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1.
Werner Schmidt 《Microgravity science and technology》2010,22(1):79-85
Various spectroscopic experiments performed on the AIRBUS ZERO G in the years 2002 to 2007 clearly exhibited optical reflection
changes as a result of gravitational changes (GIAC = Gravity Induced Absorption Change) in Phycomyces sporangiophores and corn coleoptiles. GIACs that occurred during flight parabolas in response to hyper- and microgravity
were detected by a micro dual wavelength spectrometer (MDWS) for wavelengths pairs in the visible and the near infrared. We
assume that GIACs indicate redox-changes of electron transport components such as flavins and cytochromes. Because microgravity
on the AIRBUS 300 ZERO G only amounts to moderate values of ±4 ×10 − 2
g, i.e. far below sensitivity of the MDWS, we performed an experiment on the drop tower in Bremen (Germany) that generates
microgravity as low as 4 ×10 − 5
g for 4.7 s. We detected small but significant GIACs during the microgravity phase, different in various specimen. 相似文献
2.
CAI DAYONG ZHANG CHUNLING TANG ZHIGUO DONG HAIFENG WANG PENG 《Bulletin of Materials Science》2011,34(3):525-529
Hot deformation characteristics of a Fe-base superalloy were studied at various temperatures from 1000–1200°C under strain
rates from 0·001–1 s − 1 using hot compression tests. Processing maps for hot working are developed on the basis of the variations of efficiency of
power dissipation with temperature and strain rate and interpreted by a dynamic materials model. Hot deformation equation
was given to characterize the dependence of peak stress on deformation temperature and strain rate. Hot deformation apparent
activation energy of the Fe–24Ni–11Cr–1Mo–3Ti superalloy was determined to be about 499 kJ/mol. The processing maps obtained
in a strain range of 0·1–0·7 were essentially similar, indicating that strain has no significant influence on it. The processing
maps exhibited a clear domain with a maximum of about 40–48% at about 1150°C and 0·001 s − 1. 相似文献
3.
David Brutin ZhiQuiang Zhu Ouamar Rahli JingChang Xie QuiSheng Liu Lounes Tadrist 《Microgravity science and technology》2009,21(Z1):67-76
We present in this paper the results obtained from a parabolic flight campaign regarding the contact angle and the drop interface
behavior of sessile drops created under terrestrial gravity (1g) or in microgravity (μg). This is a preliminary study before further investigations on sessile drops evaporation under microgravity. In this study,
drops are created by the mean of a syringe pump by injection through the substrate. The created drops are recorded using a
video camera to extract the drops contact angles. Three fluids have been used in this study : de-ionized water, HFE-7100 and
FC-72 and two heating surfaces: aluminum and PTFE. The results obtained evidence the feasibility of sessile drop creation
in microgravity even for low surface tension liquids (below 15 mN m − 1) such as FC-72 and HFE-7100. We also evidence the contact angle behavior depending of the drop diameter and the gravity level.
A second objective of this study is to analyze the drop interface shape in microgravity. The goal of the these experiments
is to obtain reference data on the sessile drop behavior in microgravity for future experiments to be performed in an French-Chinese
scientific instrument (IMPACHT). 相似文献
4.
5.
Polyvinyl alcohol (PVA)–polyethylene glycol (PEG) based solid polymer blend electrolytes with magnesium nitrate have been
prepared by the solution cast technique. Impedance spectroscopic technique has been used, to characterize these polymer electrolytes.
Complex impedance analysis was used to calculate bulk resistance of the polymer electrolytes. The a.c.-impedance data reveal
that the ionic conductivity of PVA–PEG–Mg(NO3)2 system is changed with the concentration of magnesium nitrate, maximum conductivity of 9·63 × 10 − 5 S/cm at room temperature was observed for the system of PVA–PEG–Mg(NO3)2 (35–35–30). However, ionic conductivity of the above system increased with the increase of temperature, and the highest conductivity
of 1·71 × 10 − 3 S/cm was observed at 100°C. The effect of ionic conductivity of polymer blend electrolytes was measured by varying the temperature
ranging from 303 to 373 K. The variation of imaginary and real parts of dielectric constant with frequency was studied. 相似文献
6.
Y. Kumashiro K. Nakamura T. Enomoto M. Tanaka 《Journal of Materials Science: Materials in Electronics》2011,22(8):966-973
The chemical vapor deposited (CVD) BP films on Si(100) (190 nm)/SiO
x
(370 nm)/Si(100) (625 μm) (SOI) and sapphire (R-plane) (600 μm) substrates were prepared by the thermal decomposition of
the B2H6–PH3–H2 system in the temperature range of 800–1050 °C for the deposition time of 1.5 h. The BP films were epitaxially grown on the
SOI substrate, but a two-step growth method, i.e., a buffer layer at lower temperature and sequent CVD process at 1000 °C
for 1.5 h was effective for obtaining a smooth film on the sapphire substrate. The electrical conduction types and electrical
properties of these films depended on the growth temperature, gases flow rates and substrates. The thermal conductivity of
the film could be replaced by the substrate, so that the calculated thermoelectric figure-of-merit (Z) for the BP films on the SOI substrate was 10−4–10−3/K at 700–1000 K. Those on the sapphire substrate were 10−6–10−5/K for the direct growth and 10−5–10−4/K for the two-step growth at 700–900 K, indicating that the film on a sapphire by two-step growth would reduce the defect
concentrations and promote the electrical conductivity. 相似文献
7.
Marina B. Ruggles-Wrenn Tufan Yeleser Geoff E. Fair Janet B. Davis 《Applied Composite Materials》2009,16(6):379-392
The tensile creep behavior of a N610™/LaPO4/Al2O3 composite was investigated at 1,100°C in laboratory air and in steam. The composite consists of a porous alumina matrix reinforced
with Nextel 610 fibers woven in an eight-harness satin weave fabric and coated with monazite. The tensile stress-strain behavior
was investigated and the tensile properties measured at 1,100°C. The addition of monazite coating resulted in ~33% improvement
in ultimate tensile strength (UTS) at 1,100°C. Tensile creep behavior was examined for creep stresses in the 32–72 MPa range.
Primary and secondary creep regimes were observed in all tests. Minimum creep rate was reached in all tests. In air, creep
strains remained below 0.8% and creep strain rates approached 2 × 10−8 s−1. Creep run-out defined as 100 h at creep stress was achieved in all tests conducted in air. The presence of steam accelerated
creep rates and significantly reduced creep lifetimes. In steam, creep strain reached 2.25%, and creep strain rate approached
2.6 × 10−6 s−1. In steam, creep run-out was not achieved. The retained strength and modulus of all specimens that achieved run-out were
characterized. Comparison with results obtained for N610™/Al2O3 (control) specimens revealed that the use of the monazite coating resulted in considerable improvement in creep resistance
at 1,100°C both in air and in steam. Composite microstructure, as well as damage and failure mechanisms were investigated. 相似文献
8.
N. A. Sobolev M. A. Oliveira R. M. Rubinger A. J. Neves M. C. Carmo V. P. Lesnikov V. V. Podolskii Y. A. Danilov E. S. Demidov G. N. Kakazei 《Journal of Superconductivity and Novel Magnetism》2007,20(6):399-403
The electrical and magnetic properties of GaSb:Mn layers deposited on (100)GaAs substrates from a laser plasma in vacuum have
been studied. It is shown that the films deposited at 200–440 °C are mosaic single crystalline and epitaxial to the substrate,
with p-type conduction. Manganese-doped layers had a hole concentration higher than 1×1019 cm−3 and fairly high values of mobility (up to 40 cm2/V s at 300 K). The layers grown at 200 °C exhibited an anomalous Hall effect up to approximately room temperature. On the
contrary, a normal Hall effect was observed in the layers grown at 440 °C. Ferromagnetic resonance measurements have revealed
the existence of ferromagnetism in the sample grown at 200 °C. The transition temperature is close to room temperature, in
full agreement with the Hall data. In the sample grown at 440 °C, the formation of ferromagnetic clusters has tentatively
been concluded. 相似文献
9.
The hot working behavior of a as-homogenized Mg–Zn–Y–Zr alloy has been investigated in the temperature range 200–400°C and
strain rate range 0.0015–7.5 s−1 using processing map. The power dissipation map reveals that a domain of dynamic recrystallisation (DRX) in the temperature
range 300–400°C and strain rate range 0.0015–0.15 s−1, with its peak efficiency of 38% at 350°C and 0.0015 s−1, which are the optimum hot working parameters. The apparent activation energy in the hot deformation process is 148 ± 3 KJ/mol
that is larger than that of ZK60 alloy because of the obstruction of Y atoms for diffusion. DRX model indicates that DRX of
Mg–Zn–Y–Zr alloy is controlled by the rate of nucleation, which is lower one order of magnitude than growth. And the rate
of nucleation depends on the process of mechanical recovery by cross-slip of screw dislocations. 相似文献
10.
In this work, pH dependent evolution of tungsten oxide (WO3) nanostructures is being reported along with physical characteristics. The synthesis was carried out via an inexpensive solvothermal
cum chemical reduction route, with sodium tungstate (Na2WO4) and cetyl trimethyl ammonium bromide (C19H42NBr) as main reactants. The X-ray diffraction, together with transmission electron microscopic studies have revealed formation
of regular polyhedral nanocrystalline structures and fractals as one goes from higher pH (= 5·5) to lower pH (= 2) values.
The average crystallite size, as calculated through Williamson–Hall plots, was varied within 2·8–6·8 nm for different pH samples.
Fourier transform infrared spectroscopy reveals in-plane bending vibration δ (W–OH), observable at ∼1630 cm − 1 and strong stretching ν (W–O–W) located at ∼814 cm − 1. Raman spectroscopy has divulged WO3 Raman active optical phonon modes positioned at ∼717 and 805 cm − 1. The thermochromic and photochromic properties of the nanoscale WO3 sample prepared at pH = 5·5, are also highlighted. 相似文献
11.
Saket Asthana 《Bulletin of Materials Science》2011,34(2):279-282
The magnetic and transport properties of the compounds Nd0·5Sr0·5Mn1-x_{{\rm 1}-{x}}Cox_{{x}}O3 (x = 0·1, 0·3 and 0·5), synthesized by citrate–gel route have been investigated. The spin transition in cobaltates at low temperatures
affects the magnetic as well as transport properties. The irreversibility behaviour between the zero-field cooled (ZFC) and
field cooled (FC) magnetization as a function of temperature becomes stronger with increasing Co content. This is understood
on the basis of glassy behaviour, which becomes more robust with increasing Co substitution. The non-saturating M–H behaviour
indicates strong magnetic inhomogeneities which may cause the magnetic phase separation at the nanoscopic length scale. The
double exchange interaction is stronger between Mn3 + –O2 − –Mn4 + as compared to Co3 + –O2 − –Co4 + pairs. Co-substitution suppresses the double exchange which will lead to cluster/spin glass like behaviour as well as semiconducting
features due to localization of charge carriers (mobile eg{e}_{\rm g} electrons). 相似文献
12.
Renzhong Xue Tao Li Zhenping Chen Yuncai Xue Junhong Hao Yuanqing Chen 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1797-1801
YBa2Cu3O7−x
(YBCO) films were prepared on LaAlO3 single crystal substrate under various firing temperatures (750–800 °C) in the crystallization process by metalorganic deposition
(MOD) method. The coating solution was made by mixing the fluorine-free precursor solution containing Y and Cu with Ba–fluorine
precursor solution (Ba-TFA). The effect of firing temperature on the structure and superconducting properties of YBCO films
was systematically investigated. The results indicated that YBCO-films were smooth, crack-free, exhibited good textures and
retain high oxygen content according to the XRD and SEM images. Sample of YBCO-film fired at 780 °C showed highest superconducting
properties including high critical transition temperature T
c=89 K, sharp transition temperature ΔT
c<1 K, and critical current density J
c=2.8 MA cm−2, which are attributable to excellent in-plane textures and dense microstructures with good connectivity between the grains. 相似文献
13.
Eldon R. Rene D. V. S. Murthy T. Swaminathan 《Clean Technologies and Environmental Policy》2010,12(5):525-535
Biofiltration is an aerobic degradation process in which a well-humidified contaminated air stream is passed through a porous
packed medium that supports a thriving population of microbes. The removal of benzene vapor was investigated in a laboratory-scale
biofilter packed with compost, inoculated with a mixed microbial consortium. This biofilter was operated continuously in six
different phases for a period of 8 months at different flow rates, 0.024–0.144 m3 h−1 with benzene concentrations ranging up to 1.7 g m−3. Under steady-state conditions, the removal efficiencies (REs) in the biofilter was consistently greater than 78% when benzene
loading was less than 20 g m−3 h−1. The maximum elimination capacity (EC) achieved in this study is 64 g m−3 h−1 at an inlet loading rate of 128 g m−3 h−1. The response of the biofilter to shutdown, restart operations and fluctuations in inlet concentration, and flow rate was
determined by subjecting the biofilter to inlet loads of up to 120 g m−3 h−1. The biofilter responded effectively to these loading conditions and was found to recover rapidly. The results from this
study suggest that a compost biofilter is effective in treating benzene vapor under steady- and transient-conditions. 相似文献
14.
YBa2Cu3O7−x
(YBCO) films were fabricated on LaAlO3 (LAO) substrate under various firing temperatures (760–870 °C) in the crystallization process by metalorganic deposition
(MOD) method using trifluoroacetates. The effect of firing temperature on the structure and properties of YBCO films was systematically
investigated. According to the XRD and SEM images, the films fired at low temperature (760–800 °C) showed poor electrical
performance due to rough surfaces and impurity phases. However, the films fired at 850 °C showed the highest critical temperature
of 90 K and the highest J
c
of 3.1 MA/cm2 which attribute to the formation of a purer YBCO phase, fewer pores, and stronger biaxial texture. 相似文献
15.
A. Hashimoto K. Iwasaki N. Nakasugi M. Nakajima O. Yagi 《Clean Technologies and Environmental Policy》2000,2(3):167-173
Mycobacterium spp. strains TA5 and TA27 (ethane-utilizing bacteria), which can degrade trichloroethylene (TCE) and 1,1,1-trichloroethane
(1,1,1-TCA), were isolated from soil. Both bacteria could cometabolically degrade dichloromethane, chloroform, 1,1-dichloroethane,
1,2-dichloroethane, 1,1,1-TCA, 1,1,2-TCA, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, and TCE with ethane as a carbon source. They could not degrade carbon tetrachloride, freon 113, or
tetrachloroethylene. The TCE degradation characteristics of strain TA27 were determined. Under a head-space gas containing
3% ethane, strain TA27 degraded more than 95% of TCE at an initial concentration of 1 mg l–1 within 3 days. We observed good growth and TCE degradation between 25 and 35 °C. At an initial TCE concentration of 30 mg l–1, it degraded 30% of TCE within 7 days. Although growth was inhibited for more than 50 mg l–1 TCE at 3% ethane concentration, good growth and 50% degradation of TCE were observed at 12% ethane concentration within 14 days.
High ethane concentration may mitigate the toxicity of TCE.
Received: 24 January 2000 / Accepted: 10 March 2000 相似文献
16.
Z. L. Ning G. J. Wang F. Y. Cao J. F. Sun J. F. Du 《Journal of Materials Science》2009,44(16):4264-4269
The engineering stress versus engineering strain curves for a Mg–2.54Nd–0.26Zn–0.32Zr cast alloy were measured by Gleeble-1500D
thermo-simulation machine in the temperature range of room temperature to 400 °C at initial strain rates of 10−4–10−2 s−1. The effects of strain rate on stress, elongation to facture, and section shrinkage were analyzed. The fractograph morphologies
were investigated by using SEM. It was found that strain rate has little effect on engineering stress for the Mg–2.54Nd–0.26Zn–0.32Zr
alloy when tested at below 250 °C. When tested at above 250 °C, low strain rate resulted in decreased engineering stress,
increased elongation to fracture, and section shrinkage. The fracture mode is cleavage fracture with elongated dimple below
250 °C and changes to typical ductile failure when tested above 250 °C. 相似文献
17.
O. P. Ostash I. M. Andreiko V. V. Kulyk I. H. Uzlov K. I. Uzlov O. I. Babachenko 《Materials Science》2008,44(4):524-529
We have established that the steels of high-and medium-strength railroad wheels in the presence of fatigue-crack-type defects
are susceptible to low-temperature (up to −60°C) embrittlement only for high amplitudes of cyclic loading, when the growth
rate of a fatigue crack exceeds 10−7 m/cycle. Here, the temperature of cyclic ductile-brittle transition for these steels constitutes −20 and −40°C, respectively.
We have shown that the permissible and temperature-independent (within the range from 20 to −60°C ) size of a fatigue crack
on the rim surface of the wheels under study does not exceed 1.9–2.5 mm for a hoop stress range of 400 MPa and 0.6–0.8 mm
for 700 MPa. These results enable us to conclude that, for high-strength railroad wheels working at low climatic temperatures,
it is necessary to carry out their flaw inspection with sensitivity to surface cracks of millimeter size.
__________
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 4, pp. 52–57, July–August, 2008. 相似文献
18.
We developed an unmanned air vehicle (UAV) suitable for small parabolic-flight experiments. The flight speed of 100 m s − 1 is sufficient for zero-gravity parabolas of 16 s duration. The flight path’s length of slightly more than 1 km and 400 m
difference in altitude is suitable for ground controlled or supervised flights. Since this fits within the limits set for
model aircraft, no additional clearance is required for operation. Our UAV provides a cost-effective platform readily available
for low-g experiments, which can be performed locally without major preparation. A payload with a size of up to 0.9 ×0.3 ×0.3 m3 and a mass of ∼5 kg can be exposed to 0 g
0–5 g
0, with g
0 being the gravitational acceleration of the Earth. Flight-duration depends on the desired acceleration level, e.g. 17 s at
0.17 g
0 (lunar surface level) or 21 s at 0.38 g
0 (Martian surface level). The aircraft has a mass of 25 kg (including payload) and a wingspan of 2 m. It is powered by a jet
engine with an exhaust speed of 450 m s − 1 providing a thrust of 180 N. The parabolic-flight curves are automated by exploiting the advantages of sophisticated micro-electronics
to minimize acceleration errors. 相似文献
19.
M. A. Chougule S. G. Pawar P. R. Godse R. D. Sakhare Shashwati Sen V. B. Patil 《Journal of Materials Science: Materials in Electronics》2012,23(3):772-778
Nanocrystalline Co3O4 thin films were prepared on glass substrates by using sol–gel spin coating technique. The effect of annealing temperature
(400–700 °C) on structural, morphological, electrical and optical properties of Co3O4 thin films were studied by X-ray diffraction (XRD), Scanning Electron Microscopy, Electrical conductivity and UV–visible
Spectroscopy. XRD measurements show that all the films are nanocrystallized in the cubic spinel structure and present a random
orientation. The crystallite size increases with increasing annealing temperature (53–69 nm). These modifications influence
the optical properties. The morphology of the sol–gel derived Co3O4 shows nanocrystalline grains with some overgrown clusters and it varies with annealing temperature. The optical band gap
has been determined from the absorption coefficient. We found that the optical band gap energy decreases from 2.58 to 2.07 eV
with increasing annealing temperature between 400 and 700 °C. These mean that the optical quality of Co3O4 films is improved by annealing. The dc electrical conductivity of Co3O4 thin films were increased from 10−4 to 10−2 (Ω cm)−1 with increase in annealing temperature. The electron carrier concentration (n) and mobility (μ) of Co3O4 films annealed at 400–700 °C were estimated to be of the order of 2.4–4.5 × 1019 cm−3 and 5.2–7.0 × 10−5 cm2 V−1 s−1 respectively. It is observed that Co3O4 thin film annealing at 700 °C after deposition provide a smooth and flat texture suited for optoelectronic applications. 相似文献
20.
Polycrystalline samples of the mixed nanoferrites, Li0·5 + 0·5x
Ti
x
Fe2·5 − 1·5x
O4 (0·02 ≤ x ≤ 0·1), were prepared by combustion method at lower temperatures compared to the conventional high temperature sintering
for the first time at low temperatures, using PEG which acts as a new fuel and oxidant. XRD patterns reveal a single-phase
cubic spinel structure. The as synthesized Li–Ti ferrites are in nanocrystalline phase. The crystallite size was found to
be in the range 16–27 nm. SEM images reveal rod-like morphology in all the samples with a discontinuous grain growth. The
B–H loops have been traced using VSM technique, for all the compositions, at room temperature and the hysteresis parameters
are calculated. Saturation magnetization decreases with increase in Ti content due to the fact that the Ti4 + ion, which is a non-magnetic ion, replaces a magnetic Fe3 + ion. The hysteresis loops show clear saturation at an applied field of ±10 kOe and the loops are highly symmetric in nature.
The cation distribution is known indirectly by using saturation magnetization values. 相似文献