Transient fading X-ray emission detected during the optical rise of a tidal disruption event

We report on the SRG/eROSITA detection of ultra-soft (kT = 47+−55 eV) X-ray emission (LX =2.5+−00.56 × 1043 erg s−1) from the tidal disruption event (TDE) candidate AT 2022dsb ∼14 d before peak optical brightness. As the optical luminosity increases after the eROSITA detection, then the 0.2–2 keV observed flux decays, decreasing by a factor of ∼39 over the 19 d after the initial X-ray detection. Multi-epoch optical spectroscopic follow-up observations reveal transient broad Balmer emission lines and a broad He II 4686 Å emission complex with respect to the pre-outburst spectrum. Despite the early drop in the observed X-ray flux, the He II 4686 Å complex is still detected for ∼40 d after the optical peak, suggesting the persistence of an obscured hard ionizing source in the system. Three outflow signatures are also detected at early times: (i) blueshifted H α emission lines in a pre-peak optical spectrum, (ii) transient radio emission, and (iii) blueshifted Ly α absorption lines. The joint evolution of this early-time X-ray emission, the He II 4686 Å complex, and these outflow signatures suggests that the X-ray emitting disc (formed promptly in this TDE) is still present after optical peak, but may have been enshrouded by optically thick debris, leading to the X-ray faintness in the months after the disruption. If the observed early-time properties in this TDE are not unique to this system, then other TDEs may also be X-ray bright at early times and become X-ray faint upon being veiled by debris launched shortly after the onset of circularization

Transport properties of concrete containing lithium slag

Lithium Slag (LS), also known as Delithiated Beta Spodumene (DBS), is a by-product of lithium extraction from spodumene ore that contains active silicon dioxide and aluminium oxide making it a potential supplementary cementitious material (SCM) for concrete. This study investigated the transport properties of concrete at 28, 90, and 180 days by incorporating LS as an SCM with cement replacement levels of 20%, 40%, and 60%. The findings reveal that 20% to 40% LS enhanced compressive strength, and reduced permeable voids, water penetration, sorptivity, and porosity, leading to improved transport properties. As LS reacts slowly, 40% LS resulted in 18.34% higher compressive strength at 180 days compared to that of the control mix. Therefore, VPV, water penetration depth, and sorptivity co-efficient of concrete with 40% LS were found 15.96%, 24.79% and 38.46%, respectively, lower than the control mix. In addition, porosity analysis confirmed that with the increase of LS in concrete, porosity decreased over time. Moreover, SEM analysis demonstrated the development of CaCO3 crystals at 40% LS, further reducing porosity. However, beyond 60% cement replacement by LS, a decline in concrete properties was observed due to unreacted LS particles. Therefore, this research underscores the potential use of LS to enhance durability of concrete

LEO Augmentation in Large-Scale Ionosphere-Float PPP-RTK Positioning

Precise point positioning-real-time kinematic (PPP-RTK) positioning combines the advantages of PPP and RTK, which enables the integer ambiguity resolution (IAR) without requiring a reference station nearby. The ionospheric corrections are delivered to users to enable fast IAR. For large-scale networks, precise interpolation of ionospheric delays is challenging. The ionospheric delays are often independently estimated by the user, in the so-called ionosphere-float mode. The augmentation of low Earth orbit (LEO) satellites can bridge this shortcoming thanks to their fast speeds and the resulting rapid geometry change. Using 30-s real dual-frequency Global Positioning System (GPS) and Beidou Navigation Satellite System (BDS) observations within a large-scale network of thousands of kilometers, this contribution tests the effects of LEO augmentation using simulated dual-frequency LEO signals from the navigation-oriented LEO constellation, CentiSpace. Results showed that the LEO augmentation makes the solution convergence less sensitive to the original Global Navigation Satellite System (GNSS)-based model strength. The improvements in the convergence times are significant. For example, in the kinematic mode, the convergence time of the 90% lines of the GPS/BDS-combined ambiguity-float horizontal solutions to 0.05 m is shortened from more than 60 to 3.5 min, and that of the GPS-only partial ambiguity resolution (PAR)-enabled horizontal solutions is shortened from more than 20 to 4.5 min. In both the ambiguity-float and PAR-enabled cases, the 68.27% (1σ) lines of both the kinematic and static horizontal and height errors can converge to 0.05 m within 4 min, and for the 90% lines, within 6.5 min in all cases. The 90% line of the GPS/BDS/LEO combined PAR-enabled solutions can converge to 0.05 m within 2.5 and 3 min in the horizontal and up direction, respectively. Results also showed that enlarged projection of the mismodeled biases on the user coordinates were observed in the LEO-augmented scenario after convergence or ambiguity resolution. This is mainly due to the lower orbital height and low elevation angles of the LEO satellites, which requires further research when real LEO navigation signals are available

Bounding of double-differenced correlated errors of multi-GNSS observations using RTK for AV positioning

Integrity monitoring of autonomous vehicle (AV) localization is essential to guarantee their safety. In this process, satellite observation errors should be bounded using proper statistical methods to calculate a protection level that is neither optimistic nor overly conservative. Therefore, a realistic weighting function that is based on real data was developed in this research to achieve that balance. When using RTK as a positioning method, a real challenge is dealing with the cross-correlation between differenced observations. In this work, the overbounding parameters, i.e. the standard deviation (STD) and mean (bias) of the observation errors, were empirically computed for numerous combinations of different signals and frequencies from multiple GNSS constellations. the Two-Step Gaussian Bounding (TSGB) method is used as it could maintain overbounding after convolution from the observation domain to the position domain. Two empirical methods were designed to obtain the overbounding parameters and build the covariance (weighting) observation matrix using one full year of satellite observations. In the first method, a mapping function was utilised to re-compute the observation residuals from the slant direction to the zenith. Accordingly, a user can simply map them back along the observed satellites directions at different elevation angles (EAs). The correlation coefficients between correlated observations are derived based on the EAs of the studied satellites, so that they can be used in the stochastic model. In a second approach, the differenced residuals were categorized based on the EAs of both the pivot and other satellites in intervals of five degrees and building look-up tables. The correlation coefficients in this case were empirically calculated using Pearson’s Correlation Coefficient equation. The overbounding mean and STD of both code and phase observation errors for both approaches were in the range of 0.0003–1.369 m and 0.007–2.497 m, respectively. While the first approach provides a tight overbounding results, the second is more conservative

Interfacial engineering of 2H‑MoS2/N-doped carbon composite for fast potassium interfacial storage

The 2H-MoS2 incorporated with N-doped carbon (2H-MoS2/NC) with high discharge capacity has attracted more research focus as an anode material for K-ion batteries (PIBs). However, large longitudinal lattice deformation at 2H-MoS2/NC heterointerfaces caused by interfacial intercalation of K ions negatively impacts the structural stability, which limits its cycling performance. In this paper, interfacial engineering has been applied to optimize the structural stability of 2H-MoS2/NC. By using first-principle simulation, the evolutions of longitudinal lattice deformation, K adsorption/diffusion performance/behaviour, interfacial strength, and electronic property with the interfacial interlayer spacing have been systematically explored. The results show that with the increase of interlayer spacing from 5.0 to 7.0 Å, the lattice deformation, interfacial strength, and K adsorption kinetics first decrease sharply with interlayer spacing in the range of 5.0–6.5 Å, and then they drop minorly at 6.5–7.0 Å. The K interfacial diffusion capability can be improved due to the decreased charge accumulation at interface that leads to weakened K–S bonding with a rising interlayer spacing. Based on variation of structural stability and K storage performance, an optimal interlayer spacing of 6.75 Å is confirmed. These findings can provide a solid theoretical basis and guidance for the experimental preparation of high-performance 2H-MoS2/NC electrode materials and further cultivate new concepts for the optimal design of two-dimensional composite electrode materials. Graphical Abstract: (Figure presented.

Tax Accounting for The Renewable Energy (Electricity) Act 2000: A Tax by Any Other Name Would Smell as Sweet

Australia has committed to reducing greenhouse gas emissions, and part of that commitment is the enactment of the Renewable Energy (Electricity) Act 2000 (Cth) (the REE Act). This article focuses on the Australian renewable Energy Target and how the REE Act impacts on the electrical generation industry to dilute greenhouse gas emissions. The research examines the market of trading ‘carbon credits’ produced under the provisions of the REE Act, which are known as Renewable Energy Credits (RECs), and views this as a taxation and subsidisation system. It aims to develop a clear understanding of the operations of the REE Act: how the REC system interacts with Australia’s two other main taxes – Income Tax and Goods and Services Tax; and how the trade in RECs may be treated in the accounts of the respective trading entities – the liable parties and the renewable energy electricity generators

FROM LEGALITY TO RESPONSIBILITY: CHARTING THE COURSE FOR AI REGULATION IN MALAYSIA

As Artificial Intelligence (AI) technologies continue to evolve rapidly, Malaysia faces the imperative of establishing a robust regulatory framework to address legal complexities and ensure responsible AI deployment. This paper examines the current landscape of AI legality in Malaysia, analysing existing laws and regulations governing AI applications across various sectors. It identifies key legal challenges, including issues related to data privacy, algorithmic transparency, liability, and ethical considerations. Emphasising the transition from mere legality to ethical responsibility, the paper advocates for a proactive approach in charting the course for AI regulation. The doctrinal research methodology is used in this paper. This paper will first discuss the use of AI in different sectors in Malaysia and then will highlight the various problems associated with it. This study also discusses newly adopted AI regulations by the EU and China, and also the progress of the USA and the UK on AI regulation. It proposes strategies for enacting a forward-looking regulatory framework that integrates ethical guidelines, promotes transparency, fosters collaboration between stakeholders, and establishes mechanisms for accountability. By navigating this trajectory towards responsible AI regulation, Malaysia can unlock the full potential of AI while upholding ethical standards, protecting individual rights, and mitigating risks associated with AI technologies

Targeted Stimulation of Micropores by CS2 Extraction on Molecular of Coal

The targeted stimulation of micropores based on the transformation of coal’s molecular structure is proposed due to the chemical properties and difficult-to-transform properties of micropores. Carbon disulfide (CS2) extraction is used as a targeted stimulation to reveal the internal evolution mechanism of micropore transformation. The variations of microcrystalline structures and micropores of bituminous coal and anthracite extracted by CS2 were analyzed with X-ray diffraction (XRD), low-temperature carbon dioxide (CO2) adsorption, and molecular simulation. The results show that CS2 extraction, with the broken chain effect, swelling effect, and aromatic ring rearrangement effect, can promote micropore generation of bituminous coal by transforming the microcrystalline structure. Furthermore, CS2 extraction on bituminous coal can decrease the average micropore size and increase the micropore volume and area. The aromatic layer fragmentation effect of CS2 extraction on anthracite, compared to the micropore generation effect of the broken chain effect and swelling effect, can enlarge micropores more remarkably, as it induces an enhancement in the average micropore size and a decline in the micropore volume and area. The research is expected to provide a theoretical basis for establishing reservoir stimulation technology based on CS2 extraction

Vegetable Nanofluid Influence on End Milling Machinability of Nickel Alloys with Minimum Quantity Lubrication

Minimum Quantity Lubrication (MQL) using vegetable oils is considered a sustainable lubrication method, particularly for machining nickel alloys. Although a significant influence of nanofluid viscosity on lubrication has been observed in MQL machining, the influence of the viscosity of nanofluids on the machinability of nickel alloys is yet to be established. This comprehensive research aimed to evaluate the influence of the viscosity of palm oil-based nanofluids on the MQL end milling of Inconel 718