| 1. |
- Fenstermacher, M.E., et al.
(författare)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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| 2. |
- Burstein, R., et al.
(författare)
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Mapping 123 million neonatal, infant and child deaths between 2000 and 2017
- 2019
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 574:7778, s. 353-358
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Tidskriftsartikel (refereegranskat)abstract
- Since 2000, many countries have achieved considerable success in improving child survival, but localized progress remains unclear. To inform efforts towards United Nations Sustainable Development Goal 3.2—to end preventable child deaths by 2030—we need consistently estimated data at the subnational level regarding child mortality rates and trends. Here we quantified, for the period 2000–2017, the subnational variation in mortality rates and number of deaths of neonates, infants and children under 5 years of age within 99 low- and middle-income countries using a geostatistical survival model. We estimated that 32% of children under 5 in these countries lived in districts that had attained rates of 25 or fewer child deaths per 1,000 live births by 2017, and that 58% of child deaths between 2000 and 2017 in these countries could have been averted in the absence of geographical inequality. This study enables the identification of high-mortality clusters, patterns of progress and geographical inequalities to inform appropriate investments and implementations that will help to improve the health of all populations. © 2019, The Author(s).
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| 3. |
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| 4. |
- Hartley, Philippa, et al.
(författare)
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SKA Science Data Challenge 2: analysis and results
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 523:2, s. 1967-1993
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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.
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| 5. |
- Hu, Q., et al.
(författare)
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Effect of Mo on high-temperature strength of refractory complex concentrated alloys: A perspective of electronegativity difference
- 2022
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 906
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Tidskriftsartikel (refereegranskat)abstract
- Refractory complex concentrated alloys, RCCAs, show great potential for ultrahigh-temperature applications. High-temperature strength is one of the key requirements for RCCAs to qualify for that purpose. Some RCCAs already show superior high-temperature strength than that of commercial Ni-based superalloys, but many other RCCAs do not. It is thus important to identify the key factors that control the high-temperature strength of RCCAs. In this work, based on a statistic analysis of the yield strength at 1000 °C (σy1000) for 55 reported RCCAs, interestingly, it is revealed that Mo-containing RCCAs have in general a higher σy1000 than those RCCAs not containing Mo. The effect of Mo is attributed to its larger electronegativity and hence the larger electronegativity difference to other alloying elements, rather than to its higher melting point. The previously established proposal that a large electronegativity difference favoring the charge transfer and creating an atomic-level pressure that contributes to the strengthening of RCCAs at room temperature, seems effective even at a high temperature of 1000 °C. In addition, the large electronegativity difference also favors the room-temperature strength of single-bcc-phase RCCAs. The findings from this work, further verified experimentally in six new RCCAs, shed light on new research directions to develop RCCAs with decent strength at both high temperatures and room temperature, using a simple descriptor on the electronegativity difference.
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| 6. |
- Wang, Z. R., et al.
(författare)
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Effect of Si addition on Curie temperature and thermal expansion coefficient of (Fe 71.2 B 24 Y 4.8 ) 96 Nb 4 Invar bulk metallic glasses
- 2024
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Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 136:4
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Tidskriftsartikel (refereegranskat)abstract
- The ultra-low thermal expansion coefficient α makes the Fe-Ni Invar alloys useful in various applications. Their low strength and low Curie temperature Tc are, however, limiting factors. Interestingly, some Fe-based bulk metallic glasses (BMGs), with inherent high strength, exhibit the clear Invar effect. In particular, the (Fe71.2B24Y4.8)96Nb4 BMG has the lowest α among Fe-based BMGs, but it unfortunately also has the lowest Tc. In this work, silicon was added into this alloy with the aim to elevate Tc while maintaining a low α. It was found that when silicon partially substituted boron, Tc did not increase significantly but α did, which is not ideal. On the other hand, when silicon partially substituted yttrium and niobium and especially niobium, Tc increased significantly while α did not, which is close to the ideal scenario. When 3% of niobium was substituted by silicon, Tc reached the maximum value of 296 °C while α remained a low value of 7.4 × 10−6/°C. Comparing to the Fe-Ni Invar alloy, although this BMG has an inferior α, it has much higher Tc (+115 °C) and strength (∼9 times), presenting a potential for application as a new Invar material with moderate (low) thermal expansion, high operating temperature, and high strength.
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| 7. |
- Chen, X, et al.
(författare)
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Bismuth Effects on Electronic Levels in GaSb(Bi)/AlGaSb Quantum Wells Probed by Infrared Photoreflectance
- 2015
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Ingår i: Chinese Physics Letters. - 0256-307X .- 1741-3540. ; 32:6
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Tidskriftsartikel (refereegranskat)abstract
- GaSb(Bi)/Al0.2Ga0.8Sb single quantum wells are characterized by a Fourier transform infrared spectrometerbased photoreflectance method at 77 K. Spatially direct and indirect transitions between the electronic levels at and above the effective band gap are well resolved. The shifts of the electronic levels with Bi incorporation are identified quantitatively. The results show that the upshift of the valence band edge is clarified to be dominant, while the Bi-induced downshift of the conduction band edge does exist and contributes to the band gap reduction in the GaSbBi quantum-well layer by (29±6)%.
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| 8. |
- Cheng, Q., et al.
(författare)
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Mechanistic origin of abnormal annealing-induced hardening in an AlCoCrFeNi 2.1 eutectic multi-principal-element alloy
- 2023
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Ingår i: Acta Materialia. - 1359-6454. ; 252
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Tidskriftsartikel (refereegranskat)abstract
- Annealing-induced hardening, also known as anneal hardening, has been often observed in cold-worked solid solution alloys. Here, we report a peculiar case of annealing-induced hardening in a dual-phase (FCC + B2) as-cast AlCoCrFeNi2.1 eutectic multi-principal-element alloy (EMPEA) without any prior cold-working history. Investigation of the relative hardness contribution of the two phases by nanoindentation experiments revealed that, although both the FCC and B2 phases harden with increasing annealing temperatures, only the FCC phase showed a similar hardening behavior while the B2 phase hardened with increasing annealing temperature. The abnormal hardening in the dual-phase AlCoCrFeNi2.1 is thus proposed to result from the hardening of the FCC phase, which was caused by the ordering strengthening from the L12 phase embedded in the FCC matrix. This ordering strengthening is further supported by the fact that the volume fraction of the L12 ordered particles exhibit a similar peak as that of the hardness value of the FCC phase. By contrast, the growth of BCC particles within the B2 matrix phase was observed, which led to an increased volume fraction of BCC particles. Transmission electron microscopy observations reveal that the BCC particles were observed as strong pinning sites against dislocation motion, which could explain the temperature-dependent hardening behavior of the B2 phase measured by nanoindentation experiments. In this study, a quantitative evaluation of strengthening contributions from the L12 and BCC particles was also performed to understand the mechanical behavior of the alloy.
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| 9. |
- Gačnik, Darja, et al.
(författare)
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Structure and superconductivity of tin-containing hftizrsnm (M = cu, fe, nb, ni) medium-entropy and high-entropy alloys
- 2021
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 14:14
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Tidskriftsartikel (refereegranskat)abstract
- In an attempt to incorporate tin (Sn) into high-entropy alloys composed of refractory metals Hf, Nb, Ti and Zr with the addition of 3d transition metals Cu, Fe, and Ni, we synthesized a series of alloys in the system HfTiZrSnM (M = Cu, Fe, Nb, Ni). The alloys were characterized crystallographically, microstructurally, and compositionally, and their physical properties were determined, with the emphasis on superconductivity. All Sn-containing alloys are multi-phase mixtures of intermetallic compounds (in most cases four). A common feature of the alloys is a microstructure of large crystalline grains of a hexagonal (Hf, Ti, Zr)5Sn3 partially ordered phase embedded in a matrix that also contains many small inclusions. In the HfTiZrSnCu alloy, some Cu is also incorporated into the grains. Based on the electrical resistivity, specific heat, and magnetization measurements, a superconducting (SC) state was observed in the HfTiZr, HfTiZrSn, HfTiZrSnNi, and HfTiZrSnNb alloys. The HfTiZrSnFe alloy shows a partial SC transition, whereas the HfTiZrSnCu alloy is non-superconducting. All SC alloys are type II superconductors and belong to the Anderson class of “dirty” superconductors.
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| 10. |
- Guo, Q., et al.
(författare)
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A study on protecting of the far side occupants based on road traffic accident reconstruction
- 2012
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Ingår i: 2012 3rd International Conference on Digital Manufacturing and Automation, ICDMA 2012. Guilin, Guangxi, 31 July - 2 August 2012. - 9780769547725 ; , s. 140-143
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Konferensbidrag (refereegranskat)abstract
- A study on injuries of far side passenger in vehicle side impact was carried out by using a real road accident. Firstly, the trace of the accident car was reproduced using PC-Crash code. The impact velocity of the passenger car calculated from PC-Crash was used as the input data for MADYMO modeling of occupant kinematics. Then the dynamic responses of the occupants were analyzed using the calculated injury parameters of the driver. Furthermore, LS-DYNA code was used to simulate the impact between the head of the driver and the left shoulder of the occupant. In the end, a MADYMO model with an airbag between driver and occupant was developed, and the protective efficiency of the airbag was showed by comparing the models with and without airbag.
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