Three dimensional discrete element modelling of the conventional compression behavior of gas hydrate bearing coal

To analyze the relationship between macro and meso parameters of the gas hydrate bearing coal(GHBC)and to calibrate the meso-parameters,the numerical tests were conducted to simulate the laboratory triaxial compression tests by PFC3D,with the parallel bond model employed as the particle contact constitutive model.First,twenty simulation tests were conducted to quantify the relationship between the macro–meso parameters.Then,nine orthogonal simulation tests were performed using four meso-mechanical parameters in a three-level to evaluate the sensitivity of the meso-mechanical parameters.Furthermore,the calibration method of the meso-parameters were then proposed.Finally,the contact force chain,the contact force and the contact number were examined to investigate the saturation effect on the meso-mechanical behavior of GHBC.The results show that:(1)The elastic modulus linearly increases with the bonding stiffness ratio and the friction coefficient while exponentially increasing with the normal bonding strength and the bonding radius coefficient.The failure strength increases exponentially with the increase of the friction coefficient,the normal bonding strength and the bonding radius coefficient,and remains constant with the increase of bond stiffness ratio;(2)The friction coefficient and the bond radius coefficient are most sensitive to the elastic modulus and the failure strength;(3)The number of the force chains,the contact force,and the bond strength between particles will increase with the increase of the hydrate saturation,which leads to the larger failure strength.

Risk Analysis Using Multi-Source Data for Distribution Networks Facing Extreme Natural Disasters

Distribution networks denote important public infrastructure necessary for people’s livelihoods.However,extreme natural disasters,such as earthquakes,typhoons,and mudslides,severely threaten the safe and stable operation of distribution networks and power supplies needed for daily life.Therefore,considering the requirements for distribution network disaster prevention and mitigation,there is an urgent need for in-depth research on risk assessment methods of distribution networks under extreme natural disaster conditions.This paper accessesmultisource data,presents the data quality improvement methods of distribution networks,and conducts data-driven active fault diagnosis and disaster damage analysis and evaluation using data-driven theory.Furthermore,the paper realizes real-time,accurate access to distribution network disaster information.The proposed approach performs an accurate and rapid assessment of cross-sectional risk through case study.The minimal average annual outage time can be reduced to 3 h/a in the ring network through case study.The approach proposed in this paper can provide technical support to the further improvement of the ability of distribution networks to cope with extreme natural disasters.

Uncovering the miRNA-mediated regulatory network involved in Ma bamboo(Dendrocalamus latiflorus)de novo shoot organogenesis

Bamboo is an important non-timber forest product and is well-known for its reluctance to regenerate.Recently we have established a de novo shoot organogenesis(DNSO)protocol in Ma bamboo(Dendrocalamus latiflorus)and revealed the transcriptomic dynamics during Ma bamboo regeneration,which suggested the potential roles of Ma bamboo microRNAs(DlamiRNAs)in this process.However,how DlamiRNAs regulate bamboo DNSO is poorly understood.Here we performed integrated analysis with sRNAome,degradome,and transcriptome sequencing by using samples covering the four stages of the bamboo DNSO process.A total of 727 DlamiRNAs showed differential expression during the bamboo DNSO process,and the core DlamiRNA-DlamRNA-mediated regulatory networks for bamboo DNSO were constructed.Based on the results,DlamiR156 was selected for further functional characterization of its potential roles in bamboo DNSO.Transgenic bamboos with increased DlamiR156 levels exhibited an enhancement in their regeneration efficiency.Conversely,when DlamiR156 levels were downregulated,the regeneration efficiencies of transgenic bamboos decreased.Our findings show that the DlamiRNA-mediated regulatory pathways are significant in the process of bamboo regeneration and will contribute to our understanding of the molecular mechanisms governing plant organogenesis in a more comprehensive manner.

Note on Cyclically Interval Edge Colorings of Simple Cycles

A proper edge t-coloring of a graph G is a coloring of its edges with colors 1, 2,..., t, such that all colors are used, and no two adjacent edges receive the same color. A cyclically interval t-coloring of a graph G is a proper edge t-coloring of G such that for each vertex, either the set of colors used on edges incident to x or the set of colors not used on edges incident to x forms an interval of integers. In this paper, we provide a new proof of the result on the colors in cyclically interval edge colorings of simple cycles which was first proved by Rafayel R. Kamalian in the paper “On a Number of Colors in Cyclically Interval Edge Colorings of Simple Cycles, Open Journal of Discrete Mathematics, 2013, 43-48”.

减数分裂联会复合体异常与不孕不育相关性研究进展

减数分裂是由二倍体的生殖细胞产生单倍体的配子的过程,是有性生殖的核心。联会复合体是同源染色体之间形成的超分子结构,具有稳定同源染色体配对、促进遗传交叉形成等功能。越来越多的研究表明联会复合体异常是造成人类不孕不育的重要原因之一。本文主要综述了联会复合体中央区域异常(如SYCE1/2/3、TEX12、SIX6OS1、SYCP1突变)及侧向元件缺陷(如SYCP2、SYCP3突变)与不孕不育的相关性研究,以期为深入理解减数分裂错误导致生殖健康问题的病理机制提供理论参考。

Jump rule for edge impacts of rolling prisms

We study experimentally and theoretically the planar dynamics of purely rolling prisms on a rough ramp, where the rolling motion is interrupted intermittently by edge impacts. The experiments were carried out for prisms made of different materials and having different geometries. We found that the angular velocities of the rolling prisms are material-independent, but they change significantly with their geometry. We modelled the dynamics of edge impacts by considering a socalled detachment front propagating across the contact interface. The detachment front represents the moving boundary between a detached region and a stress region that coexist within the interface plane. The theoretical analysis indicates that the detachment front can be characterized by a scale number, whose value converges to 0.4050 for prisms having large number of edges. A new jump rule for edge impacts is then developed, by which we can accurately reproduce the experimental observations, and explain why the motion of the prism is material-independent.

Assessment of Cultivation Method for Energy Beet Based on LCA Method

In order to establish a supply system for energy resource coupled with the environment,the production technology of sugar beets was explored as a biological energy source. The low-humic andosol as the experimental soil,the panting method was direct planting,and cultivation technique was minimum tillage direct planting method. The control was conventional tillage transplant and no tillage direct planting. The results demonstrated that data revealed that the energy cost of no tillage and a direct planting method was 105 GJ/hm2on average for two years,while that of the conventional tillage method was 112 GJ/hm2per year. The ratio of output to input showed that the direct planting with no tillage was more efficient( 3. 61) than the conventional tillage( 3. 01). Moreover,the emission of CO2into the atmosphere with no tillage and the direct planting was 71% of the conventional tillage planting technique. Therefore,direct planting without tillage reduces the impact on the environment.

Solutions for 3 Security Problems and its Application in SOA-FCA Service Components Based SDO

Service-Oriented Architecture (SOA), which is an open architecture, provides developers with more freedom. However, its security problem goes from bad to worse. By taking an insurance business in Formal Concept Analysis (SOA-FCA) Service Components based Service Data Object (SDO) data model transfer with proxy as an example, the security issue of SDO data model was analyzed in this paper and this paper proposed a mechanism to make sure that the confidentiality, integrity, and non-repudiation of SDO data model are preserved by applying encryption/decryption, digest, digital signature and so on. Finally, this mechanism was developed and its performance was evaluated in SOA-FCA Service Components.

教学技巧更新教学理念依旧:网络技术在汉语课堂的运用换汤不换药?

教育技术运用于汉语课堂教学已有超过五十年的历史。从最初的卡带、录像带到光盘,到静态的以致互动的网络技术,汉语教师们投入了时间和精力学习各种技术并将他们运用到课堂实践。每一项新的教育技术、每一个新的应用软件都给改进语言教学和改善语言学习经历带来了新的机会和新的发展可能一一通常可以促进学生使用汉语进行真实的交流。但是这些潜在可能在很大程度上依然无法在汉语教学中完全实现,因为在大多数情况下新的教育技术是根据传统的强调词汇和语法的教学方法开发并运用到教学中,注重语法词汇学习效率而忽视了真实语言交流。在这篇文章中,我们首先探究传统教学的教学理念(例如结构主义/认知派)是如何影响网络技术在课堂中的应用效果。接下来,对教学流派,教学方法以及教学技巧进行了区分和解释。然后对几种当下流行的汉语教学网络技术进行了探究,介绍它们的使用方法,总结教师的教学观念是如何影响技术在教室中的整合。我们还强调了在教育技术设计和开发过程中的设计决策环节会对教育技术适用于何种教学法产生影响。在此基础上,我们通过对打字宝一一一个通过交流式写作促进汉字学习的多模式网络平台为例,介绍在新的教学理念指导下,将教育技术运用于汉语教学的新前景。在此基础上,本文进一步分析探讨基于新教学理念设计的网络平台(打字宝)运用于传统课堂的先行研究成果以及相关挑战,并为汉语教师、研究人员以及教育技术设计开发者提供相关建议。

Correlation between knowledge of prevention COVID-19 and depression of residents in Henan province,China

Background:Coronavirus disease 2019(COVID-19) has shown explosive growth in cities in central China in recent days.Residents have the depression due to lack of corresponding prevention knowledge.Methods:A cross-sectional study was investigated 385 residents over 18 years of age.Structured questionnaire and DASS-21 scale used to explore the association between knowledge of prevention COVID-19 and depression among residents.Results:73 respondents (20.3%) suffered varying degrees of depression.The knowledge of the behavior of respondents most concerned (AOR 7.45,95%CI,1.87 ~ 29.77),the main symptoms of the COVID-19 (AOR 9.72,95%CI,1.19 ~ 79.12) and using special ambulances to transport patients or suspected patients (AOR 2.22,95%CI,1.07 ~ 4.62) was found to be significant related to depression.Conclusions:Although residents currently have a lower prevalence of depression,but there is a strong correlation between the knowledge and attitude of prevention COVID-19 and depression.Government agencies need to expand ways to spread the knowledge of prevention COVID-19.

Ternary layered boride MoAlB:A novel thermo-regulation microwave absorbing ceramic material

In the context of the fifth-generation(5G)smart era,the demand for electromagnetic wave(EMW)-absorbing materials has become increasingly prominent,so it is necessary to explore promising candidate materials.This work focuses on the exploration of the material absorbing properties of a MoAlB MAB(MAB represents a promising group of alternatives,where M stands for a transition metal,A typically denotes Al,and B is boron)phase system.First,the first-principles calculations were performed to reveal the unique crystal and layered structure of the MoAlB ceramics and to predict their potential for use as an EMW absorption material.Subsequently,a series of MoAlB ceramics were synthesized at temperatures ranging from 800 to 1300℃,and the influence of temperature on the phase compositions and microstructures of the obtained MoAlB ceramics was characterized and analyzed.Finally,the practical EMW absorption performance of the prepared MoAlB ceramics was evaluated via a combination of experiments and radar cross-sectional calculations.The MoAlB sample synthesized at 900℃ exhibits superior EMW absorption performance,achieving an impressive minimum reflection loss(RL)of−50.33 dB.The unique layered structure and good electrical conductivity of the MoAlB samples are the main reasons for their enhanced wave absorption performance,which provides interfacial polarization and multiple dielectric loss mechanisms.Therefore,this study not only contributes to the understanding of the preparation of MoAlB materials but also provides potential guidance for their utilization in the realm of electromagnetic wave absorption.

Organic crystal structure prediction via coupled generative adversarial networks and graph convolutional networks

Organic crystal structures exert a profound impact on the physicochemical properties and biological effects of organic compounds.Quantum mechanics(QM)–based crystal structure predictions(CSPs)have somewhat alleviated the dilemma that experimental crystal structure investigations struggle to conduct complete polymorphism studies,but the high computing cost poses a challenge to its widespread application.The present study aims to construct DeepCSP,a feasible pure machine learning framework for minute-scale rapid organic CSP.Initially,based on 177,746 data entries from the Cambridge Crystal Structure Database,a generative adversarial network was built to conditionally generate trial crystal structures under selected feature constraints for the given molecule.Simultaneously,a graph convolutional attention network was used to predict the density of stable crystal structures for the input molecule.Subsequently,the distances between the predicted density and the definition-based calculated density would be considered to be the crystal structure screening and ranking basis,and finally,the density-based crystal structure ranking would be output.Two such distinct algorithms,performing the generation and ranking functionalities,respectively,collectively constitute the DeepCSP,which has demonstrated compelling performance in marketed drug validations,achieving an accuracy rate exceeding 80%and a hit rate surpassing 85%.Inspiringly,the computing speed of the pure machine learning methodology demonstrates the potential of artificial intelligence in advancing CSP research.

如何发展教师数字素养——联合国教科文组织的路径与启示

信息技术高速发展,变革了教育教学方式,也对教师数字素养提出了更高的要求。联合国教科文组织在促进教育发展方面发挥着重要作用,其教育信息化战略中的关键一环就是促进教师数字素养的发展。教科文组织关注教师数字素养发展是为了使教师能够应对数字时代的挑战,更进一步是为了弥合数字鸿沟,促进教育公平。教科文组织提供开放教育资源作为教师教育的补充资源,制定框架作为促进教师教育行动的工具,组织教师培训项目作为促进资源不足国家教师实践的保障。通过了解教科文组织发展教师数字素养的理念与行动,认识其优势与缺陷,我国能够借鉴有益经验,更好地参与全球教育治理。

Study on catalytic mechanisms of Fe_(3)O_(4)-rGO_(x) in three typical advanced oxidation processes for tetracycline hydrochloride degradation

This study explored the catalytic mechanism and performance impacted by the materials ratio of Fe_(3)O_(4)-GO_(x) composites in three typical advanced oxidation processes(AOPs)of O_(3),peroxodisulfate(PDS)and photo-Fenton processes for tetracycline hydrochloride(TCH)degradation.The ratio of GO in the Fe_(3)O_(4)-GO_(x) composites exhibited different trends of degradation capacity in each AOPs based on different mechanisms.Fe_(3)O_(4)-rGO_(20wt%) exhibited the optimum catalytic performance which enhanced the ozone decomposition efficiency from 33.48%(ozone alone)to 51.83%with the major reactive oxygen species(ROS)of O_(2)·-.In PDS and photo-Fenton processes,Fe_(3)O_(4)-rGO_(5wt%) had the highest catalytic performance in PDS and H_(2)O_(2) decomposition for SO_(4)·–,and·OH generation,respectively.Compared with using PDS alone,PDS decomposition rate and TCH degradation rate could be increased by 5.97 and 1.73 times under Fe_(3)O_(4)-rGO_(5wt%) catalysis.In the photo-Fenton system,Fe_(3)O_(4)-rGO_(5wt%) with the best catalyst performance in H_(2)O_(2) decomposition,and TCH degradation rate increased by 2.02 times compared with blank group.Meantime,the catalytic mechanisms in those systems of that the ROS produced by conversion between Fe^(2+)/Fe^(3+)were also analyzed.

Sulfide metallogenic model for the ultraslow-spreading Southwest Indian Ridge

Polymetallic sulfides present in mid-ocean ridges(MORs)have become important strategic resources for humans,and a scientific metallogenic model is necessary for the investigation and exploration of these resources.Compared to fast-and slow-spreading MORs,ultraslow-spreading MORs show substantial differences in magma supply,tectonic activity,and oceanic crust structures.However,information on hydrothermal circulation and a metallogenic model related to sulfides along the ultraslow-spreading ridges is still limited,which hinders further exploration of these resources.In this study,the distribution of hydrothermal activities,as well as the characteristics of the structures,heat sources,fluid pathways,host rock types,fluid properties,and sulfide assemblages in typical hydrothermal fields along the ultraslow-spreading Southwest Indian Ridge(SWIR),have been studied.It is concluded that the hydrothermal systems along the SWIR can be categorized into three types,including local enhanced magma-controlled,one-way detachment/high-angle large-offset fault-controlled,and flip-flop detachment-controlled types,which are further categorized into five subtypes based on their distinct geological backgrounds.Herein,we present a sulfide metallogenic model called Local Enhanced Heat Supply-Deep Faults(eHeat-dFault)for the SWIR.The overall spreading rate remains almost constant(14-18 mm/year),while the magma supply is heterogeneous in the segment scale along the SWIR.Over the past two decades,various hydrothermal systems and sulfide deposits have been identified along the SWIR.A deep magma chamber(4-9 km)is developed in the ridge segment with sufficient magma supply owing to the local enhanced magma supply,while long-lived active deep detachment faults(up to 13 km)with associated metallogenic belts are developed in ridge segments with poor magma supply.Hence,the ultraslow-spreading MORs fulfill the necessary conditions of a sustained heat source and stable hydrothermal pathway for the formation of large-scale polymetallic sulfide deposits.The number of hydrothermal fields detected in the investigation area is 2-3 times that predicted by the traditional Spreading Rate-Magma Flux model,demonstrating its significant endowment for sulfide resources.A balance between magma supply and faulting may influence the type and depth of hydrothermal circulation,the frequency of hydrothermal activity along the axis,and the scale of sulfide deposits.Spreading rate was previously believed to control heat sources,magma supply,and tectonic processes.However,for the SWIR,we suggest that local enhanced heat supply and deep detachment faults have a greater influence than the spreading rate on hydrothermal circulation and sulfide mineralization.The eHeat-dFault sulfide metallogenic model proposed herein could provide guidance for further exploration and research on polymetallic sulfides in ultraslow-spreading SWIR.

Charge storage coating based triboelectric nanogenerator and its applications in self-powered anticorrosion and antifouling

As a novel energy-harvesting device,a triboelectric nanogenerator(TENG)can harvest almost all mechanical energy and transform it into electrical energy,but its output is low.Although the micro-nano structures of triboelectrode surfaces can improve their output efficiency,they lead to high costs and are not suitable for large-scale applications.To address this problem,we developed a novel TENG coating with charge-storage properties.In this study,we modified an acrylic resin,a friction material,with nano-BaTiO_(3) particles and gas phase fluorination.The charge-trapping ability of nanoparticles was used to improve the output of TENG.The short-circuit current and the output voltage of coating-based TENGs featuring charge storage and electrification reached 15μA and 800 V,respectively,without decay for longtime working.On this basis,self-powered anticorrosion and antifouling systems are designed to reduce the open circuit potential of A3 steel by 510 mV and reduce the adhesion rate of algae on the surface of metal materials.This study presents a high-output,stable,coating-based TENG with potential in practical applications for anticorrosion and antifouling.

Spatial distribution of charcoal in topsoil and its potential determinants on the Tibetan Plateau

As an important proxy for investigating past fire activities,charcoal is often used to explore the characteristics of fire distribution and its relationships with vegetation,climate,and human activities.Research into the spatial distribution and environmental determinants for charcoal,however,is still limited.In this study,we identified and counted charcoal from topsoil samples covering the Tibetan Plateau using the pollen methodology,and investigated its relationships with vegetation net primary production(NPP),elevation,climate(precipitation,mean temperature of the coldest month and warmest month)and human population by boosted regression trees(BRT).Results reveal that the concentration of microscopic charcoal,macroscopic charcoal,and total charcoal all increase from south-west to north-east,which is consistent with the trend that the population density on the Tibetan Plateau is high in the east and low in the west,suggesting that an increase in human activity is likely to promote the occurrence of fire.The BRT modeling reveals that NPP,elevation,and mean temperature of the coldest month are important factors for total charcoal concentration on the Tibetan Plateau,and the frequency and intensity of fires further increase with increasing vegetation biomass,decreasing elevation,and decreasing mean temperature of the coldest month.The spatial variation characteristics of charcoal from topsoil on the Tibetan Plateau not only reflect well the spatial fire situation in the region,but also have a good indicative significance for vegetation,climate,and human activities.

Antioxidant induced bulk passivation for efficient and stable hole transport layer-free carbon electrode perovskite solar cells

Defect passivation is one of the important strategies to improve the efficiency and stability of perovskite solar cells.In this work,2,6-di-tert-butyl-4-methylphenol(BHT)as antioxidant was introduced into the perovskite precursor solution to improve the quality of the prepared perovskite films,so that these films performed a larger and uniform grain size.Moreover,the-OH functional group in BHT interacts with I-,thus reducing the density of defect states and inhibiting the non-radiative recombination.The presence of hydrophobic groups in BHT protects the film from moisture erosion and improves the long-term stability of PSCs devices.The maximum photoelectric conversion efficiency of the constructed ITO/SnO_(2)/BHTMAPbI_(3)/Carbon device is 16.88%,and the unpackaged cell maintains the initial efficiency of 99.3%after698 h of storage under the environmental condition of 30%humidity.This work provides an efficient approach to improve the performance of printable hole transport layer-free carbon electrode perovskite solar cells.

Vegetation stability during the last two centuries on the western Tibetan Plateau:a palynological evidence

Investigating the dynamics of vegetation is an essential basis to know how to protect ecological environments and to help predict any changes in trend.Because of its fragile alpine ecosystem,the Tibetan Plateau is a particularly suitable area for studying vegetation changes and their driving factors.In this study,we present a high-resolution pollen record covering the last two centuries extracted from Gongzhu Co on the western Tibetan Plateau.Alpine steppe is the predominant vegetation type in the surrounding area throughout the past 250 years with stable vegetation composition and abundance,as revealed by pollen spectra dominated by Artemisia,Ranunculaceae,Cyperaceae,and Poaceae.Detrended canonical correspondence analysis(DCCA)of the pollen data reveals low turnover in compositional species(0.41 SD),suggesting that the vegetation in the Gongzhu catchment had no significant temporal change,despite climate change and population increases in recent decades.We additionally ran DCCA on ten other pollen records from the Tibetan Plateau with high temporal resolution(1-20 years)covering recent centuries,and the results also show that compositional species turnover(0.15-0.81 SD)is relatively low,suggesting that the vegetation stability may have prevailed across the Tibetan Plateau during recent centuries.More high-resolution pollen records and high taxonomic-resolution palaeo-vegetation records(such as sedaDNA),however,are needed to confirm the vegetation stability on the Tibetan Plateau.

基于自判别循环生成对抗网络的人脸图像翻译

人脸跨域翻译是将人脸图像从一个图像域映射到另一个图像域的过程,常见的人脸图像翻译任务包括人脸照片–素描、人脸照片–线条画跨域翻译等,可以广泛应用于现实场景,如协助刑侦、电影制作、数字娱乐.但是成对的人脸图像数据有限,且不同域之间的颜色、纹理差异较大,导致人脸图像跨域翻译仍面临着巨大挑战.现有的方法通常会产生模糊、伪影、结构失真等问题,导致较差的视觉效果.为解决这一问题,我们提出了一个自判别循环生成对抗网络,其中,生成器部分采用编码器–解码器结构,生成器对应的判别器为翻译方向相反的编码器,通过自判别的形式,使编码器(即判别器)巧妙地融合了“真/假”语义判别能力与对像素改变的敏感性,从而增强了模型的稳健性和泛化能力.其次,我们提出了一个新颖的全向像素梯度损失函数,设计的卷积核计算了每个像素周围每个方向的梯度来提取图像的梯度信息,通过约束生成图像与对应真实图像的梯度信息保持一致,从而激励模型有效地学习像素间连续变化的模式,并且该损失函数可以灵活地应用于其他生成模型以提升性能.大量的实验表明本文提出的框架能够在公开的成对的人脸照片–素描数据集(CUFS,CUFSF)以及人脸照片–线条画数据集(APDrawing)上取得优异的结果.此外,通过泛化能力验证实验,我们进一步展示了模型在真实场景数据上的强泛化能力,以及自判别循环生成对抗网络结构在非成对人脸数据集上的出色性能.