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.

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。

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。

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.

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).

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.

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.

ANovel Non-Isolated Cubic DC-DC Converter with High Voltage Gain for Renewable Energy Power Generation System

In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effectively enhance voltage gain and reduce device stress.To address the issue of low output voltage in current renewable energy power generation systems,this study proposes a novel non-isolated cubic high-gain DC-DC converter based on the traditional quadratic DC-DC boost converter by incorporating a SC and a SL-SC unit.Firstly,the proposed converter’s details are elaborated,including its topology structure,operating mode,voltage gain,device stress,and power loss.Subsequently,a comparative analysis is conducted on the voltage gain and device stress between the proposed converter and other high-gain converters.Then,a closed-loop simulation system is constructed to obtain simulation waveforms of various devices and explore the dynamic performance.Finally,an experimental prototype is built,experimental waveforms are obtained,and the experimental dynamic performance and conversion efficiency are analyzed.The theoretical analysis’s correctness is verified through simulation and experimental results.The proposed converter has advantages such as high voltage gain,low device stress,high conversion efficiency,simple control,and wide input voltage range,achieving a good balance between voltage gain,device stress,and power loss.The proposed converter is well-suited for renewable energy systems and holds theoretical significance and practical value in renewable energy applications.It provides an effective solution to the issue of low output voltage in renewable energy power generation systems.

Treasure Trees on Barren Land

As the Spring Festival draws near,Desheng Youliang Village in Nuanshui Township,Jungar Banner in Ordos City of north China’s Inner Mongolia Autonomous Region,enters a new round of apple sales.In the 2,000 cubic meters of cold storage facility,workers are busy picking,packing,and loading.

Effect of Size and Initial Water Content on the Effective Diffusion Coefficient during Convective Drying of Sweet Potato Cut into Cubic and Cylindrical Shapes

In this article, we investigated the influence of size and initial water content on the effective diffusion coefficient of sweet potatoes samples cut into cubic and cylindrical shapes. The sizes of the cubic samples are 0.5, 1, 1.5, 1.75, 2, 2.5 and 3 cm edge with a respective initial water content of 2.7, 3.76, 3.48, 2.68, 3.28, 2.17 and 2.29 kg/kgms. For cylindrical samples, the radius is set at 0.5 cm and sample heights are 1, 1.5, 2, 2.5, 3, 3.5 and 4 cm with respective water contents of 2.2, 3.19, 2.85, 2.1, 2.17, 2.39 and 2.03 kg/kgms. The effective diffusion coefficients of cubic samples are of the order of 10−10 and 10−9 m2∙s−1 grew with sample edge. As for the cylindrical samples, the effective diffusion coefficients were of the order of 10−9 m2∙s−1 and there was no linear correlation between cylinder height and their effective diffusion coefficient. As for the examination of the initial water content on the effective diffusion coefficient, it turned out that the initial water content had no influence on the effective diffusion coefficient of the sweet potato samples.

基于改进海洋捕食者优化算法和瑞雷波频散曲线的近地表地层参数反演

面波勘探是获取近地表地质结构的重要手段,利用瑞雷波频散曲线可以反演得到地层横波速度和厚度或泊松比等参数.本文提出了一种新的优化策略来处理瑞雷波频散曲线的反演问题.改进海洋捕食者算法(ACMPA)是一种改进混沌初始化,引入自适应步长和精英竞赛机制优化的反演算法.采用混沌映射进行种群位置初始化,提高初始化种群位置的质量;加入自适应函数,增强全局搜索能力;引入精英等级制度,避免算法陷入局部极值点,从而从局部和全局寻优进行优化,提高反演的收敛速度.通过正演模拟和实测数据进行测试分析,证明了改进的海洋捕食者优化算法的有效性与稳定性.该方法可以利用瑞雷波频散曲线信息反演得到近地表地层的介质参数,其收敛精度和收敛范围明显优于其他优化算法,具有较强的应用前景.

Transformation of Hexagonal Lu to Cubic LuH_(2+x)Single-Crystalline Films

With the recent report of near ambient superconductivity at room temperature in the N-doped lutetium hydride(Lu-H-N)system,the understanding of cubic Lu-H compounds has attracted worldwide attention.Generally,compared to polycrystals with non-negligible impurities,the single-crystalline form of materials with high purity can provide an opportunity to show their hidden properties.However,the experimental synthesis of single-crystalline cubic Lu-H compounds has not been reported so far.Here,we develop an easy way to synthesize highly pure LuH_(2+x)single-crystalline films by the post-annealing of Lu single-crystalline films(purity of 99.99%)in H_(2)atmosphere.The crystal and electronic structures of films were characterized by x-ray diffraction,Raman spectroscopy,and electrical transport.Interestingly,Lu films are silver-white and metallic,whereas their transformed LuH_(2+x)films become purple-red and insulating,indicating the possible formation of an unreported electronic state of Lu-H compounds.Our work provides a novel route to synthesize and explore more singlecrystalline Lu-H compounds.

Diamond/c-BN van der Waals heterostructure with modulated electronic structures

The structural and electronic properties of(100),(110), and(111) diamond/cubic boron nitride(c-BN) heterostructures are systematically investigated by first principles calculation. The interface between diamond and c-BN shows the weak van der Waals interactions, which is confirmed by the interface distance and interface binding energy. The diamond/cBN structures are the direct bandgap semiconductors with moderate bandgap values ranging from 0.647 e V to 2.948 e V.This work helps to promote the application of diamond in electronic and optoelectronic devices.

CONFORMALLY FLAT AFFINE HYPERSURFACES WITH SEMI-PARALLEL CUBIC FORM

In this paper,we study locally strongly convex affine hypersurfaces with the vanishing Weyl curvature tensor and semi-parallel cubic form relative to the Levi-Civita connection of the affine metric.As a main result,we classify these hypersurfaces as not being of a flat affine metric.In particular,2 and 3-dimensional locally strongly convex affine hypersurfaces with semi-parallel cubic forms are completely determined.

Cubic Ice Captured by In Situ Transmission Electron Microscope

Nearly a hundred years ago,the Nobel laureate Linus Pauling proposed based on the'ice rule'[1]and residual entropy theory that the structural entropy of ice is the same for common hexagonal ice(Ih)with tetrahedrally coordinated water molecules assembling into a hexagonal close-packing manner and cubic ice(ice Ic)in a cubic closepacking manner.[2]

Current and recent cigarette smoking in relation to cardiovascular and non-cardiovascular mortality in an elderly male Chinese population

OBJECTIVE To investigate the association between current and former smoking and the risk of mortality in elderly Chinese men.METHODS Our study participants were elderly(≥60 years)men recruited in a suburban town of Shanghai.Cigarette smoking status was categorized as never smoking,remote(cessation>5 years)and recent former smoking(cessation≤5 years),and light-to-moderate(≤20 cigarettes/day)and heavy current smoking(>20 cigarettes/day).Cox proportional hazards models and restricted cubic splines were used to examine the associations of interest.RESULTS The 1568 participants had a mean age of 68.6±7.1 years.Of all participants,311 were never smokers,201 were remote former smokers,133 were recent former smokers,783 were light-to-moderate current smokers and 140 were heavy current smokers.During a median follow-up of 7.9 years,all-cause,cardiovascular and non-cardiovascular deaths occurred in 267,106 and 161 participants,respectively.Heavy current smokers had the highest risk of all-cause and non-cardiovascular mortality,with an adjusted hazard ratio(HR)of 2.30(95%CI:1.34-4.07)and 3.98(95%CI:2.03-7.83)versus never smokers,respectively.Recent former smokers also had a higher risk of all-cause(HR=1.62,95%CI:1.04-2.52)and non-cardiovascular mortality(HR=2.40,95%CI:1.32-4.37)than never smokers.Cox regression restricted cubic spline models showed the highest risk of all-cause and non-cardiovascular mortality within 5 years of smoking cessation and decline thereafter.Further subgroup analyses showed interaction between smoking status and pulse rate(≥70 beats/min vs.<70 beats/min)in relation to the risk of all-cause and non-cardiovascular mortality,with a higher risk in current versus never smokers in those participants with a pulse rate below 70 beats/min.CONCLUSIONS Cigarette smoking in elderly Chinese confers significant risks of mortality,especially when recent former smoking is considered together with current smoking.