Interface state-based bound states in continuum and below-continuum-resonance modes with high-Q factors in the rotational periodic system

We have introduced a new approach to calculate the orbital angular momentum(OAM)of bound states in continuum(BICs)and below-continuum-resonance(BCR)modes in the rotational periodic system nested inside and outside by transforming the Bloch wave number from the translational periodic system.We extensively classify and study these BICs and BCR modes,which exhibit high-quality(high-Q)factors,in different regions relative to the interface of the system.These BICs and BCR modes with a high-Q factor have been studied in detail based on distinctive structural parameters and scattering theory.The outcomes of this research break the periodic limitation of interface state-based BICs,and realize more and higher symmetry interface state-based BICs and BCR modes.Moreover,we can control the region where light is captured by adjusting the frequency,and show that the Q factor of BICs is more closely related to the ordinal number of rings and the rotational symmetry number of the system.

Chiral polaritons in semiconductor perovskite metasurface enhanced by bound states in the continuum

The exploration of novel chiral optical platforms holds both fundamental and practical importances,which have shown great promise towards applications in valleytronics,chiral sensing and nanoscopic chiroptics.In this work,we combine two key concepts—chiral bound states in the continuum and exciton polaritons—to showcase a strong chiral response from polaritons.Using the finite element method,we numerically design a CsPbBr_(3)based metasurface that supports intrinsically chiral bound states in the continuum and verify the chirality by calculating the reflection spectrum and eigenpolarization mapping.We further demonstrate chirality-dependent exciton polariton angular dispersion arising from the strong coupling between the chiral BIC and excitons in CsPbBr_(3)by simulating the polariton angle-resolved absorption spectrum.Reciprocity analysis reveals that the polariton photoluminescence in different momentum space locations is selectively enhanced by chiral pumping light.Our results suggest a promising first step towards chiral polaritonics.

Using fracture-based continuum modeling of coupled geomechanical-hydrological processes for numerical simulation of hydraulic fracturing

This paper describes numerical simulation of hydraulic fracturing using fracture-based continuum modeling(FBCM)of coupled geomechanical-hydrological processes to evaluate a technique for high-density fracturing and fracture caging.The simulations are innovative because of modeling discrete fractures explicitly in continuum analysis.A key advantage of FBCM is that fracture initiation and propagation are modeled explicitly without changing the domain grid(i.e.no re-meshing).Further,multiple realizations of a preexisting fracture distribution can be analyzed using the same domain grid.The simulated hydraulic fracturing technique consists of pressurizing multiple wells simultaneously:initially without permeating fluids into the rock,to seed fractures uniformly and at high density in the wall rock of the wells;followed by fluid injection to propagate the seeded fracture density hydraulically.FBCM combines the ease of continuum modeling with the potential accuracy of modeling discrete fractures and fracturing explicitly.Fractures are modeled as piecewise planar based on intersections with domain elements;fracture geometry stored as continuum properties is used to calculate parameters needed to model individual fractures;and rock behavior is modeled through tensorial aggregation of the behavior of discrete fractures and unfractured rock.Simulations are presented for previously unfractured rock and for rock with preexisting fractures of horizontal,shallow-dipping,steeply dipping,or vertical orientation.Simulations of a single-well model are used to determine the pattern and spacing for a multiple-well design.The results illustrate high-density fracturing and fracture caging through simultaneous fluid injection in multiple wells:for previously unfractured rock or rock with preexisting shallow-dipping or horizontal fractures,and in situ vertical compressive stress greater than horizontal.If preexisting fractures are steeply dipping or vertical,and considering the same in situ stress condition,well pressurization without fluid permeation appears to be the only practical way to induce new fractures and contain fracturing within the target domain.

Enhancing the Goos-Hänchen shift based on quasi-bound states in the continuum through material asymmetric dielectric compound gratings

Quasi-bound state in the continuum(QBIC)resonance is gradually attracting attention and being applied in Goos-Hänchen(GH)shift enhancement due to its high quality(Q)factor and superior optical confinement.Currently,symmetry-protected QBIC resonance is often achieved by breaking the geometric symmetry,but few cases are achieved by breaking the material symmetry.This paper proposes a dielectric compound grating to achieve a high Q factor and high-reflection symmetry-protectede QBIC resonance based on material asymmetry.Theoretical calculations show that the symmetry-protected QBIC resonance achieved by material asymmetry can significantly increase the GH shift up to-980 times the resonance wavelength,and the maximum GH shift is located at the reflection peak with unity reflectance.This paper provides a theoretical basis for designing and fabricating high-performance GH shift tunable metasurfaces/dielectric gratings in the future.

Static-to-kinematic modeling and experimental validation of tendon-driven quasi continuum manipulators with nonconstant subsegment stiffness

Continuum robots with high flexibility and compliance have the capability to operate in confined and cluttered environments. To enhance the load capacity while maintaining robot dexterity, we propose a novel non-constant subsegment stiffness structure for tendon-driven quasi continuum robots(TDQCRs) comprising rigid-flexible coupling subsegments.Aiming at real-time control applications, we present a novel static-to-kinematic modeling approach to gain a comprehensive understanding of the TDQCR model. The analytical subsegment-based kinematics for the multisection manipulator is derived based on screw theory and product of exponentials formula, and the static model considering gravity loading,actuation loading, and robot constitutive laws is established. Additionally, the effect of tension attenuation caused by routing channel friction is considered in the robot statics, resulting in improved model accuracy. The root-mean-square error between the outputs of the static model and the experimental system is less than 1.63% of the arm length(0.5 m). By employing the proposed static model, a mapping of bending angles between the configuration space and the subsegment space is established. Furthermore, motion control experiments are conducted on our TDQCR system, and the results demonstrate the effectiveness of the static-to-kinematic model.

Nonlinear wave dispersion in monoatomic chains with lumped and distributed masses:discrete and continuum models

The main objective of this paper is to investigate the influence of inertia of nonlinear springs on the dispersion behavior of discrete monoatomic chains with lumped and distributed masses.The developed model can represent the wave propagation problem in a non-homogeneous material consisting of heavy inclusions embedded in a matrix.The inclusions are idealized by lumped masses,and the matrix between adjacent inclusions is modeled by a nonlinear spring with distributed masses.Additionally,the model is capable of depicting the wave propagation in bi-material bars,wherein the first material is represented by a rigid particle and the second one is represented by a nonlinear spring with distributed masses.The discrete model of the nonlinear monoatomic chain with lumped and distributed masses is first considered,and a closed-form expression of the dispersion relation is obtained by the second-order Lindstedt-Poincare method(LPM).Next,a continuum model for the nonlinear monoatomic chain is derived directly from its discrete lattice model by a suitable continualization technique.The subsequent use of the second-order method of multiple scales(MMS)facilitates the derivation of the corresponding nonlinear dispersion relation in a closed form.The novelties of the present study consist of(i)considering the inertia of nonlinear springs on the dispersion behavior of the discrete mass-spring chains;(ii)developing the second-order LPM for the wave propagation in the discrete chains;and(iii)deriving a continuum model for the nonlinear monoatomic chains with lumped and distributed masses.Finally,a parametric study is conducted to examine the effects of the design parameters and the distributed spring mass on the nonlinear dispersion relations and phase velocities obtained from both the discrete and continuum models.These parameters include the ratio of the spring mass to the lumped mass,the nonlinear stiffness coefficient of the spring,and the wave amplitude.

Progress in ab initio in-medium similarity renormalization group and coupled-channel method with coupling to the continuum

Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and consistent treatment of nuclear forces as inputs of modern many-body calculations,among which the in-medium similarity renormalization group(IMSRG)and its variants play a vital role.On the other hand,signifcant eforts have been made to provide a unifed description of the structure,decay,and reactions of the nuclei as open quantum systems.While a fully comprehensive and microscopic model has yet to be realized,substantial progress over recent decades has enhanced our understanding of open quantum systems around the dripline,which are often characterized by exotic structures and decay modes.To study these interesting phenomena,Gamow coupled-channel(GCC)method,in which the open quantum nature of few-body valence nucleons coupled to a deformed core,has been developed.This review focuses on the developments of the advanced IMSRG and GCC and their applications to nuclear structure and reactions.

Human immunodeficiency virus cascade–continuum of care stages and outcomes in a hospital in southern Brazil

BACKGROUND The human immunodeficiency virus(HIV)continuum of care cascade illustrates the 90-90-90 goals defined by the Joint United Nations Program on HIV/acquired immunodeficiency syndrome(UNAIDS).The care cascade includes the following five steps:Diagnosis,linkage to care,retention in care,adherence to antiretroviral therapy(ART),and viral suppression.AIM To elaborate the HIV cascade of patients diagnosed with HIV at the Nossa Senhora da Conceição Hospital(HNSC)and to determine possible local causes for the loss of patients between each step of the cascade.METHODS This retrospective cohort study included patients diagnosed with HIV infection from January 1,2015 to December 31,2016 and followed up until July 31,2019.The data were analyzed by IBM SPSS software version 25,and Poisson regression with simple robust variance was used to analyze variables in relation to each step of the cascade.Variables with P<0.20 were included in multivariable analysis,and P<0.05 was considered significant.Pearson’sχ^(2) test was used to compare the groups of patients followed up at the HNSC and those followed up at other sites.RESULTS The results were lower than those expected by the UNAIDS,with 94%of patients linked,91%retained,81%adhering to ART,and 84%in viral suppression.Age and site of follow-up were the variables with the highest statistical significance.A comparison showed that the cascade of patients from the HNSC had superior results than outpatients,with a significant difference in the last step of the cascade.CONCLUSION The specialized and continued care provided at the HNSC was associated with better results and was closer to the goals set by the UNAIDS.The development of the HIV cascade using local data allowed for the stratification and evaluation of risk factors associated with the losses occurring between each step of the cascade.

中空连续体机械臂的设计与主从任务转换避障控制

连续体机械臂具有优良的弯曲性能和柔顺灵活性,表现出了独特的环境适应性和人机交互安全性,在微创手术、灾后救援、狭窄空间检修等非结构化环境及家庭服务领域具有广阔的应用前景.然而,连续体机械臂的中央脊椎骨占据其内部空间,模块单元冗余且运动耦合导致避障运动困难等问题妨碍了其在实际场景中的应用.针对以上问题,设计了内部中空的丝驱动连续体机械臂,为末端执行器的电液气管线留置出了充足的物理空间,并通过鲍登管在结构上实现了模块单元间的运动解耦;考虑丝驱动连续体机械臂的弯曲特性,建立了解耦后的简化运动学模型和运动学闭环控制算法;构造了评估空间障碍物与连续体机械臂最短距离的计算方法;在传统变构型避障运动控制的基础上,提出了基于主从任务转换的避障控制算法,能够在末端轨迹跟踪约束下,实现对障碍的躲避,同时也可暂时舍弃对给定末端轨迹的跟踪以躲避位于末端运动轨迹附近的障碍物.仿真和实验结果表明:所设计的连续体机械臂具有良好的运动能力,轨迹跟踪控制的末端位置平均误差为2.510 mm,仅为连续体机械臂长度的0.32%;提出的主从任务转换避障控制算法有效,能够准确评估末端运动与避障运动的优先级,相关研究工作为连续体机械臂的设计和运动控制提供了新的参考和思路.

连续统视域下高校学生智能素养评价体系构建

[目的/意义]数智社会对高校学生核心素养发展提出新的要求,有待进一步明晰智能素养内涵并构建面向高校学生的智能素养评价指标体系,为学生智能素养发展状态测评、能力提升和培育提供参考支持。[方法/过程]从素养连续统的视角出发,系统梳理智能素养的缘起与发展,通过对素养内容解构与要素集结,映射于智能素养的指标体系。基于KSAVE模型提出高校学生智能素养评估框架,通过文献调研界定指标内涵,进而运用德尔菲法优化初步构建的评价指标体系,利用群决策层次分析法确定评价指标权重。[结果/结论]构建了由意识态度、知识与技能、高阶思维能力、智能伦理和价值实现5个一级指标以及19个二级指标构成的高校学生智能素养评价体系,并从认知站位、内驱路径和情景创建三个方面提出智能素养的培养策略。

陆海统筹生态保护修复的生态学基础、难点问题与对策建议

如何实现陆海和谐与统筹发展已经成为当前我国生态文明建设中面临的重大问题,沿海城市社会经济发展过程中应当统筹好陆海空间,确保生态安全已经逐渐成为共识。本文从陆海空间生态耦联关系出发,探讨了陆海生态系统连续体和海陆生态交错带的结构与功能,为陆海统筹生态保护修复提供理论基础;分析认为陆海二元结构所导致的生态系统连续体断裂与生态交错带丧失,是亟待解决的难点问题;进一步提出了保护修复生态系统连续体,恢复陆海生态廊道连通,构建多生境生态缓冲空间,并促进陆海空间协同增效的对策建议,为我国推进面向陆海统筹生态保护修复提供基础参考。

基于孔洞扩张模型的偏心受力焊接球节点延性断裂数值模拟

在单层网壳结构中,焊接球节点偏心受力,常规有限元分析无法准确确定其与延性断裂对应的极限承载力。该文采用孔洞扩张模型(VGM)对偏心受力焊接球节点的延性断裂进行研究,明确了偏心受压和偏心受拉焊接球节点的失效模式,准确确定了偏心受拉焊接球节点延性断裂的位置和极限承载力。针对孔洞扩张模型要求极小有限元网格、计算效率较低的问题,采用基于VGM的连续损伤模型(CDM),编制用户子程序,在有限元分析中删除满足断裂判据的单元,对偏心受拉焊接球节点延性断裂全过程进行了数值模拟,通过与孔洞扩张模型的对比,验证了基于VGM的连续损伤模型对焊接球节点延性断裂分析的适用性。基于VGM的连续损伤模型允许采用较大网格进行断裂后裂纹扩展的数值模拟,极大地降低了计算成本。

A model of continuum damage mechanics for high cycle fatigue of metallic materials

A non-linear continuum damage model was presented based on the irreversible thermodynamics framework developed by LEMAITRE and CHABOCHE. The proposed model was formulated by taking into account the influence of loading frequency on fatigue life. The parameters H and c are constants for frequency-independent materials, but functions of cyclic frequency for frequency-dependent materials. In addition, the expression of the model was discussed in detail at different stress ratios （R）. Fatigue test data of AlZnMgCu1.5 aluminium alloy and AMg6N alloy were used to verify the proposed model. The results showed that the model possesses a good ability of predicting fatigue life at different loading frequencies and stress ratios.

用Cluster-Continuum模型计算水溶液中VO_2^+/VO^(2+)电对溶剂化自由能

利用Cluster-Continuum模型,通过B3LYP方法计算出VO2+/VO2+电对的第一溶剂化层的水分子数分别为3和5个,并得到了水溶液中VO2+、VO2+离子的溶剂化自由能。利用此计算数值并通过热力学计算推算出VO2+/VO2+电对的标准反应电势为1.29V,与理论值相差不大。这表明利用Cluster-Continuum模型可以较为准确地描述VO2+、VO2+离子的溶剂化作用。

基于变参递归网络和递归最小二乘的连续体机器人控制

连续体机器人通常由柔性材料制成,能够承受大幅度形变,在各领域具有广阔的应用前景.然而,其软体结构和非传统的驱动机制也带来了诸多非线性因素,使得其状态和运动难以被精确建模.因此,为连续体机器人设计了一种无模型控制方案.该方案一方面通过变参递归神经网络(Varying parameter-recursive neural network,VP-RNN)求解连续体机器人的逆运动学,以实现高精度运动控制,另一方面使用递归最小二乘法(Recursive least square,RLS)基于实时数据估计和更新机器人雅可比矩阵伪逆,以避免机器人的解析建模.最后,通过仿真模拟和实物实验验证了所提出控制方案的可行性、精确性和鲁棒性,并通过一系列对比实验突出了所提出方法的优势.该方法率先研究基于递归最小二乘法的连续体机器人雅可比矩阵伪逆估计,对未来的连续体机器人研究具有一定的启示作用.

陆海连续体的生物连通性研究——以长江口上海水域鱼类为例

陆海连续体是连接陆地生态系统和开阔海洋的过渡带,其连通性对生物迁移产生重大影响,但对陆海连续体连通性的描述和量化目前仍在探索之中。本研究利用环境DNA(eDNA)宏条形码技术,通过使用针对脊椎动物的通用引物对鱼类线粒体12S rRNA基因的部分V5高变区进行扩增,获得鱼类多样性数据,并以此为基础开发了一种快捷方法来评估陆海连续体的连通性。该方法通过计算相邻站点间的Beta多样性指数来综合估算生物连通性综合指数(comprehensive index of biological connectivity,CIBC),该值范围0~1,值越大,连通性越好。2023年10月利用eDNA技术成功从长江口上海水域检测出鱼类21目,35科,86属,117种,其中支流的鱼类数量多于干流。Alpha多样性分析显示,支流的鱼类群落丰富度高于干流,但多样性略低于干流。鲤科的CIBC值显示,干流、支流连通性普遍较好。鲴科的CIBC值显示,干流上下游连通性较好。鱊科的CIBC值显示,干流上游连通性较好。虾虎鱼科的CIBC值显示,干流中上游连通性较好。整个鱼类群落的CIBC值显示,干流连通性较好,仅下游接近长江口处连通性较差,支流的连通性变化较大,干流的整体连通性优于支流。本研究方法可为研究陆海连续体连通性提供新的思路,并有助于长江口生态廊道的生态修复与综合管理。

Motivation in Foreign Language Learning: Applying the Time Continuum Model of Motivation in FLL

The research is: by using Wdolkowski's Time Continuum Model throughout a lesson plan enables the teacher to increase students'motivation and help them move closer to success in a learning environment. This research supports the theory that instruction is a network of interactions between the teacher and learner that promotes a successful learning experience. It identifies a three-part learning sequence-a beginning, middle and an end. Each part has two of six key motivational factors that when applied correctly by the teacher will maximize the success and continued motivation of the learner.

心理学视角下的价值观冲突:影响及其理论解释

价值观冲突是指个体之间由于不同的价值观念而产生的相互否定和竞争现象。在当前心理学领域的实证研究中,价值观冲突通常分为两类:一类是因价值观念或身份无法兼容而引发的长期冲突,另一类是由价值两难选择任务引发的即时冲突。这两类冲突都可能导致一系列消极的心理影响,例如增加压力感知、焦虑水平和心理紧张度。研究者主要从价值观背后的动机对立性和自我概念完整性的威胁感知两个方面,来解释价值观冲突的产生原因及其影响。未来的研究需要进一步明确价值观冲突的产生机制,扩展对调节因素的认识,并揭示其对个体的影响,以开展相应的调节与干预研究。

Nonlinear saturation of reversed shear Alfvén eigenmode via high-frequency quasi-mode generation

A nonlinear saturation mechanism for reversed shear Alfvén eigenmode(RSAE)is proposed and analyzed,and is shown to be of relevance to typical reactor parameter region.The saturation is achieved through the generation of high-frequency quasi-mode due to nonlinear coupling of two RSAEs,which is then damped due to coupling with the shear Alfvén continuum,and leads to the nonlinear saturation of the primary RSAEs.An estimation of the nonlinear damping rate is also provided.

气动软体弯曲驱动关节设计、制造与验证

根据仿生学原理,软体爬行动物在行进过程中主要是关节与躯干相互配合。通过对尺蠖的弯曲关节处的功能分析,为此设计了一种基于快速气动网格结构的“软体弯曲驱动关节”驱动器来等效软体爬行动物关节处的运动特性,完成软体爬行机器人运动。建立“软体弯曲驱动关节”静力学模型。利用分布灌注成型技术制作硅胶的材质的“软体弯曲驱动关节”。利用Yeoh二阶模型进行静力学模型分析,得到在不同的驱动气压下与弯曲角度、拉伸形变的关系,建立其在工作过程中的拉伸耦合模型。通过ABAQUS有限元分析软件和实验平台对“软体弯曲驱动关节”建立的模型进行验证弯曲轨迹末端点与测量值,模型计算值与实际值的最大误差为1.4 mm,“软体弯曲驱动关节”弯曲段的拉伸耦合模型理论模型与实际模型基本吻合。