Analytical solution approach for nonlinear buckling and postbuckling analysis of cylindrical nanoshells based on surface elasticity theory

The size-dependent nonlinear buckling and postbuckling characteristics of circular cylindrical nanoshells subjected to the axial compressive load are investigated with an analytical approach. The surface energy effects are taken into account according to the surface elasticity theory of Gurtin and Murdoch. The developed geometrically nonlinear shell model is based on the classical Donnell shell theory and the von Karman＇s hypothesis. With the numerical results, the effect of the surface stress on the nonlinear buckling and postbuckling behaviors of nanoshells made of Si and Al is studied. Moreover, the influence of the surface residual tension and the radius-to-thickness ratio is illustrated. The results indicate that the surface stress has an important effect on prebuckling and postbuekling characteristics of nanoshells with small sizes.

Numerical solutions for point masses sliding over analytical surfaces: Part 1

In this study, we introduce a system of differential equations describing the motion of a single point mass or of two interacting point masses on a surface, that is solved by a fourth-order explicit Runge–Kutta(RK4) scheme. The forces acting on the masses are gravity, the reaction force of the surface, friction, and, in case of two masses, their mutual interaction force. This latter is introduced by imposing that the geometrical distance between the coupled masses is constant. The solution is computed under the assumption that the point masses strictly slide on the surface, without leaping or rolling. To avoid complications stemming from numerical errors related to real topographies that are only known over discrete grids, we restrict our attention to simulations on analytical continuous surfaces. This study sets the basis for a generalization to more complex systems of masses, such as chains or matrices of blocks that are often used to model complex processes such as landslides and rockfalls. The results shown in this paper provide a background for a companion paper in which the system of equations is generalized, and different geometries are presented.

A full-dimensional analytical potential energy surface for the F+CH_4→HF+CH_3 reaction

A full-dimensional analytical potential energy surface （APES） for the F ＋ CH4 →HF ＋ CH3 reaction is developed based on 7127 ab initio energy points at the unrestricted coupled-cluster with single, double, and perturbative triple excitations. The correlation-consistent polarized triple-split valence basis set is used. The APES is represented with a many-body expansion containing 239 parameters determined by the least square fitting method. The two-body terms of the APES are fitted by potential energy curves with multi-reference configuration interaction, which can describe the diatomic molecules （CH, H2, HF, and CF） accurately. It is found that the APES can reproduce the geometry and vibrational frequencies of the saddle point better than those available in the literature. The rate constants based on the present APES support the experimental results of Moore et al. [Int. J. Chem. Kin. 26, 813 （1994）]. The analytical first-order derivation of energy is also provided, making the present APES convenient and efficient for investigating the title reaction with quasiclassical trajectory calculations.

Analytic Solution for Fluid Flow over an Exponentially Stretching Porous Sheet with Surface Heat Flux in Porous Medium by Means of Homotopy Analysis Method

In this paper, the analytical solution of a viscous and incompressible fluid towards an exponentially stretching porous sheet with surface heat flux in porous medium, for the boundary layer and heat transfer flow, is presented. The equations of continuity, momentum and the energy are transformed into non-linear ordinary differential by using similarity transformation. The solutions of these highly non-linear ordinary differential equations are found analytically by means of Homotopy Analysis Method (HAM). The result obtained by HAM is compared with numerical results presented in the literature. The accuracy of the HAM is indicated by close agreement of the two sets of results. By this method, an expression is obtained which is admissible for all values of effective parameters. This method has the ability to control the convergence of the solution.

On study of horizontal thin film flow of Sisko fluid due to surface tension gradient

The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonlinear ordinary differential equation is obtained by the Adomian decomposition method （ADM）. The physical quantities are derived including the pressure profile, the velocity profile, the maximum residue time, the stationary points, the volume flow rate, the average film velocity, the uniform film thickness, the shear stress, the surface tension profile~ and the vorticity vector. It is found that the velocity of the Sisko fluid film decreases when the fluid behavior index and the Sisko fluid parameter increase, whereas it increases with an increase in the inverse capillary number. An increase in the inverse capillary number results in an increase in the surface tension which in turn results in an increase in the surface tension gradient on the Sisko fluid film. The locations of the stationary points are shifted towards the moving plate with the increase in the inverse capillary number, and vice versa locations for the stationary points are found with the increasing Sisko fluid parameter. Furthermore, shear thinning and shear thickening characteristics of the Sisko fluid are discussed. A comparison is made between the Sisko fluid film and the Newtonian fluid film.

Molecular dynamics simulation of surface melting behaviours of the V(110) plane

The modified analytic embedded-atom method and molecular dynamics simulations are applied to the investigation of the surface premelting and melting behaviours of the V（110） plane by calculating the interlayer relaxation, the layer structure factor and atomic snapshots in this paper. The results obtained indicate that the premelting phenomenon occurs on the V（110） surface at about 1800K and then a liquid-like layer, which approximately keeps the same thickness up to 2020K, emerges on it. We discover that the temperature 2020K the V（110） surface starts to melt and is in a completely disordered state at the temperature of 2140K under the melting point for the bulk vanadium.

Strong Spatial Aggregation of Martian Surface Temperature Shaped by Spatial and Seasonal Variations in Meteorological and Environmental Factors

Spatio-temporal variation in the Martian surface temperature(MST)is an indicator of ground level thermal processes and hence a building block for climate models.However,the distribution of MST exhibits different levels of spatial aggregation or heterogeneity,and varies in space and time.Furthermore,the effect of regional differences in meteorological or environmental factors on the MST is not well understood.Thus,we investigated the degree of spatial autocorrelation of MST across the surface of Mars globally by Moran’s I,and identified the hot spots by GetisOrd G;*.We also estimated the regional differences in the influence of seasonally dominant factors including thermal inertia(TI),albedo,surface pressure,latitude,dust and slope on MST by a geographically weighted regression model.The results indicate(1)that MST is spatially aggregated and hot and cold spots varied over time and space.(2)Hemispheric differences in topography,surface TI and albedo were primarily responsible for the hemispheric asymmetry of hot spots.(3)The dominant factors varied by geographical locations and seasons.For example,the seasonal Hadley circulation dominates at the low-latitudes and CO;circulation at the high-latitudes.(4)Regions with extreme variations in topography and low TI were sensitive to meteorological and environmental factors such as dust and CO_(2)ice.We conclude that the spatial autocorrelation of MST and the spatial and seasonal heterogeneity of influencing factors must be considered when simulating Martian climate models.This work provides a reference for further exploration of Martian climatic processes.

层次分析-熵权法联合星点设计-响应面法优选胆汁制陈皮炮制工艺及饮片色度与成分相关性分析

目的研究胆汁制陈皮炮制的最佳工艺参数,明确饮片色度与主要成分之间的关系。方法采用星点设计-响应面法,以辅料用量、蒸制时间、干燥时间、干燥温度为考察因素,以橙皮苷、川陈皮素、橘皮素、牛磺胆酸钠含量及外观性状、醇浸出物含量为评价指标,采用层次分析-熵权法对各评价指标赋予相应权重,计算总评归一值,优选最佳炮制工艺;采用相关性分析和回归分析研究饮片色度与主要有效成分含量的相关性,构建色度-成分的回归方程。结果胆汁制陈皮最佳炮制工艺为每100g陈皮用20g蛇胆汁浸渍完全后,蒸制15min,45℃干燥162min。饮片色度值L^(*)、b^(*)值与橙皮苷、川陈皮素、橘皮素、牛磺胆酸钠4种成分含量均具有显著相关性,a^(*)值仅与牛磺胆酸钠含量具有相关性;构建了L^(*)、b^(*)值与4种成分含量及a^(*)值与牛磺胆酸钠含量的线性回归方程。结论采用星点设计-响应面法优化的胆汁制陈皮炮制工艺具有合理性、可行性,饮片色度与成分含量具有显著相关性。

苦参-黄柏药对的提取工艺研究

目的研究苦参-黄柏药对的提取工艺,为治疗肛肠疾病的新药开发提供参考依据。方法以苦参总碱(苦参碱+氧化苦参碱)含量、盐酸小檗碱含量、总黄酮含量及浸膏得率为评价指标,采用层次分析法-熵权法计算各指标权重系数,结合Box-Behnken设计-响应面法研究苦参-黄柏药对的最佳提取工艺并进行验证。结果苦参-黄柏药对的最优提取工艺为以12倍量58%乙醇浸泡30 min后提取2次,每次120 min。验证实验结果与预测值的相对误差为1.88%。结论所得提取工艺稳定、可行,可为苦参-黄柏药对的进一步应用与新药开发提供参考。

川楝子醋制工艺优化

目的优化川楝子醋制工艺。方法在单因素试验基础上,以加醋量、闷润时间、炒制时间为影响因素,川楝素、芦丁、异槲皮苷、水溶性浸出物含量的总评“归一值”(OD值)为评价指标,Box-Behnken响应面法结合层次分析(AHP)-熵权法优化醋制工艺。结果最佳条件为每100 kg饮片用38 kg醋,闷润115 min,文火炒制10 min(饮片表面温度70~90℃),OD值为90.67。结论该方法合理可行,可为醋川楝子工业化生产提供参考。

CRITIC-AHP复合赋权法结合Box-Behnken响应面法优选蜜桑叶炒制工艺

目的优选蜜桑叶的炒制工艺。方法以炒制温度、炒制时间、辅料用量为考察因素,以绿原酸、芦丁、异槲皮苷、紫云英苷、醇溶性浸出物、总黄酮、水分为指标成分,采用CRITIC熵权法及层次分析法(AHP)确定各指标成分的权重,以上述指标成分的综合评分为评价指标,采用Box-Behnken响应面法优选蜜桑叶炒制工艺并验证。结果优选的炒制工艺为加25%辅料,170℃炒制10 min。绿原酸、芦丁、异槲皮苷、紫云英苷、醇溶性浸出物、总黄酮平均含量分别为1.412,1.038,2.207,1.231,31.816,106.702 mg/g,水分平均含量为10.99%。综合评分的理论值为98.019分,实测值(97.585分)与之接近(RSD为0.843%)。结论优选出的蜜桑叶炒制工艺稳定、合理、可行,可为蜜桑叶的工业化生产提供依据。

Revealing the Regulation Effect of Surface Charge at Aromatic Interface to Dynamic Conformational Changes of α-Synuclein at Early Aggregation Stage

The aggregation ofα-synuclein(α-syn)is strongly influenced by membrane interfaces,but the mechanism of transition from monomers to oligomers at early aggregation stage is not clear.Here,we investigate the adsorption and structure changes ofα-syn on oppositely charged aromatic interfaces through in-situ surface-enhanced infrared absorption(SEIRA)spectroscopy and nano-IR technique.The results show that the synergy of electrostatic and hydrophobic interactions leads to a“fast-slow”two-step aggregation pathway on negatively charged interface.Surface adsorption induces the formation of an extended helix structure and subsequently partial helix unwinding in NAC region,which enables the hydrophobic stacking between nearby NAC regions.Stable antiparallel β-sheet rich aggregates are gradually emerging as further interactions of monomers with the fast formed“first layer”.Monomers electrostatically adsorb on positively charged interface by C-terminus with NAC region and N-terminus stretched in solvent,which serve as an aggregation core and induce further adsorption and gradual formation of aggregates with C-terminus exposure.Our results demonstrate the modulation of surface charge and synergy of electrostatic and hydrophobic interactions on the interaction modes and aggregation pathways,which provide insights into dynamic conformation changes ofα-syn at early aggregation stage and imply the important role of spatial-temporal heterogeneity of membranes inα-synucleinopathies.

基于AHP-EWM结合Box-Behnken响应面法优化黄芩多指标成分的微波提取工艺

结合层次分析法(AHP)-熵权法(EWM),通过单因素实验考察功率、液固比、提取时间、提取次数和粒度对黄芩苷、汉黄芩苷、黄芩素和汉黄芩素得率及出膏率的影响。以综合评分为响应值,利用四因素三水平Box-Behnken(BBD)响应面法优化黄芩的微波提取工艺,并通过扫描电子显微镜(SEM)观察提取前后药材粉末的微观形态变化。BBD响应面法得到的最优提取工艺条件为:微波功率390 W、液固比56 mL/g、提取时间472 s、粒度80目(180μm),此时黄芩苷、汉黄芩苷、黄芩素、汉黄芩素得率分别为16.82%、3.46%、0.30%、0.31%,出膏率73.73%,综合评分10.75。该工艺提取效果优于常见的回流提取方法,实现评价结果主客观的内在统一。

酒蒸桑寄生的炮制工艺优化及质量表征研究

目的 优化桑寄生酒蒸炮制工艺,并对其质量进行表征。方法 以扁蓄苷、槲皮苷、槲皮素含量和外观性状评分为评价指标,采用层次分析法-熵权法确定各指标权重,并以各指标综合评分为响应值,采用Box-Behnken响应面法考察料液比(g/mL)、闷润时间、蒸制时间对酒蒸桑寄生炮制工艺的影响,优化最佳炮制工艺,并进行验证。将15批不同产地桑寄生饮片按最佳炮制工艺制备酒蒸桑寄生,并对其质量进行表征。结果 酒蒸桑寄生最佳炮制工艺为取桑寄生饮片100 g,加入黄酒20 mL密封闷润2 h,常压蒸制1 h,取出,于50℃条件下干燥即得。以最佳炮制工艺制得的酒蒸桑寄生表面呈红褐色或棕褐色,其粉末呈深棕色,质地坚硬或脆,易折断,略有酒香气,味涩;茎横切面显微鉴别和薄层色谱鉴别结果同生桑寄生;水分、总灰分、酸不溶性灰分含量分别为3.92%~8.75%、2.27%~5.08%、0.19%~0.82%,水溶性浸出物含量为11.28%~18.56%,醇溶性浸出物含量为3.36%~8.58%,扁蓄苷、槲皮苷和槲皮素的含量分别为0.22~1.64、0.26~2.45、0.01~0.38 mg/g。结论 本研究成功优化了酒蒸桑寄生的炮制工艺,并对其质量进行了表征,可为该饮片的规范化炮制及质量标准建立提供参考。

基于半解析法的声学黑洞梁结构参数响应面优化

声学黑洞(Acoustic Black Hole,ABH)对弯曲波的聚集效应具有宽频、高效、实现方法简单灵活等特点,在结构减振降噪领域具有广泛的应用前景。以一维声学黑洞梁为对象,结合声学黑洞半解析建模计算方法和响应面优化方法,分析声学黑洞特征长度、截断厚度、幂律以及阻尼层特征长度和厚度这5个参数对一维声学黑洞梁减振效果的影响规律。以一维声学黑洞梁的减振效果为优化目标,对梁和阻尼的结构参数进行优化设计,优化后的一维声学黑洞梁结构在10~8000Hz频率范围内的平均加速度级降低19.03dB。研究对一维声学黑洞梁结构在减振领域的工程应用具有参考价值。

基于MATLAB的“空间解析几何”教学案例研究

在“空间解析几何”课程教学过程中,常存在绘制空间曲线和曲面的困难和缺乏直观性的问题。以MATLAB为基础,从计算功能、绘图功能和动态可视化3个方面探讨了“空间解析几何”课程教学的案例。利用MATLAB的内置函数求解多个几何问题的数值解,以及绘制空间曲面和曲线。此外,通过动态可视化方法,直观地演示了二次曲面的平行截痕法,有助于学生更好地理解和感知二次曲面的形状和性质。旨在为教师和学生提供“空间解析几何”课程教学和学习的参考。

基于Box-Behnken试验设计结合SR-AHP-EWM的经典名方半夏厚朴汤提取工艺研究

基于质量源于设计理念(QbD),设置浸泡时间、加水倍量和煎煮次数为关键工艺参数并按照Box-Behnken试验设计制备了17个批次半夏厚朴汤冻干样品。将物质基准样品质量设为标准值,通过计算各样品与物质基准的基准关联度(SR),采用主、客观赋权法相结合的方式,即层次赋权法-熵权法(AHP-EWM),确定迷迭香酸、6-姜酚、和厚朴酚与厚朴酚含量、出膏率及指纹图谱相似度5个评价指标的权重分别为0.05、0.11、0.58、0.26、0。经综合评分后,建立了预测数学模型。确定最佳工艺为加6.32倍量水,回流提取1.5 h,提取3次,经重复实验验证该工艺下所得半夏厚朴汤的综合评分为91.09,相对标准偏差(RSD)为2.2%。结果表明所提出的提取工艺稳定可靠,所得产品的质量属性与物质基准接近,可为半夏厚朴汤后续的研究开发和工业化生产奠定基础。

层次分析-熵权法结合星点设计-响应面法优选艾纳香配方颗粒成型工艺

目的优选艾纳香配方颗粒的成型工艺。方法以湿法制粒法制备艾纳香配方颗粒,在单因素试验基础上结合星点设计-响应面法,以清膏与稀释剂糊精配比、矫味剂甜菊素用量为考察因素,以成型率、休止角、吸湿率为评价指标,采用层次分析(AHP)-熵权法对评价指标赋予权重系数后进行综合评分。结果AHP-熵权法赋予成型率、休止角、吸湿率的权重系数分别为0.6420,0.3445,0.01345。优选的成型工艺为艾纳香配方颗粒清膏-糊精(1∶1.65,m/m),矫味剂甜菊素0.55%。验证试验结果显示,按优化工艺制备3批样品的综合评分的平均值为75.03。结论该成型工艺合理、可行,可为艾纳香配方颗粒的开发及应用提供实验依据。

基于AHP-CRITIC混合加权法和星点设计-效应面法的荆防活血乳膏处方优化研究

目的研究并优选荆防活血乳膏剂的制备工艺。方法以荆防活血乳膏剂的离心稳定性、耐热稳定性、涂抹分散性为考察指标,采用层次分析法(AHP)、基于指标相关性的权重确定方法(CRITIC)、AHPCRITIC混合加权法确定各评价指标的权重系数,并结合星点设计(central composite design,CCD)-效应面优化法筛选荆防活血乳膏处方中出对基质质量影响较大的3个因素硬脂酸、甘油、混合乳化剂(平平加、三乙醇胺)的用量,验证优化后的最佳处方。结果按AHP-CRITIC混合加权法得到离心稳定性、耐热稳定性、涂抹分散性的权重系数分别为0.5216,0.3372,0.1412,最佳处方比例为:硬脂酸4.4 g,甘油14.3 g,混合乳化剂4.2 g,单硬脂酸甘油酯2 g,凡士林8.5 g,二甲基硅油10 g,纯化水20 g,冰片1.5 g(2%),苯甲酸钠0.1%,荆防活血方组方药物提取干膏用量7.5 g(每100 g乳膏中含主药量约10 g)。结论优选出的荆防活血乳膏剂制备工艺经验证简单、合理,所得制剂具有良好的外观性状、涂抹分散性和稳定性。

采用改进子域模型的表贴式永磁游标电机磁场解析计算

针对传统子域解析方法在计算气隙谐波磁场丰富的表贴式永磁游标电机磁场时,出现系数矩阵维数高、计算过程复杂的问题,提出了一种改进的子域解析模型。该模型通过坐标变换,将各子域矢量磁位在二维极坐标系下的拉普拉斯方程或泊松方程变换为准笛卡尔坐标系下的方程形式,利用分离变量法计算各子域矢量磁位方程的通解,根据边界条件计算待定系数,以双曲函数的形式表示各矢量磁位的解析解。计算了空载反电动势、气隙磁密和电磁转矩,与传统子域解析方法、有限元法计算结果进行对比。仿真结果表明:改进子域解析方法与有限元法的相对误差均小于1%;与传统子域解析方法相比,空载反电动势、气隙磁密和电磁转矩计算精度分别提升了1.7%、0.87%和3.66%。实验样机的空载反电动势计算波形和测试波形也基本吻合,验证了该方法的有效性和可行性。