A NOVEL COMMUNICATION LAW FOR BILATERAL FORCE-REFLECTING SUBSYSTEM OF TELEOPERATORS WITH TIME DELAY

This paper presents a novel communication law for teleoperators in the presence of substantial time delay. This new communication law can guarantee the stability of teleoperators in any time delay. The performance of teleoperators which use this new communication law is improved greatly.

Experimental study of reflection coefficient and wave forces acting on perforated caisson

The reflection coefficient and the total horizontal forces of regular waves acting on theperforated caisson are experimentally investigated. The empirical relationship between reflection coefficient and the ratio of the total horizontal forces acting on the perforated caisson to those on solid vertical walls with the relative chamber width, relative water depth and porosity of perforated wall, etc. are given. Moreover, the results of the ratio of the total horizontal forces are also compared with formulas given by Chinese Harbour Design Criteria and Takahashi, which may be useful for the practical engineering application.

Upgraded Force on a Wall from Reflected Surface Gravity Waves

During reflection from a solid vertical wall, surface gravity waves produce a steady force on the wall, which was calculated earlier by the momentum method. Recently the linear momentum of these waves has been estimated to be twice as large as deduced from the classical Stokes drift formula. Therefore, the magnitude of the reflected wave force has been doubled here and the algebraic form of the equation is converted to be more understandable physically. Wave force equals fluid density times the square of the particle’s orbital speed and a numerical constant. Observations are welcomed to compare with the theory.

Cross-Linked Alginate Film Pore Size Determination Using Atomic Force Microscopy and Validation Using Diffusivity Determinations

The deficit of organ donors has fueled the need for advances in tissue engineering and regenerative medicine. Microencapsulation in alginate immuno-isolation membranes has been used to treat many disabling metabolic disorders, namely, phenylketonuria, kidney failure and diabetes mellitus. Systematic nutrient flux determinations are hindered by the lack of experimental data on alginate-based membrane topography and the pore size thus preventing the full therapeutic potential of the bio-membranes to be reached. In this study, samples of cross-linked alginate membranes were subjected to the following analytical characterization: 1) pore size characterization using atomic force microscopy operated in contact mode to detect and measure pore size;2) differential scanning calorimetry to confirm biopolymer cross-linking;and 3) diffusivity measurements using spectrophotometry and fluorescence microscopy to confirm the presence of through pores and to calculate reflection coefficients. The pore sizes for the pre-clinical standard formulation of 1.5% (w/v) medium viscosity alginate cross-linked with 1.5% CaCl2 and 0.5% (w/v) alginate and chitosan cross-linked with 20% CaCl2 are 5.2 nm ± 0.9 nm and 7.0 nm ± 3.1 nm, respectively. An increase in the glass transition temperatures as a function of cross-linker concentration was observed. Diffusivity values obtained from the inward diffusivity of creatinine into macrocapsules (d = 1000 μm ± 75 μm) and the outward diffusivity of FITC dextrans from macrocapsules (d = 1000 μm ± 75 μm) and microcapsules (d = 40 μm ± 5 μm) were shown to correlate strongly (R2 = 0.9835) with the ratio of solute to pore sizes, confirming the presence of through pores. Reflection coefficients approaching and exceeding unity correlate with the lack of permeability of the membranes to MW markers that are 70 kDa and greater.

部分反射直墙前二维物体的绕射和辐射问题

基于映像理论将部分反射直墙前物体的散射问题,等效于开敞水域中原物体的散射和关于直墙映像体散射的线性叠加进行求解。采用高阶边界元方法建立了部分反射直墙前二维任意形状物体波浪绕射和辐射问题的数值分析模型,通过与已发表的海底方箱和淹没圆柱结果的对比验证了数值模型的准确性。应用该模型研究了直墙反射系数幅值及相位、方箱与墙间距离等参数对水面方箱上波浪激振力、附加质量和辐射阻尼的影响。结果表明:直墙反射系数幅值越大,波浪激振力、附加质量和辐射阻尼的波动越大,附加质量在一些频率下出现负值;相位角的变化会改变波浪激振力、附加质量和辐射阻尼曲线的偏移,在低频区对升沉附加质量有显著影响;方箱距离直墙越远,方箱上的波浪激振力、附加质量和辐射阻尼随波数振荡的频率越快,峰值频率向低频侧移动。

基于气泡统一方程的声场双气泡耦合作用研究

针对声致空化现象中双气泡相互作用力展开了研究。本文基于气泡动力学的基本理论,将气泡统一方程应用到声场中双气泡的耦合作用研究中,建立了可用于计算声场中多气泡耦合的理论模型,并以此研究了不同类型的声场中双气泡次Bjerknes力的变化趋势。研究结果表明:在声压幅值较小的行进波声场中,对于非线性脉动的双气泡,其相互作用现象不仅与声场参数相关,还会受到双气泡初始体积比的影响。若固定其中一个气泡的初始体积,同时改变另一个气泡的初始体积,则双气泡间第1周期内的次Bjerknes力会在初始体积相等时达到第1个极值,随后呈现周期性的起伏,并在总体上呈增大趋势;而双气泡相互作用在声压幅值较大的行进波声场中会随初始半径比的增大持续增强,且周期性的起伏现象并不明显。在驻波声场中靠近波节的位置也能观测到这一现象。此外,本文还探究了非线性振动的双气泡在具有相同频率、不同声压幅值的组合波声场中的耦合效应。本文的研究可为声场中双气泡相互耦合作用以及气泡群动力学相关应用提供理论基础。

IRS Assisted UAV Communications against Proactive Eavesdropping in Mobile Edge Computing Networks

In this paper,we consider mobile edge computing(MEC)networks against proactive eavesdropping.To maximize the transmission rate,IRS assisted UAV communications are applied.We take the joint design of the trajectory of UAV,the transmitting beamforming of users,and the phase shift matrix of IRS.The original problem is strong non-convex and difficult to solve.We first propose two basic modes of the proactive eavesdropper,and obtain the closed-form solution for the boundary conditions of the two modes.Then we transform the original problem into an equivalent one and propose an alternating optimization(AO)based method to obtain a local optimal solution.The convergence of the algorithm is illustrated by numerical results.Further,we propose a zero forcing(ZF)based method as sub-optimal solution,and the simulation section shows that the proposed two schemes could obtain better performance compared with traditional schemes.

外磁场调控下偶极梯度半空间中弹性波的反射

本文研究了在偶极梯度弹性固体中,在外加磁场调控作用下,弹性波在界面上的反射问题.当入射波的波长与材料的微结构特征长度近似或者弹性波的频率较高时,材料的微结构效应显著增加.本文首先应用偶极应变梯度理论和麦克斯韦电磁理论推导出弹性波传播的色散方程,然后根据界面条件分别计算出P波入射和SV波入射时各种反射波与入射波的振幅比.最后,根据数值计算结果,讨论了外加磁场以及入射波长对反射波传播的影响.研究结果发现,在偶极梯度弹性固体中,微结构效应可以导致新的波动模式产生和弹性波的色散特征的出现,而外加磁场只是通过洛伦兹力的作用对弹性波传播的速度产生影响,但不会产生新的波动模式和影响弹性波的色散性质.

磁-热-弹多物理场耦合波的反射和透射

应用麦克斯韦电磁学理论引入洛伦兹力,反映外磁场对弹性波传播的影响.通过应用广义热弹性GN(Ⅱ)模型,反映热力耦合效应对弹性波传播的影响.通过色散方程和相速度,分析了外磁场和热力耦合效应对波动模式和色散特性的影响.应用连续性边界条件,计算出各种反射波和透射波与入射波的能流比,通过法向能量守恒验证了数值计算结果的可靠性.

基于分数阶LS模型的多场耦合波的反射和透射

应用麦克斯韦电磁学理论引入洛伦兹力,反映外磁场对弹性波传播的影响,运用分数阶广义热弹性LS模型,反映热力耦合效应对弹性波传播的影响.通过色散方程,分析了外磁场和热力耦合效应对波动模式和色散特性的影响.应用连续性边界条件计算出各种反射波和透射波与入射波的能流比,并通过法向能量守恒验证了数值计算结果的可靠性.

不均匀海底地形影响下柔性板与斜向来浪的相互作用

The present work analyzes the interaction of oblique waves by a porous flexible breakwater in the presence of a step-type bottom.The physical models for both scattering and trapping cases are considered and developed within the framework of small amplitude water-wave theory.Darcy’s law is used to model the wave interaction with the porous medium.It is assumed that the varying bottom extends over a finite interval,connected by a finite length of uniform bottom near an impermeable wall,and a semi-infinite length of bottom in the open water region.The boundary value problem is solved using the eigenfunction expansion method in the uniform bottom regions,while a modified mild-slope equation(MMSE)is used for the region with the varying bottom.Additionally,a mass-conserving jump condition is employed to handle the solution at slope discontinuities in the bottom.A system of equations is derived by matching the solutions at interfaces.The reflection coefficient and force on the breakwater and impermeable wall are plotted and analyzed for various parameters,such as the length of the varying bottom,depth ratio,angle of incidence,and flexural rigidity.It is observed that moderate values of flexural rigidity and depth ratio significantly contribute to an optimum reflection coefficient and reduce the wave force on the wall and breakwater.Remarkably,the outcomes of this study are assumed to be applicable in the construction of this type of breakwater in coastal regions.

孔隙率对矩形沟槽上垂直多孔屏障的波浪散射效应影响

The effect of porosity on surface wave scattering by a vertical porous barrier over a rectangular trench is studied here under the assumption of linearized theory of water waves.The fluid region is divided into four subregions depending on the position of the barrier and the trench.Using the Havelock’s expansion of water wave potential in different regions along with suitable matching conditions at the interface of different regions,the problem is formulated in terms of three integral equations.Considering the edge conditions at the submerged end of the barrier and at the edges of the trench,these integral equations are solved using multi-term Galerkin approximation technique taking orthogonal Chebyshev’s polynomials and ultra-spherical Gegenbauer polynomial as its basis function and also simple polynomial as basis function.Using the solutions of the integral equations,the reflection coefficient,transmission coefficient,energy dissipation coefficient and horizontal wave force are determined and depicted graphically.It was observed that the rate of convergence of the Galerkin method in computing the reflection coefficient,considering special functions as basis function is more than the simple polynomial as basis function.The change of porous parameter of the barrier and variation of trench width and height significantly contribute to the change in the scattering coefficients and the hydrodynamic force.The present results are likely to play a crucial role in the analysis of surface wave propagation in oceans involving porous barrier over submarine trench.

共同富裕背景下社会力量参与第三次分配:时代内涵、实践形态与路径省思

第三次分配是社会力量自愿通过慈善活动与志愿服务对各类资源进行重新配置的社会活动,是对初次分配和再分配的补充性制度安排,对于推进共同富裕具有重要价值。社会力量参与第三次分配的主要形式为慈善组织进行信息收集与募集善款、市场企业进行利益与资源共享、社会个人进行捐赠与志愿服务,但同时也面临着结构失衡、成长受阻与信任危机等现实困境。结合我国实际情况,应从法律层面、制度层面、治理层面、环境层面与监督层面反思社会力量参与第三次分配的路径:通过完善《慈善法》相关法律体系优化社会力量的参与渠道,通过公正合理的制度措施激发社会力量的参与热情,通过构建“善”治导向的共同体促进社会力量的参与长久,通过营造积极健康的慈善生态稳定社会力量的参与环境,通过建立多元协同的监督机制改善社会力量的参与实践,旨在充分发挥社会力量在第三次分配中的重要作用,在高质量发展中扎实推进共同富裕。

半椭圆型防波堤水动力特性的数值模拟

该文提出了一种新型防波堤结构:半椭圆型防波堤。采用FLOW 3D建立数值波浪水槽,模拟了波浪与半椭圆型防波堤的相互作用,并通过物理模型试验验证了数值模型的合理性。结合数值模拟结果分析了波浪参数变化对半椭圆型防波堤水动力特性的影响,结果表明:反射系数随着堤顶高程和水位之差hs与设计波高H的比值hs/H增大而增大,透射系数随hs/H增大而减小;在本研究波浪周期范围内,水深D不变时,半椭圆型防波堤对周期T较大的波浪的挡浪效果优于周期较小的工况。随着D与半椭圆型防波堤立轴b的比值D/b的增大,挡浪效果变差。波浪力随着h_(s)/H的减小而增大,随H与波长L的比值H/L的增大而减小。相同工况下,随着半椭圆型防波堤卧轴a与立轴b的比值增大,结构所受水平波浪力减小,竖直波浪力增大,防波堤自重增大,防波堤稳定性增强。半椭圆型防波堤的优势在于,其卧轴和立轴的大小关系可以根据不同的工程条件自行设计,若以椭圆长轴卧放,则比防范相同水深的半圆型防波堤更适用于软弱基床,从而更加安全可靠;若以短半轴立放,则在防范相同水深的前提下,比半圆型防波堤节省材料,从而降低建造成本。

术后轻度低体温患者组合保暖与充气式加温仪复温效果比较

目的探讨组合保暖与充气式加温仪在术后轻度低体温患者中的应用效果。方法将90例术后轻度低体温患者随机分成两组各45例。观察组使用反光毯和棉被的组合保暖方式复温,对照组使用充气式加温仪复温。结果复温后两组的升温值差异未达非劣效边界。两组体感舒适度、寒战和心血管不良事件发生率无统计学差异(均P>0.05)。结论组合保暖方式应用于轻度低体温患者的升温效率与充气式加温仪相当;体感舒适度和安全性与充气式加温仪也相似,适用于此类患者的术后复温。

强化国家战略科技力量的政策演变、理论进展与展望

强化战略科技力量对实现高水平科技自立自强、建设科技强国至关重要。文章梳理了我国战略科技力量政策的变迁历程,从内涵、要素、主体和路径对策角度分析了战略科技力量研究的理论逻辑,并通过反思现有研究对未来研究进行展望。研究发现:我国战略科技力量政策发展经历了早期探索、战略升级、全面建设三个阶段,呈现需求层级不断提升、原始创新特征逐渐强化、主体分工特征不断明确、部门协同和深度融合明显等演变特征。战略科技力量理论研究在内涵特征、历史演进、关键主体和路径对策等方面取得了初步进展,但远未达成共识并形成理论体系。未来研究应聚焦协同机制分析、测度识别和创新效应评估、科技治理制度改革,不断拓展理论研究深度,科学评估科技力量建设进程,夯实中国式现代化新征程的科技基础能力。

外磁场调控下弹性波的反射和透射

本文应用麦克斯韦电磁学理论研究了在外磁场调控下弹性波的反射和透射问题.首先根据麦克斯韦方程组推导出洛伦兹力,其次根据运动方程推导出P波、SV波和SH波的色散关系,然后根据连续的界面条件推导出反射波和透射波相对于入射波的振幅比以及能流比.通过数值计算结果,详细分析了洛伦兹力对弹性波反射和透射的影响,结果发现,洛伦兹力不改变波动模式和色散性质,只改变弹性波的传播速度大小.最后,通过法向能量守恒验证了数值计算结果的可靠性.

Possible Relevance of the Allende Meteorite Conditions in Prebiotic Chemistry: An Insight into the Chondrules and Organic Compounds

The study of the mineral and organic content of the Allende meteorite is important for our understanding of the molecular evolution of the universe as well as the ancient Earth. Previous studies have characterized the magnetic minerals present in ordinary and carbonaceous chondrites, providing information on the evolution of magnetic fields. The interaction of organic compounds with magnetic minerals is a possible source of chemical diversity, which is crucial for molecular evolution. Carbon compounds in meteorites are of great scientific interest for a variety of reasons, such as their relevance to the origins of chirality in living organisms. This study presents the characterization of organic and mineral compounds in the Allende meteorite. The structural and physicochemical characterization of the Allende meteorite was accomplished through light microscopy, powder X-ray diffraction with complementary Rietveld refinement, Raman and infrared spectroscopy, mass spectrometry, scanning electron microscopy, and atomic force microscopy using magnetic signal methods to determine the complex structure and the interaction of organic compounds with magnetic Ni-Fe minerals. The presence of Liesegang-like patterns of chondrules in fragments of the Allende structure may also be relevant to understanding how the meteorite was formed. Other observations include the presence of magnetic materials and nanorod-like solids with relatively similar sizes as well as the heterogeneous distribution of carbon in chondrules. Signals observed in the Raman and infrared spectra resemble organic compounds such as carbon nanotubes and peptide-like molecules that have been previously reported in other meteorites, making the Mexican Allende meteorite a feasible sample for the study of the early Earth and exoplanetary bodies.

梳式沉箱防波堤的水力学特性

本文通过实验研究 ,对于梳式沉箱这种新型防波堤结构的水力学特性进行了系统研究 ,论证了它能够减小波浪反射与减小结构受力的水力学机制 ;通过系列实验 ,本文给出了梳式结构受力与常用实体沉箱受力之比 (波浪力折减系数 )与各主要影响参数间相关的计算公式 ,可用以进行梳式结构的尺度选择与优化和进行梳式结构设计的初步计算。该结构已在大连港大窑湾港区岛堤工程中得到实际应用 ,实验证明梳式方案的水平波浪力仅为常用沉箱受力值的 6 2 %～73% ,可节省投资 2 4 .5 %。

Internet模型与网络遥操作系统仿真环境的建立

通过对Internet进行不同地点、时间段和数据包大小的传输时延统计 ,得到了网络传输时延近似符合正态、指数分布或对数正态分布的统计规律。根据Internet的统计模型建立了以Internet仿真器为基础的网络遥操作系统仿真环境。Internet仿真器提供统计模型的三种分布和与实测数据相同分布的时延 。