| 1. |
|
|
| 2. |
|
|
| 3. |
- Algaba, Juan-Carlos, et al.
(författare)
-
Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
- 2021
-
Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 911:1
-
Forskningsöversikt (refereegranskat)abstract
- In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M o˙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.
|
|
| 4. |
- Chen, Aifang, 1990, et al.
(författare)
-
Multidecadal variability of the Tonle Sap Lake flood pulse regime
- 2021
-
Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 35:9
-
Tidskriftsartikel (refereegranskat)abstract
- Tonle Sap Lake (TSL) is one of the world's most productive lacustrine ecosystems, driven by the Mekong River's seasonal flood pulse. This flood pulse and its long-term dynamics under the Mekong River basin's (MRB) fast socio-economic development and climate change need to be identified and understood. However, existing studies fall short of sufficient time coverage or concentrate only on changes in water level (WL) that is only one of the critical flood pulse parameters influencing the flood pulse ecosystem productivity. Considering the rapidly changing hydroclimatic conditions in the Mekong basin, it is crucial to systematically analyse the changes in multiple key flood pulse parameters. Here, we aim to do that by using observed WL data for 1960-2019 accompanied with several parameters derived from a Digital Bathymetry Model. Results show significant declines of WL and inundation area from the late 1990s in the dry season and for the whole year, on top of increased subdecadal variability. Decreasing (increasing) probabilities of high (low) inundation area for 2000-2019 have been found, in comparison to the return period of inundation area for 1986-2000 (1960-1986). The mean seasonal cycle of daily WL in dry (wet) season for 2000-2019, compared to that for 1986-2000, has shifted by 10 (5) days. Significant correlations and coherence changes between the WL and large-scale circulations (i.e., El Nino-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Indian Ocean Dipole (IOD)), indicate that the atmospheric circulations could have influenced the flood pulse in different time scales. Also, the changes in discharge at the Mekong mainstream suggest that anthropogenic drivers may have impacted the high water levels in the lake. Overall, our results indicate a declining flood pulse since the late 1990s.
|
|
| 5. |
- Hartley, Philippa, et al.
(författare)
-
SKA Science Data Challenge 2: analysis and results
- 2023
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 523:2, s. 1967-1993
-
Tidskriftsartikel (refereegranskat)abstract
- The Square Kilometre Array Observatory (SKAO) will explore the radio sky to new depths in order to conduct transformational science. SKAO data products made available to astronomers will be correspondingly large and complex, requiring the application of advanced analysis techniques to extract key science findings. To this end, SKAO is conducting a series of Science Data Challenges, each designed to familiarize the scientific community with SKAO data and to drive the development of new analysis techniques. We present the results from Science Data Challenge 2 (SDC2), which invited participants to find and characterize 233 245 neutral hydrogen (H i) sources in a simulated data product representing a 2000 h SKA-Mid spectral line observation from redshifts 0.25-0.5. Through the generous support of eight international supercomputing facilities, participants were able to undertake the Challenge using dedicated computational resources. Alongside the main challenge, 'reproducibility awards' were made in recognition of those pipelines which demonstrated Open Science best practice. The Challenge saw over 100 participants develop a range of new and existing techniques, with results that highlight the strengths of multidisciplinary and collaborative effort. The winning strategy - which combined predictions from two independent machine learning techniques to yield a 20 per cent improvement in overall performance - underscores one of the main Challenge outcomes: that of method complementarity. It is likely that the combination of methods in a so-called ensemble approach will be key to exploiting very large astronomical data sets.
|
|
| 6. |
- Li, C. -Y, et al.
(författare)
-
Observation of inhomogeneous plasmonic field distribution in a nanocavity
- 2020
-
Ingår i: Nature Nanotechnology. - : Nature Research. - 1748-3387 .- 1748-3395.
-
Tidskriftsartikel (refereegranskat)abstract
- The progress of plasmon-based technologies relies on an understanding of the properties of the enhanced electromagnetic fields generated by the coupling nanostrucutres1–6. Plasmon-enhanced applications include advanced spectroscopies7–10, optomechanics11, optomagnetics12 and biosensing13–17. However, precise determination of plasmon field intensity distribution within a nanogap remains challenging. Here, we demonstrate a molecular ruler made from a set of viologen-based, self-assembly monolayers with which we precisely measures field distribution within a plasmon nanocavity with ~2-Å spatial resolution. We observed an unusually large plasmon field intensity inhomogeneity that we attribute to the formation of a plasmonic comb in the nanocavity. As a consequence, we posit that the generally adopted continuous media approximation for molecular monolayers should be used carefully.
|
|
| 7. |
- Li, Xiaolong, 1991, et al.
(författare)
-
Solid solution softening at room temperature and hardening at elevated temperatures: a case by minor Mn addition in a (HfNbTi) 85 Mo 15 refractory high entropy alloy
- 2023
-
Ingår i: Materials Research Express. - 2053-1591. ; 10:11
-
Tidskriftsartikel (refereegranskat)abstract
- To address the conflict between room-temperature (RT) ductility and high-temperature (HT) strength in single phase bcc-structured refractory high entropy alloys, here we propose to use minor alloying to achieve solid solution softening at RT and simultaneously, solid solution hardening at HT. Our strategy was manifested by minor Mn additions in a RT brittle (HfNbTi)85Mo15 refractory high entropy alloy, where nominal Mn additions ranging from 2 at. % down to 0.03 at. % were seen to soften the base (HfNbTi)85Mo15 alloy at RT, while to harden the base alloy at the temperature range from 400 to 800 °C. The yield stress in all studied alloys showed a three-stage pattern, characterized by a temperature dependent stage at temperatures below 400 °C, followed by a temperature independent stage at intermediate temperatures ranging from 400 to 800 °C, and finally another temperature dependent stage at temperatures higher than 800 °C. The mechanisms for solid solution softening and solid solution hardening in single phase bcc-structured refractory high entropy alloys were discussed, together with their temperature dependence.
|
|
| 8. |
- Yin, X., et al.
(författare)
-
Vertical Sandwich Gate-All-Around Field-Effect Transistors with Self-Aligned High-k Metal Gates and Small Effective-Gate-Length Variation
- 2020
-
Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 0741-3106 .- 1558-0563. ; 41:1, s. 8-11
-
Tidskriftsartikel (refereegranskat)abstract
- A new type of vertical nanowire (NW)/nanosheet (NS) field-effect transistors (FETs), termed vertical sandwich gate-all-around (GAA) FETs (VSAFETs), is presented in this work. Moreover, an integration flow that is compatible with processes used in the mainstream industry is proposed for the VSAFETs. Si/SiGe epitaxy, isotropic quasi-atomic-layer etching (qALE), and gate replacement were used to fabricate pVSAFETs for the first time. Vertical GAA FETs with self-aligned high-k metal gates and a small effective-gate-length variation were obtained. Isotropic qALE, including Si-selective etching of SiGe, was developed to control the diameter/thickness of the NW/NS channels. NWs with a diameter of 10 nm and NSs with a thickness of 20 nm were successfully fabricated, and good device characteristics were obtained. Finally, the device performance was investigated and is discussed in this work. © 2019 IEEE.
|
|
| 9. |
- Chen, H., et al.
(författare)
-
Intercomparison of ten ISI-MIP models in simulating discharges along the Lancang-Mekong River basin
- 2021
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 765
-
Tidskriftsartikel (refereegranskat)abstract
- Water resources are of strategic importance for socioeconomic development. Many hydrological models (HMs) and land surface models (LSMs) have been developed for water resources assessment. However, systematic evaluation of discharge simulation from multiple models is still lacking in the Lancang-Mekong River basin. Here, we evaluated the performances of ten HMs and LSMs by evaluating their simulated discharge against observations at the basin scale. The selected models were within the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP2a) framework driven by Global Soil Wetness Project 3 (GSWP3) climate forcing data. Five discharge percentile series were used to evaluate the model performances for low, mean, and high flows. The intercomparison according to four statistical criteria revealed considerable differences exist in model performances for different discharge percentiles, indicating a large uncertainty caused by the choice of models with different degree of physical complexity and sensitivity to the quality of the input data. The models generally performed better for high flow than for low flow. Furthermore, the models generally performed better in downstream than in upstream, with the exception of close to the estuary, where complex processes involving interactions between freshwater and saline water are present. It is not surprising that the two calibrated model (WaterGAP2 and WAYS) are superior over the other models. This systematic intercomparison provides insights into the model behaviours and accuracies in discharges predicting with varying intensities, which can aid in quantifying uncertainties in water resources simulation at the basin scale. (C) 2020 Elsevier B.V. All rights reserved.
|
|
| 10. |
|
|
