双正交Hermite Cubics的对称预滤波设计

将多小波预滤波器设计的"超函数"法推广到了双正交系统,得到使联合滤波器具有m阶平衡的条件,并针对双正交Hermite Cubics,分别设计了使系统具有2阶平衡与4阶平衡的对称预滤波器.

基于Hermite Cubics的预滤波器与双正交平衡系统

首先将正交多小波系统的平衡性理论及预滤波理论推广到双正交系统,在此基础上,从不具有平衡性的Hermite Cubics双正交多小波出发,得到两组使系统的"低通"滤波器保持三阶多项式信号的预滤波器,最后给出一组基于Hermite Cubics系统的具有一阶平衡性的双正交多小波系统.

The burden of upper motor neuron involvement is correlated with the bilateral limb involvement interval in patients with amyotrophic lateral sclerosis:a retrospective observational study

Amyotrophic lateral sclerosis is a rare neurodegenerative disease characterized by the involvement of both upper and lower motor neurons.Early bilateral limb involvement significantly affects patients'daily lives and may lead them to be confined to bed.However,the effect of upper and lower motor neuron impairment and other risk factors on bilateral limb involvement is unclear.To address this issue,we retrospectively collected data from 586 amyotrophic lateral sclerosis patients with limb onset diagnosed at Peking University Third Hospital between January 2020 and May 2022.A univariate analysis revealed no significant differences in the time intervals of spread in different directions between individuals with upper motor neuron-dominant amyotrophic lateral sclerosis and those with classic amyotrophic lateral sclerosis.We used causal directed acyclic graphs for risk factor determination and Cox proportional hazards models to investigate the association between the duration of bilateral limb involvement and clinical baseline characteristics in amyotrophic lateral sclerosis patients.Multiple factor analyses revealed that higher upper motor neuron scores(hazard ratio[HR]=1.05,95%confidence interval[CI]=1.01–1.09,P=0.018),onset in the left limb(HR=0.72,95%CI=0.58–0.89,P=0.002),and a horizontal pattern of progression(HR=0.46,95%CI=0.37–0.58,P<0.001)were risk factors for a shorter interval until bilateral limb involvement.The results demonstrated that a greater degree of upper motor neuron involvement might cause contralateral limb involvement to progress more quickly in limb-onset amyotrophic lateral sclerosis patients.These findings may improve the management of amyotrophic lateral sclerosis patients with limb onset and the prediction of patient prognosis.

结合柯西分布和高斯扰动的正余弦混合优化算法

针对正余弦优化算法(SCA)存在的寻优精度低、收敛速度慢、易陷入局部最优等缺陷,提出一种结合柯西分布和高斯扰动的正余弦混合优化算法。利用Cubic混沌映射提高初始种群的个体质量;构建自适应调整的能量因子来平衡算法的全局探索和局部开发能力;通过柯西分布的逆累积分布函数方法更新个体位置,加强算法的全局探索能力;混合算法根据策略选择因子有条件地执行SCA算法和高斯扰动策略,增加迭代后期种群多样性,降低算法陷入局部极值的概率,提升算法的寻优精度和收敛速度。通过10个经典测试函数的低维与高维验证,所提算法相较于对比算法,具有更高的寻优精度和更快的收敛速度。

双种群协同演化的改进蜜獾算法

针对蜜獾算法存在的局部搜索能力不足、易陷入局部最优值等问题,提出一种双种群协同演化的改进蜜獾算法。在初始化阶段采用Cubic混沌映射对种群进行初始化,扩大可行解的搜索范围并提高种群的分布均衡性;引入融合黏菌算法和蜜獾算法的双种群优化机制,依托两者的更新优势协同推进个体逼近目标位置,进而提高整个算法的搜索效率和优化性能;采用柯西随机反向扰动策略对蜜獾种群最优位置进行扰动,以提高算法跳出局部最优的能力。通过评估单一策略的改进有效性实验、与七种对比算法的不同高维实验以及Wilcoxon秩和检验,结果表明该算法具有良好的收敛精度和求解速度。最后将改进算法应用于压缩弹簧设计和压力容器设计问题,进一步验证了改进策略的有效性及该算法的工程实用性。

基于精英引导的社会学习粒子群优化算法

为了改进经典粒子群算法(PSO)过早收敛和全局搜索能力不足的缺点,提出了一种基于精英引导的社会学习粒子群优化算法(ESLPSO)。在ESLPSO中,提出了一种分层拓扑结构的搜索方法。这一策略根据粒子的适应度表现将粒子分化为最优的精英粒子和其余的平民粒子,革新了传统种群迭代搜索的更新样本,由此加强了整个种群演化信息的引导作用。采用Cubic混沌初始化赋予了初始粒子群体在搜索空间内的广域覆盖能力。设计了精英粒子引导的社会学习策略,通过增加态叠加的不确定性更好地利用了种群演化的多维信息。在此基础上,结合极值扰动迁移机制激励粒子经历新的搜索路径和区域,增加种群的多样性,平衡种群在搜索过程中的探索和开发能力。基于12个涵盖单峰、多峰以及旋转多峰的基准测试函数集对所提算法的性能进行了验证。此外,ESLPSO与其他8种PSO改进算法的比较结果表明,ESLPSO在解决不同类型函数方面表现出了优秀的搜索性能,具有高效的求解稳定性和优异的求解结果。

星载共口径多波束赋形反射面天线设计

为了满足星载通信中多任务并行需求,提出了一种由格里高利型反射面和三个馈源喇叭天线组成的共口径多波束反射面天线,该天线能够产生两个固定轮廓波束和一个点波束。天线设计是采用射线追踪法确定点波束馈源位置以建立天线基础结构,并通过Zernike多项式和Cubic B-splines函数共同对主、副反射面进行赋形优化来完成。为了验证该方法的有效性,对口径为1.1 m的天线进行仿真设计,结果表明两个赋形轮廓波束在Ku收、发频段边缘增益(EOC gain)分别为27.7、28.0、28.0、28.2 dBi,固定点波束在服务区EOC gain不低于34 dBi并且在0~6.5°范围内的扫描波束增益不低于35 dBi。

基于改进蝴蝶搜索算法的六自由度机械臂路径规划

针对目前机械臂路径规划的主流算法,如RRT算法、蝴蝶算法和人工势场法等在全局搜索时易遇到寻优精度低、收敛速度慢,在局部搜索时易陷入局部最优解等问题,提出一种改进蝴蝶搜索算法。针对基本蝴蝶算法在种群初始化时添加了Cubic映射,在进行全局和局部搜索时加入非线性惯性权重系数和融入樽海鞘群算法,在确定最优解后加入了柯西变异,以此来提高算法收敛速度和寻优精度等问题。通过MATLAB构建六自由度机械臂和三维空间障碍物的三维模型,并进行仿真实验。结果表明:改进后的蝴蝶算法增强了收敛速度和寻优精度。最后进行了真机实验,验证了改进后的蝴蝶算法能够快速实现机械臂的路径规划。

多策略改进的鱼鹰优化算法及其应用

针对鱼鹰优化算法存在收敛速度慢、收敛精度低以及易陷入局部最优的问题,提出一种多策略融合改进的鱼鹰优化算法。首先采用Cubic混沌映射初始化种群,增加种群的多样性;其次引入互利共生策略,加强搜索个体之间的信息交流,提高算法跳出局部最优的能力;最后利用透镜成像反向学习策略,增强算法跳出局部最优的能力,平衡算法的探索与开发。通过18个基准测试函数求解对比分析、统计测试,该算法在收敛速度、寻优精度以及稳定性上都得到明显提升。此外,通过压力容器设计问题的实验对比,进一步验证了所提算法在实际工程应用中的适用性。

Fermi Rubik's Cube in High-Pressure Induced Chlorine-Rich Compounds

In the quasi-free electron model,the Fermi surface spreads into a sphere in the Brillouin zone,i.e.,the Fermi sphere.The Fermi sphere exists widely in metal systems,no matter whether the crystal is in a body-center cubic,face-center cubic,or hexagonal close-packed lattice.Here,we report a class of compounds stabilized at high pressure with Rubik’s cubic Fermi surface.

Theoretical Modeling and Surface Roughness Prediction of Microtextured Surfaces in Ultrasonic Vibration-Assisted Milling

Textured surfaces with certain micro/nano structures have been proven to possess some advanced functions,such as reducing friction,improving wear and increasing wettability.Accurate prediction of micro/nano surface textures is of great significance for the design,fabrication and application of functional textured surfaces.In this paper,based on the kinematic analysis of cutter teeth,the discretization of ultrasonic machining process,transformation method of coordinate systems and the cubic spline data interpolation,an integrated theoretical model was established to characterize the distribution and geometric features of micro textures on the surfaces machined by different types of ultrasonic vibration-assisted milling(UVAM).Based on the theoretical model,the effect of key process parameters(vibration directions,vibration dimensions,cutting parameters and vibration parameters)on tool trajectories and microtextured surface morphology in UVAM is investigated.Besides,the effect of phase difference on the elliptical shape in 2D/3D ultrasonic elliptical vibration-assisted milling(UEVAM)was analyzed.Compared to conventional numerical models,the method of the cubic spline data interpolation is applied to the simulation of microtextured surface morphology in UVAM,which is more suitable for characterizing the morphological features of microtextured surfaces than traditional methods due to the presence of numerous micro textures.The prediction of surface roughness indicates that the magnitude of ultrasonic amplitude in z-direction should be strictly limited in 1D rotary UVAM,2D and 3D UEVAM due to the unfavorable effect of axial ultrasonic vibration on the surface quality.This study can provide theoretical guidance for the design and fabrication of microtextured surfaces in UVAM.

Effect of granular shape on radial segregation in a two-dimensional drum

Granular segregation is widely observed in nature and industry.Most research has focused on segregation caused by differences in the size and density of spherical grains.However,due to the fact that grains typically have different shapes,the focus is shifting towards shape segregation.In this study,experiments are conducted by mixing cubic and spherical grains.The results indicate that spherical grains gather at the center and cubic grains are distributed around them,and the degree of segregation is low.Through experiments,a structured analysis of local regions is conducted to explain the inability to form stable segregation patterns with obviously different geometric shapes.Further,through simulations,the reasons for the central and peripheral distributions are explained by comparing velocities and the number of collisions of the grains in the flow layer.

Metastable face-centered cubic ruthenium-based binary alloy for efficient alkaline hydrogen oxidation electrocatalysis

Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocatalysts have been widely investigated toward hydrogen oxidation reaction(HOR)under alkaline electrolytes,these studies are mostly limited to conventional hexagonal-close-packed(hcp)phase,mainly arising from the lack of sufficient synthesis strategies.In this study,we report the precise synthesis of metastable binary RuW alloy with face-centered-cubic(fcc)phase.We find that the introduction of W can serve as fcc phase seeds and reduce the formation energy of metastable fcc-RuW alloy.Impressively,fcc-RuW exhibits remarkable alkaline HOR performance and stability with the activity of 0.67 mA cm_(Ru)^(-2)which is almost five and three times higher than that of hcp-Ru and commercial Pt/C,respectively,which is attributed to the optimized binding strength of adsorbed hydroxide intermediate derived from tailored electronic structure through W doping and phase engineering.Moreover,this strategy can also be applied to synthesize other metastable fcc-RuCr and fcc-RuMo alloys with enhanced HOR performances.

Synthesizing active and durable cubic ceria catalysts(<6 nm)for fast dehydrogenation of bio-polyols to carboxylic acids coproducing green H_(2)

Dehydrogenation is considered as one of the most important industrial applications for renewable energy.Cubic ceria-based catalysts are known to display promising dehydrogenation performances in this area.Large particle size(>20 nm)and less surface defects,however,hinder further application of ceria materials.Herein,an alternative strategy involving lactic acid(LA)assisted hydrothermal method was developed to synthesize active,selective and durable cubic ceria of<6 nm for dehydrogenation reactions.Detailed studies of growth mechanism revealed that,the carboxyl and hydroxyl groups in LA molecule synergistically manipulate the morphological evolution of ceria precursors.Carboxyl groups determine the cubic shape and particle size,while hydroxyl groups promote compositional transformation of ceria precursors into CeO_(2) phases.Moreover,enhanced oxygen vacancies(Vo)on the surface of CeO_(2) were obtained owing to continuous removal of O species under reductive atmosphere.Cubic CeO_(2) catalysts synthesized by the LA-assisted method,immobilized with bimetallic PtCo clusters,exhibit a record high activity(TOF:29,241 h^(-1))and Vo-dependent synergism for dehydrogenation of bio-derived polyols at 200℃.We also found that quenching Vo defects at air atmosphere causes activity loss of PtCo/CeO_(2) catalysts.To regenerate Vo defects,a simple strategy was developed by irradiating deactivated catalysts using hernia lamp.The outcome of this work will provide new insights into manufacturing durable catalyst materials for aqueous phase dehydrogenation applications.

A novel rapid cooling assembly design in a high-pressure cubic press apparatus

In traditional high-pressure–temperature assembly design, priority has been given to temperature insulation and retention at high pressures.This limits the efficiency of cooling of samples at the end of experiments, with a negative impact on many studies in high-pressure Earth andplanetary science. Inefficient cooling of experiments containing molten phases at high temperature leads to the formation of quench textures,which makes it impossible to quantify key compositional parameters of the original molten phase, such as their volatile contents. Here,we present a new low-cost experimental assembly for rapid cooling in a six-anvil cubic press. This assembly not only retains high heatingefficiency and thermal insulation, but also enables a very high cooling rate (∼600 ℃/s from 1900 ℃ to the glass transition temperature).Without using expensive materials or external modification of the press, the cooling rate in an assembly (∼600 ℃/s) with cube lengths of38.5 mm is about ten times faster than that in the traditional assembly (∼60 ℃/s). Experiments yielding inhomogeneous quenched melttextures when the traditional assembly is used are shown to yield homogeneous silicate glass without quench textures when the rapid coolingassembly is used.

组织透明化技术在器官可视化应用中的初步探讨

目的对CUBIC(clear,unobstructed brain imaging cocktails and computational analysis)组织透明化技术在小鼠不同器官中的适应性进行探讨,并探究该技术与细胞核染色及病毒示踪神经元标记技术的兼容性。方法(1)摘取并解剖新鲜灌注小鼠的脑、心以及肝,分别取1.0 cm×1.5 cm×0.5 cm的组织块,使用clear,unobstructed brain imaging cocktails and computational analysis-L(CUBIC-L)和clear,unobstructed brain imaging cocktails and computational analysis-R(CUBIC-R)组织清除液进行透明化处理;(2)对小鼠整脑进行透明化处理,应用碘化丙啶(PI)对鼠脑神经元的细胞核染色,激光片层显微镜(LSFM)获取小鼠左、右脑半球及小脑脑干的细胞核体积三维图像;(3)分别在鼠脑海马和黑质区显微注射腺相关病毒(AAV)-U6-增强型绿色荧光蛋白(EGFP),标记特定解剖部位的神经元,对完成病毒转染后的鼠脑进行透明化处理,LSFM进行三维立体成像。结果经过透明化处理的脑组织、肝组织、心脏组织都呈现透明凝胶样状态,但不同组织块的清除效率不同,脑组织清除效率最高,其次为肝脏组织,最后为心脏组织。LSFM可以对透明化并核染的脑组织进行整体积三维立体成像。AAV可以清楚的标记不同部位的神经元,配合透明化处理后可以观察到这些神经元的空间分布情况,同时还可以观察到不同部位神经元的物理投射。结论CUBIC组织透明化技术在小鼠脑组织、心组织、肝组织中具有普遍应用性,其中对脑组织的透明效率最高。CUBIC组织透明化方法与细胞核染色技术及病毒示踪神经元标记技术有很好的适配性。

Phase composition,conductivity,and sensor properties of cerium-doped indium oxide

The hydrothermal synthesis of In_(2)O_(3)and CeO_(2)–In_(2)O_(3)is investigated as well as the properties of sensor layers based on these compounds.During the synthesis of In_(2)O_(3),intermediate products In(OH)_(3)and InOOH are formed,which are the precursors of stable cubic(c-In_(2)O_(3))and metastable rhombohedral(rh-In_(2)O_(3))phases,respectively.A transition from c-In_(2)O_(3)to rh-In_(2)O_(3)is observed with the addition of CeO_(2).The introduction of cerium into rh-In_(2)O_(3)results in a decrease in the sensor response to hydrogen,while it increases in composites based on c-In_(2)O_(3).The data on the sensor activity of the composites correlate with XPS results in which CeO_(2)causes a decrease in the concentrations of chemisorbed oxygen and oxygen vacancies in rh-In_(2)O_(3).The reverse situation is observed in composites based on c-In_(2)O_(3).Compared to In_(2)O_(3)and CeO_(2)–In_(2)O_(3)obtained by other methods,the synthesized composites demonstrate maximum response to H_(2)at low temperatures by 70–100℃,and have short response time(0.2–0.5 s),short recovery time(6–7 s),and long-term stability.A model is proposed for the dependence of sensitivity on the direction of electron transfer between In_(2)O_(3)and CeO_(2).

Recension of boron nitride phase diagram based on high-pressure and high-temperature experiments

Cubic boron nitride and hexagonal boron nitride are the two predominant crystalline structures of boron nitride.They can interconvert under varying pressure and temperature conditions.However,this transformation requires overcoming significant potential barriers in dynamics,which poses great difficulty in determining the c-BN/h-BN phase boundary.This study used high-pressure in situ differential thermal measurements to ascertain the temperature of h-BN/c-BN conversion within the commonly used pressure range(3-6 GPa)for the industrial synthesis of c-BN to constrain the P-T phase boundary of h-BN/c-BN in the pressure-temperature range as much as possible.Based on the analysis of the experimental data,it is determined that the relationship between pressure and temperature conforms to the following equation:P=a+1/bT.Here,P denotes the pressure(GPa)and T is the temperature(K).The coefficients are a=-3.8±0.8 GPa and b=229.8±17.1 GPa/K.These findings call into question existing high-pressure and high-temperature phase diagrams of boron nitride,which seem to overstate the phase boundary temperature between c-BN and h-BN.The BN phase diagram obtained from this study can provide critical temperature and pressure condition guidance for the industrial synthesis of c-BN,thus optimizing synthesis efficiency and product performance.

High-Quality and Wafer-Scale Cubic Silicon Carbide Single Crystals

Cubic silicon carbide(3C-SiC)has superior mobility and thermal conduction over that of widely applied hexagonal 4H-SiC.Moreover,much lower concentration of interfacial traps between insulating oxide gate and 3C-SiC helps fabricate reliable and long-life devices like metal-oxidesemiconductor field effect transistors.However,the growth of high-quality and wafer-scale 3C-SiC crystals has remained a big challenge up to now despite decades-long efforts by researchers because of its easy transformation into other polytypes during growth,limiting the development of 3C-SiC-based devices.Herein,we report that 3C-SiC can be made thermodynamically favored from nucleation to growth on a 4H-SiC substrate by top-seeded solution growth technique,beyond what is expected by classical nucleation theory.This enables the steady growth of high-quality and large-size 3C-SiC crystals(2-4-inch in diameter and 4.0-10.0 mm in thickness)sustainable.The as-grown 3C-SiC crystals are free of other polytypes and have high-crystalline quality.Our findings broaden the mechanism of hetero-seed crystal growth and provide a feasible route to mass production of 3C-SiC crystals,offering new opportunities to develop power electronic devices potentially with better performances than those based on 4H-SiC.

Accounting for Quadratic and Cubic Invariants in Continuum Mechanics–An Overview

The differential equations of continuum mechanics are the basis of an uncountable variety of phenomena and technological processes in fluid-dynamics and related fields.These equations contain derivatives of the first order with respect to time.The derivation of the equations of continuum mechanics uses the limit transitions of the tendency of the volume increment and the time increment to zero.Derivatives are used to derive the wave equation.The differential wave equation is second order in time.Therefore,increments of volume and increments of time in continuum mechanics should be considered as small but finite quantities for problems of wave formation.This is important for calculating the generation of sound waves and water hammer waves.Therefore,the Euler continuity equation with finite time increments is of interest.The finiteness of the time increment makes it possible to take into account the quadratic and cubic invariants of the strain rate tensor.This is a new branch in hydrodynamics.Quadratic and cubic invariants will be used in differential wave equations of the second and third order in time.