11 research outputs found
Transformer-based convolutional forgetting knowledge tracking
Abstract Knowledge tracking is to analyze the mastery of students' knowledge through the learning track. This is very important for online education, since it can determine a learnerâs current knowledge level by analyzing the learning history and then make recommendations for future learning. In the past, the commonly used model for knowledge tracking is the convolutional neural network, but it has long-term sequence dependencies. With the invention of Transformer, it has excellent performance in long-sequence modeling by virtue of the attention mechanism, and is gradually introduced into the field of knowledge tracking. However, through our research, some knowledge tracking data sets have a large number of continuous and repetitive training, which will cause Transformer model to ignore the potential connections between some knowledge points. To overcome this problem, we introduce a convolutional attention mechanism to help the model perceive contextual information better. In addition, we simulate the forgetting phenomenon of students during the learning process by calculating the forgetting factor, and fuse it with the weight matrix generated by the model to improve the accuracy of the model. As a result, a Transformer-based Convolutional Forgetting Knowledge Tracking (TCFKT) model is presented in this paper. According to the experimental results conducted on the real world ASSITments2012, ASSISTments2017, KDD a, STATIC datasets, the TCFKT model outperforms other knowledge tracking models
Few-shot Action Recognition via Intra- and Inter-Video Information Maximization
Current few-shot action recognition involves two primary sources of
information for classification:(1) intra-video information, determined by frame
content within a single video clip, and (2) inter-video information, measured
by relationships (e.g., feature similarity) among videos. However, existing
methods inadequately exploit these two information sources. In terms of
intra-video information, current sampling operations for input videos may omit
critical action information, reducing the utilization efficiency of video data.
For the inter-video information, the action misalignment among videos makes it
challenging to calculate precise relationships. Moreover, how to jointly
consider both inter- and intra-video information remains under-explored for
few-shot action recognition. To this end, we propose a novel framework, Video
Information Maximization (VIM), for few-shot video action recognition. VIM is
equipped with an adaptive spatial-temporal video sampler and a spatiotemporal
action alignment model to maximize intra- and inter-video information,
respectively. The video sampler adaptively selects important frames and
amplifies critical spatial regions for each input video based on the task at
hand. This preserves and emphasizes informative parts of video clips while
eliminating interference at the data level. The alignment model performs
temporal and spatial action alignment sequentially at the feature level,
leading to more precise measurements of inter-video similarity. Finally, These
goals are facilitated by incorporating additional loss terms based on mutual
information measurement. Consequently, VIM acts to maximize the distinctiveness
of video information from limited video data. Extensive experimental results on
public datasets for few-shot action recognition demonstrate the effectiveness
and benefits of our framework.Comment: arXiv admin note: text overlap with arXiv:2207.0975
Combined Cold and Drought Stress-Induced Response of Photosynthesis and Osmotic Adjustment in <i>Elymus nutans</i> Griseb.
Elymus nutans Griseb. is a dominant forage in the QinghaiâTibetan Plateau. However, the combined cold and drought (CD) stress is a major problem inhibiting its growth, development, and yield. Here, the responses of morphological, photosynthetic, osmoregulation levels, and signal transduction under cold, drought, and CD stress were explored. Both cold- and drought-stressed plants showed varying degrees of damage. In addition, CD stress led to more severe damage than single stress, especially in total biomass, photosynthetic capacity, and electron transfer efficiency. The total biomass, net photosynthetic rate, and maximal quantum yield of photosystem II (PSII) photochemistry reduced by 61.47%, 95.80%, and 16.06% in comparison with the control, respectively. Meanwhile, CD stress was accompanied by lower chlorophyll contents, down-regulated expression level of key photosynthetic enzymes (EnRbcS, EnRbcL, and EnRCA), stomatal closure, disrupted chloroplast ultrastructure, and reduced starch content. Furthermore, CD stress induced some adaptability responses in cold- and drought-tolerant E. nutans seedlings. The combined stress provoked alterations in both cold- and drought-related transcription factors and responsive genes. EnCBF12, EnCBF9, EnCBF14, and EnCOR14α were significantly up-regulated under cold or drought stress, and the transcript level of EnCBF3 and EnCBF12 was even 2.94 and 12.59 times higher than control under CD treatment, which indicated the key role of transcription factors activation in coping with CD stress. In addition, the content of soluble sugar, reducing sugar, proline, glycine betaine, and other osmolytes was significantly improved under CD stress. Therefore, we demonstrated that exposure to CD stress led to severe morphological and photosynthetic damage and revealed the acclimation to the cold and drought stress combination via osmotic adjustment and transcription factors activation in the Tibetan wild E. nutans
Paclobutrazol Ameliorates Low-Light-Induced Damage by Improving Photosynthesis, Antioxidant Defense System, and Regulating Hormone Levels in Tall Fescue
Paclobutrazol (PBZ) is a plant-growth regulator (PGR) in the triazole family that enhances plant tolerance to environmental stresses. Low-light (LL) intensity is a critical factor adversely affecting the growth of tall fescue (Festuca arundinacea Schreb.). Therefore, in this study, tall fescue seedlings were treated with PBZ under control and LL conditions to investigate the effects of PBZ on enhancing LL stress resistance by regulating the growth, photosynthesis, oxidative defense, and hormone levels. Our results reveal that LL stress reduced the total biomass, chlorophyll (Chl) content, photosynthetic capacity, and photochemical efficiency of photosystem II (PSII) but increased the membrane lipid peroxidation level and reactive oxygen species (ROS) generation. However, the application of PBZ increased the photosynthetic pigment contents, net photosynthetic rate (Pn), maximum quantum yield of PSII photochemistry (Fv/Fm), ribulose-1,5-bisphosphate carboxylase (RuBisCO) activity, and starch content. In addition, PBZ treatment activated the antioxidant enzyme activities, antioxidants contents, ascorbate acid-glutathione (AsA-GSH) cycle, and related gene expression, lessening the ROS burst (H2O2 and O2∙−). However, the gibberellic acid (GA) anabolism was remarkably decreased by PBZ treatment under LL stress, downregulating the transcript levels of kaurene oxidase (KO), kaurenoic acid oxidase (KAO), and GA 20-oxidases (GA20ox). At the same time, PBZ treatment up-regulated 9-cis-epoxycarotenoid dioxygenase (NCED) gene expression, significantly increasing the endogenous abscisic acid (ABA) concentration under LL stress. Thus, our study revealed that PBZ improves the antioxidation and photosynthetic capacity, meanwhile increasing the ABA concentration and decreasing GA concentration, which ultimately enhances the LL stress tolerance in tall fescue
Evolution by duplication: paleopolyploidy events in plants reconstructed by deciphering the evolutionary history of VOZ transcription factors
Abstract Background Facilitated by the rapid progress of sequencing technology, comparative genomic studies in plants have unveiled recurrent whole genome duplication (i.e. polyploidization) events throughout plant evolution. The evolutionary past of plant genes should be analyzed in a background of recurrent polyploidy events in distinctive plant lineages. The Vascular Plant One Zinc-finger (VOZ) gene family encode transcription factors associated with a number of important traits including control of flowering time and photoperiodic pathways, but the evolutionary trajectory of this gene family remains uncharacterized. Results In this study, we deciphered the evolutionary history of the VOZ gene family by analyses of 107 VOZ genes in 46 plant genomes using integrated methods: phylogenic reconstruction, Ks-based age estimation and genomic synteny comparisons. By scrutinizing the VOZ gene family phylogeny the core eudicot Îł event was well circumscribed, and relics of the precommelinid Ï duplication event were detected by incorporating genes from oil palm and banana. The more recent T and Ï polyploidy events, closely coincident with the species diversification in Solanaceae and Poaceae, respectively, were also identified. Other important polyploidy events captured included the âsalicoidâ event in poplar and willow, the âearly legumeâ and âsoybean specificâ events in soybean, as well as the recent polyploidy event in Physcomitrella patens. Although a small transcription factor gene family, the evolutionary history of VOZ genes provided an outstanding record of polyploidy events in plants. The evolutionary past of VOZ gene family demonstrated a close correlation with critical plant polyploidy events which generated species diversification and provided answer to Darwinâs âabominable mysteryâ. Conclusions We deciphered the evolutionary history of VOZ transcription factor family in plants and ancestral polyploidy events in plants were recapitulated simultaneously. This analysis allowed for the generation of an idealized plant gene tree demonstrating distinctive retention and fractionation patterns following polyploidy events
Assessing the effect of wind power peaking characteristics on the maximum penetration level of wind power
Boosting exciton mobility approaching Mott-Ioffe-Regel limit in RuddlesdenâPopper perovskites by anchoring the organic cation
Abstract Exciton transport in two-dimensional RuddlesdenâPopper perovskite plays a pivotal role for their optoelectronic performance. However, a clear photophysical picture of exciton transport is still lacking due to strong confinement effects and intricate exciton-phonon interactions in an organic-inorganic hybrid lattice. Herein, we present a systematical study on exciton transport in (BA)2(MA) nâ1Pb n I3n+1 RuddlesdenâPopper perovskites using time-resolved photoluminescence microscopy. We reveal that the free exciton mobilities in exfoliated thin flakes can be improved from around 8 cm2âVâ1âsâ1 to 280 cm2Vâ1sâ1 by anchoring the soft butyl ammonium cation with a polymethyl methacrylate network at the surface. The mobility of the latter is close to the theoretical limit of Mott-Ioffe-Regel criterion. Combining optical measurements and theoretical studies, it is unveiled that the polymethyl methacrylate network significantly improve the lattice rigidity resulting in the decrease of deformation potential scattering and lattice fluctuation at the surface few layers. Our work elucidates the origin of high exciton mobility in RuddlesdenâPopper perovskites and opens up avenues to regulate exciton transport in two-dimensional materials
Long-Lived Hot Carriers in Two-Dimensional Perovskites: The Role of Alternating Cations in Interlayer Space
Solar absorbers featuring prolonged hot-carrier (HC)
cooling are
highly desired for the development of HC solar cells. Two-dimensional
(2D) hybrid perovskites are known for their exceptional stability
and tunable optoelectronic properties. Nevertheless, their hot-carrier
dynamics have been inadequately investigated. Here, we demonstrate
ultraslow hot-carrier cooling with a lifetime >2 ns and long HC
diffusion
length in 2D (ACA)(MA)PbI4 (ACA = acetamidinium) with alternating
cations in the interlayer space (ACI), surpassing those of 3D MAPbBr3 and 2D RuddlesdenâPopper (PEA)2PbI4. Our nonadiabatic molecular dynamics simulations with spinâorbit
coupling show that the enhanced HC cooling in the ACI-phase 2D perovskite
is due to multiple split-off bands and reduced electronâphonon
coupling. Furthermore, the hot electrons can be efficiently extracted
from (ACA)(MA)PbI4 and then transferred to the electron-transporting
layer. These new insights highlight the benefit of manipulating interlayer
cations in 2D perovskites as an advantageous approach to control long-lived
hot carriers, thus potentially enhancing photovoltaic device performance
Boosting Exciton Mobility Approaching Mott-Ioffe-Regel Limit in RuddlesdenâPopper Perovskites by Anchoring the Organic Cation
The supporting file contain related data for the manuscript of "Boosting Exciton Mobility Approaching Mott-Ioffe-Regel Limit in RuddlesdenâPopper Perovskites by Anchoring the Organic Cation"