In-plane macrocrack initiation of as-deposited, thermally aged, and in-service used thermal barrier coatings (TBCs) with different levels of pores and microcracks, affecting the Young's modulus ...(E^sub c^), have been studied using a newly developed protruded TBC bending technique in conjunction with a finite-element stress analysis. In-plane macrocracking along splat boundaries initiates from a curved edge of protruded TBC under the out-of-plane and shear applied and residual stresses resolved from the in-plane components. The TBC macrocracking is characterized by the critical strain energy density (σ^sub e^*)^sup 2^/E^sub c^, which represents the material propensity, i.e., the ratio of the interfacial cohesive energy to the critical microcrack size (γ^sub f^/a^sub c^), and the residual stress effect. The cracking behavior strongly depends on the type of TBC, subjected to different thermal history, and the substrate machining. Ungrooved substrate specimen tests indicate that while the as-deposited TBC has through-thickness fluctuation in (σ^sub e^*)^sup 2^/E^sub c^, the aged and used TBC exhibits a trough and peak of (σ^sub e^*)^sup 2^/E^sub c^ near the middle section, respectively. In grooved or thinner substrate specimens of the TBCs where the residual stress is partially relieved, cracking further away from the interface occurs at lower and constant (σ^sub e^*)^sup 2^/E^sub c^ representing γ^sub f^/a^sub c^. It is interpreted that the through-thickness variations of (σ^sub e^*)^sup 2^/E^sub c^ in the ungrooved substrate specimen of the various TBCs are more largely affected by the out-of-plane compressive residual stress than γ^sub f^/a^sub c^. PUBLICATION ABSTRACT
Second gadolinium loading to Super-Kamiokande Hiraide, K.; Kameda, J.; Kanemura, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
August 2024, Letnik:
1065
Journal Article
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Odprti dostop
The first loading of gadolinium (Gd) into Super-Kamiokande in 2020 was successful, and the neutron capture efficiency on Gd reached 50%. To further increase the Gd neutron capture efficiency to 75%, ...26.1 tons of Gd2(SO4)3⋅8H2O was additionally loaded into Super-Kamiokande (SK) from May 31 to July 4, 2022. As the amount of loaded Gd2(SO4)3⋅8H2O was doubled compared to the first loading, the capacity of the powder dissolving system was doubled. We also developed new batches of gadolinium sulfate with even further reduced radioactive impurities. In addition, a more efficient screening method was devised and implemented to evaluate these new batches of Gd2(SO4)3⋅8H2O. Following the second loading, the Gd concentration in SK was measured to be 333.5±2.5 ppm via an Atomic Absorption Spectrometer (AAS). From the mean neutron capture time constant of neutrons from an Am/Be calibration source, the Gd concentration was independently measured to be 332.7 ± 6.8(sys.) ± 1.1(stat.) ppm, consistent with the AAS result. Furthermore, during the loading the Gd concentration was monitored continually using the capture time constant of each spallation neutron produced by cosmic-ray muons, and the final neutron capture efficiency was shown to become 1.5 times higher than that of the first loaded phase, as expected.
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•We conducted additional loading of 26.1 tons of Gd2(SO4)3⋅8H2O to Super-Kmaioknade in 2022.•Developed new batches of gadolinium sulfate with reduced radioactive impurities.•Gd concentration in SK measured to be 333.5±2.5 ppm by an AAS.•Gd concentration derived from the neutron capture time is consistent with AAS.•Demonstrated a 1.5 times higher neutron capture efficiency as expected.
Search results for nucleon decays p→e^{+}X, p→μ^{+}X, n→νγ (where X is an invisible, massless particle) as well as dinucleon decays np→e^{+}ν, np→μ^{+}ν, and np→τ^{+}ν in the Super-Kamiokande ...experiment are presented. Using single-ring data from an exposure of 273.4 kton·yr, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of τ_{p→e^{+}X}>7.9×10^{32} yr, τ_{p→μ^{+}X}>4.1×10^{32} yr, τ_{n→νγ}>5.5×10^{32} yr, τ_{np→e^{+}ν}>2.6×10^{32} yr, τ_{np→μ^{+}ν}>2.2×10^{32} yr, and τ_{np→τ^{+}ν}>2.9×10^{31} yr at a 90% confidence level are obtained. Some of these searches are novel.
The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in ...Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.
A study on dynamic impurity–defect interaction in Cu-doped, P-doped and Cu–P-doped ferritic alloys all containing residual S has been made in terms of the influence of post-irradiation annealing ...(PIA: at 573–958
K for 0.1–1000
h) on the intergranular S and P segregation and the microhardness. In a Cu-doped alloy, which shows no P segregation, PIA produced a greater rate and magnitude of S segregation than thermal annealing (TA). Grain-boundary P enrichment was achieved during an early stage of lower-temperature PIA but not during that of TA in P-containing alloys. A Cu–P-doped alloy showed a stronger effect of the PIA on the P segregation rate than a P-doped alloy. Intergranular P desegregation and S segregation concurrently occurred at higher PIA temperatures. There was a tendency for the microhardness to increase with increasing amount of segregated P. The kinetics of the impurity segregation was analyzed using a modified McLean theory. Based on the estimated activation energies, it is shown that the S segregation in the post-irradiation-annealed Cu-doped alloy is controlled by vacancy-enhanced diffusion while the P segregation in P-containing alloys subjected to lower-temperature PIA proceeds via mobile P–interstitial complexes. By applying a Gaussian relaxation model, the P desegregation during prolonged PIA at higher temperatures was found to be assisted by the formation and migration of vacancies.
This paper examines how in-service and thermal environmental attack influence the mechanical properties (22–950°C) of CoNiCrAlY coatings over René 80 substrates in gas turbine blades using a small ...punch (SP) testing technique in conjunction with scanning Auger microprobe analysis. SP tests have clearly demonstrated strong dependence of mechanical degradation of near surface coatings on the elevated temperature environmental condition. The room temperature (RT) ductility in blade coatings decreased with increasing operating time under combined fuels of kerosene and liquefied natural gas (LNG) despite softening in used coatings. All the coatings depicted lower ductility at 825°C in air than at RT but not in vacuum so that the oxidizing environment would produce deleterious effects. In-service operation under the combined fuels led to a two-fold increase in the ductile—brittle transition temperature (DBTT) over coatings observed under mainly LNG because of more extensive oxidation and grain boundary sulfidation. However, the DBTT of coating did not change during thermal ageing at 870°C in air that produced only oxidation. These findings imply that the grain boundary sulfidation would exert a stronger embrittling effect on the CoNiCiAlY coatings than the oxidation.
We present a search for differences in the oscillations of antineutrinos and neutrinos in the Super-Kamiokande-I, -II, and -III atmospheric neutrino sample. Under a two-flavor disappearance model ...with separate mixing parameters between neutrinos and antineutrinos, we find no evidence for a difference in oscillation parameters. Best-fit antineutrino mixing is found to be at (Δm2,sin2 2θ)=(2.0×10(-3) eV2, 1.0) and is consistent with the overall Super-K measurement.
Reactions involving clay minerals during low-grade metamorphism at the depth of an ancient accretionary complex in the Shimanto Belt, Kyushu, Japan, were studied by integrated transmission electron ...microscopy–energy dispersive X-ray spectroscopy and X-ray diffraction analyses of the bulk rock and clay fraction. The analyzed metasediment (the Kitagawa unit) contain an incipient sub-horizontal slaty cleavage. Illite crystallinity data and mica
b dimensions indicate that the conditions of metamorphic deformation were anchizone–epizone grade and intermediate pressure. Cleavage formation was linked to two reactions involving clay minerals: (1) the recrystallization of 1
M-dominant matrix mica, inherited from the original sedimentary fabric, into thick, defect-free 2
M
1 packets along cleavage planes; and (2) the formation of chlorite from 7
Å berthierine. Balanced equations among the clay phases, based on compositional data and their relative abundance, suggest that the decomposition of matrix mica resulted in the formation of paragenetic mica and chlorite along the cleavage planes, without significant elemental outflux. Although a modal increase in phyllosilicates is not indicated by the data, the growth of chlorite and mica along cleavage planes may have a large influence on the rheological properties of a décollement and may be related to the occurrence of the seismic–aseismic transition at ~
350
°C.
►Pervasive slaty cleavages develop in the Kitagawa unit in the Shimanto Belt, Japan. ►Low-grade metamorphism resulted in mica–chlorite paragenesis along the cleavages. ►The reactions proceeded without modal fluctuations of phyllosilicate content. ►Subhorizontal mica–chlorite networks may contribute to aseismic behavior of deep décollement.
Hypervelocity impact experiments are carried out with alumina ceramic targets at impact velocities of 2–4
km/s. The fractal dimension (or roughness exponent) of fragment surfaces is estimated by two ...different methods (different length scales). One is a divider method (large scale) and the other is a gas-absorption one (small scale). The obtained fractal dimensions are different: ∼2.2–2.4 for larger scale and ∼2.5–2.7 for smaller scale. These values are regardless of the degree of fragmentation.
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