63 research outputs found
Ask Question First for Enhancing Lifelong Language Learning
Lifelong language learning aims to stream learning NLP tasks while retaining
knowledge of previous tasks. Previous works based on the language model and
following data-free constraint approaches have explored formatting all data as
"begin token (\textit{B}) + context (\textit{C}) + question (\textit{Q}) +
answer (\textit{A})" for different tasks. However, they still suffer from
catastrophic forgetting and are exacerbated when the previous task's pseudo
data is insufficient for the following reasons: (1) The model has difficulty
generating task-corresponding pseudo data, and (2) \textit{A} is prone to error
when \textit{A} and \textit{C} are separated by \textit{Q} because the
information of the \textit{C} is diminished before generating \textit{A}.
Therefore, we propose the Ask Question First and Replay Question (AQF-RQ),
including a novel data format "\textit{BQCA}" and a new training task to train
pseudo questions of previous tasks. Experimental results demonstrate that
AQF-RQ makes it easier for the model to generate more pseudo data that match
corresponding tasks, and is more robust to both sufficient and insufficient
pseudo-data when the task boundary is both clear and unclear. AQF-RQ can
achieve only 0.36\% lower performance than multi-task learning.Comment: This paper has been accepted for publication at COLING 202
Temperature- and field angular-dependent helical spin period characterized by magnetic dynamics in a chiral helimagnet
The chiral magnets with topological spin textures provide a rare platform to
explore topology and magnetism for potential application implementation. Here,
we study the magnetic dynamics of several spin configurations on the monoaxial
chiral magnetic crystal via broadband ferromagnetic resonance (FMR)
technique at cryogenic temperature. In the high-field forced ferromagnetic
state (FFM) regime, the obtained frequency f vs. resonance field Hres
dispersion curve follows the well-known Kittel formula for a single FFM, while
in the low-field chiral magnetic soliton lattice (CSL) regime, the dependence
of Hres on magnetic field angle can be well-described by our modified Kittel
formula including the mixture of a helical spin segment and the FFM phase.
Furthermore, compared to the sophisticated Lorentz micrograph technique, the
observed magnetic dynamics corresponding to different spin configurations allow
us to obtain temperature- and field-dependent proportion of helical spin
texture and helical spin period ratio L(H)/L(0) via our modified Kittel
formula. Our results demonstrated that field- and temperature-dependent
nontrivial magnetic structures and corresponding distinct spin dynamics in
chiral magnets can be an alternative and efficient approach to uncovering and
controlling nontrivial topological magnetic dynamics.Comment: 29 pages (including Supporting Information), 7 figures, accepted by
SCIENCE CHINA Physics, Mechanics & Astronom
Sea Coral-like NiCo2O4@(Ni, Co)OOH Heterojunctions for Enhancing Overall Water-Splitting
It is highly challenging to develop efficient and low-cost catalysts to meet stringent requirements on high current density for industrial water electrolysis application. We developed sea coral-like NiCo2O4@(Ni, Co)OOH heterojunctions, synthesized based on an epitaxial in-grown method using poly(ethylene glycol) (PEG) as a template, and explored its as efficient electrocatalyst for water-splitting. A two-electrode based alkaline electrolyzer was fabricated using NiCo2O4@(Ni, Co)OOH|| NiCo2O4@(Ni, Co)OOH, which achieved a current density value of 100 mA.cm−2 with a low potential of 1.83 V and high current density approached 600 mA.cm−2 at potential of 2.1 V along with a strong stability. These are superior to most reported data for the electrocatalysts operated at high current densities. In-situ calculations based on density function theory reveal that the occurrence of water-splitting on the NiCo2O4@(Ni, Co)OOH heterojunction surface. First-principles molecular dynamics simulation reveals that the stretching vibrations of metallic bonds of NiCo2O4@(Ni, Co)OOH heterojunctions open the hydrogen bonds of water. Understanding the mechanism of water-splitting at the heterojunction from in-situ theoretical calculations is helpful to develop new generation industrial catalysts
Current development and future challenges in microplastic detection techniques: a bibliometrics-based analysis and review.
Microplastics have been considered a new type of pollutant in the marine environment and have attracted widespread attention worldwide in recent years. Plastic particles with particle size less than 5 mm are usually defined as microplastics. Because of their similar size to plankton, marine organisms easily ingest microplastics and can threaten higher organisms and even human health through the food chain. Most of the current studies have focused on the investigation of the abundance of microplastics in the environment. However, due to the limitations of analytical methods and instruments, the number of microplastics in the environment can easily lead to overestimation or underestimation. Microplastics in each environment have different detection techniques. To investigate the current status, hot spots, and research trends of microplastics detection techniques, this review analyzed the papers related to microplastics detection using bibliometric software CiteSpace and COOC. A total of 696 articles were analyzed, spanning 2012 to 2021. The contributions and cooperation of different countries and institutions in this field have been analyzed in detail. This topic has formed two main important networks of cooperation. International cooperation has been a common pattern in this topic. The various analytical methods of this topic were discussed through keyword and clustering analysis. Among them, fluorescent, FTIR and micro-Raman spectroscopy are commonly used optical techniques for the detection of microplastics. The identification of microplastics can also be achieved by the combination of other techniques such as mass spectrometry/thermal cracking gas chromatography. However, these techniques still have limitations and cannot be applied to all environmental samples. We provide a detailed analysis of the detection of microplastics in different environmental samples and list the challenges that need to be addressed in the future
Maximizing spin-orbit torque efficiency of Ta(O)/Py via modulating oxygen-induced interface orbital hybridization
Spin-orbit torques due to interfacial Rashba and spin Hall effects have been
widely considered as a potentially more efficient approach than the
conventional spin-transfer torque to control the magnetization of ferromagnets.
We report a comprehensive study of spin-orbit torque efficiency in
Ta(O)/Ni81Fe19 bilayers by tuning low-oxidation of \b{eta}-phase tantalum, and
find that the spin Hall angle {\theta}DL increases from ~ -0.18 of the pure
Ta/Py to the maximum value ~ -0.30 of Ta(O)/Py with 7.8% oxidation.
Furthermore, we distinguish the efficiency of the spin-orbit torque generated
by the bulk spin Hall effect and by interfacial Rashba effect, respectively,
via a series of Py/Cu(0-2 nm)/Ta(O) control experiments. The latter has more
than twofold enhancement, and even more significant than that of the former at
the optimum oxidation level. Our results indicate that 65% enhancement of the
efficiency should be related to the modulation of the interfacial Rashba-like
spin-orbit torque due to oxygen-induced orbital hybridization cross the
interface. Our results suggest that the modulation of interfacial coupling via
oxygen-induced orbital hybridization can be an alternative method to boost the
change-spin conversion rate.Comment: 15 pages, 4 figure
Enhancing the biosynthesis of riboflavin in the recombinant Escherichia coli BL21 strain by metabolic engineering
In this study, to construct the riboflavin-producing strain R1, five key genes, ribA, ribB, ribC, ribD, and ribE, were cloned and ligated to generate the plasmid pET-AE, which was overexpressed in Escherichia coli BL21. The R1 strain accumulated 182.65 ± 9.04 mg/l riboflavin. Subsequently, the R2 strain was constructed by the overexpression of zwf harboring the constructed plasmid pAC-Z in the R1 strain. Thus, the level of riboflavin in the R2 strain increased to 319.01 ± 20.65 mg/l (74.66% increase). To further enhance ribB transcript levels and riboflavin production, the FMN riboswitch was deleted from E. coli BL21 with CRISPR/Cas9 to generate the R3 strain. The R4 strain was constructed by cotransforming pET-AE and pAC-Z into the R3 strain. Compared to those of E. coli BL21, the ribB transcript levels of R2 and R4 improved 2.78 and 3.05-fold, respectively. The R4 strain accumulated 437.58 ± 14.36 mg/l riboflavin, increasing by 37.17% compared to the R2 strain. These results suggest that the deletion of the FMN riboswitch can improve the transcript level of ribB and facilitate riboflavin production. A riboflavin titer of 611.22 ± 11.25 mg/l was achieved under the optimal fermentation conditions. Ultimately, 1574.60 ± 109.32 mg/l riboflavin was produced through fed-batch fermentation with 40 g/l glucose. This study contributes to the industrial production of riboflavin by the recombinant E. coli BL21
Current-driven magnetization dynamics and their correlation with magnetization configurations in perpendicularly magnetized tunnel junctions
We study spin-transfer-torque driven magnetization dynamics of a
perpendicular magnetic tunnel junction (MTJ) nanopillar. Based on the
combination of spin-torque ferromagnetic resonance and microwave spectroscopy
techniques, we demonstrate that the free layer (FL) and the weak pinned
reference layer (RL) exhibit distinct dynamic behaviors with opposite frequency
vs. field dispersion relations. The FL can support a single coherent spin-wave
(SW) mode for both parallel and antiparallel configurations, while the RL
exhibits spin-wave excitation only for the antiparallel state. These two SW
modes corresponding to the FL and RL coexist at an antiparallel state and
exhibit a crossover phenomenon of oscillation frequency with increasing the
external magnetic field, which could be helpful in the mutual synchronization
of auto-oscillations for SW-based neuromorphic computing.Comment: 13 pages, 5 figure
Thickness-dependent magnetic properties in Pt[CoNi]n multilayers with perpendicular magnetic anisotropy
We systematically investigated the Ni and Co thickness-dependent
perpendicular magnetic anisotropy (PMA) coefficient, magnetic domain
structures, and magnetization dynamics of Pt(5 nm)/[Co(t_Co nm)/Ni(t_Ni
nm)]5/Pt(1 nm) multilayers by combining the four standard magnetic
characterization techniques. The magnetic-related hysteresis loops obtained
from the field-dependent magnetization M and anomalous Hall resistivity (AHR)
\r{ho}_xy found that the two serial multilayers with t_Co = 0.2 and 0.3 nm have
the optimum PMA coefficient K_U well as the highest coercivity H_C at the Ni
thickness t_Ni = 0.6 nm. Additionally, the magnetic domain structures obtained
by Magneto-optic Kerr effect (MOKE) microscopy also significantly depend on the
thickness and K_U of the films. Furthermore, the thickness-dependent linewidth
of ferromagnetic resonance is inversely proportional to K_U and H_C, indicating
that inhomogeneous magnetic properties dominate the linewidth. However, the
intrinsic Gilbert damping constant determined by a linear fitting of
frequency-dependent linewidth does not depend on Ni thickness and K_U. Our
results could help promote the PMA [Co/Ni] multilayer applications in various
spintronic and spin-orbitronic devices.Comment: 17 pages, 4 figure
Mastering Complex Control in MOBA Games with Deep Reinforcement Learning
We study the reinforcement learning problem of complex action control in the
Multi-player Online Battle Arena (MOBA) 1v1 games. This problem involves far
more complicated state and action spaces than those of traditional 1v1 games,
such as Go and Atari series, which makes it very difficult to search any
policies with human-level performance. In this paper, we present a deep
reinforcement learning framework to tackle this problem from the perspectives
of both system and algorithm. Our system is of low coupling and high
scalability, which enables efficient explorations at large scale. Our algorithm
includes several novel strategies, including control dependency decoupling,
action mask, target attention, and dual-clip PPO, with which our proposed
actor-critic network can be effectively trained in our system. Tested on the
MOBA game Honor of Kings, our AI agent, called Tencent Solo, can defeat top
professional human players in full 1v1 games.Comment: AAAI 202
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