Timing analysis of the black hole candidate EXO 1846–031 with Insight-HXMT monitoring

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT,NICER and MAXI.This outburst can be classified roughly into four different states.Type-C quasi-periodic oscillations(QPOs)observed by NICER(about 0.1-6 Hz)and Insight-HXMT(about 0.7-8 Hz)are also reported in this work.Meanwhile,we study various physical quantities related to QPO frequency.The QPO rms-frequency relationship in the energy band 1-10 keV indicates that there is a turning pointing in frequency around2 Hz,which is similar to that of GRS 1915+105.A possible hypothesis for the relationship above may be related to the inclination of the source,which may require a high inclination to explain it.The relationships between QPO frequency and QPO rms,hardness,total fractional rms and count rate have also been found in other transient sources,which can indicate that the origin of type-C QPOs is non-thermal.

The influence of the Insight-HXMT/LE time response on timing analysis

The LE is the low energy telescope that is carried on Insight-HXMT.It uses swept charge devices(SCDs)to detect soft X-ray photons.LE’s time response is caused by the structure of the SCDs.With theoretical analysis and Monte Carlo simulations we discuss the influence of LE time response(LTR)on the timing analysis from three aspects:the power spectral density,the pulse profile and the time lag.After the LTR,the value of power spectral density monotonously decreases with the increasing frequency.The power spectral density of a sinusoidal signal reduces by a half at frequency 536 Hz.The corresponding frequency for quasi-periodic oscillation(QPO)signals is 458 Hz.The root mean square(RMS)of QPOs holds a similar behaviour.After the LTR,the centroid frequency and full width at half maxima(FWHM)of QPOs signals do not change.The LTR reduces the RMS of pulse profiles and shifts the pulse phase.In the time domain,the LTR only reduces the peak value of the cross-correlation function while it does not change the peak position;thus it will not affect the result of the time lag.When considering the time lag obtained from two instruments and one among them is LE,a 1.18 ms lag is expected caused by the LTR.The time lag calculated in the frequency domain is the same as that in the time domain.

Effect of Heat Treatment on the Microstructure and Mechanical Properties of the Modified 718 Alloy

M718 alloy with an extra high Mo content of 7.50 wt% which reduced Nb addition and increased A1 and Ti additionswithin the composition specifications of 718 alloy has been designed to increase the service temperature of 718 alloy. Andthe effect of the heat treatment on the microstructure and mechanical properties of M718 alloy has been investigated in thisstudy. The results showed that Laves phase precipitated on the grain boundaries of M718 alloy instead of 6-Ni3Nb phase in718 alloy, and γ″ and γ′ phases precipitated in the matrix of M718 alloy as that in 718 alloy. Increasing the solutiontemperature from 960 to 1050 ℃ noticeably reduced the intergranular precipitation of Laves phase. The precipitation ofLaves phase was appropriate at 1020 ℃ for improving the grain boundary cohesion. Increasing the two-stage agingtemperatures markedly increased the sizes of γ″ and γ′ phases. As a result, the strength of M718 alloy increased.

Element Segregation and Solidification Behavior of a Nb, Ti, Al Co-Strengthened Superalloy ЭК151

The as-cast microstructure, element segregation and solidification behavior of a multi-alloyed superalloy ЭК151 have been investigated. The results show that the severe element segregation leads to the complicated precipitations at the inter-dendritic region, including η-Ni3(Ti, Nb), eutectic(γ + γ’) and Laves, which shows the characteristics of both Ti, Al-strengthened and Nb-strengthened alloys. Differential thermal analysis, heating and quenching tests reveal the solidification sequence as follows: Liquids →γ matrix →(Nb, Ti)C →η-Ni 3(Ti, Nb) →eutectic( γ+γ’) → Laves. The melting points are between 1250 and 1260 °C for(Nb, Ti)C, between 1200 and 1210 °C for η phase, between 1180 and 1190 °C for eutectic(γ+γ’) and Laves. γ’ initially precipitates from matrix at 1150 °C and achieves the maximum precipitation at 1130 °C. According to the microstructure evolution captured during solidification and composition analysis by an energy dispersive spectrometer and electron probe microanalyzer,(Nb, Ti)/Al ratio is put forward to explain the formation of η-Ni3(Ti, Nb) and eutectic( γ+γ’). The solidification of γ matrix increased the Nb, Ti concentration in the residual liquids, so the high(Nb, Ti)/Al ratio would result in the formation of η-Ni3(Ti, Nb); the precipitation of the phase consumed Nb and Ti and decreased the(Nb, Ti)/Al ratio in the liquid, which led to the precipitation of eutectic(γ + γ’). Laves formed by the sides of η-Ni3(Ti, Nb) and in front of the eutectic( γ + γ’) after Al, Ti were further depleted by the two phases and Cr, Co, Mo were rejected to liquids.

An improved technique for global daily sunshine duration estimation using satellite imagery

This paper presems an improved model for global sunshine duration estimation. The methodology incorporates geostationary satellite images by including snow cover information, sun and satellite angles and a trend correction factor for seasons, for the determination of cloud cover index. The effectiveness of the proposed methodology has been tested using Meteosat geostationary satellite images in the visible band with a temporal resolution of 1 h and spatial resolution of 2.5 km×2.5 km, for the Brue Catchment in the southwest of England. Validation results show a significant improvement in the estimation of global sunshine duration by the proposed method as compared to its predecessor （R2 is improved from 0.68 to 0.83, root mean squared error （RMSE） from 2.37 h/d to 1.19 h/d and the mean biased error （MBE） from 0.21 h/d to 0.08 h/d）. Further studies are needed to test this method in other parts of the world with different climate and geographical conditions.

Distribution of Phosphorus and Its Effects on Precipitation Behaviors and Tensile Properties of IN718C Cast Superalloy

The effect of phosphorus on the precipitations of γ",γ’ and δ phases and associated tensile properties in IN718C alloy are investigated in this study.It is revealed that P atoms are dissolved in the grain interior to a relatively high degree and hence influence the precipitation behaviors in the grain interior and improve the tensile strength of IN718C alloy.γ" and γ’ phases did not precipitate in the alloy without P addition during air cooling,while γ" and γ’ phases precipitated in the grain interior during air cooling in the alloys with P addition,and the amounts of γ" and γ’ phases increased with increasing P content.Therefore,the Vickers micro-hardness in the as-cast state increased gradually with increasing P content.In double-aging state,the sizes of γ" and γ’ phases in the alloys with P addition were larger than that in the alloy without P addition,while the sizes were invariable when the P content(wt%)was higher than 0.015.Therefore,the micro-hardness and tensile strength of IN718C alloy treated by double aging increased first and then kept invariable with increasing P content.The precipitations of δ phases both in the grain interior and on grain boundaries were inhibited by P markedly.The inhibitory effect of P on δ phase enhanced gradually with increasing content of P,but the plasticity increased first and then decreased.What is more,the crack tended to propagate into the matrix around the particles(Laves phases and NbC carbides)in the alloys without P addition at the beginning of the tensile fracture,while it tended to propagate along the interfaces between the matrix and those particles in the alloys with P addition,which resulted from the synthetical effect of P on γ" γ’ and δ phases.