57 research outputs found

    In-plane ferroelectric tunnel junctions based on 2D α-In\u3csub\u3e2\u3c/sub\u3eSe\u3csub\u3e3\u3c/sub\u3e/ semiconductor heterostructures

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    Ferroelectric tunnel junctions (FTJs) have great potential for application in high-density non-volatile memories. Recently, α-In2Se3 was found to exhibit robust in-plane and out-of-plane ferroelectric polarizations at a monolayer thickness, which is ideal to serve as a ferroelectric component in miniaturized electronic devices. In this work, we design two-dimensional van der Waals heterostructures composed of an α-In2Se3 ferroelectric and a hexagonal IV–VI semiconductor and propose an in-plane FTJ based on these heterostructures. Our first-principles calculations show that the electronic band structure of the designed heterostructures can be switched between insulating and metallic states by ferroelectric polarization. We demonstrate that the in-plane FTJ exhibits two distinct transport regimes, tunneling and metallic, for OFF and ON states, respectively, leading to a giant tunneling electroresistance effect with the OFF/ON resistance ratio exceeding 1 × 104. Our results provide a promising approach for the highdensity ferroelectric memory based on the 2D ferroelectric/semiconductor heterostructures

    Environmental DNA captures elasmobranch diversity in a temperate marine ecosystem

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    Abstract: Many sharks, skates, and rays (elasmobranchs) are highly threatened by the activities of commercial fisheries, and a clear understanding of their distributions, diversity, and abundance can guide protective measures. However, surveying and monitoring elasmobranch species can be highly invasive or resource‐intensive, and utilization of non‐invasive environmental DNA‐based methods may overcome these problems. Here, we studied spatial and seasonal variation in the elasmobranch community of the Western English Channel using environmental DNA (eDNA) collected from surface and bottom waters periodically over an annual cycle (2017–2018). In total we recovered 13 elasmobranch species within eDNA samples, and the number of transformed eDNA reads was positively associated with species (hourly) catch data resolved from 105‐year time series trawl data (1914–2018). These results demonstrate the ability of eDNA to detect and semi‐quantitatively reflect the prevalence of historically dominant and rare elasmobranch species in this region. Notably, eDNA recorded a greater number of species per sampling event than a conventional trawl survey in the same area over the same sampling years (2017–2018). Several threatened species were recovered within the eDNA, including undulate ray, porbeagle shark, and thresher shark. Using eDNA, we found differences in elasmobranch communities among sampling stations and between seasons, but not between sampling depths. Collectively, our results suggest that non‐invasive eDNA‐based methods can be used to study the spatial and seasonal changes in the diversity and abundance of whole elasmobranch communities within temperate shelf habitats. Given the threatened status of many elasmobranchs in human‐impacted marine environments, eDNA analysis is poised to provide key information on their diversity and distributions to inform conservation‐focused monitoring and management

    内部注意在维度层面对视觉工作记忆的影响

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    Visual working memory is a memory system with limited capacity, thus internal attention plays a crucial role in selecting, controlling, and maintaining its stored content. Retro-cues are an important tool to study the influence of internal attention on visual working memory. Retro-cues are an important paradigm for studying the influence of internal attention on visual working memory. Depending on the different content of the cue, it can be divided into object-based retro-cue and dimension-based retro-cue and there are significant differences between them. The emergence of dimension-based retro-cue in recent years has become one of the hot topics of research. There are articles summarizing the research contents of object-based retro-cue, but the contents and progress of research on dimension-based retro-cue have not been sorted out and summarized. In this paper, we find that compared with object-based retro-cue, dimension-based retro-cue is more global, fragile; the effect of dimension-based retro-cue is influenced by visual dimensions, the number of memory sequences, individual differences and other factors; and the intrinsic mechanism of retro-cue benefits may be based on the reasons of preventing memory from time-based decay or taking non-target objects as the cost. Finally, we make suggestions for future directions and research.peerReviewe

    视觉工作记忆中数量和精度的权衡关系是否受个体自发控制

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    There is a negative correlation between the quality and quantity of memory representations in visual working memory, and this negative correlation is seen as a trade-off between quantity and quality. However, it is unclear whether this trade-off is entirely stimulus-driven or can be controlled voluntarily by individuals according to task demands, which has led to a debate on the mechanism of memory resource allocation. This paper systematically reviews the development of research on whether the trade-off between quantity and quality is subject to individual voluntary control, and point out this voluntary control is influenced by the exposure duration and working memory capacity, and some suggestions for future research are proposed.peerReviewe

    不同情绪面孔的视觉工作记忆表现差异 [The Performance Difference of Visual Working Memory between Various Emotional Faces]

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    Among social-emotional stimuli, emotional faces occupy an important position, which specifically refer to human faces with certain facial expressions. The visual working memory is a limited workspace where information can be saved online and can be accessed and operated by advanced cognitive function during the maintenance period. A large number of behavioral and electrophysiological studies have shown that there are differences in visual working memory performance of different emotional faces. Specifically, angry faces can enhance the visual working memory performance; fearful faces may cause some damage to visual working memory; sad faces will impair face recognition encoding in visual working memory. However, the visual working memory of happy emotional faces is mainly reflected in the choice of attention compared with other emotional faces, and the time is slightly delayed compared with that of angry faces. This paper sorts out the relevant research on the differences in visual working memory performance produced by different emotional faces as stimuli, and tries to summarize the possible reasons for these differences.peerReviewe

    视觉工作记忆中回溯线索效应的影响因素 [The Influencing Factors of Retro-Cue Effect in Visual Working Memory]

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    The visual working memory is a temporary storage system, which encodes, maintains and retrieves visual information. The researchers have found that adding retro-cues to the maintenance phase of memory leads to changes in participants’ memory performance, which is the retro-cue effect. The magnitude of the retro-cue effect is not set in stone, but changes with the changes of its influencing factors. However, there is no study to summarize the influencing factors of the retro-clue effect. This paper looked into the articles related to the study of the retro-cue effect and summarized the influencing factors of the retro-cue effect: memory items, maintenance interval time, interference in maintenance interval, and types of retro-cue. Based on this, future research can explore the factors that influence the retro-cue effect in other dimensions. At the same time, since retro-cue can improve memory performance and cognitive processing, these influencing factors should be reasonably controlled when using retro-cues. The internal attention mechanism of visual working memory could be further explored and the understanding of visual working memory mechanism could be promoted.peerReviewe

    Numerical Simulation Research on the Process of Reburning South American Coal and Cornstalk

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    Photo-chemical smog and acid rain formed from many pollutants including NOx are serious problems that have attracted much attention due to their negative influences on the atmosphere, plants, animals and even building materials. Effective measures of controlling NOx emissions are necessary. In this study, a computational fluid dynamics (CFD) software, Ansys Fluent 14.5, has been applied to research the processes of South American coal (SAm) reburning and cornstalk reburning. The influences of reburn zone excess air coefficient, reburning fuel fraction (Rff) and the secondary air temperature on the furnace combustion and NOx reduction have been determined. Results show that, in the simulated data range, the lower reburn zone excess air coefficient, the greater the rate of denitration for both SAm reburning and cornstalk reburning. The highest rates of denitration for SAm reburning and cornstalk reburning were 56.15% and 66.89%, respectively, in comparison to the conventional combustion. The denitration rate increases with the increase of reburning fuel fraction. However, when the reburning fuel fraction increases beyond a certain level, fuels within the furnace will undergo incomplete combustion. Under the premise of the fuel burnout, a relatively good case occurs at the reburning fuel fraction of 20% for the two kinds of reburning, and the NOx removal rate is 60.57% for cornstalk reburning, which is 7.61% higher than that of the SAm reburning. Temperature also has certain influences on the denitration effect and it shows that, in the lower temperature range, the higher the temperature of the secondary air, the higher the denitration rate. However, as temperature reaches a certain value, the denitration effect is no longer enhanced but reduced. For the two kinds of reburning, the case with the secondary air at 500 K is a relatively good one, and the NOx removal rate reaches 66.36% for cornstalk reburning, while it is 55% for SAm reburning. Overall, cornstalk reburning provides a higher NOx reduction rate in comparison to SAm reburning

    A Novel Method of Kinetic Analysis and Its Application to Pulverized Coal Combustion under Different Oxygen Concentrations

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    Currently, many efforts have been made to improve the approach to build kinetic models. Based on mathematical algorithms, a novel method (named DIM method) of kinetic analysis was introduced in detail. A formula combining differential and integral was deduced and applied to the determination of the mechanism function f(α). Subsequently, multivariable linear regression was conducted to simultaneously obtain the apparent activation energy E, pre-exponential factor A, and oxygen concentration exponent n. In the application of pulverized coal combustion under different oxygen concentrations (3%, 5%, 10%, 15%, and 21%), E, A, and n were calculated as 258,164 J/mol, 6.660 × 1017 s−1, and 3.326, respectively, and the mechanism function f(α) was determined as the Avrami-Erofeev equation. A validation was performed under a 7% oxygen concentration, which shows that the DIM method has a higher accuracy. This work can provide a reference for the study of kinetic analysis

    In-plane ferroelectric tunnel junctions based on 2D α-In2Se3/semiconductor heterostructures

    No full text
    Abstract Ferroelectric tunnel junctions (FTJs) have great potential for application in high-density non-volatile memories. Recently, α-In2Se3 was found to exhibit robust in-plane and out-of-plane ferroelectric polarizations at a monolayer thickness, which is ideal to serve as a ferroelectric component in miniaturized electronic devices. In this work, we design two-dimensional van der Waals heterostructures composed of an α-In2Se3 ferroelectric and a hexagonal IV–VI semiconductor and propose an in-plane FTJ based on these heterostructures. Our first-principles calculations show that the electronic band structure of the designed heterostructures can be switched between insulating and metallic states by ferroelectric polarization. We demonstrate that the in-plane FTJ exhibits two distinct transport regimes, tunneling and metallic, for OFF and ON states, respectively, leading to a giant tunneling electroresistance effect with the OFF/ON resistance ratio exceeding 1 × 104. Our results provide a promising approach for the high-density ferroelectric memory based on the 2D ferroelectric/semiconductor heterostructures
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