A TWO-DIMENSIONAL GLIMM TYPE SCHEME ON CAUCHY PROBLEM OF TWO-DIMENSIONAL SCALAR CONSERVATION LAW

In this paper,we construct a new two-dimensional convergent scheme to solve Cauchy problem of following two-dimensional scalar conservation law{ tu ＋ xf（u） ＋ yg（u） = 0,u（x,y,0） = u0（x,y）.In which initial data can be unbounded.Although the existence and uniqueness of the weak entropy solution are obtained,little is known about how to investigate two-dimensional or higher dimensional conservation law by the schemes based on wave interaction of 2D Riemann solutions and their estimation.So we construct such scheme in our paper and get some new results.

Two-dimensional polymer-based nanosheets for electrochemical energy storage and conversion

Over the past decades, two-dimensional（2D） nanomaterials possessing planar layered architecture and unique electronic structures have been being quickly developed, due to their wide potential application in the fields of chemistry, physics, and materials science. As a new family of 2D nanomaterials, 2D polymerbased nanosheets, featuring excellent characters, such as tunable framework structures, light weight, flexibility, high specific surface, and good semiconducting properties, have been emerging as one kind of promising functional materials for optoelectronics, gas separation, catalysis and sensing, etc. In this review, the recent progress in synthetic approach and characterization of 2D polymer-based nanosheets were summarized, and their current advances in electrochemical energy storage and conversion including second batteries, supercapacitors, oxygen reduction and hydrogen evolution were discussed systematically.

Two-dimensional semiconductor heterostructures for photocatalytic CO_(2)conversion

The CO_(2)reduction into carbon-contained fuel via solar energy offers the powerful tools to realize the zero-emission carbon cycle.Owing to the intriguing features of the two-dimensional(2D)heterostructures,it is susceptible to modulate the electronic structure as well as the surface geometry for optimizing the photocatalytic CO_(2)reactivity.From this perspective,we surveyed the fundamental insights of 2D semiconductor heterostructures,involving the fabrication strategies and classification of the 2D semiconductor heterostructure.Also,we have detailly discussed the overview of 2D semiconductor heterostructure for optimizing CO_(2)photocatalytic influenced factors,including the solar energy utilization,photogenerated carriers separation,and redox reaction kinetics.Afterwards,we showed the significant advantages of 2D heterostructures in elevating CO_(2)photoreduction performance,focusing on activity,selectivity and photostability.By analyzing the limitations and developments,we ended by putting forward insights into the further researches about the CO_(2)photocatalysts and reactor design,even industrial applications.

Experimental study on energy storage and dissipation characteristics of granite under two-dimensional compression with constant confining pressure

To study the energy storage and dissipation characteristics of deep rock under two-dimensional compression with constant confining pressure,the single cyclic loading-unloading two-dimensional compression tests were performed on granite specimens with two height-to-width(H/W)ratios under five confining pressures.Three energy density parameters(input energy density,elastic energy density and dissipated energy density)in the axial and lateral directions of granite specimens under different confining pressures were calculated using the area integral method.The experimental results show that,for the specimens with a specific H/W ratio,these three energy density parameters in the axial and lateral directions increase nonlinearly with the confining pressure as quadratic polynomial functions.Under constant confining pressure compression,the linear energy storage law of granite specimens in the axial and lateral directions was founded.Using the linear energy storage law in different directions,the elastic energy density in various directions(axial elastic energy density,lateral elastic energy density and total elastic energy density)of granite under any specific confining pressures can be calculated.When the H/W ratio varies from 1:1 to 2:1,the lateral compression energy storage coefficient increases and the corresponding axial compression energy storage coefficient decreases,while the total compression energy storage coefficient is almost independent of the H/W ratio.

基于滑模自抗扰的储能变流器控制策略

为了提高储能变流器(PCS)的动态性能,设计基于降阶级联扩张状态观测器(ESO)和互补滑模控制(CSMC)的改进自抗扰控制(ADRC)策略,将改进ADRC策略应用于PCS的双向DC/AC变流器电压外环.改进ESO为降阶级联ESO以提高状态变量和系统总扰动的估计速度,增加扰动估计能力;更改PD控制为CSMC以设计状态误差反馈律,提升PCS的系统鲁棒性;设计改进指数趋近律以抑制抖振现象.为了证明改进ADRC策略相较于PI控制和传统ADRC的优越性,建立仿真模型并搭建相关实验平台.仿真与实验结果表明,改进ADRC策略减小了PCS暂态时直流母线电压波动,提高了PCS交流侧功率响应速度,改善了交流侧的输出电能质量.

基于SPH-FEM转换算法的砷化镓划片损伤过程研究

为了进一步提高半导体激光器巴条制造质量,改善解理加工过程中划片损伤情况,采用SPH-FEM转换算法研究划片速度和载荷对单晶砷化镓(gallium arsenide,GaAs)划片损伤的影响。基于广义胡克定律计算出砷化镓{100}晶面<110>晶向的各向异性机械力学特征参数,采用SPHFEM转换算法仿真金刚石刀头划片实验,将划片过程中损伤的有限元转换为粒子,研究损伤粒子在刀头作用下的运动轨迹,确定出划片的损伤过程。研究表明,该方法较好地解决了传统有限元法大变形区域发生网格畸变所导致的计算误差问题,揭示了不同加工参数对砷化镓材料划片损伤的影响,并得到了实验验证,为脆性材料的划片损伤过程提供了新的途径和思路。

耕地“非粮化”治理的实践困境及法治进路

在保障粮食安全背景下,耕地“非粮化”成为耕地治理的重点。当下的耕地“非粮化”治理面临立法理念冲突、法律禁令模糊、行政执法失范及治理依据存忧等现实困境。耕地“非粮化”的基础是土地承包经营权,该权利的“物权”基因意味着“非粮化”属于经济自由权,对其干预应当采取设定法律义务方式,同时对行政机关执法活动进行法律授权。具体来说,在法律约束机制方面,要明确“非粮化”的权利本位、建立效益与安全价值冲突平衡机制、完整列举“非粮化”的义务负担;在激励补偿方面,构建以财政补贴或行政奖励为核心的粮食补偿机制;在执法机制方面,规范“非粮化”执法主体及权限配置,建立“非粮化”行政执法暂停机制,尝试构建“非粮化”行政速裁机制。

破产法修改中的重整制度

破产法规定的重整程序在司法实践中发挥挽救重要企业作用的同时,也逐步显现出其存在的制度不足与缺陷,需进行修订。法院受理债权人提出的清算申请后,应允许其他债权人申请转换重整程序。债务人申请破产清算后,仍有权申请转换重整程序。法院对重整申请应进行识别审查,对明显不具有挽救价值和可能者应不予受理。重整计划提交期限应适当延长,以应对投资人招聘难等困境。要强化管理人的信息披露义务,并建立争议解决、责任追究等制度。因无法列示穷尽法律上和实践中的不同权益组别,法律对重整计划表决分组的规定应为指导性。权益不因重整计划受到不利影响的债权人等利害关系人不参与表决。法院对重整计划的正常批准或强制批准,都必须审查并保障反对组别及同意组别中反对者个人享有的法定清偿权利。至少应有一个债权人组表决通过重整计划,法院方可强制批准。强制批准重整计划应设有听证及异议救济程序。立法应限制重整计划二次表决的间隔期间。二次表决前,可以协商调整原表决通过组别的清偿权利,但应保障受不利影响组别均享有表决权。破产法应对于未及时申报债权之债权人,在重整计划执行完毕后依同类债权清偿条件向债务人行使权利,予以严格限制。立法应在因法律政策调整、市场情况变化等导致重整计划无法执行时,设置计划变更制度。

Conservation laws for Birkhoffian systems of Herglotz type

Conservation laws for the Birkhoffian system and the constrained Birkhoffian system of Herglotz type are studied. We propose a new differential variational principle, called the Pfaff-Birkhoff-d＇Alembert principle of Herglotz type. Birkhoff＇s equations for both the Birkhoffian system and the constrained Birkhoffian system of Herglotz type are obtained. According to the relationship between the isochronal variation and the nonisochronal variation, the conditions of the invariance for the Pfaff-Birkhoff-d＇Alembert principle of Herglotz type are given. Then, the conserved quantities for the Birkhoffian system and the constrained Birkhoffian system of Herglotz type are deduced. Furthermore, the inverse theorems of the conservation theorems are also established.

Guckenheimer structure of solution of Riemann problem with four pieces of constants in two space dimensions for scalar conservation laws

By using the generalized characteristic analysis method, the two-dimensional four-wave Riemann problem for scalar conservation laws, which is nonconvex along the y direction, was studied. Riemann solutions, which involve the Guckenheimer structure, were constructed.

Studies on convergence and scaling law of Thomson backscattering spectra in strong fields

With the saddle point analysis method for the Bessel function structure and property, the convergence problem and the scaling laws of Thomson backscattering spectra are solved and studied in both cases that are for the plane wave laser field without and with applied external constant magnetic field. Some unclear points appeared in previous work are clarified. The extension of the method to a general situation for the laser field with an arbitrary polarization is discussed. We also make a simple analysis and discussion about the optimal spectra dependence of field parameters and its implication to practical applications.

长江流域“十年禁渔”的行刑衔接机制研究

长江流域“十年禁渔”在实体法和程序法两个层面均存在着行刑衔接机制不畅的问题。实体法上表现为非法捕捞水产品行为“罪”与“非罪”难以界分,危害珍贵、濒危野生动物行为“过失犯”未予规定,非法交易渔获物行为的构罪标准单一;程序法上则表现为行刑证据转化、案件移送等方面存在困难。究其原因,主要在于相关规范滞后和阙如,刑事优先原则泛化适用,环境行政权和司法权的结构性矛盾。因此,必须从实体和程序两个层面切入对于“长江十年禁渔”的行刑衔接机制进行调适:在实体层面,应当注重立法论与解释论的并行,从廓清非法捕捞水产品罪的构成要件,增设过失损害珍贵、濒危野生动物罪,明确掩饰、隐瞒犯罪所得、犯罪所得收益罪的三维入罪标准等三个方面完善立法路径,并且要坚持定性与定量相统一的解释进路。在程序层面,则要立足于“三位一体”的程序配置,重塑案件移送制度,健全行刑证据转化机制,并且要规范渔政公安联合执法机制。

我国新修订《促进科技成果转化法》实施效果评估——来自高校的证据

为进一步深化对政策实施效果,特别是政策综合效果的研究,以我国新修订的《促进科技成果转化法》(以下简称“新《转化法》”)为对象,运用我国28个省份高校2011—2020年相关数据,采用断点回归方法,将政策实施时间作为驱动变量,分别从高校科技成果转化经济效果和高校科技成果转化率两个方面评估政策实施效果,并基于科技资源配置理论进一步分析政策的作用机制。结果显示,新《转化法》对高校科技成果转化具有显著的促进作用,主要表现为对高校专利成果转化的促进作用,其作用机制主要通过调节科技财力资源、人力资源、物力资源、网络资源与高校科技成果转化率的关系正向促进高校科技成果转化。因此,应持续推动完善科技成果转化投入机制和优化科研人员激励机制,鼓励校企间知识分享和资源互补、高校和研究院所间跨学科交流和资源共享,提高高校科技成果转化价值。

散粒体滑坡涌浪运动特征与能量转化规律研究

滑坡涌浪灾害造成的伤亡和损失一般远超滑坡灾害本身,已引起广泛关注。针对该类灾害的预测评价一直是研究的难点,精细刻画滑坡涌浪运动特征和能量转化规律是解决问题的关键和前提。因此,以天然碎石模拟散粒体滑坡,建立缩尺的矩形水槽滑坡涌浪三维物理试验模型,研究滑坡体积、速度和水深对堆积体形态和涌浪特征的影响以及滑体与水体能量转化规律。研究结论包括:(1)滑体通过冲击、挤压和抬升水体形成涌浪的特征受滑体规模和形态影响显著;厚度大且速度快的滑体趋向产生非线性过渡波,厚度小且速度低的滑体一般产生非线性震荡波;(2)基于试验提出的体积效应和速度效应揭示了一定水深的涌浪规模与滑坡体积和速度呈正相关规律,水深效应则解释了一定波能的涌浪在波形和速度上的分布差异,结果表明浅水比深水工况涌浪高度平均高出67%、波速平均高出51.17%;(3)基于试验的数值反演总结了滑体势能与波能转化率为1.00%~3.07%,由于三维试验中滑体与水体在水平和环向的扩散造成更多能量耗散,相较二维试验转化率较低。通过探讨散粒体滑坡运动过程和首浪产生、传播及爬高特征,揭示滑体-水体能量转化基本规律,研究成果对滑坡涌浪防灾减灾工作具有一定的理论价值和意义。

Two-Dimensional Materials for High-Performance Oxygen Evolution Reaction:Fundamentals,Recent Progress,and Improving Strategies

The oxygen evolution reaction(OER)plays an essential role in many energy storage and conversion technologies,but its high overpotential and sluggish kinetics seriously restrict its energy efficiency.The development of efficient and inexpensive OER electrocatalysts remains a grand challenge.Twodimensional(2D)materials with their unique structure and electronic properties have wide application prospects for OER.In this review,first introducing OER electrocatalytic mechanisms and some crucial parameters for evaluating OER electrocatalysts,the latest progress in the design and construction of 2D materials for OER is systematically discussed,including layered double hydroxides,2D carbon materials,transition metal dichalcogenides,metal oxide and phosphide nanosheets,metal–organic frameworks,covalent-organic frameworks,and MXenes.Obviously,some effective design and optimization strategies to improve the electrocatalytic activity and durability of 2D materials such as OER electrocatalysts have been comprehensively generalized.The advantages and shortcomings of these 2D materials are analyzed in detail,and their practical applications are explained in depth,which is crucial for the rational design of high-performance OER electrocatalysts.Finally,the challenges and future development opportunities for 2D materials in enhanced OER are discussed.Our review is expected to provide clear guidance for the development of new low-cost 2D materials for advanced OER electrocatalysts.

Ultrathin origami accordion-like structure of vacancy-rich graphitized carbon nitride for enhancing CO_(2) photoreduction

Retaining the ultrathin structure of two-dimensional materials is very important for stabilizing their catalytic performances.However,aggregation and restacking are unavoidable,to some extent,due to the van der Waals interlayer interaction of two-dimensional materials.Here,we address this challenge by preparing an origami accordion structure of ultrathin twodimensional graphitized carbon nitride(oa-C_(3)N_(4))with rich vacancies.This novel structured oa-C_(3)N_(4) shows exceptional photocatalytic activity for the CO_(2) reduction reaction,which is 8.1 times that of the pristine C_(3)N_(4).The unique structure not only prevents restacking but also increases light harvesting and the density of vacancy defects,which leads to modification of the electronic structure,regulation of the CO_(2) adsorption energy,and a decrease in the energy barrier of the carbon dioxide to carboxylic acid intermediate reaction.This study provides a new avenue for the development of stable highperformance two-dimensional catalytic materials.

Can two-dimensional graphdiyne-based materials be novel materials for perovskite solar cell applications?

Two-dimensional(2D)graphdiyne(GDY)-based materials have attracted attention in the solar cell research community owing to their unique physicochemical properties and hydrophobic nature which can serve as moisture resistance from the surrounding medium.Benefiting from these,the performance and stability ofperovskite solar cells(PSCs)can be greatly improved via the addition of 2D GDY-based materials.This mini-review summarizes the recent development of 2D GDY-based materials for PSC application.The roles of 2D GDY-based materials,such as hole transporting material,electron transporting material,dopant material in perovskite film and interfacial layer,are discussed in detail.Moreover,we provide future perspectives in this field,aiming to help further progress efficient and stable 2D GDY-based materials in PSCs.

Cu nanoparticle-decorated two-dimensional carbon nanosheets with superior photothermal conversion efficiency of 65 % for highly efficient disinfection under near-infrared light

Low photothermal conversion efficiency restricts the antibacterial application of photothermal materials.In this work,two-dimensional carbon nanosheets(2D C)were prepared and decorated with Cu nanoparticles(2D C/Cu)by using a simple soluble salt template method combined with ultrasonic exfoliation.The photothermal conversion efficiency of 2 D C/Cu system can be optimized by changing the content of Cu nanoparticles,where the 2D C/Cu2 showed the best photothermal conversion efficiency(á)of 65.05%under 808 nm near-infrared light irradiation.In addition,the photothermal performance can affect the release behavior of Cu ions.This superior photothermal property combined with released Cu ions can endow this 2D hybrid material with highly efficient antibacterial efficacy of 99.97%±0.01%,99.96%±0.01%,99.97%±0.01%against Escherichia coli,Staphylococcus aureus,and methicillin-resistant Staphylococcus aureus,respectively,because of the synergetic effect of photothermy and ion release.In addition,this 2D hybrid system exhibited good cytocompatibility.Hence,this study provides a novel strategy to enhance the photothermal performance of 2D materials and thus will be beneficial for development of antibiotics-free antibacterial materials with safe and highly efficient bactericidal activity.

Two-dimensional hybrid nanomaterials derived from MXenes(Ti3C2Tx)as advanced energy storage and conversion applications

The development of two-dimensional hybrid nanomaterial derived from MXenes as high performance electrode material is the key component for the advanced ene rgy storage and conversion systems.In the past decades,MXene derived nanomaterials have attracted greatly interest in scientific activity and potential applications because of their unique synergistic properties such as high thermal stability,excellent electrical conductivity,large surface area,easy to handle and outstanding electro and photo chemical properties.This review is focused on the synthesis of hybrid nanomaterials from MXene(Ti3C2Tx)for renewable energy conversion and storage application including hydrogen evolution reaction,supercapacitor,lithium-ion batteries and photocatalysis.Finally,we also summarized the prospect and opportunities of novel two-dimensional hybrid nanomaterials derived MXene(Ti3C2Tx)fo r futuristic sustainable energy technology.

Recent Advances in Two-dimensional Materials for Electrochemical Energy Storage and Conversion

With the increased energy demand,developing renewable and clean energy technologies becomes more and more significant to mitigate climate warming and alleviate the environmental pollution.The key point is design and synthesis of low cost and efficient materials for a wide variety of electrochemical reactions.Over the past ten years,two-dimensional(2D)nanomaterials that graphene represents have been paid much attention as a class of the most promising candidates for heterogeneous electrocatalysts in electrochemical storage and conversion.Their unique properties,such as good chemical stability,good flexibility,and good electronic properties,along with their nanosized thickness and large specific area,make them exhibit comprehensively good performances for energy storage and conversion.Here,we present an overview on the recent advances in electrochemical applications of graphene,graphdiyne,transition metal dichalcogenides(TMDs),and MXenes for supercapacitors(SCs),oxygen reduction reaction(ORR),and hydrogen evolution reaction(HER).