Microstructures and mechanical properties of Co-9.5Al-5W-16Ni-6Cr-xTa (at% where x=0, 1.8, 2.8, named as 0Ta, 1.8Ta and 2.8Ta) alloys are investigated. Microstructures of heat-treated samples are ...composed of gamma and cubical gamma ' precipitates. The gamma ' solvus temperature increases obviously with Ta additions. The yield strength as well as creep strength is improved with the addition of Ta. Ta additions affect the high-temperature tensile deformation mechanism. The gamma ' phase of the three alloys is rafted along the tensile axis direction during creep tests at 900 degree C. The creep strength of 2.8Ta alloy is approaching the level of a first-generation Ni-base single-crystal superalloy.
ABSTRACT
In this paper, we presented a detailed timing analysis of a prominent outburst of 4U 0115+63 detected by Insight-HXMT in 2017 August. The spin period of the neutron star was determined to be ...3.613 98 ± 0.000 02 s at MJD 57978. We measured the period variability and extract the orbital elements of the binary system. The angle of periastron evolved with a rate of $0.048^\circ \pm 0.003^\circ \rm \, yr^{-1}$. The light curves are folded to sketch the pulse profiles in different energy ranges. A multipeak structure in 1–10 keV is clearly illustrated. We introduced wavelet analysis into our data analysis procedures to study quasi-periodic oscillation (QPO) signals and perform a detailed wavelet analysis in many different energy ranges. Through the wavelet spectra, we report the discovery of a QPO at the frequency of ∼10 mHz. In addition, the X-ray light curves showed multiple QPOs in the period of ∼16–32 and ∼67–200 s. We found that the ∼100 s QPO was significant in most of the observations and energies. There exist positive relations between X-ray luminosity and their Q-factors and S-factors, while the QPO periods have no correlation with X-ray luminosity. In wavelet phase maps, we found that the pulse phase of ∼67–200 s QPO is drifting frequently while that of ∼16–32 s QPO is scarcely drifting. The dissipation of oscillations from high energy to low energy was also observed. These features of QPOs in 4U 0115+63 provide a new challenge to our understanding of their physical origins.
Abstract
Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we have recorded over 1.2 × 10
4
single pulses from PSR B0823+26 (J0826+2637) at 1.25 GHz with 500 MHz bandwidth. ...These high-sensitivity observations detected with FAST are unprecedented. We investigated potentially interesting emission features by analyzing the polarimetric individual pulses during the bright state. The average pulse profile has a weak postcursor component and a wide interpulse along with a narrow main pulse. The pulse energy distribution of the main pulse shows the presence of triple emission modes. When the emission ceases in the main pulse component, low-level emission in the interpulse component is detected, whereas the absence of any emission in the postcursor component is shown. In the postcursor emission region, bright pulses are detected in 422 rotations with the relative pulse energy described by a power-law distribution with index of −2.52 ± 0.09, while the peak flux density ratio appears to follow a logarithmic normal distribution. The intervals between bright pulses can be described with a Poisson process with the occurrence rate estimated to be one bright pulse every 14 s. The fluctuation spectral analysis reveals the existence of a form of periodic amplitude modulation unrelated to subpulse drifting in both the main pulse and interpulse components. Furthermore, the modulation patterns in the main pulse and interpulse are found to be locked in pulse longitude, signifying some information transfer between the two magnetic polar regions.
•New phase (Co,W,Ta)3B2 was found in the transient liquid phase joint.•The preferred growth orientation of the borides was 〈0 0 1〉matrix.•Borides enjoy a significant orientation relationship with the ...substrate.•The direction of concentration gradient of boron govern growth orientation.
γ′-Strengthened Co-base single crystal superalloy was jointed with B-Ni76CrWB alloy powder by transient liquid phase bonding. The growth mechanism of the borides of preferred orientation formed in the diffusion affect zone of the joint was investigated. Results indicated that the prepared borides were (Co,W,Ta)3B2 and were long plate-shaped in three dimensions. The preferred growth orientation of the borides in the diffusion affect zone of transient liquid phase joint was 〈0 0 1〉 matrix, enjoying a significant orientation relationship with the substrate.
ABSTRACT
The study aimed to determine the effects of methionine hydroxy analog chelate zinc on the tibia quality, mineral deposit, apparent retention of nutrients, and liver metallothionein (MT) ...expression level of aged laying hens. A total of 960 layers (Hy-Line Grey, 57 wk old) were randomly assigned into 4 groups, and each group had 8 replicates of 30 hens. During the first 2 wk, groups were fed a basal diet without extra zinc (Zn: 35.08 mg/kg). During the ensuing 14 wk, 4 levels of Zn (inorganic Zn: 80 mg/kg; organic Zn: 20, 40, 80 mg/kg) were added to the diet. The results indicated that both the Zn source and level did influence tibia strength and calcium (Ca) and Zn concentrations of tibia (P < 0.05), whereas there were no differences in the copper (Cu) and phosphorus (P) concentrations of the tibia and the tibia length (P > 0.05). Moreover, dietary supplementation with 40 or 80 mg/kg of organic Zn showed higher Zn and Ca concentrations in the tibia and higher tibia strength. The Cu concentration in the liver showed no difference among the 4 treatments, whereas the Zn concentration in the liver increased with the increasing Zn level. The apparent retention of P, iron (Fe), and manganese (Mn) was not affected by the Zn level or source (P > 0.05). However, the organic Zn group increased the apparent retention of Cu, Zn, Ca, crude protein (CP), and energy, and the group supplemented with 40 or 80 mg/kg of organic Zn obtained significant effects (P < 0.05). Moreover, dietary supplementation with 40 or 80 mg/kg organic Zn increased the MT mRNA expression of the liver at week 72, whereas 20 mg/kg of organic Zn decreased it (P < 0.05). In conclusion, this study suggested that an optimum dietary (40 mg/kg) organic Zn level plays a key role in promoting the apparent retention of minerals and nutrients, trace element deposit, and MT mRNA expression.
An experimental investigation into noise reduction of supersonic jets through nozzle trailing-edge modifications was conducted, whereby far-field acoustic measurements were captured for two different ...stepped nozzles under two distinct under-expanded conditions. When compared to a baseline nozzle, results show that stepped nozzles lead to significant noise reductions at certain polar and azimuthal angles. In particular, a maximum noise reduction of 6 dB is observed for the longest stepped nozzle at a nozzle-pressure-ratio of 4 and 0° azimuthal angle. Spectral analysis shows that the noise reduction is mainly due to reduction in broadband shock associated noise and elimination of jet screech phenomenon. Abrupt changes in nozzle lip lengths of the stepped nozzles appear to disrupt acoustic feedback loop, thus resulting in screech cessation. Qualitative schlieren imaging and quantitative schlieren measurements were subsequently performed to correlate the shock structures and density gradient fields with the resulting noise components. Unlike those produced by the baseline nozzle, shock structures generated by the stepped nozzles are highly irregular and the jet plumes undergo discernible deflections. Lastly, the reduction in broadband shock associated noise is related to the lower shock strengths, as demonstrated by the density gradient profiles.
Glitches correspond to sudden jumps of rotation frequency ( ) and its derivative ( ) of pulsars, the origin of which remains not well understood yet, partly because the jump processes of most ...glitches are not well time-resolved. There are three large glitches of the Crab pulsar, detected in 1989, 1996, and 2017, which were found to have delayed spin-up processes before the normal recovery processes. Here we report two additional glitches of this pulsar that occurred in 2004 and 2011 for which we discovered delayed spin-up processes, and present refined parameters of the largest glitch, which occurred in 2017. The initial rising time of the glitch is determined as <0.48 hr. The two glitches that occurred in 2004 and 2011 had delayed spin-up time scales (τ1) of 1.7 0.8 days and 1.6 0.4 days, respectively. We also carried out a statistical study of these five glitches with observed spin-up processes. We find that the Δ versus relation of these five glitches is similar to those with no detected delayed spin-up process, indicating that they are similar to the others in nature except that they have larger amplitudes. For these five glitches, the amplitudes of the delayed spin-up process ( ) and recovery process (Δ d2), their time scales (τ1, τ2), and permanent changes in spin frequency (Δ p) and total frequency step (Δ g) have positive correlations. From these correlations, we suggest that the delayed spin-up processes are common for all glitches, but are too short and thus difficult to be detected for most glitches.
Abstract
We present a study of timing properties of the accreting pulsar 2S 1417-624 observed during its 2018 outburst, based on Swift/BAT, Fermi/GBM, Insight-HXMT and NICER observations. We report a ...dramatic change of the pulse profiles with luminosity. The morphology of the profile in the range 0.2-10.0 keV switches from double to triple peaks at ∼2.5 $\rm \times 10^{37}{\it D}_{10}^2\ erg\ s^{-1}$ and from triple to quadruple peaks at ∼7 $\rm \times 10^{37}{\it D}_{10}^2\ erg\ s^{-1}$. The profile at high energies (25-100 keV) shows significant evolutions as well. We explain this phenomenon according to existing theoretical models. We argue that the first change is related to the transition from the sub to the super-critical accretion regime, while the second to the transition of the accretion disc from the gas-dominated to the radiation pressure-dominated state. Considering the spin-up as well due to the accretion torque, this interpretation allows to estimate the magnetic field self-consistently at ∼7 × 1012 G.
A novel plate-shaped ω phase formed in a Ti–30Nb–3Pd (wt.%) shape memory alloy during quenching in addition to the formation of α″ martensite, retained β and fine-particle ω phases. The ω and β ...phases were fully transformed to α″ with a (1
1
0)
α″ twin structure during room temperature deformation.
Herein, the effect of Ta addition (0 and 2 wt pct) on the tensile properties of a Ni-Co base superalloy was investigated in the temperature range of 23–900 °C. The results revealed that the addition ...of Ta improved the strength of the superalloy at all experimental temperatures and increased the plasticity at 760 °C. In addition, the microstructural observations indicate that Ta addition promoted the precipitation of
γ
′ precipitates, as well as the precipitation of (Ta, Ti)-rich MC carbides. The addition of 2 wt pct Ta promoted twinning and, thus, transformed the fracture mechanism of the alloy from an intergranular brittle fracture to a mixed ductile and brittle fracture at 760 °C. Furthermore, the tensile properties and the related microstructures, deformation mechanisms, and fracture mechanisms of the experimental alloys are discussed. Finally, we demonstrated that the combined effect of the increase in the grain boundary strength, the reduction in the critical resolved shear stress, and the promotion of twinning induced the synchronous improvement of strength and plasticity of the alloy at 760 °C.
PDF
