球罐球壳板的划线与切割

球壳板划线与切割的精度直接影响着球罐现场组装质量,本文论述了采用三维坐标系下解析几何的方法计算球壳板上切割点与检查点的划线尺寸,并利用划线尺寸进行划线,通过分析原切割模具存在的缺点,重新设计计算了切割模具,提高了球壳板划线与切割的精度     

自适应Radau伪谱法自由漂浮空间机器人轨迹规划

为解决Gauss伪谱法(GPM)计算速度和求解精度之间的矛盾,在多段Radau伪谱法的基础上,提出了求解自由漂浮空间机器人(FFSM)最优路径规划问题的hp自适应Radau伪谱法(hp-RPM).与传统的Gauss伪谱法不同,该方法并不是单纯通过增加节点数量来提高精度,而是在每次迭代的过程中对整个路径分段个数和各个路径子区间的宽度进行合理的分配,并能配置每个子区间内节点的数量.通过增加分段个数可以减小子区间内所需节点个数,以此降低多项式阶数、提高计算速度.基于上述理论,首先建立了多臂FFSM系统动力学模型,并给出了运动过程中系统模型更新方法;然后将连续最优轨迹规划问题离散化,完成了hp自适应Radau伪谱法的设计;最后利用hp-RPM解决两连杆FFSM系统轨迹规划问题并进行了仿真实验.结果表明:在初始条件相同的情况下,两种方法得到的位置、速度规划曲线相似,但hp-RPM在各个节点处的误差明显低于GPM计算误差;在精度要求较高,初始节点较多的情况下,hp-RPM可以在保证精度的同时有效的提高计算速度.     

基于特征分布的建筑墙体裂缝图像识别方法

针对当前以人工智能为基础的墙体裂缝识别主要以图像识别为主,容易受到裂痕特征分布不均匀的影响,识别精度不高的问题,提出基于特征分布和高斯混合模型的建筑墙体裂缝图像识别方法.采用Harris角点检测算法对墙体图像进行角点求解处理,对建筑墙体图像进行预处理;通过选择掩模平滑法对墙体图像进行增强处理,将特征分布和高斯混合模型相结合,实现对建筑墙体裂缝图像的高精度识别.结果表明,该方法识别精度较高且识别时间短,预处理效果明显增强.     

高温矿井用蓄冰球受控循环风降温技术的研究

随着矿井开采深度的增加和采掘机械化水平的不断提高,矿井高温热害问题越来越严重。为保障采矿工业持续健康发展,必须采取相应措施进行治理。文章就近年来国内外高温矿井降温技术发展的现状和趋势及井下循环风的利用方面进行了研究,提出了高温矿井用蓄冰球受控循环风降温技术。     

COMMENTS ON ZELENÝ'S PAPER CONCERNING COGNITIVE EQUILIBRIA

Bivariate Pareto distributions arise naturally when it comes to comparing the performances of two systems. In this note, explicit expressions are derived for a relative measure of performance for every known bivariate Pareto distribution. The calculations involve the use of Gauss hypergeometric function.     

One-pot synthesis of hematite-alumina hollow sphere composite by ultrasonic spray pyrolysis technique with high adsorption capacity toward PAHs

A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al₂O₃ – Fe₂O₃ nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al₂O₃ or Fe₂O₃ showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g^?1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance.     

Algorithms and tools for high-throughput geometry-based analysis of crystalline porous materials

Crystalline porous materials have a variety of uses, such as for catalysis and separation. Identifying suitable materials for a given application can, in principle, be done by screening material databases. Such a screening requires automated high-throughput analysis tools that calculate structural properties for all materials contained in a database so they can be compared with search queries, grouped or classified. One important aspect of the structural analysis of materials such as zeolites and metal organic frameworks is the investigation of the geometrical parameters describing pores. Here, we present algorithms and tools to efficiently calculate some of these important parameters. Our tools are based on the Voronoi decomposition, which for a given arrangement of atoms in a periodic domain provides a graph representation of the void space. The resulting Voronoi network is analyzed to obtain the diameter of the largest included sphere and the largest free sphere, which are two geometrical parameters that are frequently used to describe pore geometry. Accessibility of nodes in the network is also determined for a given guest molecule and the resulting information is later used to retrieve dimensionality of channel systems as well as in Monte Carlo sampling of accessible surfaces and volumes. The presented algorithms are implemented in a software tool, Zeo++, which includes a modified version of the Voro++ library. We present example applications of our algorithms and tools using zeolite frameworks currently listed in the Atlas of Zeolite Frameworks.     

Role of moving planes and moving spheres following Dupin cyclides

We provide explicit representations of three moving planes that form a μ-basis for a standard Dupin cyclide. We also show how to compute μ-bases for Dupin cyclides in general position and orientation from their implicit equations. In addition, we describe the role of moving planes and moving spheres in bridging between the implicit and rational parametric representations of these cyclides.     

A Gauss–Newton full-waveform inversion for material profile reconstruction in viscoelastic semi-infinite solid media

An inversion framework employing a Gauss–Newton method is developed to reconstruct material profiles in heterogeneous, viscoelastic, semi-infinite domains. In particular, a full-waveform inversion approach is investigated to image the elastic and attenuating parameters of a layered media. To account for the viscoelasticity of the medium, a Generalized Maxwell Body with one spring and two Maxwell elements in parallel (GMB2) is adopted in the forward and inverse wave propagation problems. Perfectly-matched-layers were introduced as wave absorbing buffers to simulate the semi-infinite extent of the domain. Using transient wave equations endowed with the GMB2 constitutive relation and the PML, a partial-differential-equations-constrained optimization scheme was implemented that lead to classic KKT (Karush–Kuhn–Tucker) conditions including time-dependent state, adjoint, and time-invariant control problems. An optimal solution of the viscoelastic parameters was obtained using a reduced-space approach based on a line search algorithm where the search direction was computed by the Gauss–Newton method. Considerable improvements on the accuracy and convergence rate of solutions were made by the developed Gauss–Newton inversion procedure compared to previous research using the Fletcher–Reeves method.     

滚球半径法确定瓦斯抽放泵站放空管合理安置区域

为了确定瓦斯抽放泵站放空管合理安置区域。在滚球半径法推算原理的基础上,利用几何知识,使用AutoCAD绘图软件绘制瓦斯抽放泵站放空管合理安置区域,而非传统方法的若干公式计算。AutoCAD绘图软件作图的方法避免了《GB 50057-2010建筑物防雷设计规范》附录D中传统方法繁琐的计算。确定瓦斯抽放泵站放空管合理安置区域作图法直观、简单、清晰、明了,简化了瓦斯抽放泵站防雷设计工作。为科学合理确定瓦斯抽放泵站放空管位置提供了依据。