking ordered (LPSO) structure phases, and an Mg 88 Zn 5 Y 7 alloy was used to obtain specimens consisting of an LPSO phase. The microfracture testing of the two-phase specimen revealed that the fracture behaviour changed from brittle to ductile as the testing temperature increased. By contrast, the LPSO-phase specimen remained brittle even at the elevated temperature and the intrinsic fracture toughness values obtained at both testing temperatures were nearly identical. Ex situ transmission electron microscopy of the two-phase specimen showed that mechanical twinning in the α-Mg phase did not occur at the elevated temperature, although it was activated at RT. This suggests that the plastic deformation mode in the α-Mg phase plays a crucial part in the enhanced crack growth resistance of the two-phase alloy at the elevated temperature

  19. Characterization of Elevated Temperature Properties of Heat Exchanger and Steam Generator Alloys

    International Nuclear Information System (INIS)

    Wright, J.K.; Carroll, L.J.; Benz, J.K.; Simpson, J.A.; Wright, R.N.; Lloyd, W.R.; Chapman, J.A.

    2010-01-01

    The Next Generation Nuclear Plant project is considering Alloy 800H and Alloy 617 for steam generator and intermediate heat exchangers. It is envisioned that a steam generator would operate with reactor outlet temperatures from 750 to 800 C, while an intermediate heat exchanger for primary to secondary helium would operate up to an outlet temperature of 950 C. Although both alloys are of interest due in part to their technical maturity, a number of specific properties require further characterization for design of nuclear components. Strain rate sensitivity of both alloys has been characterized and is found to be significant above 600 C. Both alloys also exhibit dynamic strain aging, characterized by serrated flow, over a wide range of temperatures and strain rates. In general dynamic strain aging is observed to begin at higher temperatures and serrated flow persists to higher temperatures in Alloy 617 compared to Alloy 800H. Dynamic strain aging is a concern for these materials since it is observed to result in reduced ductility for many solid solution alloys. The role of dynamic strain aging in the creep-fatigue behavior of Alloy 617 at temperatures of 800 C and above has also been examined in detail. Serrated flow is found to persist in cyclic stress-strain curves up to nearly the cycle to failure in some temperature and strain regimes. Results of those experiments and implications for creep-fatigue testing protocols will be described.

  20. Elevated Temperature Photophysical Properties and Morphological Stability of CdSe and CdSe/CdS Nanoplatelets

    Energy Technology Data Exchange (ETDEWEB)

    Rowland, Clare E. [Department; Center; Fedin, Igor [Department; Diroll, Benjamin T. [Center; Liu, Yuzi [Center; Talapin, Dmitri V. [Center; Department; Schaller, Richard D. [Department; Center

    2018-01-03

    Elevated temperature optoelectronic performance of semiconductor nanomaterials remains an important issue for applications. Here we examine two-dimensional CdSe nanoplatelets (NPs) and CdS/CdSe/CdS shell/core/shell sandwich NPs at temperatures ranging from 300-700 K using static and transient spectroscopies as well as in-situ transmission electron microscopy. NPs exhibit reversible changes in PL intensity, spectral position, and emission linewidth with temperature elevation up to ~500 K, losing a factor of ~8 to 10 in PL intensity at 400 K relative to ambient. Temperature elevation above ~500 K yields thickness dependent, irreversible degradation in optical properties. Electron microscopy relates stability of the NP morphology up to near 600 K followed by sintering and evaporation at still higher temperatures. The mechanism of reversible PL loss, based on differences in decay dynamics between time-resolved photoluminescence and transient absorption, arise primarily from hole trapping in both NPs and sandwich NPs.

  1. Molecular and genotoxic effects in Mytilus galloprovincialis exposed to tritiated water at an elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Dallas, L.; Jha, A. [School of Biological Sciences, Plymouth University (United Kingdom); Bean, T.; Lyons, B. [Cefas Weymouth Laboratory (United Kingdom); Turner, A. [School of Geography, Earth and Environmental Sciences, Plymouth University (United Kingdom)

    2014-07-01

    Radioactive contaminants do not occur in isolation; organisms are also exposed to fluctuations in biological, biotic and physico-chemical factors, such as competition, other contaminants, salinity and temperature. Thermal discharge from nuclear facilities is considered to be one of the most important environmental issues surrounding these establishments, second only to the release of radionuclides. Cooling water from nuclear institutions is one of the major sources of tritium ({sup 3}H) to the aquatic environment; temperature is therefore an abiotic factor of particular concern when it comes to assessing the potential detrimental impacts of {sup 3}H exposure in marine species. In this context, we used a molecular approach to elucidate the potential mechanisms behind the genotoxicity of tritiated water (HTO) to marine mussels, at 'normal' and elevated temperatures. Mussels were exposed to control seawater or 15 MBq L{sup -1} HTO at 15 and 25 deg. C for 7 days, with haemolymph and gill tissue sampling (for comet assay to detect DNA strand breaks and gene expression analysis, respectively) after 0, 1, 12, 72 and 168 h. In addition, a Cu concentration of 40 μg L{sup -1} (previously established as genotoxic under these exposure conditions) was used concurrently as a positive control (at 15 deg. C). Tissue-specific accumulation of {sup 3}H was also determined, allowing the calculation of dose rates using the ERICA tool. Comparison of DNA strand breakage (DSB) as a function of time suggested that significant levels of DSB were induced earlier in haemocytes of mussels exposed to HTO at 25 deg. C compared to 15 deg. C (72 h vs. 168 h). Alterations in transcriptional expression of key genes also suggest that the 72 h time point is critical, with gill showing reduced expression of hsp70, hsp90, mt20, p53 and rad51 during HTO exposure at the elevated temperature. In contrast, HTO exposure at 15 deg. C resulted in significant up-regulation of the same genes after 72

  2. Time-dependent deformation at elevated temperatures in basalt from El Hierro, Stromboli and Teide volcanoes

    Science.gov (United States)

    Benson, P. M.; Fahrner, D.; Harnett, C. E.; Fazio, M.

    2014-12-01

    Time dependent deformation describes the process whereby brittle materials deform at a stress level below their short-term material strength (Ss), but over an extended time frame. Although generally well understood in engineering (where it is known as static fatigue or "creep"), knowledge of how rocks creep and fail has wide ramifications in areas as diverse as mine tunnel supports and the long term stability of critically loaded rock slopes. A particular hazard relates to the instability of volcano flanks. A large number of flank collapses are known such as Stromboli (Aeolian islands), Teide, and El Hierro (Canary Islands). Collapses on volcanic islands are especially complex as they necessarily involve the combination of active tectonics, heat, and fluids. Not only does the volcanic system generate stresses that reach close to the failure strength of the rocks involved, but when combined with active pore fluid the process of stress corrosion allows the rock mass to deform and creep at stresses far lower than Ss. Despite the obvious geological hazard that edifice failure poses, the phenomenon of creep in volcanic rocks at elevated temperatures has yet to be thoroughly investigated in a well controlled laboratory setting. We present new data using rocks taken from Stromboli, El Heirro and Teide volcanoes in order to better understand the interplay between the fundamental rock mechanics of these basalts and the effects of elevated temperature fluids (activating stress corrosion mechanisms). Experiments were conducted over short (30-60 minute) and long (8-10 hour) time scales. For this, we use the method of Heap et al., (2011) to impose a constant stress (creep) domain deformation monitored via non-contact axial displacement transducers. This is achieved via a conventional triaxial cell to impose shallow conditions of pressure (<25 MPa) and temperature (<200 °C), and equipped with a 3D laboratory seismicity array (known as acoustic emission, AE) to monitor the micro

  3. Interactive effects of seawater acidification and elevated temperature on biomineralization and amino acid metabolism in the mussel Mytilus edulis.

    Science.gov (United States)

    Li, Shiguo; Liu, Chuang; Huang, Jingliang; Liu, Yangjia; Zheng, Guilan; Xie, Liping; Zhang, Rongqing

    2015-11-01

    Seawater acidification and warming resulting from anthropogenic production of carbon dioxide are increasing threats to marine ecosystems. Previous studies have documented the effects of either seawater acidification or warming on marine calcifiers; however, the combined effects of these stressors are poorly understood. In our study, we examined the interactive effects of elevated carbon dioxide partial pressure (P(CO2)) and temperature on biomineralization and amino acid content in an ecologically and economically important mussel, Mytilus edulis. Adult M. edulis were reared at different combinations of P(CO2) (pH 8.1 and 7.8) and temperature (19, 22 and 25°C) for 2 months. The results indicated that elevated P(CO2) significantly decreased the net calcification rate, the calcium content and the Ca/Mg ratio of the shells, induced the differential expression of biomineralization-related genes, modified shell ultrastructure and altered amino acid content, implying significant effects of seawater acidification on biomineralization and amino acid metabolism. Notably, elevated temperature enhanced the effects of seawater acidification on these parameters. The shell breaking force significantly decreased under elevated P(CO2), but the effect was not exacerbated by elevated temperature. The results suggest that the interactive effects of seawater acidification and elevated temperature on mussels are likely to have ecological and functional implications. This study is therefore helpful for better understanding the underlying effects of changing marine environments on mussels and other marine calcifiers. © 2015. Published by The Company of Biologists Ltd.

  4. Tensile properties of strip casting 6.5 wt% Si steel at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hao-Ze, E-mail: lhzqq83@163.com; Liu, Zhen-Yu, E-mail: zyliu@mail.neu.edu.cn

    2015-07-15

    Tensile behaviors of strip casting 6.5 wt% Si steel are tested at elevated temperatures ranging from 300 °C to 800 °C. A detailed study of the morphology of the fracture surface and the ordered phase at each deforming temperature is carried out by a scanning electron microscope and a transmission electron microscope. The results show that the deforming temperature rather than the ordered degree determines the tensile properties. As the deforming temperature increases, the stress level in the whole deforming stage continually decreases, whereas the elongation gradually increases. The ductile–brittle transition occurs around 350 °C. The elongation of 2% at 300 °C rapidly increases up to 16.4% at 350 °C and the corresponding fracture mode transforms from the complete cleavage fracture to the mixture of the very limited cleavage fracture, intergranular dimple fracture and the dimple fracture. Serrated flow is observed at 350 °C and 400 °C probably due to the occurrence of dynamic strain aging. Due to the gradually weakened grain boundary cohesion with the deforming temperature increasing, intergranular dimple pattern dominates the fracture surface at 600 °C and the elongation slowly increases from 16.4% at 350 °C to 22.8% at 600 °C. At 700 °C and 800 °C, the much more enhanced dynamic recovery, the substantially decreased stress levels which contribute to the inhibition of the intergranular dimple fracture, the much lower content of the B2 ordered phase at 700 °C, and the completely disordered state at 800 °C give rise to the dramatically improved elongations of 88.8% and 130.8%, respectively.

  5. Elevated temperatures are associated with stress in rooftop-nesting Common Nighthawk (Chordeiles minor) chicks.

    Science.gov (United States)

    Newberry, Gretchen N; Swanson, David L

    2018-01-01

    Grasslands and riparian forests in southeastern South Dakota have been greatly reduced since historical times, primarily due to conversion to row-crop agriculture. Common Nighthawk ( Chordeiles minor ) nesting habitat includes grasslands, open woodlands and urban rooftops, but nesting sites in southeastern South Dakota are confined to rooftops, as natural nesting habitat is limited. Nighthawks nesting on exposed rooftop habitats may encounter thermal conditions that increase operative temperatures relative to vegetated land cover types. Mean humidity has increased and mean wind speed and cloud cover have decreased during the nighthawk breeding season from 1948 to 2016 in southeastern South Dakota. These changes might contribute to increasing operative temperatures at exposed rooftop nest sites and this could influence chick condition. We studied nest micro-climate and the plasma stress response for 24 rooftop-nesting nighthawk chicks from 17 nests during 2015 and 2016. High humidity prior to blood collection reduced both baseline and stress-induced plasma corticosterone (CORT). In contrast, high maximum temperatures during the day before sampling increased stress-induced CORT. The magnitude of the chick stress response was significantly negatively related to maximum wind speed for the week prior to CORT measurement. Other weather and micro-climate variables were not significant effectors of CORT metrics. Most chicks had low baseline CORT and were able to mount a stress response, but a subset of chicks ( n = 4) showed elevated baseline CORT and a negative association between the magnitude of stress response and ambient temperature. For this subset, mean ambient temperature for the day before sampling was significantly higher (2.3°C) than for chicks with typical baseline CORT levels. These data suggest that regional climate change trends could affect the ability of nighthawk chicks to mount a stress response, which, in turn, might influence the susceptibility of

  6. Cellulose-Hemicellulose Interactions at Elevated Temperatures Increase Cellulose Recalcitrance to Biological Conversion

    Energy Technology Data Exchange (ETDEWEB)

    Mittal, Ashutosh [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Himmel, Michael E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Kumar, Rajeev [University of California, Riverside; Oak Ridge National Laboratory; ; Smith, Micholas Dean [Oak Ridge National Laboratory; University of Tennessee; Petridis, Loukas [Oak Ridge National Laboratory; University of Tennessee; Ong, Rebecca G. [Michigan Technological University; Cai, Charles M. [University of California, Riverside; Oak Ridge National Laboratory; Balan, Venkatesh [University of Houston; Dale, Bruce E. [Michigan State University; Ragauskas, Arthur J. [Oak Ridge National Laboratory; University of Tennessee; Smith, Jeremy C. [Oak Ridge National Laboratory; University of Tennessee; Wyman, Charles E. [University of California, Riverside; Oak Ridge National Laboratory

    2018-01-23

    It has been previously shown that cellulose-lignin droplets' strong interactions, resulting from lignin coalescence and redisposition on cellulose surface during thermochemical pretreatments, increase cellulose recalcitrance to biological conversion, especially at commercially viable low enzyme loadings. However, information on the impact of cellulose-hemicellulose interactions on cellulose recalcitrance following relevant pretreatment conditions are scarce. Here, to investigate the effects of plausible hemicellulose precipitation and re-association with cellulose on cellulose conversion, different pretreatments were applied to pure Avicel(R) PH101 cellulose alone and Avicel mixed with model hemicellulose compounds followed by enzymatic hydrolysis of resulting solids at both low and high enzyme loadings. Solids produced by pretreatment of Avicel mixed with hemicelluloses (AMH) were found to contain about 2 to 14.6% of exogenous, precipitated hemicelluloses and showed a remarkably much lower digestibility (up to 60%) than their respective controls. However, the exogenous hemicellulosic residues that associated with Avicel following high temperature pretreatments resulted in greater losses in cellulose conversion than those formed at low temperatures, suggesting that temperature plays a strong role in the strength of cellulose-hemicellulose association. Molecular dynamics simulations of hemicellulosic xylan and cellulose were found to further support this temperature effect as the xylan-cellulose interactions were found to substantially increase at elevated temperatures. Furthermore, exogenous, precipitated hemicelluloses in pretreated AMH solids resulted in a larger drop in cellulose conversion than the delignified lignocellulosic biomass containing comparably much higher natural hemicellulose amounts. Increased cellulase loadings or supplementation of cellulase with xylanases enhanced cellulose conversion for most pretreated AMH solids; however, this approach

  7. Effect of elevated temperatures on the mechanical behavior of basalt textile reinforced refractory concrete

    International Nuclear Information System (INIS)

    Rambo, Dimas Alan Strauss; Andrade Silva, Flávio de; Toledo Filho, Romildo Dias; Fonseca Martins Gomes, Otávio da

    2015-01-01

    Highlights: • The thermo-mechanical behavior of basalt TRC is investigated. • The fiber polymer coating can become a deterministic factor in the TRC response. • Pre-heating the TRC at 150 °C leads to a matrix–polymer interlocking mechanism. • Above 400 °C a sudden drop in the TRC tensile response is observed. - Abstract: The work in hand presents the results of an experimental investigation on the thermo-mechanical properties of a textile refractory composite reinforced with polymer coated basalt fibers under tensile loading. The composites were produced as a laminate material using basalt bi-directional fabric layers as reinforcement. A high alumina cement matrix was used in the matrix composition which was designed using the compressible packing method. A series of uniaxial tensile tests was performed under temperatures ranging from 25 to 1000 °C. The cracking mechanisms were discussed and compared to that obtained at room temperature. Thermogravimetry and X-ray diffraction analysis were used to study the deterioration/phase changes as a function of the studied temperatures. Scanning electron microscopy (SEM) was used to study the damage processes in the fiber–matrix interfaces after exposure to high temperatures. The obtained results indicated that the presence and the type of coating can become a deterministic factor in the tensile response of the composite submitted to elevated temperatures. A sudden drop in the serviceability limit state of the composite was observed above 400 °C, caused by the degradation of the polymer used as a fiber surface coating, the degradation of the basalt fiber and by the dehydration process of the refractory matrix

  8. Study the effect of elevated dies temperature on aluminium and steel round deep drawing

    International Nuclear Information System (INIS)

    Lean, Yeong Wei; Azuddin, M.

    2016-01-01

    Round deep drawing operation can only be realized by expensive multi-step production processes. To reduce the cost of processes while expecting an acceptable result, round deep drawing can be done at elevated temperature. There are 3 common problems which are fracture, wrinkling and earing of deep drawing a round cup. The main objective is to investigate the effect of dies temperature on aluminium and steel round deep drawing; with a sub-objective of eliminate fracture and reducing wrinkling effect. Experimental method is conducted with 3 different techniques on heating the die. The techniques are heating both upper and lower dies, heating only the upper dies, and heating only the lower dies. 4 different temperatures has been chosen throughout the experiment. The experimental result then will be compared with finite element analysis software. There is a positive result from steel material on heating both upper and lower dies, where the simulation result shows comparable as experimental result. Heating both upper and lower dies will be the best among 3 types of heating techniques. (paper)

  9. Copper(II) oxide solubility behavior in aqueous sodium phosphate solutions at elevated temperatures

    International Nuclear Information System (INIS)

    Ziemniak, S.E.; Jones, M.E.; Combs, K.E.S.

    1990-02-01

    A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of copper(II) oxide (CuO) in aqueous sodium phosphate solutions at temperatures between 292 and 535 K. Copper solubilities are observed to increase continuously with temperature and phosphate concentration. The measured solubility is examined via a Cu(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reactions are obtained from a least- squares analysis of the data. Altogether, thermochemical properties are established for five anionic complexes: Cu(OH) 3 - , Cu(OH) 4 = , Cu(OH) 2 (HPO 4 ) = , Cu(OH) 3 (H 2 PO 4 ) = , and Cu(OH) 2 (PO 4 ) ≡ . Precise thermochemical parameters are also derived for the Cu(OH) + hydroxocomplex based on CuO solubility behavior previously observed in pure water (*) at elevated temperatures. The relative ease of Cu(II) ion hydrolysis is such that Cu(OH) 3 - species become the preferred hydroxocomplex for pH ≥ 9.4. 20 refs., 8 figs., 6 tabs

  10. Performance of Hg1-xCdxTe infrared focal plane array at elevated temperature

    Science.gov (United States)

    Singh, Anand; Pal, Ravinder

    2017-04-01

    The simulated optical and electrical performance of the infrared HgCdTe focal plane array (FPA) for elevated operation temperature is reported. The depleted absorber layer is explored for equilibrium mode of operation up to 160 K. A resonant cavity is created to improve photon-matter interaction and hence, reduces the required absorption volume. The volume of the active region of HgCdTe detector is reduced by 70% in this manner. Dark current density is decreased without compromising the quantum efficiency. The effect of the reduced band filling effect leading to higher absorption coefficient and more efficient utilization of incident flux is employed. High quantum efficiency is achieved in a thin compositionally graded n+/ν/π/p HgCdTe photo-diode. This architecture helps to minimize the requirement of charge handling capacity in the CMOS read-out integrated circuit (ROIC) as the operation temperature is increased. Quantum efficiency ˜30% or above is shown to be sufficient for Noise Equivalent Temperature Difference (NETD) less than 20 mK with the reported design.

  11. Numerical predictions of dry oxidation of iron and low-carbon steel at moderately elevated temperatures

    International Nuclear Information System (INIS)

    Henshall, G.A.

    1996-11-01

    Wrought and cast low-carbon steel are candidate materials for the thick (e.g. 10 cm) outer barrier of nuclear waste packages being considered for use in the potential geological repository at Yucca Mountain. Dry oxidation is possible at the moderately elevated temperatures expected at the container surface (323-533 K or 50-260 C). Numerical predictions of dry oxidation damage were made based on experimental data for iron and low-carbon steel and parabolic oxidation theory. The Forward Euler method was implemented to integrate the parabolic rate law for arbitrary, complex temperature histories. Assuming growth of a defect-free, adherent oxide, the surface penetration of a low-carbon steel barrier following 5000 years of exposure to a severe, but repository-relevant, temperature history is predicted to be only about 0.127 mm, less than 0.13% of the expected container thickness of 10 cm. Allowing the oxide to spall upon reaching a critical thickness increases the predicted metal penetration values, but degradation is still computed to be negligible. Thus, dry oxidation is not expected to significantly degrade the performance of thick, corrosion allowance barriers constructed of low-carbon steel

  12. Development of optical tools for the characterization of selective solar absorber at elevated temperature

    Science.gov (United States)

    Giraud, Philemon; Braillon, Julien; Delord, Christine; Raccurt, Olivier

    2016-05-01

    Durability of solar components for CSP (Concentrated Solar Power Plant) technologies is a key point to lower cost and ensure their large deployment. These technologies concentrated the solar radiation by means of mirrors on a receiver tube where it is collected as thermal energy. The absorbers are submitted to strong environmental constraints and the degradation of their optical properties (emittance and solar absorbance) have a direct impact on performance. The objective is to develop new optical equipment for characterization of this solar absorber in condition of use that is to say in air and at elevated temperature. In this paper we present two new optical test benches developed for optical characterization of solar absorbers in condition of use up to 800°C. The first equipment is an integrated sphere with heated sample holder which measures the hemispherical reflectance between 280 and 2500 nm to calculate the solar absorbance at high temperature. The second optical test bench measures the emittance of samples up to 1000°C in the range of 1.25 to 28.57 µm. Results of high temperature measurements on a series of metallic absorbers with selective coating and refractory material for high thermal receiver are presented.

  13. Effect of Elevated CO2 Concentration, Elevated Temperature and No Nitrogen Fertilization on Methanogenic Archaeal and Methane-Oxidizing Bacterial Community Structures in Paddy Soil.

    Science.gov (United States)

    Liu, Dongyan; Tago, Kanako; Hayatsu, Masahito; Tokida, Takeshi; Sakai, Hidemitsu; Nakamura, Hirofumi; Usui, Yasuhiro; Hasegawa, Toshihiro; Asakawa, Susumu

    2016-09-29

    Elevated concentrations of atmospheric CO2 ([CO2]) enhance the production and emission of methane in paddy fields. In the present study, the effects of elevated [CO2], elevated temperature (ET), and no nitrogen fertilization (LN) on methanogenic archaeal and methane-oxidizing bacterial community structures in a free-air CO2 enrichment (FACE) experimental paddy field were investigated by PCR-DGGE and real-time quantitative PCR. Soil samples were collected from the upper and lower soil layers at the rice panicle initiation (PI) and mid-ripening (MR) stages. The composition of the methanogenic archaeal community in the upper and lower soil layers was not markedly affected by the elevated [CO2], ET, or LN condition. The abundance of the methanogenic archaeal community in the upper and lower soil layers was also not affected by elevated [CO2] or ET, but was significantly increased at the rice PI stage and significantly decreased by LN in the lower soil layer. In contrast, the composition of the methane-oxidizing bacterial community was affected by rice-growing stages in the upper soil layer. The abundance of methane-oxidizing bacteria was significantly decreased by elevated [CO2] and LN in both soil layers at the rice MR stage and by ET in the upper soil layer. The ratio of mcrA/pmoA genes correlated with methane emission from ambient and FACE paddy plots at the PI stage. These results indicate that the decrease observed in the abundance of methane-oxidizing bacteria was related to increased methane emission from the paddy field under the elevated [CO2], ET, and LN conditions.

  14. Simulating forest productivity along a neotropical elevational transect: temperature variation and carbon use efficiency

    Science.gov (United States)

    Marthews, T.; Malhi, Y.; Girardin, C.; Silva-Espejo, J.; Aragão, L.; Metcalfe, D.; Rapp, J.; Mercado, L.; Fisher, R.; Galbraith, D.; Fisher, J.; Salinas-Revilla, N.; Friend, A.; Restrepo-Coupe, N.; Williams, R.

    2012-04-01

    A better understanding of the mechanisms controlling the magnitude and sign of carbon components in tropical forest ecosystems is important for reliable estimation of this important regional component of the global carbon cycle. We used the JULES vegetation model to simulate all components of the carbon balance at six sites along an Andes-Amazon transect across Peru and Brazil and compared the results to published field measurements. In the upper montane zone the model predicted a vegetation dieback, indicating a need for better parameterisation of cloud forest vegetation. In the lower montane and lowland zones simulated ecosystem productivity and respiration were predicted with reasonable accuracy, although not always within the error bounds of the observations. Model-predicted carbon use efficiency in this transect surprisingly did not increase with elevation, but remained close to the 'temperate' value 0.5. This may be explained by elevational changes in the balance between growth and maintenance respiration within the forest canopy, as controlled by both temperature- and pressure-mediated processes.

  15. Evaluation of elevated temperature influence on mechanical properties of a commercial unrefined bagasse fiber-polypropylene composite

    Directory of Open Access Journals (Sweden)

    Foroogh Dastoorian

    2014-11-01

    Full Text Available An experimental investigation was conducted to evaluate the effect of elevated temperatures, ranging from room temperature to 80oC, on mechanical characteristics of a commercial bagasse fiber/polypropylene composite. The test results were used to determine the temperature dependencies of the mechanical properties of the studied composite material at temperatures up to 80°C in order to develop temperature adjustment factors for the use in structural applications. The results have shown that as temperature increases, the material become more ductile due to increased plastic deformation gets lower stiffness and fails at higher strains. The resulted adjustment factors were different for each loading mode and the results also have indicated that the influence of elevated temperatures on values of modulus was higher than that on strengths.

  16. Evaluation of conversion relationships for impression creep test at elevated temperatures

    International Nuclear Information System (INIS)

    Hyde, T.H.; Sun, W.

    2009-01-01

    This paper contains some results related to the evaluation of the conversion relationships between impression creep test data and conventional uniaxial creep test date, for determining the secondary creep properties at elevated temperature. Some important aspects, including conversion factors, specimen dimensions, typical test results and validity of the test technique etc are briefly reviewed. The method used to determine the conversion factors is based on a reference stress approach using the results of finite element (FE) analyses; this is described in the paper. The conversion factors (reference parameters) obtained from 2-dimensional (2D) and 3-dimensional (3D) FE analyses are compared and the effects of specimen geometry, on the conversion relationships, are assessed. The recommendations on the use of these conversion factors, in practical impression creep testing, are given. Proposals for future exploitation of the technique are addressed.

  17. Isolation of non-sulphur photosynthetic bacterial strains efficient in hydrogen production at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.P.; Srivastava, S.C. (Banaras Hindu Univ., Varanasi (IN). Centre of Advanced Study in Botany)

    1991-01-01

    Four strains of non-sulphur photosynthetic bacteria were isolated from root zone associations of aquatic plants like Azolla, Salvinia and Eichhornia, as well as the deep-water rice. Based on the gross cell morphology and pigmentation, the isolates resembled Rhodopseudomonas sp. and have been designated as BHU strains 1 to 4, respectively. When subjected to elevated temperature (from 33-45{sup o}C), substantial growth/hydrogen production could be observed only in strains 1 and 4. Strains 2 and 3 on the other hand, showed diminished growth and negligible hydrogen photoproduction. The BHU strains 1 and 4 have been selected as the most active (thermostable) hydrogen producing strains of local origin as far as the Indian tropical climate is concerned. (author).

  18. Investigation of isochronous stress-strain formulations for elevated temperature structural design

    International Nuclear Information System (INIS)

    Koo, Gyeong Hoi; Kim, Jong Bum

    2012-01-01

    For elevated temperature design evaluations by the ASME-NH rules, the most important material data is the isochronous stress-strain curves, which can provide design creep information. The main purpose of this paper is to investigate appropriate formulations to be able to generate the isochronous stress-strain curves and implement it to the computer program which is coded the ASME-NH design evaluation procedures. To do this, formulations by the strain-time relationship are investigated in detail and the sensitivity studies for rapid initial transient creep contributions, slower and longer transient creep contribution, and secondary creep contributions are carried out for type 316 austenitic stainless steel. From the results of this study, it is found that the strain-time relationship formulations can well describe the isochronous stress-strain curves with the transient creep contributions

  19. Standard test methods for elevated temperature tension tests of metallic materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 These test methods cover procedure and equipment for the determination of tensile strength, yield strength, elongation, and reduction of area of metallic materials at elevated temperatures. 1.2 Determination of modulus of elasticity and proportional limit are not included. 1.3 Tension tests under conditions of rapid heating or rapid strain rates are not included. 1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  20. Plant nutrient mobilization in temperate heathland responds to elevated CO2, temperature and drought

    DEFF Research Database (Denmark)

    Andresen, Louise C.; Michelsen, Anders; Jonasson, Sven

    2010-01-01

    Temperate terrestrial ecosystems are currently exposed to increased atmospheric CO2 and progressive climatic changes with increased temperature and periodical drought. We here present results from a field experiment, where the effects of these three main climate change related factors...... decreased in response to drought. These complex changes in availability and release of nutrients from soil organic matter turnover and mineralization in response to elevated CO2 and climate change may influence the future plant carbon sequestration and species composition at temperate heathlands....... in Deschampsia soil, and microbial immobilization of N and P decreased in warmed Calluna soil. Warming tended to increase microbial N and P in Calluna but not in Deschampsia soil in fall, and more microbial C was accumulated under drought in Calluna soil. The effects of warming were often counteracted or erased...

  1. Elevated temperature creep and fatigue damage of a 2.25 Cr--1 Mo steel weldment

    International Nuclear Information System (INIS)

    Van Den Avyle, J.A.

    1978-01-01

    In weldments between dissimilar metals wide variations occur in metallurgical structure and mechanical properties, so that for good structural design it is necessary to understand the mechanical response of individual microstructural segments of the weld. This study investigates elevated temperature properties of a 2.25 Cr--1 Mo ferritic steel base metal welded with Chromenar 382V (Inconel 82) filler metal. Creep and low-cycle fatigue tests at 866 0 K (1100 0 F) show the filler metal and heat affected zone to be much stronger than the base metal. Optical microscopy does not show significant aging effects in the short-term fatigue tests or creep tests of 1180 hour duration

  2. Influence of Fly Ash on the Compressive Strength of Foamed Concrete at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Ahmad H.

    2014-01-01

    Full Text Available Foamed concrete is a lightweight concrete that is widely used in the construction industry recently. This study was carried out to investigate the influence of fly ash as a cement replacement material to the residual compressive strength of foamed concrete subjected to elevated temperature. For this study, the foamed concrete density was fixed at 1300 kg/m3 and the sand-cement ratio and water-cement was set at 1:2 and 0.45, respectively. The samples were prepared and tested at the age of 28 days. Based on the results, it has been found that with 25% inclusion of fly ash, the percentage of compressive strength loss was decreased by 3 – 50%.

  3. Global climate change and tree nutrition : effects of elevated CO2 and temperature

    International Nuclear Information System (INIS)

    Lukac, M.; Calfapietra, C.; Lagomarsino, A.; Loreto, F.

    2010-01-01

    The availability of nutrients for plant uptake can limit the productivity and survival of forest ecosystems. Information about multiple interacting factors regarding the availability of essential nutrients and their roles in plant metabolism is needed in order to understand the full impact of climate change. This paper presented the known effects of elevated carbon dioxide (CO 2 ) and temperature on tree nutrition, with particular reference to the mobilization and immobilization processes instead of pools. Existing gaps in knowledge were identified and future research priorities were suggested. This review focused on the major nutrients, notably nitrogen (N) and phosphorous (P) and how the processes that alter their cycling and availability are influenced by the effects of climate change. 143 refs., 3 figs.

  4. Variation in the transcriptional response of threatened coral larvae to elevated temperatures.

    Science.gov (United States)

    Polato, Nicholas R; Altman, Naomi S; Baums, Iliana B

    2013-03-01

    Coral populations have declined worldwide largely due to increased sea surface temperatures. Recovery of coral populations depends in part upon larval recruitment. Many corals reproduce during the warmest time of year when further increases in temperature can lead to low fertilization rates of eggs and high larval mortality. Microarray experiments were designed to capture and assess variability in the thermal stress responses of Acropora palmata larvae from Puerto Rico. Transcription profiles showed a striking acceleration of normal developmental gene expression patterns with increased temperature. The transcriptional response to heat suggested rapid depletion of larval energy stores via peroxisomal lipid oxidation and included key enzymes that indicated the activation of the glyoxylate cycle. High temperature also resulted in expression differences in key developmental signalling genes including the conserved WNT pathway that is critical for pattern formation and tissue differentiation in developing embryos. Expression of these and other important developmental and thermal stress genes such as ferritin, heat shock proteins, cytoskeletal components, cell adhesion and autophagy proteins also varied among larvae derived from different parent colonies. Disruption of normal developmental and metabolic processes will have negative impacts on larval survival and dispersal as temperatures rise. However, it appears that variation in larval response to high temperature remains despite the dramatic population declines. Further research is needed to determine whether this variation is heritable or attributable to maternal effects. © 2013 Blackwell Publishing Ltd.

  5. Fatigue Behavior of IM7/BMI 5250-4 Composite at Room and Elevated Temperatures

    Science.gov (United States)

    2015-03-01

    to the ancient Egyptians and their use of clay bricks reinforced with straw, but it is most commonly used in steel-reinforce concrete today [5, p...the temperature increases during the first part of the cure cycle, the viscosity of the resin decreases until the resin becomes a fluid. At about 165...C, the viscosity reaches a minimum value then begins to rise. During the hold at 191°C, a continuous cross-linked network is formed. Crosslinking

  6. Computational and Experimental Design of Fe-Based Superalloys for Elevated-Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, Peter K. [Univ. of Tennessee, Knoxville, TN (United States); Fine, Morris E. [Northwestern Univ., Evanston, IL (United States); Ghosh, Gautam [Northwestern Univ., Evanston, IL (United States); Asta, Mark D. [Univ. of California, Berkeley, CA (United States); Liu, Chain T. [Auburn Univ., AL (United States); Sun, Zhiqian [Univ. of Tennessee, Knoxville, TN (United States); Huang, Shenyan [Univ. of Tennessee, Knoxville, TN (United States); Teng, Zhenke [Univ. of Tennessee, Knoxville, TN (United States); Wang, Gongyao [Univ. of Tennessee, Knoxville, TN (United States)

    2012-04-13

    Analogous to nickel-based superalloys, Fe-based superalloys, which are strengthened by coherent B2- type precipitates are proposed for elevated-temperature applications. During the period of this project, a series of ferritic superalloys have been designed and fabricated by methods of vacuum-arc melting and vacuum-induction melting. Nano-scale precipitates were characterized by atom-probe tomography, ultrasmall- angle X-ray scattering, and transmission-electron microscopy. A duplex distribution of precipitates was found. It seems that ferritic superalloys are susceptible to brittle fracture. Systematic endeavors have been devoted to understanding and resolving the problem. Factors, such as hot rolling, precipitate volume fractions, alloy compositions, precipitate sizes and inter-particle spacings, and hyperfine cooling precipitates, have been investigated. In order to understand the underlying relationship between the microstructure and creep behavior of ferric alloys at elevated temperatures, in-situ neutron studies have been carried out. Based on the current result, it seems that the major role of β' with a 16%-volume fraction in strengthening ferritic alloys is not load sharing but interactions with dislocations. The oxidation behavior of one ferritic alloy, FBB8 (Fe-6.5Al-10Ni-10Cr-3.4Mo-0.25Zr-0.005B, weight percent), was studied in dry air. It is found that it possesses superior oxidation resistance at 1,023 and 1,123 K, compared with other creep-resistant ferritic steels [T91 (modified 9Cr-1Mo, weight percent) and P92 (9Cr-1.8W-0.5Mo, weight percent)]. At the same time, the calculation of the interfacial energies between the -iron and B2-type intermetallics (CoAl, FeAl, and NiAl) has been conducted.

  7. Rigor mortis development at elevated temperatures induces pale exudative turkey meat characteristics.

    Science.gov (United States)

    McKee, S R; Sams, A R

    1998-01-01

    Development of rigor mortis at elevated post-mortem temperatures may contribute to turkey meat characteristics that are similar to those found in pale, soft, exudative pork. To evaluate this effect, 36 Nicholas tom turkeys were processed at 19 wk of age and placed in water at 40, 20, and 0 C immediately after evisceration. Pectoralis muscle samples were taken at 15 min, 30 min, 1 h, 2 h, and 4 h post-mortem and analyzed for R-value (an indirect measure of adenosine triphosphate), glycogen, pH, color, and sarcomere length. At 4 h, the remaining intact Pectoralis muscle was harvested, and aged on ice 23 h, and analyzed for drip loss, cook loss, shear values, and sarcomere length. By 15 min post-mortem, the 40 C treatment had higher R-values, which persisted through 4 h. By 1 h, the 40 C treatment pH and glycogen levels were lower than the 0 C treatment; however, they did not differ from those of the 20 C treatment. Increased L* values indicated that color became more pale by 2 h post-mortem in the 40 C treatment when compared to the 20 and 0 C treatments. Drip loss, cook loss, and shear value were increased whereas sarcomere lengths were decreased as a result of the 40 C treatment. These findings suggested that elevated post-mortem temperatures during processing resulted in acceleration of rigor mortis and biochemical changes in the muscle that produced pale, exudative meat characteristics in turkey.

  8. Effects of selected thermophilic microorganisms on crude oils at elevated temperatures and pressures. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Premuzic, E.T.; Lin, M.S.

    1995-07-01

    During the past several years, a considerable amount of work has been carried out showing that microbially enhanced oil recovery (MEOR) is promising and the resulting biotechnology may be deliverable. At the Brookhaven National Laboratory (BNL), systematic studies have been conducted which dealt with the effects of thermophilic and thermoadapted bacteria on the chemical and physical properties of selected types of crude oils at elevated temperatures and pressures. Particular attention was paid to heavy crude oils from Venezuela, California, Alabama, Arkansas, Wyoming, Alaska, and other oil producing areas. Current studies indicate that during the biotreatment several chemical and physical properties of crude oils are affected. The oils are (1) emulsified; (2) acidified; (3) there is a qualitative and quantitative change in light and heavy fractions of the crudes; (4) there are chemical changes in fractions containing sulfur compounds; (5) there is an apparent reduction in the concentration of trace metals; (6) the qualitative and quantitative changes appear to be microbial species dependent; and (7) there is a distinction between {open_quotes}biodegraded{close_quotes} and {open_quotes}biotreated{close_quotes} oils. Preliminary results indicate the introduced microorganisms may become the dominant species in the bioconversion of oils. These studies also indicate the biochemical interactions between crude oils and microorganisms follow distinct trends, characterized by a group of chemical markers. Core-flooding experiments have shown significant additional crude oil recoveries are achievable with thermophilic microorganisms at elevated temperatures similar to those found in oil reservoirs. In addition, the biochemical treatment of crude oils has technological applications in downstream processing of crude oils such as in upgrading of low grade oils and the production of hydrocarbon based detergents.

  9. Development of rules for design at elevated temperatures (the RAMSES-group)

    International Nuclear Information System (INIS)

    Schaller, K.H.; Jakubowicz, H.; Petrequin, P.; Roche, R.; Weisz, M.

    1977-01-01

    The design of structures of liquid-metal-cooled fast breeder reactors of the pool-type in France has to correspond to the national regulations and takes into account the rules adopted by other countries, essentially the U.S. ASME-CODE Ill and the CODE CASE 1592 for elevated temperatures. The existing rules need complements or modifications for the following reasons: the materials employed are not covered exactly by the specifications; the properties given are not necessarily equivalent; the simplified rules (normally on the base of an elastic calculation) are often penalizing as are not valid for the type of loads considered (an example are the ratcheting rules); the use of some rules, for example the creep-fatigue interaction tends to overestimate the safety-coefficients really obtained (long tensile-hold-time followed by a transient in compression is the best example for the austenitic-type steels); the environmental effects are excluded. The French Atomic Energy Commission has founded, for the reasons mentioned above, a working group, the RAMSES-GROUP (Regles d'Analyse Mecanique des Structures), in order to codify the information needed, taking into account the experience obtained in more than ten years of fast-reactor operation. The group, including experts of three departments (DMECN, DEMT, DRNR) has adopted a number of recommendations; projects of recommendations and basic experimental work are on going. The final scope is to obtain a coherent network of rules for the design of structures in the elevated-temperature range. The already adopted recommendations codify the characteristics of the materials mainly employed in the primary system ready for use in finite element computer programs and the procedures to follow for analysis. As inelastic stress-and strain-evaluations have become possible economically by use of programs of the CEASEMT-SYSTEM, the problem of simplified rules based on elastic computations can be very often avoided

  10. SU-F-I-27: Measurement of SAR and Temperature Elevation During MRI Scans

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Y [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2016-06-15

    Purpose: The poor reliability and repeatability of the manufacturer-reported SAR values on clinical MRI systems have been acknowledged. The purpose of this study is to not only measure SAR values, but also RF-induced temperature elevation at 1.5 and 3T MRI systems. Methods: SAR measurement experiment was performed at 1.5 and 3T. Three MRI RF sequences (T1w TSE, T1w inversion recovery, and T2w TSE) with imaging parameters were selected. A hydroxyl-ethylcelluose (HEC) gelled saline phantom mimicking human body tissue was made. Human torso phantom were constructed, based on Korean adult standard anthropometric reference data (Fig.1). FDTD method was utilized to calculate the SAR distribution using Sim4Life software. Based on the results of the simulation, 4 electrical field (E-field) sensors were located inside the phantom. 55 Fiber Bragg Grating (FBG) temperature sensors (27 sensors in upper and lower cover lids, and one sensor located in the center as a reference) were located inside the phantom to measure temperature change during MRI scan (Fig.2). Results: Simulation shows that SAR value is 0.4 W/kg in the periphery and 0.001 W/kg in the center (Fig.2). One 1.5T and one of two 3T MRI systems represent that the measured SAR values were lower than MRI scanner-reported SAR values. However, the other 3T MRI scanner shows that the averaged SAR values measured by probe 2, 3, and 4 are 6.83, 7.59, and 6.01 W/kg, compared to MRI scanner-reported whole body SAR value (<1.5 W/kg) for T2w TSE (Table 1). The temperature elevation measured by FBG sensors is 5.2°C in the lateral shoulder, 5.1°C in the underarm, 4.7°C in the anterior axilla, 4.8°C in the posterior axilla, and 4.8°C in the lateral waist for T2w TSE (Fig.3). Conclusion: It is essential to assess the safety of MRI system for patient by measuring accurate SAR deposited in the body during clinical MRI.

  11. Mediating water temperature increases due to livestock and global change in high elevation meadow streams of the Golden Trout Wilderness

    Science.gov (United States)

    Sebastien Nussle; Kathleen R. Matthews; Stephanie M. Carlson

    2015-01-01

    Rising temperatures due to climate change are pushing the thermal limits of many species, but how climate warming interacts with other anthropogenic disturbances such as land use remains poorly understood. To understand the interactive effects of climate warming and livestock grazing on water temperature in three high elevation meadow streams in the Golden Trout...

  12. Plant growth response to direct and indirect temperature effects varies by vegetation type and elevation in a subarctic tundra

    NARCIS (Netherlands)

    De Long, Jonathan R.; Kardol, P.; Sundqvist, Maja K.; Veen, G. F.; Wardle, David A.

    2015-01-01

    There has been growing recent use of elevational gradients as tools for assessing effects of temperature changes on vegetation properties, because these gradients enable temperature effects to be considered over larger spatial and temporal scales than is possible through conventional experiments.

  13. Measurement of temperature elevation in tissue for the optimum and safe use of scalpel-type ultrasonic surgery devices

    International Nuclear Information System (INIS)

    Koch, C; Nuernberger, H; Reimann, H P

    2004-01-01

    Using temperature sensors of specific design, the temperature elevation during application of a Harmonic Scalpel was determined in liver tissue. The influence of different treatment techniques and application parameters on the heat produced was determined. The measurements can be used to assess the risk of harmful bioeffects and to optimise performance and treatment techniques with respect to minimum thermal load

  14. Elevated seawater temperature disrupts the microbiome of an ecologically important bioeroding sponge.

    Science.gov (United States)

    Ramsby, Blake D; Hoogenboom, Mia O; Whalan, Steve; Webster, Nicole S

    2018-04-01

    Bioeroding sponges break down calcium carbonate substratum, including coral skeleton, and their capacity for reef erosion is expected to increase in warmer and more acidic oceans. However, elevated temperature can disrupt the functionally important microbial symbionts of some sponge species, often with adverse consequences for host health. Here, we provide the first detailed description of the microbial community of the bioeroding sponge Cliona orientalis and assess how the community responds to seawater temperatures incrementally increasing from 23°C to 32°C. The microbiome, identified using 16S rRNA gene sequencing, was dominated by Alphaproteobacteria, including a single operational taxonomic unit (OTU; Rhodothalassium sp.) that represented 21% of all sequences. The "core" microbial community (taxa present in >80% of samples) included putative nitrogen fixers and ammonia oxidizers, suggesting that symbiotic nitrogen metabolism may be a key function of the C. orientalis holobiont. The C. orientalis microbiome was generally stable at temperatures up to 27°C; however, a community shift occurred at 29°C, including changes in the relative abundance and turnover of microbial OTUs. Notably, this microbial shift occurred at a lower temperature than the 32°C threshold that induced sponge bleaching, indicating that changes in the microbiome may play a role in the destabilization of the C. orientalis holobiont. C. orientalis failed to regain Symbiodinium or restore its baseline microbial community following bleaching, suggesting that the sponge has limited ability to recover from extreme thermal exposure, at least under aquarium conditions. © 2018 John Wiley & Sons Ltd.

  15. Cycling-induced degradation of LiCoO2 thin-film cathodes at elevated temperature

    International Nuclear Information System (INIS)

    Van Sluytman, J.S.; West, W.C.; Whitacre, J.F.; Alamgir, F.M.; Greenbaum, S.G.

    2006-01-01

    The cycle life of LiCoO 2 -based all solid-state thin-film cells has been studied at room temperature, and at elevated temperatures of 50, 100, and 150 deg. C. X-ray diffraction, as well as Raman analysis, has been used to complement the electrochemical data in examining structural and chemical changes. XRD and Raman spectroscopy data indicate that elevated temperature soaks of the thin-film batteries in the quiescent state causes no discernable changes in the LiCoO 2 cathode layer. However, when the thin-film batteries are cycled at elevated temperatures, decreases in average grain size of the LiCoO 2 film occur with dramatic concomitant charge and discharge capacity loss

  16. Cycling-induced degradation of LiCoO{sub 2} thin-film cathodes at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Van Sluytman, J.S.; Alamgir, F.M.; Greenbaum, S.G. [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, NY 10021 (United States); West, W.C.; Whitacre, J.F. [Electrochemical Technologies Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2006-04-01

    The cycle life of LiCoO{sub 2}-based all solid-state thin-film cells has been studied at room temperature, and at elevated temperatures of 50, 100, and 150{sup o}C. X-ray diffraction, as well as Raman analysis, has been used to complement the electrochemical data in examining structural and chemical changes. XRD and Raman spectroscopy data indicate that elevated temperature soaks of the thin-film batteries in the quiescent state causes no discernible changes in the LiCoO{sub 2} cathode layer. However, when the thin-film batteries are cycled at elevated temperatures, decreases in average grain size of the LiCoO{sub 2} film occur with dramatic concomitant charge and discharge capacity loss. (author)

  17. Range-wide latitudinal and elevational temperature gradients for the world's terrestrial birds: implications under global climate change.

    Directory of Open Access Journals (Sweden)

    Frank A La Sorte

    Full Text Available Species' geographical distributions are tracking latitudinal and elevational surface temperature gradients under global climate change. To evaluate the opportunities to track these gradients across space, we provide a first baseline assessment of the steepness of these gradients for the world's terrestrial birds. Within the breeding ranges of 9,014 bird species, we characterized the spatial gradients in temperature along latitude and elevation for all and a subset of bird species, respectively. We summarized these temperature gradients globally for threatened and non-threatened species and determined how their steepness varied based on species' geography (range size, shape, and orientation and projected changes in temperature under climate change. Elevational temperature gradients were steepest for species in Africa, western North and South America, and central Asia and shallowest in Australasia, insular IndoMalaya, and the Neotropical lowlands. Latitudinal temperature gradients were steepest for extratropical species, especially in the Northern Hemisphere. Threatened species had shallower elevational gradients whereas latitudinal gradients differed little between threatened and non-threatened species. The strength of elevational gradients was positively correlated with projected changes in temperature. For latitudinal gradients, this relationship only held for extratropical species. The strength of latitudinal gradients was better predicted by species' geography, but primarily for extratropical species. Our findings suggest threatened species are associated with shallower elevational temperature gradients, whereas steep latitudinal gradients are most prevalent outside the tropics where fewer bird species occur year-round. Future modeling and mitigation efforts would benefit from the development of finer grain distributional data to ascertain how these gradients are structured within species' ranges, how and why these gradients vary among

  18. Interactive effect of elevated pCO2 and temperature on the larval development of an inter-tidal organism, Balanus amphitrite Darwin (Cirripedia: Thoracica)

    Digital Repository Service at National Institute of Oceanography (India)

    Baragi, L.V.; Anil, A.C.

    selected based on present day pCO2 (~400 µatm) and predicted concentration for the year 2100 (~750 µatm) (Stocker et al., 2013). Four treatments were used in this study: (1) Control treatment - ambient temperature (~30 °C) and ambient pCO2 (~400 µatm); (2...) Elevated pCO2 treatment - ambient temperature (~30 °C) and elevated pCO2 (~750 µatm); (3) Elevated temperature treatment - elevated temperature (~34 °C) and ambient pCO2 (~400 µatm); and (4) Synergistic treatment - elevated temperature (~34 °C...

  19. Elevated temperature increases carbon and nitrogen fluxes between phytoplankton and heterotrophic bacteria through physical attachment

    KAUST Repository

    Arandia-Gorostidi, Nestor

    2016-12-06

    Quantifying the contribution of marine microorganisms to carbon and nitrogen cycles and their response to predicted ocean warming is one of the main challenges of microbial oceanography. Here we present a single-cell NanoSIMS isotope analysis to quantify C and N uptake by free-living and attached phytoplankton and heterotrophic bacteria, and their response to short-term experimental warming of 4 °C. Elevated temperature increased total C fixation by over 50%, a small but significant fraction of which was transferred to heterotrophs within 12 h. Cell-to-cell attachment doubled the secondary C uptake by heterotrophic bacteria and increased secondary N incorporation by autotrophs by 68%. Warming also increased the abundance of phytoplankton with attached heterotrophs by 80%, and promoted C transfer from phytoplankton to bacteria by 17% and N transfer from bacteria to phytoplankton by 50%. Our results indicate that phytoplankton-bacteria attachment provides an ecological advantage for nutrient incorporation, suggesting a mutualistic relationship that appears to be enhanced by temperature increases.

  20. Testing the potential of an elevated temperature IRSL signal from K-feldspar

    DEFF Research Database (Denmark)

    Buylaert, Jan-Pieter; Murray, A.S.; Thomsen, Kristina Jørkov

    2009-01-01

    on laboratory tests (recycling ratio, recuperation, dose recovery) we show that our SAR protocol is suitable for these samples. The observed post-IR IR fading rates (mean g2days = 1.62 ± 0.06%/decade, n = 24; assuming logarithmic fading) are significantly lower than those measured at 50 °C (mean g2days = 3...... the conventional IRSL signal stimulated at 50 °C and detected in the blue–violet region of the spectrum. One of these was the post-IR IR signal in which first an IR bleach is carried out at a low temperature (e.g. 100 s at 50 °C) and a remaining IRSL signal is measured at an elevated temperature (100 s at 225 °C......; detection in the blue–violet region). It is the latter signal that is of interest in this paper. We test such a post-IR IR dating protocol on K-feldspar extracts from a variety of locations and depositional environments and compare the results with those from the conventional IR at 50 °C protocol. Based...

  1. Density and Viscosity Measurement of Diesel Fuels at Combined High Pressure and Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Carl Schaschke

    2013-07-01

    Full Text Available We report the measurement of the viscosity and density of various diesel fuels, obtained from British refineries, at elevated pressures up to 500 MPa and temperatures in the range 298 K to 373 K. The measurement and prediction procedures of fluid properties under high pressure conditions is of increasing interest in many processes and systems including enhanced oil recovery, automotive engine fuel injection, braking, and hydraulic systems. Accurate data and understanding of the fluid characteristic in terms of pressure, volume and temperature is required particularly where the fluid is composed of a complex mixture or blend of aliphatic or aromatic hydrocarbons. In this study, high pressure viscosity data was obtained using a thermostatically-controlled falling sinker-type high pressure viscometer to provide reproducible and reliable viscosity data based on terminal velocity sinker fall times. This was supported with density measurements using a micro-pVT device. Both high-pressure devices were additionally capable of illustrating the freezing points of the hydrocarbon mixtures. This work has, thus, provided data that can extend the application of mixtures of commercially available fuels and to test the validity of available predictive density and viscosity models. This included a Tait-style equation for fluid compressibility prediction. For complex diesel fuel compositions, which have many unidentified components, the approach illustrates the need to apply appropriate correlations, which require accurate knowledge or prediction of thermodynamic properties.

  2. Creep and precipitation behaviors of AL6XN austenitic steel at elevated temperatures

    Science.gov (United States)

    Meng, L. J.; Sun, J.; Xing, H.

    2012-08-01

    Creep behaviors of the solution-treated AL6XN austenitic stainless steel have been investigated at 873-1023 K and 120-260 MPa. The results showed that the creep stress exponent and activation energy of the AL6XN steel are 5 and 395.4 kJ/mol, respectively in the power-law breakdown regime. TEM observations revealed that dislocations distributed homogenously in grains. The creep deformation mechanism is mainly attributed to viscous dislocation glide. Precipitates in the steel after creep deformation were additionally analyzed by TEM, and the results showed that there are four different types of precipitates, such as M23C6, M6C, σ phase and Laves phase. The M23C6 carbides were observed at grain boundaries in the steel after creep at 873 K. The M6C, σ phase and Laves phase precipitates were found when the creep temperature increases to 923-1023 K. Although the AL6XN steel exhibited low steady state creep rates, a high volume fraction of brittle precipitates of σ and Laves phases reduced the creep lifetime of the steel at elevated temperatures.

  3. Creep and precipitation behaviors of AL6XN austenitic steel at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Meng, L.J. [School of Materials Science and Engineering, Shanghai Jiaotong University, Dongchuan Road 800, Shanghai 200240 (China); Sun, J., E-mail: jsun@sjtu.edu.cn [School of Materials Science and Engineering, Shanghai Jiaotong University, Dongchuan Road 800, Shanghai 200240 (China); Xing, H. [School of Materials Science and Engineering, Shanghai Jiaotong University, Dongchuan Road 800, Shanghai 200240 (China)

    2012-08-15

    Creep behaviors of the solution-treated AL6XN austenitic stainless steel have been investigated at 873-1023 K and 120-260 MPa. The results showed that the creep stress exponent and activation energy of the AL6XN steel are 5 and 395.4 kJ/mol, respectively in the power-law breakdown regime. TEM observations revealed that dislocations distributed homogenously in grains. The creep deformation mechanism is mainly attributed to viscous dislocation glide. Precipitates in the steel after creep deformation were additionally analyzed by TEM, and the results showed that there are four different types of precipitates, such as M{sub 23}C{sub 6}, M{sub 6}C, {sigma} phase and Laves phase. The M{sub 23}C{sub 6} carbides were observed at grain boundaries in the steel after creep at 873 K. The M{sub 6}C, {sigma} phase and Laves phase precipitates were found when the creep temperature increases to 923-1023 K. Although the AL6XN steel exhibited low steady state creep rates, a high volume fraction of brittle precipitates of {sigma} and Laves phases reduced the creep lifetime of the steel at elevated temperatures.

  4. Elevated temperature increases carbon and nitrogen fluxes between phytoplankton and heterotrophic bacteria through physical attachment

    KAUST Repository

    Arandia-Gorostidi, Nestor; Weber, Peter K; Alonso-Sá ez, Laura; Moran, Xose Anxelu G.; Mayali, Xavier

    2016-01-01

    Quantifying the contribution of marine microorganisms to carbon and nitrogen cycles and their response to predicted ocean warming is one of the main challenges of microbial oceanography. Here we present a single-cell NanoSIMS isotope analysis to quantify C and N uptake by free-living and attached phytoplankton and heterotrophic bacteria, and their response to short-term experimental warming of 4 °C. Elevated temperature increased total C fixation by over 50%, a small but significant fraction of which was transferred to heterotrophs within 12 h. Cell-to-cell attachment doubled the secondary C uptake by heterotrophic bacteria and increased secondary N incorporation by autotrophs by 68%. Warming also increased the abundance of phytoplankton with attached heterotrophs by 80%, and promoted C transfer from phytoplankton to bacteria by 17% and N transfer from bacteria to phytoplankton by 50%. Our results indicate that phytoplankton-bacteria attachment provides an ecological advantage for nutrient incorporation, suggesting a mutualistic relationship that appears to be enhanced by temperature increases.

  5. Concrete for PCRV's: Mechanical properties at elevated temperatures and residual mechanical behaviour after triaxial preloading

    International Nuclear Information System (INIS)

    Aschl, H.; Moosecker, W.

    1979-01-01

    During the lifetime of reactor vessels stress states will change as a result of changes in loading and heating, shrinkage and creep. For the design of prestressed concrete reactor vessels information is required about the behaviour of concrete under multiaxial short- and long-term loading at elevated temperatures. Therefore, tests were carried out at the Institut fuer Massivbau of the Technical University of Munich to study the properties of mass concrete under uniaxial loading at 353 K. Additionally, biaxial creep of concrete up to 368 K was investigated. Some of the uniaxial test specimens were sealed with a copper foil to avoid drying. The concrete contained calzite gravel. The thermal expansion coefficient of predried concrete was 9.5 x 10 -6 , of sealed concrete 13.6 x 10 -6 and of unsealed concrete 13.2 x 10 -6 . The modulus of elasticity at 353 K (393 K) was reduced by 10 (13)% for sealed and by 15 (22)% for unsealed specimens. Total shrinkage deformations of heated concrete were 190 to 225 microstrains for sealed and 250 to 350 microstrains for unsealed specimens. Creep deformations were highly dependent upon temperature being about 3 times higher at 353 K for sealed and unsealed concrete. (orig.)

  6. Statistical analysis of elevated-temperature, strain-controlled fatigue data on Type 304 stainless steel

    International Nuclear Information System (INIS)

    Diercks, D.R.; Raske, D.T.

    1976-01-01

    The available elevated-temperature, strain-controlled, uniaxial fatigue data on Type 304 stainless steel (435 data points) are summarized, and variables that influence cyclic life are divided into first- and second-order categories. The first-order variables, which include strain range, strain rate, temperature, and tensile hold time, were used in a multivariable regression analysis to describe the observed variation in fatigue life. Goodness of fit with respect to these variables as well as the appropriateness of the transformations employed are discussed. Confidence intervals are estimated, and a comparison with the ASME Boiler and Pressure Vessel Code Case 1592 creep-fatigue design curve is made for a particular set of conditions. The second-order variables include the laboratories at which the data were generated, the different heats from which the test specimens were fabricated, and the heat treatments that preceded testing. These variables were statistically analyzed to determine their effect on fatigue life. The results are discussed, and the heats and heat treatments that are most resistant to fatigue damage under these loading and environmental conditions are identified

  7. Fatigue crack growth behaviour of 21/4Cr1Mo steel tube at elevated temperature

    International Nuclear Information System (INIS)

    Bulloch, J.H.; Buchanan, L.W.

    1987-01-01

    The fatigue crack growth characteristics of 21/4Cr1Mo steel tube have been examined at 588 0 C over the frequency range 0.02-20 Hz and dwell time range 10-960 min. All tests were conducted under load control in laboratory air at an R-ratio of 0.5. The elevated temperature fatigue crack growth characteristics were adequately described in terms of the stress intensity range ΔKAPPA. The continuous cyclic test data exhibited a significant effect of frequency that agreed well with predicted effects using a simple mathematical model of the high temperature fatigue process. With the dwell time range of 10-100 min there was a significant dwell time effect on the critical ΔKAPPA level for creep-fatigue interactive growth. At dwell times > 100 min the dwell time effect saturates. When creep-fatigue interactive growth occurs, growth rates reside above the maximum for continuum-controlled fatigue crack growth, and exhibit a da/dN varies as ΔKAPPA 10 dependence; failure is then intergranular in nature. (author)

  8. The effect of elevated CO2 and temperature on nutrient uptake by plants grown in basaltic soil

    Science.gov (United States)

    Villasenor Iribe, E.; Dontsova, K.; Juarez, S.; Le Galliard, J. F.; Chollet, S.; Llavata, M.; Massol, F.; Barré, P.; Gelabert, A.; Daval, D.; Troch, P.; Barron-Gafford, G.; Van Haren, J. L. M.; Ferrière, R.

    2017-12-01

    Mineral weathering is an important process in soil formation. The interactions between the hydrologic, geologic and atmospheric cycles often determine the rate at which weathering occurs. Elements and nutrients weathered from the soil by water can be removed from soils in the runoff and seepage, but they can also remain in situ as newly precipitated secondary minerals or in biomass as a result of plant uptake. Here we present data from an experiment that was conducted at the controlled environment facility, Ecotron Ile-de-France (Saint-Pierre-les-Nemours, France) that studied mineral weathering and plant growth in granular basaltic material with high glass content that is being used to simulate soil in large scale Biosphere 2 Landscape Evolution Observatory (LEO) project. The experiment used 3 plant types: velvet mesquite (Prosopis velutina), green spangletop (Leptochloa dubia), and alfalfa (Medicago sativa), which were grown under varying temperature and CO2 conditions. We hypothesized that plants grown under warmer, higher CO2 conditions would have larger nutrient concentrations as more mineral weathering would occur. Results of plant digestions and analysis showed that plant concentrations of lithogenic elements were significantly influenced by the plant type and were different between above- and below-ground parts of the plant. Temperature and CO2 treatment effects were less pronounced, but we observed significant temperature effect on plant uptake. A number of major and trace elements showed increase in concentration with increase in temperature at elevated atmospheric CO2. Effect was observed both in the shoots and in the roots, but more significant differences were observed in the shoots. Results presented here indicate that climate change would have strong effect on plant uptake and mobility of weathered elements during soil formation and give further evidence of interactions between abiotic and biological processes in terrestrial ecosystems.

  9. Effects of long-term elevated temperature on covering, sheltering and righting behaviors of the sea urchin Strongylocentrotus intermedius

    Science.gov (United States)

    Zhang, Lisheng; Zhang, Lingling; Shi, Dongtao; Wei, Jing; Chang, Yaqing

    2017-01-01

    Increases in ocean temperature due to climate change are predicted to change the behaviors of marine invertebrates. Altered behaviors of keystone ecosystem engineers such as echinoderms will have consequences for the fitness of individuals, which are expected to flow on to the local ecosystem. Relatively few studies have investigated the behavioral responses of echinoderms to long-term elevated temperature. We investigated the effects of exposure to long-term (∼31 weeks) elevated temperature (∼3 °C above the ambient water temperature) on covering, sheltering and righting behaviors of the sea urchin Strongylocentrotus intermedius. Long-term elevated temperature showed different effects on the three behaviors. It significantly decreased covering behavior, including both covering behavior reaction (time to first covering) and ability (number of covered sea urchins and number of shells used for covering). Conversely, exposure to long-term elevated temperature significantly increased sheltering behavior. Righting response in S. intermedius was not significantly different between temperature treatments. The results provide new information into behavioral responses of echinoderms to ocean warming. PMID:28348933

  10. Elevated body temperature is linked to fatigue in an Italian sample of relapsing-remitting multiple sclerosis patients.

    Science.gov (United States)

    Leavitt, V M; De Meo, E; Riccitelli, G; Rocca, M A; Comi, G; Filippi, M; Sumowski, J F

    2015-11-01

    Elevated body temperature was recently reported for the first time in patients with relapsing-remitting multiple sclerosis (RRMS) relative to healthy controls. In addition, warmer body temperature was associated with worse fatigue. These findings are highly novel, may indicate a novel pathophysiology for MS fatigue, and therefore warrant replication in a geographically separate sample. Here, we investigated body temperature and its association to fatigue in an Italian sample of 44 RRMS patients and 44 age- and sex-matched healthy controls. Consistent with our original report, we found elevated body temperature in the RRMS sample compared to healthy controls. Warmer body temperature was associated with worse fatigue, thereby supporting the notion of endogenous temperature elevations in patients with RRMS as a novel pathophysiological factor underlying fatigue. Our findings highlight a paradigm shift in our understanding of the effect of heat in RRMS, from exogenous (i.e., Uhthoff's phenomenon) to endogenous. Although randomized controlled trials of cooling treatments (i.e., aspirin, cooling garments) to reduce fatigue in RRMS have been successful, consideration of endogenously elevated body temperature as the underlying target will enhance our development of novel treatments.

  11. Elevated Temperature, Notched Compression Performance of Out of Autoclave Processed Composites

    Science.gov (United States)

    Grimsley, Brian W.; Sutter, James K.; Dixon, Genevieve D.; Smeltzer, Satn S.

    2013-01-01

    Curved honeycomb sandwich panels composed of carbon fiber reinforced toughened-epoxy polymer facesheets are being evaluated for potential use as payload fairing components on the NASA heavy-lift space launch system (HL-SLS). These proposed composite sandwich panels provide the most efficient aerospace launch structures, and offer mass and thermal advantages when compared with existing metallic payload fairing structures. NASA and industry are investigating recently developed carbon fiber epoxy prepreg systems which can be fabricated using out-of autoclave (OOA) processes. Specifically, OOA processes using vacuum pressure in an oven and thereby significantly reducing the cost associated with manufacturing large (up to 10 m diameter) composite structures when compared with autoclave. One of these OOA composite material systems, CYCOM(R) 5320-1, was selected for manufacture of a 1/16th scale barrel portion of the payload fairing; such that, the system could be compared with the well-characterized prepreg system, CYCOM(R) 977-3, typically processed in an autoclave. Notched compression coupons for each material were obtained from the minimum-gauge flat laminate [60/-60/0]S witness panels produced in this manufacturing study. The coupons were also conditioned to an effective moisture equilibrium point and tested according to ASTM D6484M-09 at temperatures ranging from 25 C up to 177 C. The results of this elevated temperature mechanical characterization study demonstrate that, for thin coupons, the OHC strength of the OOA laminate was equivalent to the flight certified autoclave processed composite laminates; the limitations on the elevated temperature range are hot-wet conditions up to 163 C and are only within the margins of testing error. At 25 C, both the wet and dry OOA material coupons demonstrated greater OHC failure strengths than the autoclave processed material laminates. These results indicate a substantial improvement in OOA material development and

  12. Variations of bubble cavitation and temperature elevation during lesion formation by high-intensity focused ultrasound.

    Science.gov (United States)

    Zhou, Yufeng; Gao, Xiaobin Wilson

    2013-08-01

    High-intensity focused ultrasound (HIFU) is emerging as an effective therapeutic modality in both thermal ablations for solid tumor/cancer and soft-tissue fragmentation. Mechanical and thermal effects, which play an important role in the HIFU treatment simultaneously, are dependent on the operating parameters and may vary with the progress of therapy. Mechanical erosion in the shape of a "squid," a "dumbbell" lesion with both mechanical and thermal lesions, or a "tadpole" lesion with mechanical erosion at the center and thermal necrosis on the boundary in the transparent gel phantom could be produced correspondingly with the pulse duration of 5-30 ms, which is much longer than histotripsy burst but shorter than the time for tissue boiling, and pulse repetition frequency (PRF) of 0.2-5 Hz. Meanwhile, variations of bubble cavitation (both inertial and stable cavitation) and temperature elevation in the focal region (i.e., z = -2.5, 0, and 2.5 mm) were measured by passive cavitation detection (PCD) and thermocouples during the therapeutic procedure, respectively. Stable cavitation increased with the pulse duration, PRF, and the number of pulses delivered. However, inertial cavitation was found to increase initially and then decrease with long pulse duration and high PRF. Temperature in the pre-focal region is always higher than those at the focal and post-focal position in all tests. Great variations of PCD signals and temperature elevation are due to the generation and persistence of large bubble, which is resistant to collapse and occurs with the increase of pulse duration and PRF. Similar lesion pattern and variations were also observed in ex vivo porcine kidneys. Hyperechoes in the B-mode ultrasound image were comparable to the shape and size of lesions in the dissected tissue. Thermal lesion volume increased with the increase of pulse duration and PRF, but mechanical erosion reached its maximum volume with the pulse duration of 20 ms and PRF of 1

  13. Limited Capacity for Faster Digestion in Larval Coral Reef Fish at an Elevated Temperature.

    Science.gov (United States)

    McLeod, Ian M; Clark, Timothy D

    2016-01-01

    The prevalence of extreme, short-term temperature spikes in coastal regions during summer months is predicted to increase with ongoing climate change. In tropical systems, these changes are predicted to increase the metabolic demand of coral reef fish larvae while also altering the plankton communities upon which the larvae feed during their pelagic phase. The consequences of these predictions remain speculative in the absence of empirical data on the interactive effects of warm temperatures on the metabolism, postprandial processes and growth responses of coral reef fish larvae. Here, we tested the effect of increased temperature on the metabolism, postprandial performance and fine-scale growth patterns of a coral reef fish (Amphiprion percula) in the latter half of its ~11-d larval phase. First, we measured the length and weight of fed versus fasted larvae (N = 340; mean body mass 4.1±0.05 mg) across fine temporal scales at a typical current summer temperature (28.5°C) and a temperature that is likely be encountered during warm summer periods later this century (31.5°C). Second, we measured routine metabolic rate (Mo2 routine) and the energetics of the postprandial processes (i.e., digestion, absorption and assimilation of a meal; termed specific dynamic action (SDA)) at both temperatures. Larvae fed voraciously when provided with food for a 12-hour period and displayed a temperature-independent increase in mass of 40.1% (28.5°C) and 42.6% (31.5°C), which was largely associated with the mass of prey in the gut. A subsequent 12-h fasting period revealed that the larvae had grown 21.2±4.8% (28.5°C) and 22.8±8.8% (31.5°C) in mass and 10.3±2.0% (28.5°C) and 7.8±2.6% (31.5°C) in length compared with pre-feeding values (no significant temperature effect). Mo2 routine was 55±16% higher at 31.5°C and peak Mo2 during the postprandial period was 28±11% higher at 31.5°C, yet elevated temperature had no significant effect on SDA (0.51±0.06 J at 28.5°C vs

  14. Limited Capacity for Faster Digestion in Larval Coral Reef Fish at an Elevated Temperature.

    Directory of Open Access Journals (Sweden)

    Ian M McLeod

    Full Text Available The prevalence of extreme, short-term temperature spikes in coastal regions during summer months is predicted to increase with ongoing climate change. In tropical systems, these changes are predicted to increase the metabolic demand of coral reef fish larvae while also altering the plankton communities upon which the larvae feed during their pelagic phase. The consequences of these predictions remain speculative in the absence of empirical data on the interactive effects of warm temperatures on the metabolism, postprandial processes and growth responses of coral reef fish larvae. Here, we tested the effect of increased temperature on the metabolism, postprandial performance and fine-scale growth patterns of a coral reef fish (Amphiprion percula in the latter half of its ~11-d larval phase. First, we measured the length and weight of fed versus fasted larvae (N = 340; mean body mass 4.1±0.05 mg across fine temporal scales at a typical current summer temperature (28.5°C and a temperature that is likely be encountered during warm summer periods later this century (31.5°C. Second, we measured routine metabolic rate (Mo2 routine and the energetics of the postprandial processes (i.e., digestion, absorption and assimilation of a meal; termed specific dynamic action (SDA at both temperatures. Larvae fed voraciously when provided with food for a 12-hour period and displayed a temperature-independent increase in mass of 40.1% (28.5°C and 42.6% (31.5°C, which was largely associated with the mass of prey in the gut. A subsequent 12-h fasting period revealed that the larvae had grown 21.2±4.8% (28.5°C and 22.8±8.8% (31.5°C in mass and 10.3±2.0% (28.5°C and 7.8±2.6% (31.5°C in length compared with pre-feeding values (no significant temperature effect. Mo2 routine was 55±16% higher at 31.5°C and peak Mo2 during the postprandial period was 28±11% higher at 31.5°C, yet elevated temperature had no significant effect on SDA (0.51±0.06 J at 28.5

  15. Limited tolerance by insects to high temperatures across tropical elevational gradients and the implications of global warming for extinction.

    Science.gov (United States)

    García-Robledo, Carlos; Kuprewicz, Erin K; Staines, Charles L; Erwin, Terry L; Kress, W John

    2016-01-19

    The critical thermal maximum (CTmax), the temperature at which motor control is lost in animals, has the potential to determine if species will tolerate global warming. For insects, tolerance to high temperatures decreases with latitude, suggesting that similar patterns may exist along elevational gradients as well. This study explored how CTmax varies among species and populations of a group of diverse tropical insect herbivores, the rolled-leaf beetles, across both broad and narrow elevational gradients. Data from 6,948 field observations and 8,700 museum specimens were used to map the elevational distributions of rolled-leaf beetles on two mountains in Costa Rica. CTmax was determined for 1,252 individual beetles representing all populations across the gradients. Initial morphological identifications suggested a total of 26 species with populations at different elevations displaying contrasting upper thermal limits. However, compared with morphological identifications, DNA barcodes (cytochrome oxidase I) revealed significant cryptic species diversity. DNA barcodes identified 42 species and haplotypes across 11 species complexes. These 42 species displayed much narrower elevational distributions and values of CTmax than the 26 morphologically defined species. In general, species found at middle elevations and on mountaintops are less tolerant to high temperatures than species restricted to lowland habitats. Species with broad elevational distributions display high CTmax throughout their ranges. We found no significant phylogenetic signal in CTmax, geography, or elevational range. The narrow variance in CTmax values for most rolled-leaf beetles, especially high-elevation species, suggests that the risk of extinction of insects may be substantial under some projected rates of global warming.

  16. Properties of a Laser Shock Wave in Al-Cu Alloy under Elevated Temperatures: A Molecular Dynamics Simulation Study

    Directory of Open Access Journals (Sweden)

    Xiankai Meng

    2017-01-01

    Full Text Available The laser shock wave (LSW generated by the interaction between a laser and a material has been widely used in laser manufacturing, such as laser shock peening and laser shock forming. However, due to the high strain rate, the propagation of LSW in materials, especially LSW at elevated temperatures, is difficult to study through experimental methods. A molecular dynamics simulation was used in this study to investigate the propagation of LSW in an Al-Cu alloy. The Hugoniot relations of LSW were obtained at different temperatures and the effects of elevated temperatures on shock velocity and shock pressure were analyzed. Then the elastic and plastic wave of the LSW was researched. Finally, the evolution of dislocations induced by LSW and its mechanism under elevated temperatures was explored. The results indicate that the shock velocity and shock pressure induced by LSW both decrease with the increasing temperatures. Moreover, the velocity of elastic wave and plastic wave both decrease with the increasing treatment temperature, while their difference decreases as the temperature increases. Moreover, the dislocation atoms increases with the increasing temperatures before 2 ps, while it decreases with the increasing temperatures after 2 ps. The reason for the results is related to the formation and evolution of extended dislocations.

  17. Gas leak tightness of SiC/SiC composites at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Hayasaka, Daisuke, E-mail: hayasaka@oasis.muroran-it.ac.jp [OASIS, Muroran Institute of Technology, Muroran, Hokkaido (Japan); Graduate School of Engineering, Muroran Institute of Technology, Muroran, Hokkaido (Japan); Park, Joon-Soo. [OASIS, Muroran Institute of Technology, Muroran, Hokkaido (Japan); Kishimoto, Hirotatsu [OASIS, Muroran Institute of Technology, Muroran, Hokkaido (Japan); Graduate School of Engineering, Muroran Institute of Technology, Muroran, Hokkaido (Japan); Kohyama, Akira [OASIS, Muroran Institute of Technology, Muroran, Hokkaido (Japan)

    2016-11-01

    Highlights: • NITE-SiC/SiC has extremely densified microstructure compared with other SiC/SiC composite like CVI. • Excellent helium and hydrogen gas-leak tightness of SiC/SiC composites by DEMO-NITE method from prototype industrialization production line was presented. • The excellence against stainless steel and Zircaloy at elevated temperature, together with generic excellent properties of SiC will be inevitable for innovative blanket and divertors for DEMO- and power- fusion reactors. - Abstract: SiC/SiC composite materials are attractive candidates for high heat flux components and blanket of fusion reactor, mainly due to their high temperature properties, radiation damage tolerance and low induced radioactivity. One of the challenges for SiC/SiC application in fusion reactors is to satisfy sufficient gas leak tightness of hydrogen and helium isotopes. Although many efforts have been carried-out, SiC/SiC composites by conventional processes have not been successful to satisfy the requirements, except SiC/SiC composites by NITE-methods. Toward the early realization of SiC/SiC components into fusion reactor systems process development of NITE-process has been continued. Followed to the brief introduction of recently developed DEMO-NITE process, baseline properties and hydrogen and helium gas leak tightness is presented. SiC/SiC claddings with 10 mm in diameter and 1 mm in wall thickness are tested by gas leak tightness system developed. The leak tightness measurements are done room temperature to 400 °C. Excellent gas leak tightness equivalent or superior to Zircaloy claddings for light water fission reactors is confirmed. The excellent gas leak tightness suggests nearly perfect suppression of large gas leak path in DEMO-NITE SiC/SiC.

  18. Properties, sustainability and elevated temperature behavior of concrete containing Portland limestone cement

    Science.gov (United States)

    El-Hawary, Moetaz; Ahmed, Mahmoud

    2017-09-01

    The utilization of some type of cheap filler as partial cement replacement is an effective way of improving concrete sustainability. With the recent trends to reduce water to cement ratio and improve compaction, there is no enough space or water for complete hydration of cement. This means that actually, a portion of mixed cement acts as expensive filler. Replacing this portion with cheaper filler that requires less energy to produce is, therefore, beneficial. Crushed limestone is the most promising filler. This work is to investigate the effect of the amount of limestone fillers on the sustainability and the fresh and mechanical properties of the resulting concrete. A rich mix is designed with a low water/cement ratio of 0.4. Lime is introduced as a replacement percentage of cement. Ratios of 0, 10, 20 and 30% were used. Slump, compressive strength, specific gravity and water absorption are evaluated for every mix. In addition, the effect of the amount of lime on the residual strength of concrete subjected to elevated temperatures is also investigated. Samples are subjected to six different temperature stations of 20, 100, 200, 300, 500 and 700°C for six hours before being cooled and subsequently tested for compressive strength and specific gravity. Sustainability of the tested mixes is evaluated through reductions in the emitted carbon dioxide, energy and reduction in cost. Based on the annual use of concrete in Kuwait, the sustainability benefits resulting from the use of limestone filler in Kuwait are evaluated and assessed. The paper is concluded with the recommendation of the use of 15% limestone filler as partial cement replacement where the properties and the behavior under high temperature of the resulting concrete are almost the same as those of conventional concrete with considerable cost and sustainability benefits.

  19. Decomposition and particle release of a carbon nanotube/epoxy nanocomposite at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Schlagenhauf, Lukas [Empa - Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Functional Polymers (Switzerland); Kuo, Yu-Ying; Bahk, Yeon Kyoung [Empa - Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Advanced Analytical Technologies (Switzerland); Nüesch, Frank [Empa - Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Functional Polymers (Switzerland); Wang, Jing, E-mail: Jing.Wang@ifu.baug.ethz.ch [Empa - Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Advanced Analytical Technologies (Switzerland)

    2015-11-15

    Carbon nanotubes (CNTs) as fillers in nanocomposites have attracted significant attention, and one of the applications is to use the CNTs as flame retardants. For such nanocomposites, possible release of CNTs at elevated temperatures after decomposition of the polymer matrix poses potential health threats. We investigated the airborne particle release from a decomposing multi-walled carbon nanotube (MWCNT)/epoxy nanocomposite in order to measure a possible release of MWCNTs. An experimental set-up was established that allows decomposing the samples in a furnace by exposure to increasing temperatures at a constant heating rate and under ambient air or nitrogen atmosphere. The particle analysis was performed by aerosol measurement devices and by transmission electron microscopy (TEM) of collected particles. Further, by the application of a thermal denuder, it was also possible to measure non-volatile particles only. Characterization of the tested samples and the decomposition kinetics were determined by the usage of thermogravimetric analysis (TGA). The particle release of different samples was investigated, of a neat epoxy, nanocomposites with 0.1 and 1 wt% MWCNTs, and nanocomposites with functionalized MWCNTs. The results showed that the added MWCNTs had little effect on the decomposition kinetics of the investigated samples, but the weight of the remaining residues after decomposition was influenced significantly. The measurements with decomposition in different atmospheres showed a release of a higher number of particles at temperatures below 300 °C when air was used. Analysis of collected particles by TEM revealed that no detectable amount of MWCNTs was released, but micrometer-sized fibrous particles were collected.

  20. Dynamic modeling of nutrient removal by a MBR operated at elevated temperatures.

    Science.gov (United States)

    Sarioglu, M; Sayi-Ucar, N; Cokgor, E; Orhon, D; van Loosdrecht, M C M; Insel, G

    2017-10-15

    The process performance of a MBR operated on municipal sewage at elevated temperatures was evaluated by dynamic modeling. The enhanced biological phosphorus removal (EBPR) performance varied from 40% to 95% with process temperature ranging from 24 to 38 °C. The respective maximum substrate uptake rate (q PHA ) was estimated at 1.5 gCOD S /gCOD X .day -1 for Glycogen Accumulating Organisms (GAO) and 4.7 gCOD S /gCOD X .day -1 for Phosphate Accumulating Organisms (PAO) with Arrhenius coefficients (θ) for GAOs and PAOs of 1.06 and 1.04 respectively. With these parameters the effluent PO 4 levels of the MBR operated for 450 days could be well described. In addition, the impact of mesophilic conditions and low influent P/VFA levels on GAO proliferation was evaluated under dynamic process conditions. Nitrification process was temporarily impaired at high temperatures around 38 °C. Simulations revealed that the contribution of the anoxic reactor to the total overall denitrification was limited to 40%The contribution of simultaneous nitrification and denitrification (SNdN) process to the denitrification was around 40-50% depending upon dissolved oxygen levels in aerobic and MBR tanks. The large contribution of SNdN was due to gas/liquid mass transfer limitation conditions mediated by high mixed liquor viscosities (20-35 mPa.S) in MBR system. The membrane flux was 43 L/m 2 /h corresponding to the specific permeability (K) of 413 L/m 2 /h/bar at 38 °C. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Decomposition and particle release of a carbon nanotube/epoxy nanocomposite at elevated temperatures

    International Nuclear Information System (INIS)

    Schlagenhauf, Lukas; Kuo, Yu-Ying; Bahk, Yeon Kyoung; Nüesch, Frank; Wang, Jing

    2015-01-01

    Carbon nanotubes (CNTs) as fillers in nanocomposites have attracted significant attention, and one of the applications is to use the CNTs as flame retardants. For such nanocomposites, possible release of CNTs at elevated temperatures after decomposition of the polymer matrix poses potential health threats. We investigated the airborne particle release from a decomposing multi-walled carbon nanotube (MWCNT)/epoxy nanocomposite in order to measure a possible release of MWCNTs. An experimental set-up was established that allows decomposing the samples in a furnace by exposure to increasing temperatures at a constant heating rate and under ambient air or nitrogen atmosphere. The particle analysis was performed by aerosol measurement devices and by transmission electron microscopy (TEM) of collected particles. Further, by the application of a thermal denuder, it was also possible to measure non-volatile particles only. Characterization of the tested samples and the decomposition kinetics were determined by the usage of thermogravimetric analysis (TGA). The particle release of different samples was investigated, of a neat epoxy, nanocomposites with 0.1 and 1 wt% MWCNTs, and nanocomposites with functionalized MWCNTs. The results showed that the added MWCNTs had little effect on the decomposition kinetics of the investigated samples, but the weight of the remaining residues after decomposition was influenced significantly. The measurements with decomposition in different atmospheres showed a release of a higher number of particles at temperatures below 300 °C when air was used. Analysis of collected particles by TEM revealed that no detectable amount of MWCNTs was released, but micrometer-sized fibrous particles were collected

  2. Decomposition and particle release of a carbon nanotube/epoxy nanocomposite at elevated temperatures

    Science.gov (United States)

    Schlagenhauf, Lukas; Kuo, Yu-Ying; Bahk, Yeon Kyoung; Nüesch, Frank; Wang, Jing

    2015-11-01

    Carbon nanotubes (CNTs) as fillers in nanocomposites have attracted significant attention, and one of the applications is to use the CNTs as flame retardants. For such nanocomposites, possible release of CNTs at elevated temperatures after decomposition of the polymer matrix poses potential health threats. We investigated the airborne particle release from a decomposing multi-walled carbon nanotube (MWCNT)/epoxy nanocomposite in order to measure a possible release of MWCNTs. An experimental set-up was established that allows decomposing the samples in a furnace by exposure to increasing temperatures at a constant heating rate and under ambient air or nitrogen atmosphere. The particle analysis was performed by aerosol measurement devices and by transmission electron microscopy (TEM) of collected particles. Further, by the application of a thermal denuder, it was also possible to measure non-volatile particles only. Characterization of the tested samples and the decomposition kinetics were determined by the usage of thermogravimetric analysis (TGA). The particle release of different samples was investigated, of a neat epoxy, nanocomposites with 0.1 and 1 wt% MWCNTs, and nanocomposites with functionalized MWCNTs. The results showed that the added MWCNTs had little effect on the decomposition kinetics of the investigated samples, but the weight of the remaining residues after decomposition was influenced significantly. The measurements with decomposition in different atmospheres showed a release of a higher number of particles at temperatures below 300 °C when air was used. Analysis of collected particles by TEM revealed that no detectable amount of MWCNTs was released, but micrometer-sized fibrous particles were collected.

  3. Elevational variation in body-temperature response to immune challenge in a lizard

    Directory of Open Access Journals (Sweden)

    Francisco Javier Zamora-Camacho

    2016-04-01

    Full Text Available Immunocompetence benefits animal fitness by combating pathogens, but also entails some costs. One of its main components is fever, which in ectotherms involves two main types of costs: energy expenditure and predation risk. Whenever those costs of fever outweigh its benefits, ectotherms are expected not to develop fever, or even to show hypothermia, reducing costs of thermoregulation and diverting the energy saved to other components of the immune system. Environmental thermal quality, and therefore the thermoregulation cost/benefit balance, varies geographically. Hence, we hypothesize that, in alpine habitats, immune-challenged ectotherms should show no thermal response, given that (1 hypothermia would be very costly, as the temporal window for reproduction is extremely small, and (2 fever would have a prohibitive cost, as heat acquisition is limited in such habitat. However, in temperate habitats, immune-challenged ectotherms might show a febrile response, due to lower cost/benefit balance as a consequence of a more suitable thermal environment. We tested this hypothesis in Psammodromus algirus lizards from Sierra Nevada (SE Spain, by testing body temperature preferred by alpine and non-alpine lizards, before and after activating their immune system with a typical innocuous pyrogen. Surprisingly, non-alpine lizards responded to immune challenge by decreasing preferential body-temperature, presumably allowing them to save energy and reduce exposure to predators. On the contrary, as predicted, immune-challenged alpine lizards maintained their body-temperature preferences. These results match with increased costs of no thermoregulation with elevation, due to the reduced window of time for reproduction in alpine environment.

  4. The effect of elevated die temperature on deformation of deep drawn round metal cup

    Science.gov (United States)

    Basril, M. A. M.; Hafsyam, Y. M.; Azuddin, M.; Choudhury, I. A.

    2017-06-01

    One of the major considerations in the current deep drawing practice is the product quality. In this research, the effect of heating temperature on the drawability of the round metal cup has been investigated. Firstly, round metal cups of aluminium and mild steel were drawn from the blank diameters of 60 mm, 65 mm and 70 mm. The experiment conducted at room temperature first, then at 50°C and 100°C. The elongation of the major and minor strains along the cup profile after the process is measured and analysed. On the other hand, the defects from the experiment output and ABAQUS/CAE simulation are compared. The result from experiment shows that the highest major elongation is 11.64 mm and it is happened to a deep drawn aluminium round cup with LDR of 1.69 at temperature of 100°C. On the other hand, for deep drawn mild steel round cup, shows highest major elongation of 12.44 mm for a cup with LDR of 1.56 at 100°C. Both of these statements indicates that the higher temperature could improve the formability of the deep drawn parts besides reducing the probability of the defect to be happened.

  5. Habitat pollution and thermal regime modify molecular stress responses to elevated temperature in freshwater mussels (Anodonta anatina: Unionidae)

    International Nuclear Information System (INIS)

    Falfushynska, H.; Gnatyshyna, L.; Yurchak, I.; Ivanina, A.; Stoliar, O.; Sokolova, I.

    2014-01-01

    Elevated temperature and pollution are common stressors in freshwater ecosystems. We study cellular stress response to acute warming in Anodonta anatina (Unionidae) from sites with different thermal regimes and pollution levels: a pristine area and an agriculturally polluted site with normal temperature regimes (F and A, respectively) and a polluted site with elevated temperature (N) from the cooling pond of an electrical power plant. Animals were exposed to different temperatures for 14 days and stress response markers were measured in gills, digestive gland and hemocytes. Mussels from site N and A had elevated background levels of lactate dehydrogenase activity indicating higher reliance on anaerobic metabolism for ATP production and/or redox maintenance. Exposure to 25 °C and 30 °C induced oxidative stress (indicated by elevated levels of lipid peroxidation products) in digestive gland and gills of mussels from A and F sites, while in mussels from N sites elevated oxidative stress was only apparent at 30 °C. Temperature-induced changes in levels of antioxidants (superoxide dismutase, metallothioneins and glutathione) were tissue- and population-specific. Acute warming led to destabilization of lysosomal membranes and increased frequencies of nuclear lesions in mussels from F and A sites but not in their counterparts from N site. Elevated temperature led to an increase in the frequency of micronuclei in hemocytes in mussels from F and A sites at 25 °C and 30 °C and in mussels from N site at 30 °C. The mussels from N site also demonstrated better survival at elevated temperature (30 °C) than their counterparts from the F and A sites. Taken together, these data indicate that long-term acclimation and/or adaptation of A. anatina to elevated temperatures result in increased thermotolerance and alleviate stress response to moderate temperature rise. In contrast, extreme warming (30 °C) is harmful to mussels from all populations indicating limit to this induced

  6. Habitat pollution and thermal regime modify molecular stress responses to elevated temperature in freshwater mussels (Anodonta anatina: Unionidae)

    Energy Technology Data Exchange (ETDEWEB)

    Falfushynska, H.; Gnatyshyna, L.; Yurchak, I. [Research Laboratory of Comparative Biochemistry and Molecular Biology, Ternopil National Pedagogical University, Kryvonosa Str 2, 46027 Ternopil (Ukraine); Ivanina, A. [Department of Biological Sciences, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223 (United States); Stoliar, O. [Research Laboratory of Comparative Biochemistry and Molecular Biology, Ternopil National Pedagogical University, Kryvonosa Str 2, 46027 Ternopil (Ukraine); Sokolova, I., E-mail: isokolov@uncc.edu [Department of Biological Sciences, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223 (United States)

    2014-12-01

    Elevated temperature and pollution are common stressors in freshwater ecosystems. We study cellular stress response to acute warming in Anodonta anatina (Unionidae) from sites with different thermal regimes and pollution levels: a pristine area and an agriculturally polluted site with normal temperature regimes (F and A, respectively) and a polluted site with elevated temperature (N) from the cooling pond of an electrical power plant. Animals were exposed to different temperatures for 14 days and stress response markers were measured in gills, digestive gland and hemocytes. Mussels from site N and A had elevated background levels of lactate dehydrogenase activity indicating higher reliance on anaerobic metabolism for ATP production and/or redox maintenance. Exposure to 25 °C and 30 °C induced oxidative stress (indicated by elevated levels of lipid peroxidation products) in digestive gland and gills of mussels from A and F sites, while in mussels from N sites elevated oxidative stress was only apparent at 30 °C. Temperature-induced changes in levels of antioxidants (superoxide dismutase, metallothioneins and glutathione) were tissue- and population-specific. Acute warming led to destabilization of lysosomal membranes and increased frequencies of nuclear lesions in mussels from F and A sites but not in their counterparts from N site. Elevated temperature led to an increase in the frequency of micronuclei in hemocytes in mussels from F and A sites at 25 °C and 30 °C and in mussels from N site at 30 °C. The mussels from N site also demonstrated better survival at elevated temperature (30 °C) than their counterparts from the F and A sites. Taken together, these data indicate that long-term acclimation and/or adaptation of A. anatina to elevated temperatures result in increased thermotolerance and alleviate stress response to moderate temperature rise. In contrast, extreme warming (30 °C) is harmful to mussels from all populations indicating limit to this induced

  7. Processing and characterization of transformation-toughened ceramics with strength retention to elevated temperatures. Final report

    International Nuclear Information System (INIS)

    Cutler, R.A.; Brinkpeter, C.B.; Vircar, A.V.; Shetty, D.K.

    1994-09-01

    Monolithic and three-layered Al 2 O 3 -- 15 vol % ZrO 2 composites were fabricated by slip casting aqueous slurries. The outer and inner layers of three-layer composites contained unstabilized and partially stabilized ZrO 2 , respectively. Transformation of part of the unstabilized ZrO 2 led to surface compressive stresses in the outer layers. Strain gage, x-ray, indentation crack length, and strength measurements were used to determine the magnitude of residual stresses in the composites. The strength of the three-layer composites (∼1200 MPa) was 500--700 MPa higher than that of the monolithic outer layer composites at room temperature and 350 MPa higher at 750 degree C. The strength differential decreased rapidly above the m → t transformation temperature. Three-layered composites showed excellent damage resistance and improved reliability. Cam follower rollers were fabricated to demonstrate the applicability of this technique for making automotive components

  8. Effect of Sr addition on microstructure and elevated temperature mechanical properties of Mg–3Zn–1Y alloy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Junwei [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Peng, Xiaodong, E-mail: pxd@cqu.edu.cn [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); National Engineering Research Center for Magnesium Alloys, Chongqing 400044 (China); Li, Mengluan; Wei, Guobing [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Xie, Weidong [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); National Engineering Research Center for Magnesium Alloys, Chongqing 400044 (China); Yang, Yan [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China)

    2016-02-08

    The effects of Sr addition on the microstructure and elevated temperature mechanical behavior of Mg–3Zn–1Y alloys have been investigated in this research. The results show that α-Mg, W-phase and S-phase are found in the Sr-containing alloys. The S-phase has a higher thermal stability than W-phase, which significantly improves the elevated temperature mechanical properties of the alloy. To further confirm the crystal structure of the S-phase, high resolution transmission electron microscopy analysis was performed and the phase was confirmed to be Mg{sub 6}Zn{sub 2}Sr{sub 1}. With increasing content of Sr, the elevated temperature mechanical properties of the Mg–3Zn–1Y are improved. When the Sr content reached to 0.9 wt%, the alloy shows a much higher ultimate tensile strength of 204 MPa and yield strength of 171 MPa at 250 °C.

  9. Selected durability studies of geopolymer concrete with respect to carbonation, elevated temperature, and microbial induced corrosion

    Science.gov (United States)

    Badar, Mohammad Sufian

    This thesis reports a comprehensive study related to the experimental evaluation of carbonation in reinforced geopolymer concrete, the evaluation of geopolymer concretes at elevated temperature, and the resistance of geopolymer concrete to microbial induced corrosion (MIC). Carbonation: Reinforced concretes, made of geopolymer, prepared from two class F fly ashes and one class C fly ash, were subjected to accelerated carbonation treatment for a period of 450 days. Electrochemical, microstructure and pore structure examinations were performed to evaluate the effect of corrosion caused due to carbonation. GPC specimens prepared from class F fly ash exhibited lower corrosion rates by a factor of 21, and higher pH values (pH>12) when compared with concrete specimens prepared from class C Fly ash (GPCMN). Microstructure and pore characterization of GPC prepared using class F fly ash revealed lower porosity by a factor of 2.5 as compared with thier counterparts made using GPC-MN. The superior performace of GPC prepared with the class F fly ash could be attributed to the dense pore structure and formation of the protective layer of calcium and sodium alumino silicate hydrates (C/N-A-S-H) geopolymeric gels around the steel reinforcement. Elevated Temperature: Geopolymers are an emerging class of cementitious binders which possess a potential for high temperature resistance that could possibly be utilized in applications such as nozzles, aspirators and refractory linings. This study reports on the results of an investigation into the performance of a fly ash based geopolymer binder in high temperature environments. Geopolymer concrete (GPC) was prepared using eleven types of fly ashes obtained from four countries. High content alumina and silica sand was used in the mix for preparing GPC. GPC was subjected to thermal shock tests following ASTM C 1100-88. The GPC samples prepared with tabular alumina were kept at 1093° C and immediately quenched in water. GPC specimens

  10. Elevated temperature triggers human respiratory syncytial virus F protein six-helix bundle formation

    International Nuclear Information System (INIS)

    Yunus, Abdul S.; Jackson, Trent P.; Crisafi, Katherine; Burimski, Irina; Kilgore, Nicole R.; Zoumplis, Dorian; Allaway, Graham P.; Wild, Carl T.; Salzwedel, Karl

    2010-01-01

    Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection in infants, immunocompromised patients, and the elderly. The RSV fusion (F) protein mediates fusion of the viral envelope with the target cell membrane during virus entry and is a primary target for antiviral drug and vaccine development. The F protein contains two heptad repeat regions, HR1 and HR2. Peptides corresponding to these regions form a six-helix bundle structure that is thought to play a critical role in membrane fusion. However, characterization of six-helix bundle formation in native RSV F protein has been hindered by the fact that a trigger for F protein conformational change has yet to be identified. Here we demonstrate that RSV F protein on the surface of infected cells undergoes a conformational change following exposure to elevated temperature, resulting in the formation of the six-helix bundle structure. We first generated and characterized six-helix bundle-specific antibodies raised against recombinant peptides modeling the RSV F protein six-helix bundle structure. We then used these antibodies as probes to monitor RSV F protein six-helix bundle formation in response to a diverse array of potential triggers of conformational changes. We found that exposure of 'membrane-anchored' RSV F protein to elevated temperature (45-55 deg. C) was sufficient to trigger six-helix bundle formation. Antibody binding to the six-helix bundle conformation was detected by both flow cytometry and cell-surface immunoprecipitation of the RSV F protein. None of the other treatments, including interaction with a number of potential receptors, resulted in significant binding by six-helix bundle-specific antibodies. We conclude that native, untriggered RSV F protein exists in a metastable state that can be converted in vitro to the more stable, fusogenic six-helix bundle conformation by an increase in thermal energy. These findings help to better define the mechanism of

  11. Soil respiration patterns and rates at three Taiwanese forest plantations: dependence on elevation, temperature, precipitation, and litterfall.

    Science.gov (United States)

    Huang, Yu-Hsuan; Hung, Chih-Yu; Lin, I-Rhy; Kume, Tomonori; Menyailo, Oleg V; Cheng, Chih-Hsin

    2017-11-15

    Soil respiration contributes to a large quantity of carbon emissions in the forest ecosystem. In this study, the soil respiration rates at three Taiwanese forest plantations (two lowland and one mid-elevation) were investigated. We aimed to determine how soil respiration varies between lowland and mid-elevation forest plantations and identify the relative importance of biotic and abiotic factors affecting soil respiration. The results showed that the temporal patterns of soil respiration rates were mainly influenced by soil temperature and soil water content, and a combined soil temperature and soil water content model explained 54-80% of the variation. However, these two factors affected soil respiration differently. Soil temperature positively contributed to soil respiration, but a bidirectional relationship between soil respiration and soil water content was revealed. Higher soil moisture content resulted in higher soil respiration rates at the lowland plantations but led to adverse effects at the mid-elevation plantation. The annual soil respiration rates were estimated as 14.3-20.0 Mg C ha -1  year -1 at the lowland plantations and 7.0-12.2 Mg C ha -1  year -1 at the mid-elevation plantation. When assembled with the findings of previous studies, the annual soil respiration rates increased with the mean annual temperature and litterfall but decreased with elevation and the mean annual precipitation. A conceptual model of the biotic and abiotic factors affecting the spatial and temporal patterns of the soil respiration rate was developed. Three determinant factors were proposed: (i) elevation, (ii) stand characteristics, and (iii) soil temperature and soil moisture. The results indicated that changes in temperature and precipitation significantly affect soil respiration. Because of the high variability of soil respiration, more studies and data syntheses are required to accurately predict soil respiration in Taiwanese forests.

  12. The impact of elevated CO2 and temperature on grain quality of rice grown under open-air field conditions.

    Science.gov (United States)

    Jing, Liquan; Wang, Juan; Shen, Shibo; Wang, Yunxia; Zhu, Jianguo; Wang, Yulong; Yang, Lianxin

    2016-08-01

    Rising atmospheric CO2 is accompanied by global warming. However, interactive effects of elevated CO2 and temperature have not been well studied on grain quality of rice. A japonica cultivar was grown in the field using a free-air CO2 enrichment facility in combination with a canopy air temperature increase system in 2014. The gas fumigation (200 µmol mol(-1) above ambient CO2 ) and temperature increase (1 °C above ambient air temperature) were performed from tillering until maturity. Compared with the control (ambient CO2 and air temperature), elevated CO2 increased grain length and width as well as grain chalkiness but decreased protein concentrations. In contrast, the increase in canopy air temperature had less effect on these parameters except for grain chalkiness. The starch pasting properties of rice flour and taste analysis of cooked rice indicated that the palatability of rice was improved by CO2 and/or temperature elevation, with the combination of the two treatments showing the most significant changes compared with ambient rice. It is concluded that projected CO2 in 2050 may have larger effects on rice grain quality than the projected temperature increase. Although deterioration in milling suitability, grain appearance and nutritional quality can be expected, the taste of cooked rice might be better in the future environment. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

  13. ELEVATED TEMPERATURE, SOIL MOISTURE AND SEASONALITY BUT NOT CO2 AFFECT CANOPY ASSIMILATION AND SYSTEM RESPIRATION IN SEEDLING DOUGLAS-FIR ECOSYSTEMS

    Science.gov (United States)

    We investigated the effects of elevated atmospheric CO2 and air temperature on C cycling in trees and associated soil system, focusing on canopy CO2 assimilation (Asys) and system CO2 loss through respiration (Rsys). We hypothesized that both elevated CO2 and elevated temperature...

  14. DOES SOIL CO2 EFFLUX ACCLIMATIZETO ELEVATED TEMPERATURE AND CO2 DURING LONG-TERM TREATMENT OF DOUGLAS-FIR SEEDLINGS?

    Science.gov (United States)

    We investigated the effects of elevated soil temperature and atmospheric CO2 efflux (SCE) during the third an fourth years of study. We hypothesized that elevated temperature would stimulate SCE, and elevated CO2 would also stimulate SCE with the stimulation being greater at hig...

  15. Higher Temperature at Lower Elevation Sites Fails to Promote Acclimation or Adaptation to Heat Stress During Pollen Germination

    Directory of Open Access Journals (Sweden)

    Lluvia Flores-Rentería

    2018-04-01

    Full Text Available High temperatures associated with climate change are expected to be detrimental for aspects of plant reproduction, such as pollen viability. We hypothesized that (1 higher peak temperatures predicted with climate change would have a minimal effect on pollen viability, while high temperatures during pollen germination would negatively affect pollen viability, (2 high temperatures during pollen dispersal would facilitate acclimation to high temperatures during pollen germination, and (3 pollen from populations at sites with warmer average temperatures would be better adapted to high temperature peaks. We tested these hypotheses in Pinus edulis, a species with demonstrated sensitivity to climate change, using populations along an elevational gradient. We tested for acclimation to high temperatures by measuring pollen viability during dispersal and germination stages in pollen subjected to 30, 35, and 40°C in a factorial design. We also characterized pollen phenology and measured pollen heat tolerance using trees from nine sites along a 200 m elevational gradient that varied 4°C in temperature. We demonstrated that this gradient is biologically meaningful by evaluating variation in vegetation composition and P. edulis performance. Male reproduction was negatively affected by high temperatures, with stronger effects during pollen germination than pollen dispersal. Populations along the elevational gradient varied in pollen phenology, vegetation composition, plant water stress, nutrient availability, and plant growth. In contrast to our hypothesis, pollen viability was highest in pinyons from mid-elevation sites rather than from lower elevation sites. We found no evidence of acclimation or adaptation of pollen to high temperatures. Maximal plant performance as measured by growth did not occur at the same elevation as maximal pollen viability. These results indicate that periods of high temperature negatively affected sexual reproduction, such that

  16. Combined effects of elevated temperature and CO2 enhance threat from low temperature hazard to winter wheat growth in North China.

    Science.gov (United States)

    Tan, Kaiyan; Zhou, Guangsheng; Lv, Xiaomin; Guo, Jianping; Ren, Sanxue

    2018-03-12

    We examined the growth and yield of winter wheat (Triticum aestivum) in response to the predicted elevated CO 2 concentration and temperature to determine the mechanism of the combined impacts in North China Plain. An elevated treatment (CO 2 : 600 μmol mol -1 , temperature: +2.5~3.0 °C, ECTI) and a control treatment (ambient CO 2 and temperature, CK) were conducted in open-top chambers from October 2013 to June 2016. Post-winter growth stages of winter wheat largely advanced and shifted to a cooler period of nature season under combined impact of elevated CO 2 and temperature during the entire growing season. The mean temperature and accumulated photosynthetic active radiations (PAR) over the post-winter growing period in ECTI decreased by 0.8-1.5 °C and 10-13%, respectively compared with that in CK, negatively impacted winter wheat growth. As a result, winter wheat in ECTI suffered from low temperature hazards during critical period of floret development and anthesis and grain number per ear was reduced by 10-31% in the three years. Although 1000-kernel weight in ECTI increased by 8-9% mainly due to elevated CO 2 , increasing CO 2 concentration from 400 to 600 μmol mol -1 throughout the growth stage was not able to offset the adverse effect of warming on winter wheat growth and yield.

  17. Microstructural stability of austenitic stainless steels on exposure to irradiation and elevated temperatures

    International Nuclear Information System (INIS)

    Parameswaran, P.; Radhika, M.; Saroja, S.; Vijayalakshmi, M.; Nanda Gopal, M.

    2011-01-01

    Cold worked 316 stainless steels employed as core material in fast reactors on exposure to neutron irradiation to 40 dpa at ∼ 450 deg C have resulted in microstructural changes in terms of formation of voids and extensive precipitation of carbides, eta phase and nickel silicides. As a consequence there is degradation in the mechanical properties of the material, particularly ductility. In order to achieve higher burnup it is essential to find better materials, which would exhibit less void swelling and retain the microstructure over long radiation doses. Accordingly alloy D9 with appropriate modifications of Ni and Cr content with Ti additions has been developed. Further modification of alloy D9 with respect to minor alloying additions namely Si and P is being studied, in order to enhance the radiation resistance for extending the service life of components. The effectiveness of these elements can be achieved if and only if they are retained in solution over long time of exposure at high temperatures and irradiation. Therefore, the thermal stability of the newly developed improved D9 alloys, with a constant Ti:C ratio and different levels of Si and P has been studied with respect to microstructural evolution and its influence on the mechanical properties. Thermal aging behavior of the alloy with varying titanium contents at elevated temperatures was also studied in detail to identify the optimum alloying levels. The alloys in the 20% cold worked condition exhibit austenitic grains interspersed with bands of fine cold worked grains. On aging in the temperature range of 873-1073K for various durations upto two years the alloy showed the presence of different phases such as M 23 C 6 , intermetallics and TiC whose quantity varies with temperature. The hardness values showed a trend of an initial increase in all the alloys but at longer times the hardness either showed saturation or a decrease followed by saturation. The microstructural parameters like grain size and

  18. Elevated temperature is more effective than elevated [CO2 ] in exposing genotypic variation in Telopea speciosissima growth plasticity: implications for woody plant populations under climate change.

    Science.gov (United States)

    Huang, Guomin; Rymer, Paul D; Duan, Honglang; Smith, Renee A; Tissue, David T

    2015-10-01

    Intraspecific variation in phenotypic plasticity is a critical determinant of plant species capacity to cope with climate change. A long-standing hypothesis states that greater levels of environmental variability will select for genotypes with greater phenotypic plasticity. However, few studies have examined how genotypes of woody species originating from contrasting environments respond to multiple climate change factors. Here, we investigated the main and interactive effects of elevated [CO2 ] (CE ) and elevated temperature (TE ) on growth and physiology of Coastal (warmer, less variable temperature environment) and Upland (cooler, more variable temperature environment) genotypes of an Australian woody species Telopea speciosissima. Both genotypes were positively responsive to CE (35% and 29% increase in whole-plant dry mass and leaf area, respectively), but only the Coastal genotype exhibited positive growth responses to TE . We found that the Coastal genotype exhibited greater growth response to TE (47% and 85% increase in whole-plant dry mass and leaf area, respectively) when compared with the Upland genotype (no change in dry mass or leaf area). No intraspecific variation in physiological plasticity was detected under CE or TE , and the interactive effects of CE and TE on intraspecific variation in phenotypic plasticity were also largely absent. Overall, TE was a more effective climate factor than CE in exposing genotypic variation in our woody species. Our results contradict the paradigm that genotypes from more variable climates will exhibit greater phenotypic plasticity in future climate regimes. © 2015 John Wiley & Sons Ltd.

  19. Behavior of carbon readsorbed on tungsten during low energy Ar ion irradiation at elevated temperatures

    International Nuclear Information System (INIS)

    Pranevicius, L.; Pranevicius, L.L.; Milcius, D.; Templier, C.; Bobrovaite, B.

    2008-01-01

    A study of the behavior of carbon sputtered and readsorbed after scattering collisions with particles of surrounding gas on the tungsten surface affected by Ar ion irradiation with the flux equal to 2 x 10 16 cm -2 s -1 extracted from plasma under 300 V negative bias voltage in the temperature range 370-870 K was performed. The dependence of the W sample weight change on the working gas pressure in the range 0.1-10 Pa was registered and the information was deduced about prevailing sputtering-redeposition processes. The depth profiles of carbon at the tungsten surface were measured. We found that carbon distribution profiles in tungsten depend on the C redeposition rate for fixed ion irradiation parameters. Three regimes have been distinguished: (i) at working gas pressure equal to 5 Pa and more, the C redeposition rate prevails the sample surface erosion rate and the W surface is covered by continuous amorphous carbon film (the C film growth regime), (ii) at working gas pressure equal to about 1 Pa, the C redepostion rate is approximately equal to the erosion rate and the W surface is partially covered by redeposited carbon, and (iii) at working gas pressure less than 0.2 Pa, the erosion rate prevails the C redeposition rate (the W surface erosion regime). In the regime of balanced redeposition and erosion deep C penetration depth into nanocrystalline W was registered. It is suggested that under simultaneous C adsorption and ion irradiation at elevated temperature C adatoms are driven from the W surface into grain boundaries and into the bulk by the difference in chemical potentials between the activated W surface and grain boundaries. As the W surface is covered by amorphous C film, the grain boundaries are blocked and the efficiency of carbon transport decreases

  20. Hydrogen isotope exchange of organic compounds in dilute acid at elevated temperatures

    International Nuclear Information System (INIS)

    Werstiuk, N.H.

    1987-01-01

    Introduction of one or more deuterium (or tritium) atoms into organic molecules can be accomplished in many ways depending on the nature of the substrate and the extent and sterochemistry of deuteriation or tritiation required. Some of the common methods include acid- and base-catalyzed exchange of carbonyl compounds, metal hydride reductions, dissolving metal reductions, catalytic reduction of double bonds, chromatographic exchange, homogeneous and heterogeneous metal-catalyzed exchange, base-catalyzed exchange of carbon acids other than carbonyl compounds and acid-catalyzed exchange via electrophilic substitution. Only the latter three methods have been used for perdeuteriation of organic compounds. A very useful compendium of labeling methods with examples has been available to chemists for some time. Although metal-catalyzed exchange has been used extensively, the method suffers from some deficiencies: irreproducibility of catalyst surfaces, catalyst poisoning, side reactions such as coupling and hydrogenolysis of labile groups and low deuterium incorporation. Usually a number of cycles are required with fresh catalyst and fresh deuterium source to achieve substantial isotope incorporation. Acid-catalyzed exchange of aromatics and alkenes, strongly acidic media such as liquid DBr, concentrated DBr, acetic acid/stannic chloride, concentrated D 3 PO 4 , concentrated DC1, D 3 PO 4 /BF 3 SO 2 , 50-80% D 2 SO 4 and DFSO 4 /SbF 5 at moderate temperatures (<100 degrees) have been used to effect exchange. The methods are not particularly suitable for large scale deuteriations because of the cost and the fact that the recovery and upgrading of the diluted deuterium pool is difficult. This paper describes the hydrogen isotope exchange of a variety of organic compounds in dilute aqueous acid (0.1-0.5 M) at elevated temperatures (150-300 degrees)

  1. Experimental and Computational Investigation of High Entropy Alloys for Elevated-Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, Peter [Univ. of Tennessee, Knoxville, TN (United States); Zhang, Fan [CompuTherm LLC, Madison, WI (United States); Zhang, Chuan [CompuTherm LLC, Madison, WI (United States); Wang, Gongyao [Univ. of Tennessee, Knoxville, TN (United States); Xie, Xie [Univ. of Tennessee, Knoxville, TN (United States); Diao, Haoyan [Univ. of Tennessee, Knoxville, TN (United States); Kuo, Chih-Hsiang [Univ. of Tennessee, Knoxville, TN (United States); An, Zhinan [Univ. of Tennessee, Knoxville, TN (United States); Hemphill, Michael [Univ. of Tennessee, Knoxville, TN (United States)

    2016-07-30

    tomography (APT), and transmission electron microscopy (TEM). In-situ neutron diffraction experiments were conducted to study the strengthening effect of B2 phase on tensile properties of Al0.3CoCrFeNi HEAs directly. The results shows the creep behavior of Al0.3CoCrFeNi is superior to conventional alloys, and the heat treatment introduces secondary B2 phase into the FCC matrix, which increase the yielding strength, decrease the ductility, diminish the serrated flow during compression tests at high temperatures. In summary, the outcomes of the development of the HEAs with creep resistance include: (1) Suitable candidates, for the application to boilers and steam and gas turbines at temperatures above 760 °C and a stress of 35 MPa. (2) Fundamental understanding on the precipitate stability and deformation mechanisms of both single-phase and precipitate-strengthened alloys at room and elevated temperatures, and (3) The demonstration of an integrated approach, coupling modeling [thermodynamic calculations and crystal-plasticity finite-element modeling (CPFEM)] and focused experiments, to identify HEAs that outperform conventional alloys for high-temperature applications, which will be applicable for the discovery and development of other high-temperature materials in the power-generating industry.

  2. Effect of Elevated Atmospheric CO2 and Temperature on Leaf Optical Properties and Chlorophyll Content in Acer saccharum (Marsh.)

    Science.gov (United States)

    Carter, Gregory A.; Bahadur, Raj; Norby, Richard J.

    1999-01-01

    Elevated atmospheric CO2 pressure and numerous causes of plant stress often result in decreased leaf chlorophyll contents and thus would be expected to alter leaf optical properties. Hypotheses that elevated carbon dioxide pressure and air temperature would alter leaf optical properties were tested for sugar maple (Acer saccharum Marsh.) in the middle of its fourth growing season under treatment. The saplings had been growing since 1994 in open-top chambers at Oak Ridge, Tennessee under the following treatments: 1) Ambient CO2 pressure and air temperature (control); 2) CO2 pressure approximately 30 Pa above ambient; 3) Air temperatures 3 C above ambient; 4) Elevated CO2 and air temperature. Spectral reflectance, transmittance, and absorptance in the visible spectrum (400-720 nm) did not change significantly (rho = 0.05) in response to any treatment compared with control values. Although reflectance, transmittance, and absorptance at 700 nm correlated strongly with leaf chlorophyll content, chlorophyll content was not altered significantly by the treatments. The lack of treatment effects on pigmentation explained the non-significant change in optical properties in the visible spectrum. Optical properties in the near-infrared (721-850 nm) were similarly unresponsive to treatment with the exception of an increased absorptance in leaves that developed under elevated air temperature alone. This response could not be explained by the data, but might have resulted from effects of air temperature on leaf internal structure. Results indicated no significant potential for detecting leaf optical responses to elevated CO2 or temperature by the remote sensing of reflected radiation in the 400-850 nm spectrum.

  3. Environmental temperature affects prevalence of blood parasites of birds on an elevation gradient: implications for disease in a warming climate.

    Directory of Open Access Journals (Sweden)

    Itzel Zamora-Vilchis

    Full Text Available BACKGROUND: The rising global temperature is predicted to expand the distribution of vector-borne diseases both in latitude and altitude. Many host communities could be affected by increased prevalence of disease, heightening the risk of extinction for many already threatened species. To understand how host communities could be affected by changing parasite distributions, we need information on the distribution of parasites in relation to variables like temperature and rainfall that are predicted to be affected by climate change. METHODOLOGY/PRINCIPAL FINDINGS: We determined relations between prevalence of blood parasites, temperature, and seasonal rainfall in a bird community of the Australian Wet Tropics along an elevation gradient. We used PCR screening to investigate the prevalence and lineage diversity of four genera of blood parasites (Plasmodium, Haemoproteus, Leucocytozoon and Trypanosoma in 403 birds. The overall prevalence of the four genera of blood parasites was 32.3%, with Haemoproteus the predominant genus. A total of 48 unique lineages were detected. Independent of elevation, parasite prevalence was positively and strongly associated with annual temperature. Parasite prevalence was elevated during the dry season. CONCLUSIONS/SIGNIFICANCE: Low temperatures of the higher elevations can help to reduce both the development of avian haematozoa and the abundance of parasite vectors, and hence parasite prevalence. In contrast, high temperatures of the lowland areas provide an excellent environment for the development and transmission of haematozoa. We showed that rising temperatures are likely to lead to increased prevalence of parasites in birds, and may force shifts of bird distribution to higher elevations. We found that upland tropical areas are currently a low-disease habitat and their conservation should be given high priority in management plans under climate change.

  4. Oxidation of iridium coating on rhenium coated graphite at elevated temperature in stagnated air

    International Nuclear Information System (INIS)

    Huang, Yongle; Bai, Shuxin; Zhang, Hong; Ye, Yicong

    2015-01-01

    Highlights: • Continuous and dense Ir coatings were prepared on graphite by electrodepostion. • The purification of the as-prepared Ir coating was higher than about 99.98%. • The Ir/Re/C specimen kept integrity without significant failures after oxidation. • The average oxidation rate of the Ir coating was about 0.219 mg/(cm 2 min). • Penetrating holes at gains boundaries resulted in the failure of the Ir coating. - Abstract: Continuous and dense iridium coatings were prepared on the rhenium coated graphite specimens by electrodeposition. The iridium/rhenium coated graphite (Ir/Re/C) specimens were oxidized at elevated temperatures in stagnated air for 3600 s. The purification of the as-prepared Ir coating was higher than about 99.98% with the main impurity elements Si, Al, Fe and Ru. After oxidation, the Ir/Re/C specimens kept integrity without significant failures and the average oxidation rate was about 0.219 mg/(cm 2 min). Pores were found at the grain boundaries and concentrated to penetrating holes with the growth of Ir grains, which resulted in disastrous failures of the Ir coating

  5. Oxidation of iridium coating on rhenium coated graphite at elevated temperature in stagnated air

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yongle; Bai, Shuxin, E-mail: NUDT_MSE_501@163.com; Zhang, Hong; Ye, Yicong

    2015-02-15

    Highlights: • Continuous and dense Ir coatings were prepared on graphite by electrodepostion. • The purification of the as-prepared Ir coating was higher than about 99.98%. • The Ir/Re/C specimen kept integrity without significant failures after oxidation. • The average oxidation rate of the Ir coating was about 0.219 mg/(cm{sup 2} min). • Penetrating holes at gains boundaries resulted in the failure of the Ir coating. - Abstract: Continuous and dense iridium coatings were prepared on the rhenium coated graphite specimens by electrodeposition. The iridium/rhenium coated graphite (Ir/Re/C) specimens were oxidized at elevated temperatures in stagnated air for 3600 s. The purification of the as-prepared Ir coating was higher than about 99.98% with the main impurity elements Si, Al, Fe and Ru. After oxidation, the Ir/Re/C specimens kept integrity without significant failures and the average oxidation rate was about 0.219 mg/(cm{sup 2} min). Pores were found at the grain boundaries and concentrated to penetrating holes with the growth of Ir grains, which resulted in disastrous failures of the Ir coating.

  6. Elevated Temperature, Residual Compressive Strength of Impact-Damaged Sandwich Structure Manufactured Out-of-Autoclave

    Science.gov (United States)

    Grimsley, Brian W.; Sutter, James K.; Burke, Eric R.; Dixon, Genevieve D.; Gyekenyesi, Thomas G.; Smeltzer, Stanley S.

    2012-01-01

    Several 1/16th-scale curved sandwich composite panel sections of a 10 m diameter barrel were fabricated to demonstrate the manufacturability of large-scale curved sections using minimum gauge, [+60/-60/0]s, toughened epoxy composite facesheets co-cured with low density (50 kilograms per cubic meters) aluminum honeycomb core. One of these panels was fabricated out of autoclave (OoA) by the vacuum bag oven (VBO) process using Cycom(Registered Trademark) T40-800b/5320-1 prepreg system while another panel with the same lay-up and dimensions was fabricated using the autoclave-cure, toughened epoxy prepreg system Cycom(Registered Trademark) IM7/977-3. The resulting 2.44 m x 2 m curved panels were investigated by non-destructive evaluation (NDE) at NASA Langley Research Center (NASA LaRC) to determine initial fabrication quality and then cut into smaller coupons for elevated temperature wet (ETW) mechanical property characterization. Mechanical property characterization of the sandwich coupons was conducted including edge-wise compression (EWC), and compression-after-impact (CAI) at conditions ranging from 25 C/dry to 150 C/wet. The details and results of this characterization effort are presented in this paper.

  7. Effect of microstructure on elevated temperature LCF behaviour of nimonic PE16 superalloy

    International Nuclear Information System (INIS)

    Valsan, M.; Bhanu Sankara Rao, K.; Mannan, S.L.

    1989-01-01

    The influence of microstructure on elevated temperature low cycle fatigue (LCF) behaviour of Nimonic PE16 superalloy has been studied. Samples with the following three different prior microstructures were chosen for testing: (A) a fine grain structure, free from carbides and γ'(1313K/4h); (B) microstructure with intra and intergranular M 23 C 6 and uniform distribution of spherical and peak aged γ' of 18 nm diameter (1313K/4h + 1073K/2h + 973K/16h); and (C) microstructure with predominantly intergranular MC and uniform distribution of coarse γ' of 35 nm diameter (1313K/4h+1173K/1h+1023K/8h). Total strain controlled LCF tests were carried out on all the three microstructures at 823 and 923K and at a constant strain rate of 3.2x10 -3 s -1 over strain amplitudes ranging from ±0.25 ±1.00 per cent. (author). 54 refs., 17 figs., 3 tabs

  8. Estimation of Fracture Parameters for Leak-before-Break Assessment on Elevated Temperature

    International Nuclear Information System (INIS)

    Lee, S. Y.; Kim, N. H.; Koo, G. H.; Kim, D. J.

    2015-01-01

    When the liquid sodium leaks this interaction may cause the fire that is harmful to safety of the reactor. Therefore, it is necessary to prevent against sodium fire in SFRs. Leak-before-Break(LBB) concept, had been devised for this purpose and has following advantage than Double-ended Guillotine Break(DEGB) design. If DEGB is excluded, the number of extinguish facilities and firewalls against the sodium fire can be minimize. LBB concept, has been well established and had many experience in regard of light water reactors(LWRs). But LBB assessment to SFRs is more complicated because SFRs is operated on elevated temperature region. On this region, because creep damage occurs to material and grows defects LBB assessment to SFRs should be considering creep effects. The procedure and method for this purpose are provided RCC-MRx A16 that is France code. To calculate fracture parameters such as K and J are required to some coefficients and equations which have been limited in RCC-MRx A16. Thus, in this study obtained K and J using finite element analysis for the sub-model including the crack. In this study, fracture parameters for LBB assessment were estimated by finite element analysis. This result will be applicable to LBB assessment of PGSFR

  9. Hypothesis for thermal activation of the caspase cascade in apoptotic cell death at elevated temperatures

    Science.gov (United States)

    Pearce, John A.

    2013-02-01

    Apoptosis is an especially important process affecting disease states from HIV-AIDS to auto-immune disease to cancer. A cascade of initiator and executioner capsase functional proteins is the hallmark of apoptosis. When activated the various caspases activate other caspases or cleave structural proteins of the cytoskeleton, resulting in "blebbing" of the plasma membrane forming apoptotic bodies that completely enclose the disassembled cellular components. Containment of the cytosolic components within the apoptotic bodies differentiates apoptosis from necroptosis and necrosis, both of which release fragmented cytosol and other cellular constituents into the intracellular space. Biochemical models of caspase activation reveal the extensive feedback loops characteristic of apoptosis. They clearly explain the failure of Arrhenius models to give accurate predictions of cell survival curves in hyperthermic heating protocols. Nevertheless, each of the individual reaction velocities can reasonably be assumed to follow Arrhenius kinetics. If so, the thermal sensitivity of the reaction velocity to temperature elevation is: ∂k/∂T = Ea [k/RT2]. Particular reaction steps described by higher activation energies, Ea, are likely more thermally-sensitive than lower energy reactions and may initiate apoptosis in the absence of other stress signals. Additionally, while the classical irreversible Arrhenius formulation fails to accurately represent many cell survival and/or dye uptake curves - those that display an early stage shoulder region - an expanded reversible model of the law of mass action equation seems to prove effective and is directly based on a firm theoretical thermodynamic foundation.

  10. Coupled Effect of Elevated Temperature and Cooling Conditions on the Properties of Ground Clay Brick Mortars

    Science.gov (United States)

    Ali Abd El Aziz, Magdy; Abdelaleem, Salh; Heikal, Mohamed

    2013-12-01

    When a concrete structure is exposed to fire and cooling, some deterioration in its chemical resistivity and mechanical properties takes place. This deterioration can reach a level at which the structure may have to be thoroughly renovated or completely replaced. In this investigation, four types of cement mortars, ground clay bricks (GCB)/sand namely 0/3, 1/2, 2/1 and 3/0, were used. Three different cement contents were used: 350, 400 and 450 kg/m3. All the mortars were prepared and cured in tap water for 3 months and then kept in laboratory atmospheric conditions up to 6 months. The specimens were subjected to elevated temperatures up to 700°C for 3h and then cooled by three different conditions: water, furnace, and air cooling. The results show that all the mortars subjected to fire, irrespective of cooling mode, suffered a significant reduction in compressive strength. However, the mortars cooled in air exhibited a relativity higher reduction in compressive strength rather than those water or furnace cooled. The mortars containing GCB/sand (3/0) and GCB/sand (1/2) exhibited a relatively higher thermal stability than the others.

  11. Computed estimates of maximum temperature elevations in fetal tissues during transabdominal pulsed Doppler examinations.

    Science.gov (United States)

    Bly, S H; Vlahovich, S; Mabee, P R; Hussey, R G

    1992-01-01

    Measured characteristics of ultrasonic fields were obtained in submissions from manufacturers of diagnostic ultrasound equipment for devices operating in pulsed Doppler mode. Simple formulae were used with these data to generate upper limits to fetal temperature elevations, delta Tlim, during a transabdominal pulsed Doppler examination. A total of 236 items were analyzed, each item being a console/transducer/operating-mode/intended-use combination, for which the spatial-peak temporal-average intensity, ISPTA, was greater than 500 mW cm-2. The largest calculated delta Tlim values were approximately 1.5, 7.1 and 8.7 degrees C for first-, second- and third-trimester examinations, respectively. The vast majority of items yielded delta Tlim values which were less than 1 degree C in the first trimester. For second- and third-trimester examinations, where heating of fetal bone determines delta Tlim, most delta Tlim values were less than 4 degrees C. The clinical significance of the results is discussed.

  12. Study of creep collapse of tubes subject to external pressure at elevated temperature

    International Nuclear Information System (INIS)

    Takikawa, N.

    1982-01-01

    Intermediate heat exchanger (IHX) tubes of VHTR form the boundary between the primary and secondary coolants of the reactor. The tubes are subject to external pressures at a postulated secondary coolant depressurization accident, which might lead to creep collapse. Therefore, it is necessary to ensure the integrity against creep collapse by analysis. The objective of this work is to study a simplified analytical method for predicting collapse time of a curved tube subjected to an external pressure. The study is made based on the comparison of experimental collapse time of curved and straight tubes. Creep collapse tests were conducted under an elevated temperature and an external pressure. Test results showed that curved tubes had longer collapse time than straight tubes with the same cross sectional ovality. The simplified analytical method for a curved tube is proposed in this report, which is to compute collapse time of a straight tube with the same ovality. And in this method the computed time is considered as collapse time of the curved tube. The above test results show that this simplified method gives the conservative collapse time. And it is confirmed by additional IHX tube tests that the method is applicable to creep collapse analysis of IHX tubes

  13. Experimental strength evaluation of cylinders with a flat head subjected to internal pressure at elevated temperature

    International Nuclear Information System (INIS)

    Suzuki, Mitsuru; Makino, Yutaka

    1978-01-01

    The experiments using component test models such as a cylinder with a flat head and F.E.M. elastic analyses to investigate the secondary stress, peak stress and creep-fatigue interaction effect are described. The comparison of uniaxial stress with multiaxial stress about deformation and strength at elevated temperatures are also described here. The results of experiments and analysis are summarized as follows: (1) The maximum stress as the equivalent stress is the most suitable for the prediction of the creep failure life of cylinders subjected to internal pressure using the uniaxial creep test results. And the Mises's equivalent stress is the suitable for this prediction using the data of the onset of the uniaxial tertiary creep. (2) In the creep characteristics of the cylinder there, is no tertiary creep stage, and the rupture elongation of the cylinder accords with the elongation of the onset of the uniaxial tertiary creep. (3) It was recognized that the secondary stress occurred at the corner of the cylinder with a flat head has a little effect on creep and creep-fatigue life. (4) The life reduction effect due to the creep-fatigue interaction around the corner was recognized by the linear damage rule and compared with the value of Code Case 1592. (5) A difference of failure modes by imposed conditions for vessel with the size-discontinuity section was recognized by the cyclic internal pressure tests with hold time. (author)

  14. FDTD analysis of body-core temperature elevation in children and adults for whole-body exposure

    Energy Technology Data Exchange (ETDEWEB)

    Hirata, Akimasa; Asano, Takayuki; Fujiwara, Osamu [Department of Computer Science and Engineering, Nagoya Institute of Technology (Japan)], E-mail: ahirata@nitech.ac.jp

    2008-09-21

    The temperature elevations in anatomically based human phantoms of an adult and a 3-year-old child were calculated for radio-frequency whole-body exposure. Thermoregulation in children, however, has not yet been clarified. In the present study, we developed a computational thermal model of a child that is reasonable for simulating body-core temperature elevation. Comparison of measured and simulated temperatures revealed thermoregulation in children to be similar to that of adults. Based on this finding, we calculated the body-core temperature elevation in a 3-year-old child and an adult for plane-wave exposure at the basic restriction in the international guidelines. The body-core temperature elevation in the 3-year-old child phantom was 0.03 deg. C at a whole-body-averaged specific absorption rate of 0.08 W kg{sup -1}, which was 35% smaller than in the adult female. This difference is attributed to the child's higher body surface area-to-mass ratio.

  15. FDTD analysis of body-core temperature elevation in children and adults for whole-body exposure.

    Science.gov (United States)

    Hirata, Akimasa; Asano, Takayuki; Fujiwara, Osamu

    2008-09-21

    The temperature elevations in anatomically based human phantoms of an adult and a 3-year-old child were calculated for radio-frequency whole-body exposure. Thermoregulation in children, however, has not yet been clarified. In the present study, we developed a computational thermal model of a child that is reasonable for simulating body-core temperature elevation. Comparison of measured and simulated temperatures revealed thermoregulation in children to be similar to that of adults. Based on this finding, we calculated the body-core temperature elevation in a 3-year-old child and an adult for plane-wave exposure at the basic restriction in the international guidelines. The body-core temperature elevation in the 3-year-old child phantom was 0.03 degrees C at a whole-body-averaged specific absorption rate of 0.08 W kg(-1), which was 35% smaller than in the adult female. This difference is attributed to the child's higher body surface area-to-mass ratio.

  16. FDTD analysis of body-core temperature elevation in children and adults for whole-body exposure

    International Nuclear Information System (INIS)

    Hirata, Akimasa; Asano, Takayuki; Fujiwara, Osamu

    2008-01-01

    The temperature elevations in anatomically based human phantoms of an adult and a 3-year-old child were calculated for radio-frequency whole-body exposure. Thermoregulation in children, however, has not yet been clarified. In the present study, we developed a computational thermal model of a child that is reasonable for simulating body-core temperature elevation. Comparison of measured and simulated temperatures revealed thermoregulation in children to be similar to that of adults. Based on this finding, we calculated the body-core temperature elevation in a 3-year-old child and an adult for plane-wave exposure at the basic restriction in the international guidelines. The body-core temperature elevation in the 3-year-old child phantom was 0.03 deg. C at a whole-body-averaged specific absorption rate of 0.08 W kg -1 , which was 35% smaller than in the adult female. This difference is attributed to the child's higher body surface area-to-mass ratio

  17. Dynamic Fracture Initiation Toughness at Elevated Temperatures With Application to the New Generation of Titanium Aluminide Alloys. Chapter 8

    Science.gov (United States)

    Shazly, Mostafa; Prakash, Vikas; Draper, Susan; Shukla, Arun (Editor)

    2006-01-01

    Recently, a new generation of titanium aluminide alloy, named Gamma-Met PX, has been developed with better rolling and post-rolling characteristics. I'revious work on this alloy has shown the material to have higher strengths at room and elevated temperatures when compared with other gamma titanium aluminides. In particular, this new alloy has shown increased ductility at elevated temperatures under both quasi-static and high strain rate uniaxial compressive loading. However, its high strain rate tensile ductility at room and elevated temperatures is limited to approx. 1%. In the present chapter, results of a study to investigate the effects of loading rate and test temperature on the dynamic fracture initiation toughness in Gamma-Met PX are presented. Modified split Hopkinson pressure bar was used along with high-speed photography to determine the crack initiation time. Three-point bend dynamic fracture experiments were conducted at impact speeds of approx. 1 m/s and tests temperatures of up-to 1200 C. The results show that thc dynamic fracture initiation toughness decreases with increasing test temperatures beyond 600 C. Furthermore, thc effect of long time high temperature air exposure on the fracture toughness was investigated. The dynamic fracture initiation toughness was found to decrease with increasing exposure time. The reasons behind this drop are analyzed and discussed.

  18. Novel development of the micro-tensile test at elevated temperature using a test structure with integrated micro-heater

    Science.gov (United States)

    Ang, W. C.; Kropelnicki, P.; Soe, Oak; Ling, J. H. L.; Randles, A. B.; Hum, A. J. W.; Tsai, J. M. L.; Tay, A. A. O.; Leong, K. C.; Tan, C. S.

    2012-08-01

    This paper describes the novel development of a micro-tensile testing method that allows testing at elevated temperatures. Instead of using a furnace, a titanium/platinum thin film micro-heater was fabricated on a conventional dog-bone-shaped test structure to heat up its gauge section locally. An infrared (IR) camera with 5 µm resolution was employed to verify the temperature uniformity across the gauge section of the test structure. With this micro-heater-integrated test structure, micro-tensile tests can be performed at elevated temperatures using any conventional tensile testing system without any major modification to the system. In this study, the tensile test of the single crystal silicon (SCS) thin film with (1 0 0) surface orientation and tensile direction was performed at room temperature and elevated temperatures, up to 300 °C. Experimental results for Young's modulus as a function of temperature are presented. A micro-sized SCS film showed a low dependence of mechanical properties on temperature up to 300 °C.

  19. Temporal variability in Cu speciation, phytotoxicity, and soil microbial activity of Cu-polluted soils as affected by elevated temperature.

    Science.gov (United States)

    Fu, Qing-Long; Weng, Nanyan; Fujii, Manabu; Zhou, Dong-Mei

    2018-03-01

    Global warming has obtained increasing attentions due to its multiple impacts on agro-ecosystem. However, limited efforts had been devoted to reveal the temporal variability of metal speciation and phytotoxicity of heavy metal-polluted soils affected by elevated temperature under the global warming scenario. In this study, effects of elevated temperature (15 °C, 25 °C, and 35 °C) on the physicochemical properties, microbial metabolic activities, and phytotoxicity of three Cu-polluted soils were investigated by a laboratory incubation study. Soil physicochemical properties were observed to be significantly altered by elevated temperature with the degree of temperature effect varying in soil types and incubation time. The Biolog and enzymatic tests demonstrated that soil microbial activities were mainly controlled and decreased with increasing incubation temperature. Moreover, plant assays confirmed that the phytotoxicity and Cu uptake by wheat roots were highly dependent on soil types but less affected by incubation temperature. Overall, the findings in this study have highlighted the importance of soil types to better understand the temperature-dependent alternation of soil properties, Cu speciation and bioavailability, as well as phytotoxicity of Cu-polluted soils under global warming scenario. The present study also suggests the necessary of investigating effects of soil types on the transport and accumulation of toxic elements in soil-crop systems under global warming scenario. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Impact of needle age on the response of respiration in Scots pine to long-term elevation of carbon dioxide concentration and temperature

    International Nuclear Information System (INIS)

    Zha, T.; Ryyppo, A.; Kellomaki, S.; Wang, K-Y.

    2002-01-01

    The effects of needle age, elevated carbon dioxide and temperature on needle respiration in Scots pine was studied during a four-year period. Results showed that respiration rates and specific leaf area decreased in elevated atmospheric carbon dioxide concentration relative to ambient conditions, but increased in elevated temperature and when elevated atmospheric carbon dioxide and elevated temperature were combined. Starch and soluble sugar concentrations for a given needle age increased in elevated carbon dioxide, but decreased slightly under combined elevated temperature and elevated carbon dioxide conditions. Respiration rate and specific leaf area were highest in current year needles in all treatment modes. All treatment modes enhanced the difference in respiration between current year and older needles relative to ambient conditions. Carbohydrate concentration or specific leaf area remained unchanged in response to any treatment. Under ambient conditions the temperature coefficient of respiration increased slightly in elevated carbon dioxide regardless of age, however, there was significant decline at elevated temperature as well as when both carbon dioxide concentration and temperature were elevated, indicating acclimation of respiration to temperature. 48 refs., 2 tabs., 7 figs

  1. Microstructural Stability and Oxidation Resistance of 9-12 Chromium Steels at Elevated Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Dogan, O.N.; Alman, D.E.; Jablonski, P.D.; Hawk, J.A.

    2006-05-01

    Various martensitic 9-12 Cr steels are utilized currently in fossil fuel powered energy plants for their good elevated temperature properties such as creep strength, steam side oxidation resistance, fire side corrosion resistance, and thermal fatigue resistance. Need for further improvements on the properties of 9-12 Cr steels for higher temperature (>600oC) use is driven by the environmental concerns (i.e., improve efficiency to reduce emissions and fossil fuel consumption). In this paper, we will discuss the results of the research done to explore new subsitutional solute solution and precipitate hardening mechanisms for improved strength of 9-12 Cr martensitic steels. Stability of the phases present in the steels will be evaluated for various temperature and time exposures. A comparison of microstructural properties of the experimental steels and commercial steels will also be presented.

    The influence of a Ce surface treatment on oxidation behavior of a commercial (P91) and several experimental steels containing 9 to 12 weight percent Cr was examined at 650ºC in flowing dry and moist air. The oxidation behavior of all the alloys without the Ce modification was significantly degraded by the presence of moisture in the air during testing. For instance the weight gain for P91 was two orders of magnitude greater in moist air than in dry air. This was accompanied by a change in oxide scale from the formation of Cr-based scales in dry air to the formation of Fe-based scales in moist air. The Ce surface treatment was very effective in improving the oxidation resistance of the experimental steels in both moist and dry air. For instance, after exposure to moist air at 650ºC for 2000 hours, an experimental alloy with the cerium surface modification had a weight gain three orders of magnitude lower than the alloy without the Ce modification and two orders of magnitude lower than P91. The Ce surface treatment suppressed the formation of Fe-based scales and

  2. Life prediction methodology for thermal-mechanical fatigue and elevated temperature creep design

    Science.gov (United States)

    Annigeri, Ravindra

    Nickel-based superalloys are used for hot section components of gas turbine engines. Life prediction techniques are necessary to assess service damage in superalloy components resulting from thermal-mechanical fatigue (TMF) and elevated temperature creep. A new TMF life model based on continuum damage mechanics has been developed and applied to IN 738 LC substrate material with and without coating. The model also characterizes TMF failure in bulk NiCoCrAlY overlay and NiAl aluminide coatings. The inputs to the TMF life model are mechanical strain range, hold time, peak cycle temperatures and maximum stress measured from the stabilized or mid-life hysteresis loops. A viscoplastic model is used to predict the stress-strain hysteresis loops. A flow rule used in the viscoplastic model characterizes the inelastic strain rate as a function of the applied stress and a set of three internal stress variables known as back stress, drag stress and limit stress. Test results show that the viscoplastic model can reasonably predict time-dependent stress-strain response of the coated material and stress relaxation during hold times. In addition to the TMF life prediction methodology, a model has been developed to characterize the uniaxial and multiaxial creep behavior. An effective stress defined as the applied stress minus the back stress is used to characterize the creep recovery and primary creep behavior. The back stress has terms representing strain hardening, dynamic recovery and thermal recovery. Whenever the back stress is greater than the applied stress, the model predicts a negative creep rate observed during multiple stress and multiple temperature cyclic tests. The model also predicted the rupture time and the remaining life that are important for life assessment. The model has been applied to IN 738 LC, Mar-M247, bulk NiCoCrAlY overlay coating and 316 austenitic stainless steel. The proposed model predicts creep response with a reasonable accuracy for wide range of

  3. Development of Refractory Ceramics for The Oxygen Evolution Reaction (OER) Electrocatalyst Support for Water Electrolysis at elevated temperatures

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Prag, Carsten Brorson; Polonsky, J.

    2012-01-01

    Commercial TaC and Si3N4 powders were tested as possible electrocatalyst support materials for the Oxygen Evolution Reaction (OER) for PEM water electrolysers, operating at elevated temperatures. TaC and Si3N4 were characterised by thermogravimmetric and differential thermal analysis...

  4. The role of elevated temperature exposure on structural evolution and fatigue strength of eutectic AlSi12 alloys

    Czech Academy of Sciences Publication Activity Database

    Konečná, R.; Nicoletto, G.; Kunz, Ludvík; Riva, E.

    2016-01-01

    Roč. 83, č. 1 (2016), s. 24-35 ISSN 0142-1123 Institutional support: RVO:68081723 Keywords : Piston * Al-Si alloy * Elevated temperature * Fatigue strength Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.899, year: 2016

  5. Additive effects of the herbicide glyphosate and elevated temperature on the branched coral Acropora formosa in Nha Trang, Vietnam

    NARCIS (Netherlands)

    Amid, C.; Olstedt, M.; Gunnarsson, J.S.; Lan, Le H.; Tran Thi Minh, H.; Brink, van den P.J.; Hellström, M.; Tedengren, M.

    2017-01-01

    The combined effects of the herbicide glyphosate and elevated temperature were studied on the tropical staghorn coral Acropora formosa, in Nha Trang bay, Vietnam. The corals were collected from two different reefs, one close to a polluted fish farm and one in a marine-protected area (MPA). In the

  6. Below-ground process responses to elevated CO2 and temperature: a discussion of observations, measurement methods, and models

    Science.gov (United States)

    Elise Pendall; Scott Bridgham; Paul J. Hanson; Bruce Hungate; David W. Kicklighter; Dale W. Johnson; Beverly E. Law; Yiqi Luo; J. Patrick Megonigal; Maria Olsrud; Michael G. Ryan; Shiqiang Wan

    2004-01-01

    Rising atmospheric CO2 and temperatures are probably altering ecosystem carbon cycling, causing both positive and negative feedbacks to climate. Below-ground processes play a key role in the global carbon (C) cycle because they regulate storage of large quantities of C, and are potentially very sensitive to direct and indirect effects of elevated...

  7. ATR-IR spectroscopic cell for in situ studies at solid-liquid interface at elevated temperatures and pressures

    NARCIS (Netherlands)

    Koichumanova, Kamila; Visan, Aura; Geerdink, Bert; Lammertink, Rob G.H.; Mojet, Barbara; Seshan, Kulathuiyer; Lefferts, Leonardus

    2017-01-01

    An in situ ATR-IR spectroscopic cell suitable for studies at solid-liquid interface is described including the design and experimental details in continuous flow mode at elevated temperatures (230 °C) and pressures (30 bar). The design parameters considered include the cell geometry, the procedure

  8. ATP and phosphocreatine utilization in single human muscle fibres during the development of maximal power output at elevated muscle temperatures.

    Science.gov (United States)

    Gray, Stuart R; Söderlund, Karin; Ferguson, Richard A

    2008-05-01

    In this study, we examined the effect of muscle temperature (Tm) on adenosine triphosphate (ATP) and phosphocreatine utilization in single muscle fibres during the development of maximal power output in humans. Six male participants performed a 6-s maximal sprint on a friction-braked cycle ergometer under both normal (Tm = 34.3 degrees C, s = 0.6) and elevated (T(m) = 37.3 degrees C, s = 0.2) muscle temperature conditions. During the elevated condition, muscle temperature of the legs was raised, passively, by hot water immersion followed by wrapping in electrically heated blankets. Muscle biopsies were taken from the vastus lateralis before and immediately after exercise. Freeze-dried single fibres were dissected, characterized according to myosin heavy chain composition, and analysed for ATP and phosphocreatine content. Single fibres were classified as: type I, IIA, IIAX25 (1 - 25% IIX isoform), IIAX50 (26 - 50% IIX), IIAX75 (51 - 75% IIX), or IIAX100 (76 - 100% IIX). Maximal power output and pedal rate were both greater (P < 0.05) during the elevated condition by 258 W (s = 110) and 22 rev . min(-1) (s = 6), respectively. In both conditions, phosphocreatine content decreased significantly in all fibre types, with a greater decrease during the elevated condition in type IIA fibres (P < 0.01). Adenosine triphosphate content was also reduced to a greater (P < 0.01) extent in type IIA fibres during the elevated condition. The results of the present study indicate that after passive elevation of muscle temperature, there was a greater decrease in ATP and phosphocreatine content in type IIA fibres than in the normal trial, which contributed to the higher maximal power output.

  9. Studies in RF power communication, SAR, and temperature elevation in wireless implantable neural interfaces.

    Directory of Open Access Journals (Sweden)

    Yujuan Zhao

    Full Text Available Implantable neural interfaces are designed to provide a high spatial and temporal precision control signal implementing high degree of freedom real-time prosthetic systems. The development of a Radio Frequency (RF wireless neural interface has the potential to expand the number of applications as well as extend the robustness and longevity compared to wired neural interfaces. However, it is well known that RF signal is absorbed by the body and can result in tissue heating. In this work, numerical studies with analytical validations are performed to provide an assessment of power, heating and specific absorption rate (SAR associated with the wireless RF transmitting within the human head