An accretion-jet model for M87: interpreting the spectral energy distribution and Faraday rotation measure

M87 is arguably the best supermassive black hole (BH) to explore the jet and/or accretion physics due to its proximity and fruitful high-resolution multi-waveband observations. We model the multi-wavelength spectral energy distribution (SED) of M87 core that observed at a scale of 0.4 arcsec ($\sim 10^5R_{\rm g}$, $R_{\rm g}$ is gravitational radius) as recently presented by Prieto et al. Similar to Sgr A*, we find that the millimeter bump as observed by Atacama Large Millimeter/submillimeter Array (ALMA) can be modeled by the synchrotron emission of the thermal electrons in advection dominated accretion flow (ADAF), while the low-frequency radio emission and X-ray emission may dominantly come from the jet. The millimeter radiation from ADAF dominantly come from the region within $10R_{\rm g}$, which is roughly consistent with the recent very long baseline interferometry observations at 230\,GHz. We further calculate the Faraday rotation measure (RM) from both ADAF and jet models, and find that the RM predicted from the ADAF is roughly consistent with the measured value while the RM predicted from the jet is much higher if jet velocity close to the BH is low or moderate (e.g., $v_{\rm jet}\lesssim0.6\,c$). With the constraints from the SED modeling and RM, we find that the accretion rate close to the BH horizon is $\sim (0.2-1)\times10^{-3}{M}_{\odot} \rm yr^{-1}\ll\dot{\it M}_{\rm B}\sim 0.2\it {M}_{\odot} \rm yr^{-1}$ ($\dot{M}_{\rm B}$ is Bondi accretion rate), where the electron density profile, $n_{\rm e}\propto r^{\sim -1}$, in the accretion flow is consistent with that determined from X-ray observation inside the Bondi radius and recent numerical simulations.Comment: 8 pages, 3 figures, accepted for publication in Ap

High performance IC clock networks with grid and tree topologies

In this dissertation, an essential step in the integrated circuit (IC) physical design flow—the clock network design—is investigated. Clock network design entailsa series of computationally intensive, large-scale design and optimization tasks for the generation and distribution of the clock signal through different topologies. The lack or inefficacy of the automation for implementing high performance clock networks, especially for low-power, high speed and variation-aware implementations, is the main driver for this research. The synthesis and optimization methods for the two most commonly used clock topologies in IC design—the grid topology and the tree topology—are primarily investigated.The clock mesh network, which uses the grid topology, has very low skew variation at the cost of high power dissipation. Two novel clock mesh network designmethodologies are proposed in this dissertation in order to reduce the power dissipation. These are the first methods known in literature that combine clock meshsynthesis with incremental register placement and clock gating for power saving purposes. The application of the proposed automation methods on the emerging resonant rotary clocking technology, which also has the grid topology, is investigated in this dissertation as well.The clock tree topology has the advantage of lower power dissipation compared to other traditional clock topologies (e.g. clock mesh, clock spine, clock tree with cross links) at the cost of increased performance degradation due to on-chip variations. A novel clock tree buffer polarity assignment flow is proposed in this dissertation in order to reduce these effects of on-chip variations on the clock tree topology. The proposed polarity assignment flow is the first work that introduces post-silicon, dynamic reconfigurability for polarity assignment, enabling clock gating for low power operation of the variation-tolerant clock tree networks.Ph.D., Electrical Engineering -- Drexel University, 201

Research progress and scientific challenges in the depressurization exploitation mechanism of clayey-silt natural gas hydrates in the northern South China Sea

Natural gas hydrate reservoirs in the northern South China Sea primarily comprise clayey silt, making exploitation more challenging relative to sandy reservoirs in other countries and regions. This paper provides an overview of the latest research developments in the exploitation mechanism covering the past five years, focusing on hydrate phase transition, multiphase flow in the decomposition zone, the seepage regulation of reservoir stimulation zone, and production capacity simulation, all of which are relevant to the previously conducted two rounds of hydrate trial production in offshore areas of China. The results indicate that the phase transition of clayey-silt hydrate remains in a dynamic equilibrium, with the decomposition efficiency mainly controlled by the coupling of heat and flow and high heat consumption during decomposition. The decomposition zone exhibits strong hydrophilicity, easy adsorption, and sudden permeability changes. A temperature drop is present that is concentrated near the wellbore, and once a water lock has formed, the gas-phase flow capacity significantly decreases, leading to potential secondary hydrate formation. To enhance permeability and increase production, it is imperative to implement reservoir and temperature field reconstruction based on initial formation alterations, which will further optimize and improve the transport capacity of the reservoir.Document Type: Current minireviewCited as: Lu, C., Qin, X., Sun, J., Wang, R., Cai, J. Research progress and scientific challenges in the depressurization exploitation mechanism of clayey-silt natural gas hydrates in the northern South China Sea. Advances in Geo-Energy Research, 2023, 10(1): 14-20. https://doi.org/10.46690/ager.2023.10.0

CUEING: a lightweight model to Capture hUman attEntion In driviNG

Discrepancies in decision-making between Autonomous Driving Systems (ADS) and human drivers underscore the need for intuitive human gaze predictors to bridge this gap, thereby improving user trust and experience. Existing gaze datasets, despite their value, suffer from noise that hampers effective training. Furthermore, current gaze prediction models exhibit inconsistency across diverse scenarios and demand substantial computational resources, restricting their on-board deployment in autonomous vehicles. We propose a novel adaptive cleansing technique for purging noise from existing gaze datasets, coupled with a robust, lightweight convolutional self-attention gaze prediction model. Our approach not only significantly enhances model generalizability and performance by up to 12.13% but also ensures a remarkable reduction in model complexity by up to 98.2% compared to the state-of-the art, making in-vehicle deployment feasible to augment ADS decision visualization and performance

Joint Optimization of Computation, Communication and Caching in D2D-Assisted Caching-Enhanced MEC System

Article discusses how, in the era of intelligent applications, Mobile Edge Computing (MEC) is emerging as a promising technology that provides abundant resources for mobile devices. The authors of the article introduce a novel Device-to-Device (D2D)-assisted system to address this challenge

Life history traits of low-toxicity alternative bisphenol S on Daphnia magna with short breeding cycles : A multigenerational study

Due to relatively lower toxicity, bisphenol S (BPS) has become an alternative to previously used bisphenol A. Nevertheless, the occurrence of BPS and its ecological impact have recently attracted increasing attentions because the toxicology effect of BPS with life cycle or multigenerational exposure on aquatic organisms remains questionable. Herein, Daphnia magna (D. magna) multigenerational bioassays spanning four generations (F0–F3) and single-generation recovery (F1 and F3) in clean water were used to investigate the ecotoxicology of variable chronic BPS exposure. For both assays, four kinds of life-history traits (i.e., survival, reproduction, growth and ecological behavior) were examined for each generation. After an 18-day exposure under concentration of 200 μg/L, the survival rate of D. magna was less than 15 % for the F2 generation, whereas all died for the F3 generation. With continuous exposure of four generations of D. magna at environmentally relevant concentrations of BPS (2 μg/L), inhibition of growth and development, prolonged sexual maturity, decreased offspring production and decreased swimming activity were observed for the F3 generation. In particular, it is difficult for D. magna to return to its normal level through a single-generation recovery in clean water in terms of reproductive function, ecological behavior and population health. Hence, multi-generational exposure to low concentrations of BPS can have adverse effects on population health of aquatic organisms with short breeding cycles, highlighting the necessity to assess the ecotoxicology of chronic BPS exposure for public health.publishedVersionPeer reviewe