Search

ABSTRACTPulsed vapour fluxes with proper controlled time duration were proved to be an important controlling dimension for the deposition of a desired thin film. In this work, deep oscillation magnetron sputtering was employed to tailor the ionized pulsed flux for Nb and Cr thin film grown on AISI 304 stainless steel. Through tuning the micropulse oscillating voltage-off time from 10 to 40 μs, Nb and Cr thin films showed an obvious variation on microstructure owing to the deposition flux transited from continuous to chopped ones. The deposited Nb thin films showed Nb(110) preferred orientation experienced a nanocrystallization process with compressive residual stress showing a slightly decrease. While Cr thin films showed Cr(110) preferred orientation without an obvious nancrystallization trend with its compressive stress turning to be tensile. The tailoring of the microstructure and properties relied on interval time between the two interrupted ionized deposition flux.

Pulsed vapour fluxes with proper controlled time duration were proved to be an important controlling dimension for the deposition of a desired thin film. In this work, deep oscillation magnetron sputtering was employed to tailor the ionized pulsed flux for Nb and Cr thin film grown on AISI 304 stainless steel. Through tuning the micropulse oscillating voltage-off time from 10 to 40 µs, Nb and Cr thin films showed an obvious variation on microstructure owing to the deposition flux transited from continuous to chopped ones. The deposited Nb thin films showed Nb(110) preferred orientation experienced a nanocrystallization process with compressive residual stress showing a slightly decrease. While Cr thin films showed Cr(110) preferred orientation without an obvious nancrystallization trend with its compressive stress turning to be tensile. The tailoring of the microstructure and properties relied on interval time between the two interrupted ionized deposition flux.

Carbide-free bainitic steels with the bainitic ferrite (BF) as matrix constituent have been widely used and manufactured. The mixed microstructure of pre-formed martensite (M), BF, and retained austenite (RA) was obtained by quenching for a short time below the martensitic transformation temperature followed by austempering. A similar amount of fresh martensite was obtained by interrupted austempering at the same temperature. Results show that the carbon distribution among these constituents in the mixed microstructure plays a major role in controlling mechanical properties. The carbon content of M and BF in the M-BF-RA microstructure is lower than that of BF-M-RA microstructure, while that of RA was reversed. Mechanical properties of the M-BF-RA microstructure exhibit higher toughness, higher product of strength and elongation as well as higher yield ratio, rather than strength, compared to that of the BF-M-RA microstructure. It can be attributed to toughened pre-formed martensite with low carbon content and mechanical stable RA with high carbon content. In addition, the pre-formed martensite decreases the block size, leading to the increase of high angle grain boundaries, which further improves toughness. The high carbon fresh martensite BF increased the strength of the BF-M-RA microstructure, but sharply decreases ductility and toughness.

We use the Insight-HXMT data collected during the 2019 outburst from X-ray pulsar 4U 1901+03 to complement the orbital parameters reported by Fermi/GBM. Using the Insight-HXMT, we examine the correlation between the derivative of the intrinsic spin frequency and bolometric flux based on accretion torque models. It was found that the pulse profiles significantly evolve during the outburst. The existence of two types of the profile's pattern discovered in the Insight-HXMT data indicates that this source experienced transition between a super-critical and a sub-critical accretion regimes during its 2019 outburst. Based on the evolution of the pulse profiles and the torque model, we derive the distance to 4U 1901+03 as 12.4±0.2kpc.

We study the 2018 outburst of Aql X-1 via the monitor of all sky X-ray image (MAXI) data. We show that the outburst starting in February 2018 is a member of short-lowclass in the frame of outburst duration and the peak count rate although the outburst morphology is slightly different from the other fast-rise-exponential-decay (FRED) type outbursts with a milder rising stage. We study the partial accretion in the weak propeller stage of Aql X-1 via the MAXI data of the 2018 outburst. We report on the spectral analysis of 3 observations of Aquila X-1 obtained by Insight – hard X-ray modulation telescope (Insight-HXMT) during the late decay stage of the 2018 outburst. We discuss that the data taken by Insight-HXMT is just after the transition to the weak propeller stage. Our analysis shows the necessity of a comptonization component to take into account the existence of an electron cloud resulting photons partly up-scattered.

We present a detailed timing study of the brightest persistent X-ray source Sco X-1 using the data collected by the Hard X-ray Modulation Telescope (Insight-HXMT) from July 2017 to August 2018. A complete Z-track hardness-intensity diagram (HID) is obtained. The normal branch oscillations (NBOs) at ∼ 6 Hz in the lower part of the normal branch (NB) and the flare branch oscillations (FBOs) at ∼ 16 Hz in the beginning part of the flaring branch (FB) are found in observations with the Low Energy X-ray Telescope (LE) and the Medium Energy X-ray Telescope (ME) of Insight-HXMT, while the horizontal branch oscillations (HBOs) at ∼ 40 Hz and the kilohertz quasi-periodic oscillations (kHz QPOs) at ∼ 800 Hz are found simultaneously above 20 keV for the first time on the horizontal branch (HB) by the High Energy X-ray Telescope (HE) and ME. We find that for all types of the observed QPOs, the centroid frequencies are independent of energy, while the root mean square (rms) increases with energy; the centroid frequencies of both the HBOs and kHz QPOs increase along the Z-track from the top to the bottom of the HB; and the NBOs show soft phase lags increasing with energy. A continuous QPO transition from the FB to NB in ∼ 200 s are also detected. Our results indicate that the non-thermal emission is the origin of all types of QPOs, the innermost region of the accretion disk is non-thermal in nature, and the corona is nonhomogeneous geometrically.

A new black hole X-ray binary (BHXRB) MAXI J1535-571 was discovered by MAXI during its outburst in 2017. Using observations taken by the first Chinese X-ray satellite, the Hard X-ray Modulation Telescope (dubbed as Insight-HXMT), we perform a joint spectral analysis (2-150 keV) in both energy and time domains. The energy spectra provide the essential input for probing the intrinsic Quasi-Periodic Oscillation (QPO) fractional rms spectra (FRS). Our results show that during the intermediate state, the energy spectra are in general consistent with those reported by Swift/XRT and NuSTAR. However, the QPO FRS become harder and the FRS residuals may suggest the presence of either an additional power-law component in the energy spectrum or a turn-over in the intrinsic QPO FRS at high energies.

The evidences for the influence of thermonuclear (type-I) X-ray bursts upon the surrounding environments in neutron star low-mass X-ray binaries (LMXB) were detected previously via spectral and timing analyses. Benefitting from a broad energy coverage of Insight-HXMT, we analyze one photospheric radius expansion (PRE) burst, and find an emission excess at soft X-rays. Our spectral analysis shows that, such an excess is not likely relevant to the disk reflection induced by the burst emission and can be attributed to an enhanced pre-burst/persistent emission. We find that the burst and enhanced persistent emissions sum up to exceed Eddington luminosity by ∼ 40 percentages. We speculate that the enhanced emission is from a region beyond the PRE radius, or through the Comptonization of the corona.

The long-term evolution of the centroid energy of the CRSF in Her X-1 is still a mystery. We report a new measurement from a campaign between Insight-HXMT and NuSTARperformed in February 2018. Generally, the two satellites show well consistent results of timing and spectral properties. The joint spectral analysis confirms that the previously observed long decay phase has ended, and that the line energy instead keeps constant around 37.5keV after flux correction.

Roll forming has been widely used to manufacture constant cross-section products because of high quality, efficiency and low cost. It is quite epidemic in producing automobile parts made of advanced high strength steels (AHSS) nowadays. However, with the development of the vehicle industry and diversity of the products, variable cross-section profiles have attracted more and more attention. The traditional roll forming technique is difficult to meet the requirements. Chain-die forming which was introduced in recent years makes it possible. Chain-die forming is an extension of roll forming and its key characteristic is enlarging the rotation radii of the moulds, by which the deformation zone is extended. The study focused on the finite element simulations of Chain-die forming U profiles with variable cross-section, including variable width and height. The feasibility of Chain-die forming producing variable cross-section products was verified by the perfect simulation results. The advantage of Chain-die forming was that there was no need to design the intermediate moulds except the finished-profile ones, which reduced the mould quantity immensely. Then the cost was lower.

The surface topography of engineering components is known to affect fatigue behaviour. However, defining topography based on the average roughness (Ra) parameter is considered to be inadequate when correlating to fatigue performance. Alternative correlations utilising areal topographic parameters would therefore be valuable. This has been addressed through areal topographic measurements and fatigue testing of an advanced nickel based superalloy, Alloy720Li. Low cycle and high cycle fatigue tests were performed at ambient temperature on specimens manufactured via different turning parameters to obtain S-N curves for different finishes. Supporting fractography is presented to emphasise the role of surface topography on fatigue crack initiation. The effects of different turned surface finishes on fatigue crack initiation are demonstrated and discussed.

AbstractThe performance diagnostic analysis of a gas turbine is accomplished by estimating a set of internal engine health parameters from available sensor measurements. No physical measuring instruments however can ever completely eliminate the presence of measurement uncertainties. Sensor measurements are often distorted by noise and bias leading to inaccurate estimation results. This paper explores the impact of measurement noise on Gas Turbine GPA analysis. The analysis is demonstrated with a test case where gas turbine performance simulation and diagnostics code TURBOMATCH is used to build a performance model of a model engine similar to Rolls-Royce Trent 500 turbofan engine, and carry out the diagnostic analysis with the presence of different levels of measurement noise. Conclusively, to improve the reliability of the diagnostic results, a statistical analysis of the data scattering caused by sensor uncertainties is made. The diagnostic tool used to deal with the statistical analysis of measurement noise impact is a model-based method utilizing a non-linear GPA.

The semi-solid slurry of A356 aluminum alloy was prepared through a serpentine pouring channel, which is a new method proposed recently for semi-solid forming process, and the effect of pouring temperature and bend number in the channel on the slurry microstructure was investigated and the slurry was finally rheo-die cast. The results show that when the pouring temperatures are between 640oC and 680oC, the slurry of A356 aluminum alloy with spherical primary a-Al grains can be prepared under the given conditions. The more the bend numbers in the channel are, the better the slurry is, i.e. the primary a-Al grains are more spherical and finer. The results also show that the as-cast ultimate strength and elongation of the rheo-die castings can reach 250MPa and 8.613.2% respectively. After T6 heat treatment, the ultimate strength and elongation of the rheo-die castings can reach 320MPa and 8.011.3% respectively. The work undertaken demonstrates eventually that the serpentine pouring channel process is a good method for semi-solid rheo-die casting or rheo-forming of metallic materials, the process is simple and the slurry cost is not expensive.

AbstractSupport vector machines (SVMs) are well known to give good results on many pattern recognition problems, but they exhibit classification speeds that are substantially slower than those of neural networks. One can speed up SVM classification by reducing the complexity of the decision function, which can be obtained by decreasing the number of support vectors. An iterative process is proposed to prune SVM and avoid obvious decline in classification accuracy. Computational results indicate that the number of support vectors is related to the size of training set, and that simplified SVMs with many fewer support vectors have classification accuracy nearly equal to that of original SVM. The proposed method is also compared with previous research, with results that support it as an effective method to obtain a simplified SVM for large problems.

Two experiment campaigns were conducted on the HL-2A tokamak in 2003 and 2004 after the first plasma was obtained at the end of 2002. Progresses in many aspects have been made, especially in the divertor discharge and feedback control of plasma configuration. Up to now, the following operation parameters have been achieved: Ip = 320 kA, Bt = 2.2 T and discharge duration Td = 1580 ms. With the feedback control of plasma current and horizontal position, an excellent repeatability of the discharge has been achieved. The tokamak has been operated at both limiter configuration and single null (SN) divertor configuration. The HL-2A SN divertor configuration is simulated with the MHD equilibrium code SWEQU. When the divertor configuration is formed, the impurity radiation in the main plasma decreases remarkably.

The response of gas exchange and chlorophyll fluorescence along with changes in simulated rainfall were studied in water stressed plants Hedysarum fruticosumvar. mongolicum (H.f.m.). Net photosynthetic rate (PN), stomatal conductance (gs), leaf water potential (Ψleaf), and apparent carboxylation efficiency (PN/Ci) were significantly increased with the increase of rainfall. However, they did not change synchronously. The complete recovery of both PNand PN/Ciappeared 3 d after watering while gsand Ψleafwere recovered 1 d after treatment. Gas exchange characters increased sharply from 5 to 15 mm rainfall and then maintained steady state with increasing rainfall. During the initial phase of water recovery, photosystem 2 (PS2) activity was not affected and its complete recovery occurred also 3 d after rainfall. Hence the recovery of PNwas attributed to both opening of stomata and increase in carboxylation efficiency. Furthermore, PS2 activity was really impaired by water stress and could recover to the normal status when the water stress disappeared.

Gas exchange, photochemical efficiency, and leaf water potential (Ψl) of Salix matsudana(non-indigenous species), S. microstachyaand S. gordejevii(indigenous species) were studied in Hunshandak Sandland, China. Ψlof all the three species decreased from 06:00 to 12:00, and increased afterwards. S. matsudanashowed higher values of Ψlthan others. Net photosynthetic rate (PN) and stomatal conductance (gs) of S. matsudanawere the lowest among all, with the maximum PNat 10:00 being 75% of that of S. gordejevii. Compared with the indigenous species, the non-indigenous S. matsudanahad also lower transpiration rate (E) and water use efficiency (WUE). The values of Fv/Fmin all the species were lower from 06:00 to 14:00 than those after 14:00, indicating an obvious depression in photochemical efficiency of photosystem 2 in both non-indigenous and native species. However, it was much more depressed in S. matsudana, the non-indigenous tree. PNwas positively correlated to gsand negatively related to Ψl. The relationship between gsand vapour pressure difference (VPD) was exponential, while negative linear correlation was found between gsand Ψl.

Net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), leaf water potential (ψleaf), leaf nitrogen content, and photosynthetic nitrogen use efficiency (PNUE) were compared between a typical C4plant, Agriophyllum squarrosumand a C3plant, Leymus chinensis, in Hunshandak Sandland, China. The plant species showed different diurnal gas exchange patterns on June 12–14 when photosynthetic photon flux density (PPFD), air temperature (Tair), and water potential were moderate. PN, E, and gsof A. squarrosumshowed distinct single peak while those of L. chinensiswere depressed at noon and had two peaks in their diurnal courses. Gas exchange traits of both species showed midday depression under higher photosynthetic photon flux density (PPFD) and Tairwhen Ψleafwas significantly low down on August 6–8. However, those of A. squarrosumwere depressed less seriously. Moreover, A. squarrosumhad higher PN, Ψleaf, water use efficiency (WUE), and PNUE than L. chinensis. Thus A. squarrosumwas much more tolerant to heat and high irradiance and could utilise the resources on sand area more efficiently than L. chinensis. Hence species like A. squarrosummay be introduced and protected to reconstruct the degraded sand dunes because of their higher tolerance to stress and higher resource use efficiency.

Net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), and leaf water potential (Ψl) of an annual pioneer C4grass (Agriophyllum squarrosum) were compared under different simulated precipitation events in a field of Hunshandak Sandland, China. The increase of soil water content (SWC) had significant effect on these physiological traits (p<0.001). In the vegetative stage, the values of PN, E, and gswent up sharply when SWC increased at the beginning, while they went down with continuous increase of SWC. PN, E, and gsincreased 1.4, 1.7, and 1.7 fold, respectively, with SWC range from 6.7 to 11.6 %. In the reproductive stage, similar trends were found, except for the climate with a higher SWC. This indicated that A. squarrosumwas very sensitive to the small increment of SWC which might have a large photosynthetic potential. Ψlincreased by about 8 % as the SWC changed from 6.7 to 8.8 %, and then maintained a steady level when the SWC was higher than 8.8 %, while the values of PN, E, and gskept increasing even after this SWC. This might indicate that the adjustment of Ψlresponse to the changes of SWC lagged that of the photosynthetic parameters.

Only three tree species, i.e. Ulmus pumila, Malus baccata,and Prunus padus, are distributed in Hunshandak Sandland (HS) in Inner Mongolia, China. Field studies of gas exchange and chlorophyll (Chl) fluorescence of these three tree species were conducted in three arid periods of growth season 2002. Net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), and Fv/Fmof U. pumilawere higher than in M. baccataand P. padus, especially in the midday. Hence M. baccataand P. paduswere more sensitive to high temperature and irradiance than U. pumilain HS. This may be a reason for wide distribution of U. pumilain HS. M. baccataand P. padusare adapted to the back slope of fixed dune, because the micro-habitat is relatively cool and less irradiated than the slope facing sun. Water use efficiency (WUE) of U. pumilawas lower than that of M. baccataand P. padus, and thus U. pumiladoes not form forests in this region, because the soil is dry.

In Huanshandak Sandland, China, net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), intercellular CO2concentration (Ci), water use efficiency (WUE), photochemical efficiency of photosystem 2 (Fv/Fm), and leaf nitrogen content were compared for Hedysarum fruticosumvar. mongolicum(H.f.m.), a nitrogen fixing shrub, and Salix gordejevii(S.g.), a nitrogen non-fixing shrub. PN, E, and gsof the two shrubs were similar in trends, i.e.two peaks were observed in diurnal courses. However, except Ci, other parameters of H.f.m.were higher during the measured days than those of S.g.The midday depression of PNwas mainly due to decrease in stomata conductance and to reduction of Fv/Fmat midday. The higher PNof H.f.m.was consistent with the higher leaf N content and there was a positive relation between them. In addition, several C4traits were found in H.f.m., i.e.high saturation irradiance and WUE, low dark respiration rate, and Ci, which partly resulted in higher PN. This seems to indicate that the C3plant H.f.m.may have C4photosynthesis pathway or C4enzymes.

Alloys of Ti–(25–37)V–15Cr–(1–7)Al (wt-%) were compressed at temperatures in the range 25–600°C. The dislocation structure of the deformed alloys was studied using transmission electron microscopy (TEM). It was found that at room temperature, alloys with Al > 5% were very brittle and could not be deformed plastically. Alloys with 3–5%Al can be plastically deformed at room temperature but dislocations were present in bands. At a temperature of 400°C, superdislocations of 111type, which were usually present in bands, have been observed in alloys with more than ~3%Al additions. In contrast, a high density of wavy dislocations, which were identified as of ½ 111type, were found in an alloy with 2%Al after deformation either at room or at elevated temperatures.

In this paper, mainly describies the configuration of automation system, modelling method of mathematical model, and management information system for mini-steel plant in China. Finally, introduces the results and economic benefit of these automation system.

HAHSS is an interactive software package for CAD of high accuracy and high speed servo, which has many computational functions such as system identification, model reduction, model transformation, digital controller design, system simulation, etc.. an efficient user interface and perfect supervisory function. In this paper, the efficient user interface and perfect supervisory function of HAHSS is mainly described, which includes three man-machine interaction approaches, data-base management, error detection, on-line user assistance and program reverse action. These are intended to render HAHSS far more flexible and convenient to use and appropriate to all kinds of users.

The effects of thermal exposure on microstructural changes in βTi–25V–15Cr–(2–4)Al alloys (all compositions in wt%) have been investigated. Plasma melted alloys were either HIPped, extruded or forged before being exposed at 550°C for 24–1000h. It was found that αprecipitation occurred in samples of Ti–25V–15Cr–3Al which were exposed at 550°C for 24h. The amount of precipitation increased with exposure time and the composition of the αphase changed gradually. EDX analysis on TEM samples showed increasing Al and Ti and decreasing V and Cr in the precipitates with exposure time. In samples which were exposed at 550°C for over 100h α2was observed. The variation of Al from 2 to 4wt% increased the precipitation and the kinetics of αto α2ordering. The results are discussed in terms of the effects of Al and oxygen on α2precipitation in βTiVCrAl alloys.