This paper proposes a fixed-time anti-saturation (FT-AS) control scheme with a simple control loop for the 6-Degree-of-Freedom tracking (6-DOF) control problem of spacecraft with parameter uncertainties, external disturbances and input saturation. Considering the external disturbance and parameter uncertainties, the dynamical model of the tracking error is established. The traditional methods of handling input saturation usually add anti-saturation subsystems in the control system to suppress the impact of input overshoot. However, this paper directly inputs the input overshoot into the tracking error model, thus constructing a modified lumped disturbance term that includes the influence of input overshoot. Then, a novel fixed-time disturbance observer (FT-DO) is designed to estimate and compensate for this modified lumped disturbance. Therefore, there is no need to add the anti-saturation structures in the control loop, significantly reducing the complexity of the system. Finally, an observer-based fixed-time non-singular terminal sliding mode (FT-NTSM) controller is designed to guarantee the fixed-time stability of the whole system. In this way, the convergence time of the proposed scheme does not depend on the system’s initial conditions. Simulation results illustrate that the proposed method keeps the control input within the limit while achieving high-precision tracking control of attitude and position.

We present WALLABY pilot data release 1, the first public release of H i pilot survey data from the Wide-field ASKAP L-band Legacy All-sky Blind Survey (WALLABY) on the Australian Square Kilometre Array Pathfinder. Phase 1 of the WALLABY pilot survey targeted three $60\,\mathrm{deg}^{2}$ regions on the sky in the direction of the Hydra and Norma galaxy clusters and the NGC 4636 galaxy group, covering the redshift range of $z \lesssim 0.08$ . The source catalogue, images and spectra of nearly 600 extragalactic H i detections and kinematic models for 109 spatially resolved galaxies are available. As the pilot survey targeted regions containing nearby group and cluster environments, the median redshift of the sample of $z \approx 0.014$ is relatively low compared to the full WALLABY survey. The median galaxy H i mass is $2.3 \times 10^{9}\,{\rm M}_{{\odot}}$ . The target noise level of $1.6\,\mathrm{mJy}$ per 30′′ beam and $18.5\,\mathrm{kHz}$ channel translates into a $5 \sigma$ H i mass sensitivity for point sources of about $5.2 \times 10^{8} \, (D_{\rm L} / \mathrm{100\,Mpc})^{2} \, {\rm M}_{{\odot}}$ across 50 spectral channels ( ${\approx} 200\,\mathrm{km \, s}^{-1}$ ) and a $5 \sigma$ H i column density sensitivity of about $8.6 \times 10^{19} \, (1 + z)^{4}\,\mathrm{cm}^{-2}$ across 5 channels ( ${\approx} 20\,\mathrm{km \, s}^{-1}$ ) for emission filling the 30′′ beam. As expected for a pilot survey, several technical issues and artefacts are still affecting the data quality. Most notably, there are systematic flux errors of up to several 10% caused by uncertainties about the exact size and shape of each of the primary beams as well as the presence of sidelobes due to the finite deconvolution threshold. In addition, artefacts such as residual continuum emission and bandpass ripples have affected some of the data. The pilot survey has been highly successful in uncovering such technical problems, most of which are expected to be addressed and rectified before the start of the full WALLABY survey.

A shear-improved Smagorinsky model is introduced based on results concerning mean-shear effects in wall-bounded turbulence. The Smagorinsky eddy-viscosity is modified as vT =(Csδ)2(|S|—|〈S〉|): the magnitude of the mean shear |〈S〉|is subtracted from the magnitude of the instantaneous resolved rate-of-strain tensor |S|; CS is the standard Smagorinsky constant and Δ denotes the grid spacing. This subgrid-scale model is tested in large-eddy simulations of plane-channel flows at Reynolds numbers Reτ = 395 and Reτ = 590. First comparisons with the dynamic Smagorinsky model and direct numerical simulations for mean velocity, turbulent kinetic energy and Reynolds stress profiles, are shown to be extremely satisfactory. The proposed model, in addition to being physically sound and consistent with the scale-by-scale energy budget of locally homogeneous shear turbulence, has a low computational cost and possesses a high potential for generalization to complex non-homogeneous turbulent flows.

The Square Kilometre Array (SKA) is a planned large radio interferometer designed to operate over a wide range of frequencies, and with an order of magnitude greater sensitivity and survey speed than any current radio telescope. The SKA will address many important topics in astronomy, ranging from planet formation to distant galaxies. However, in this work, we consider the perspective of the SKA as a facility for studying physics. We review four areas in which the SKA is expected to make major contributions to our understanding of fundamental physics: cosmic dawn and reionisation; gravity and gravitational radiation; cosmology and dark energy; and dark matter and astroparticle physics. These discussions demonstrate that the SKA will be a spectacular physics machine, which will provide many new breakthroughs and novel insights on matter, energy, and spacetime.

The bulk van der Waals crystal Mn3Si2Te6 (MST) has been irradiated with a proton beam of 2 MeV at a fluence of 1×1018 H+ cm-2. The temperature dependent magnetization measurements show a drastic decrease in the magnetization of 49.2% in the H//c direction observed in ferrimagnetic state. This decrease in magnetization is also reflected in the isothermal magnetization curves. No significant change in the ferrimagnetic transition temperature (75 K) was reflected after irradiation. Electron paramagnetic resonance (EPR) spectroscopy shows no magnetically active defects present after irradiation. Here, experimental findings gathered from MST bulk crystals via magnetic measurements, magnetocaloric effect, and heat capacity are discussed.

van der Waals (vdW) magnetic materials show promise in being the foundation for future spintronic technology. The magnetic behavior of Fe2.7GeTe2 (FGT), a vdW itinerant ferromagnet, was investigated before and after proton irradiation. Proton irradiation of the sample was carried out at a fluence of 1×1018 cm-2. The magnetization measurements revealed a small increase of saturation magnetization (Ms) of about 4% upon proton irradiation of the sample, in which, the magnetic field was applied parallel to the c-axis. X-ray photoelectron spectroscopy for pristine and irradiated FGT revealed a general decrease in intensity after irradiation for Ge and Te and an increase in peak intensity of unavoidable surface iron oxide. Furthermore, no noticeable change in the Curie temperature (TC =152 K) is observed in temperature dependent magnetization variation. This work signifies the importance of employing protons in tuning the magnetic properties of vdW materials.

Cultivated pastures in southern China are being used to improve forage productivity and animal performance, but studies on grazing behaviour of goats in these cultivated pastures are still rare. In the current study, the grazing behaviour of Yunling black goats under low (5 goats/ha) and high (15 goats/ha) stocking rates (SRs) was evaluated. Data showed that the proportion of time goats spent on activities was: eating (0.59–0.87), ruminating (0.05–0.35), walking (0.03–0.06) and resting (0.01–0.03). Compared with low SR, goats spent more time eating and walking, and less time ruminating and resting under high SR. Goats had similar diet preferences under both SR and preferred to eat grasses (ryegrass and cocksfoot) more than a legume (white clover). The distribution of eating time on each forage species was more uniform under high v. low SR. Bites/step, bite weight and daily intake were greater under low than high SR. Results suggest that the SR affects grazing behaviour of goats on cultivated pasture, and identifying an optimal SR is critical for increasing bite weight and intake.

The PM10 (airborne particulate matter with aerodynamic diameter <10 mm) in Beijing has a distinct seasonality, with industrial, domestic and natural sources providing a heterogeneous cocktail of airborne particulate matter (PM). Collections were made during late winter, summer and high wind dust storms to determine composition and probable sources of this PM. The concentration of the PM during winter (174 μg m–3) was approximately four times higher than summer (37 μg m–3) with dust storms raising the concentration further (200 μg m–3). During the winter the PM was dominated by combustion products (66% filter area). During the summer combustion products and loess contributed ~35% to the filter area each, but during elevated wind speeds (>10 mph) loess completely dominated the collections (96% filter area). The majority of the PM10 collected was in the respirable (PM2.5) size range (winter 99.7%, summer 96.6%, dust storms 82.3%). The loess in Beijing comprises quartz, feldspar, calcite, chlorite and mica and is in the coarse silt to sand (20–60 mm) size range. The collections are therefore likely to be made up of finer silt and clay, primarily derived from of the erosion of cultivated land. Using a plasmid assay, the Beijing particulate matter was found to have little or no surface free radical activity.

The triplite LiFeSO4F displays both the highest potential ever reported for an Fe-based compound, as well as a comparable specific energy with that of popular LiFePO4. The synthesis is still a challenge because the present approaches are connected with long time, special equipments or organic reagents, etc. In this work, the triplite LiFeSO4F powder was synthesized through an ambient two-step solid-state route. The reaction process and phase purity were analyzed, coupled with structure refinement and electrochemical test.

The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.

The present study investigated the effects of different levels of urea nitrogen (N) fertilizer on nutrient accumulation, in vitro rumen gas production and fermentation characteristics of forage oat straw (FOS) from oats (Avena sativa L. ‘Qinghai 444’) grown in the Tibet region of China. Fertilizer, applied at seeding (day 1), stem elongation (days 52–54) and heading (days 63–67), increased plant height and prolonged the maturity stage of the plant by 4–11 days compared with the non-fertilized control. Oat plants were harvested at maturity at the node 3–4 cm above ground, and then separated into grains and FOS. Both FOS and grain yields increased quadratically with increasing N fertilization, and their theoretical maximums occurred at the N fertilizing rates of 439 and 385 kg/ha, respectively. Increases in N fertilization did not affect the hemicellulose content of FOS, but substantially promoted the accumulation of crude protein, cellulose and lignin, resulting in a decrease in the energy content available for metabolism. A 72-h incubation of FOS with rumen fluids from lactating cows showed that increasing N resulted in FOS that showed a slower fermentation rate, decreased in vitro dry matter disappearance and lower cumulative gas production, but unchanged fermentation gas composition. Nitrogen fertilization increased the final pH in culture fluids and decreased the microbial volatile fatty acid (VFA) production. The molar proportions of acetate and propionate were not affected, but molar propionate proportion decreased linearly with increasing urea fertilization, and consequently, the ratio of lipogenic (e.g., acetate and butyrate)-to-glucogenic acids (propionate) tended to increase. In brief, increasing urea N fertilization promoted the growth of forage oats and increased the biomass yield as well as the crude protein and cellulose content of FOS. Considering the negative effect of increased lignin content on nutrient digestibility and total VFA production, the suggested range of urea N fertilization is 156–363 kg N/ha for forage oats planted in Tibet to retain the nutritive value of FOS in the rumen.

A completely randomized experiment for planting highland barley in 36 field plots of the Lhasa Agricultural Experiment Station was applied to investigate the effect of urea nitrogen (N) fertilization levels of 0 (control), 156, 258, 363, 465 and 570 kg/ha on nutrient accumulation, in vitro rumen gas production and fermentation characteristics of highland barley straw (HBS). Each urea application was divided into three portions of 0.4, 0.3 and 0.3 and sequentially fertilized at seeding (growth stage (GS) 0), stem elongation (GS 32) and heading (GS 49), respectively. The maturity stage lasted 5–13 days longer in response to the urea N fertilization compared with the control. After removing grains, HBS biomass was harvested at maturity. The biomass yields of leaf, stem, straw and grain were increased quadratically with increasing urea N fertilization, and HBS and grain yields peaked at the estimated urea N fertilization levels of 385 and 428 kg/ha, respectively. The increase of urea N fertilization increased the accumulation of crude protein, cellulose and lignin, and decreased the content of ash and hemicellulose in HBS, resulting in a decrease of the energy content available to be metabolized. After incubating HBS for 72 h with rumen fluids from lactating cows, the urea N fertilization decreased in vitro dry matter disappearance and cumulative gas production, and slightly altered fermentation end-gas composition. Urea N fertilization decreased microbial volatile fatty acid production, but did not alter the ratio of lipogenic acetate and butyrate to glucogenic propionate. In a brief, the current urea N fertilization strategy promoted the growth of the highland barley and increased biomass yield, protein and cellulose accumulation of HBS. A urea N fertilization level ⩽385 kg/ha could be sufficient for growth of highland barley in Tibet without a consequent nutritive reduction in ruminal digestion.

Based on the Bayesian Inference (BI) method, the Mixture-Model approach is improved to combine all kinematic data, including the coordinative position($\vec{x}$), proper motion ($\vec{\mu}$) and radial velocity(v), to separate the motion of the cluster from field stars, as well as to determine the intrinsic kinematic status and dynamical effects of the cluster, such as the mass segregation, anisotropy etc.. Meanwhile, the membership probability of individual stars are estimated as by product results. This method has been testified by simulation of toy models and also successfully used for well studied open clusters, such as M67 and NGC188. It is expected to largely help the studies of open clusters while combine the coming GAIA data.

The current sample of star clusters (SCs) is still incomplete beyond 1.8 kpc. The Pan-STARRS1 with its wide field of views and sensitive cameras provides us an opportunity to identify and characterize SCs as much as possible. By using a star counting algorithm, we obtained a total of 491 stellar density enhancements in a field of 20° × 20° toward the Galactic Anti-Center (GAC), of which 50 are known SCs. The remaining 441 candidates are verified with radii, interstellar reddening, distances, and ages with proper motions and multiple bands photometries. Our results push the completeness of SCs almost near the edge of GAC. With the revised SC sample, the separation between Sagittarius and Perseus arms are about 3.2 ± 0.2 kpc and the widths of the nearby spiral arms—Sagittarius, Orion, and Perseus—with are 1.4 ± 0.1, 1.6 ± 0.1, and 3.3 ± 0.2 kpc, respectively.

We compare the host galaxies of 902 supernovae, including Type Ia, II and Ibc, which are selected by cross-matching the Asiago Supernova Catalog with the SDSS DR7. We further selected 213 galaxies by requiring the light fraction of spectral observations > 15%, which could represent well the global properties of the galaxies. The diagrams related to Dn(4000), HδA, stellar masses, SFRs and specific SFRs for the SNe hosts show that almost all SNe II and most of SNe Ibc occur in SF galaxies. A significant fraction of SNe Ia occurs in AGNs and Absorp galaxies. These results are compared with those of the 689 comparison galaxies where the SDSS fiber captures < 15% of the total light. These comparison galaxies appear biased towards higher 12+log(O/H) (~0.1dex) at a given stellar mass, suggesting the aperture effect should be kept in mind when the properties of the hosts for different types of SNe are discussed.