立足核心素养,提升关键能力,发展创新思维——以“直线与椭圆的位置关系中角的转化策略”的教学为例

新高考强调对创新能力的考查,本文通过对高三一模解析几何解答题的多视角分析,探究了直线与椭圆位置关系中角的转化的基本策略;教师通过对不同解法的对比分析,优选算法,规范表达,提升学生直观想象、数学运算、逻辑推理素养,发展阅读理解能力、信息加工能力等关键能力,培养学生归纳猜想与类比推理能力,发展批判性思维等创新思维。

初中几何代数化教学的思考——基于圆中角转化问题

为了提升学生数学素养,文章基于圆中角转化问题,对初中几何代数化教学进行了思考,并提出了相关建议,包括深化理解,把握联系;丰富策略,扩展思维;渗透思想,提升素养。

从一道中考题的解法探究看核心素养的培养

数学解题教学中,多题一解可以训练学生通解通法、常规常法,但一题多解更可以训练学生逻辑推理、灵活思维,对于培养数学核心素养有着重要意义。本文通过一道中考题的一题多解,来探究二倍角的转化策略,探讨核心素养的培养。

蟹爪式耙取机构的优选

本文将确定由曲柄摇杆机构转化为曲柄直导杆机构的三个转化参数，并指出由耙取机构插入段开始时的转化角θ（Ｎｙ）所对应的曲柄导杆机构为最佳转化机构。

三角函数在抛物线大题中的应用

锐角三角函数在初中阶段使用程度不是很高,在很多情况只是为了计算一些三角函数的值,并没有利用三角函数的恒等变换技巧,以及三角的思想来解决问题.事实上无论在平面几何还是在函数中,三角函数都有着广泛的用途,该文主要讨论三角函数在抛物线中的使用技巧.

电视胸腔镜手术对非小细胞肺癌患者肺功能及血清TGF-α、CA21-1水平的影响

目的观察电视胸腔镜手术对非小细胞肺癌患者肺功能及血清转化生长因子α(TGF-α)、细胞角蛋白19片段(CA21-1)水平的影响。方法选取南阳市中心医院2018年6月-2019年2月收治的104例非小细胞肺癌患者,随机分为两组,各52例。对照组行小切口开胸腔手术,观察组行电视胸腔镜手术,比较两组肺功能、血清TGF-α、CA21-1水平。结果与术前相比,两组术后FEV1、MVV、DLCO均降低,且对照组较观察组低,差异有统计学意义(P<0.05);与术前相比,两组术后血清TGF-α、CA21-1水平均降低,且观察组较对照组低,差异有统计学意义(P<0.05)。结论对非小细胞肺癌患者实施电视胸腔镜手术,可减轻其肺功能损伤,降低血清TGF-α、CA21-1水平,应用效果显著,值得临床推广应用。

Adaptive multicascade attribute reduction based on quantum-inspired mixed co-evolution

Due to the fact that conventional heuristic attribute reduction algorithms are poor in running efficiency and difficult in accomplishing the co-evolutionary reduction mechanism in the decision table, an adaptive multicascade attribute reduction algorithm based on quantum-inspired mixed co-evolution is proposed. First, a novel and efficient self- adaptive quantum rotation angle strategy is designed to direct the participating populations to mutual adaptive evolution and to accelerate convergence speed. Then, a multicascade model of cooperative and competitive mixed co-evolution is adopted to decompose the evolutionary attribute species into subpopulations according to their historical performance records, which can increase the diversity of subpopulations and select some elitist individuals so as to strengthen the sharing ability of their searching experience. So the global optimization reduction set can be obtained quickly. The experimental results show that, compared with the existing algorithms, the proposed algorithm can achieve a higher performance for attribute reduction, and it can be considered as a more competitive heuristic algorithm on the efficiency and accuracy of minimum attribute reduction.

Corrosion properties of ECAP-processed Mg-Al-Ca-Mn alloys with separate Al2Ca and Mg2Ca phases

To investigate the effect of separate Al_(2)Ca and Mg_(2)Ca phases on the corrosion properties of Mg−Al−Ca−Mn alloys,OM,SEM,immersion and electrochemical tests were conducted on the as-cast and ECAP Al_(2)Ca-containing(2Ca)and Mg_(2)Ca-containing(4Ca)alloys.At the beginning of corrosion,the two as-cast alloys are corroded slowly compared with ECAP alloys.With prolonging the corrosion time,the corrosion of ECAP alloys becomes slighter than that of as-cast alloys,which is mainly ascribed to the dispersion and refinement of the second phase in ECAP alloys.Moreover,the corrosion degree of 2Ca alloys is always slighter than that of 4Ca alloys,suggesting that Al_(2)Ca phase is more beneficial to the enhancement of corrosion resistance of Mg−Al−Ca−Mn based alloys than Mg_(2)Ca phase.Finally,based on the examinations of corrosion surface and electrochemical testing results,different corrosion mechanisms caused by the distributions and morphology of Al_(2)Ca and Mg_(2)Ca phases are discussed.

Stereodynamics of O（^3P）＋H2 at Scattering Energies of 0.5, 0.75, and 1.0 eV

Quasiclassical trajectory calculation of the title reaction O（^3P）＋H2→OH＋H at three different scattering energies of 0.5, 0.75, and 1.0 eV on the lowest electronic potential energy surface 1^3A＂ has been done. Distribution P（θr） of polar angles between the relative velocityk of the reactant and rotational angular momentum vector j＇ of the product, distribution P（φr） of the azimuthal as well as dihedral angles correlating k-k＇-j＇, 3-dimensional distri-bution, and polarization-dependent differential cross sections （PDDCSs）dependent upon the scattering angle of the product molecule OH between the relative velocity k of the reactant and k＇ of the product at different scattering energies of 0.5, 0.75, and 1.0 eV are presented and discussed.

Linear Support Vector Machine Based Inter-harmonic Modeling and Parameter Estimation

There are often system. The high measure many inter-harmonics in power t accuracy of inter-harmonics order, amplitude and initial phase is needed. A new approach is presented for inter-harmonic modeling and parameter estimation based on linear support vector machine （SVM）. Firstly, parameter estimation of linear model is realized based on standard linear SVM. Then, interharmonic model is transformed to a linear model according to trigonometric functions. The approach obtains order of inter-harmonic model with windowed Blackman-Tukey （BT） spectrum analysis, and gets number and frequency of harmonics. Finally, the linear SVM is applied to estimate the inter-harmonic parameters, amplitude and initial phase. The simulation results show that the proposed approach has high precision and good antinoise. The accuracy of three parameters are all higher than 98%.

Stability margin of the quadruped bionic robot with spinning gait

Spinning gait is valuable for quadruped robot,which can be used to avoid obstacles quickly for robot walking in unstructured environment. A kind of bionic flexible body is presented for quadruped robot to perform the spinning gait. The spinning gait can be achieved by coordinated movement of body laterally bending and legs swing,which can improve the mobility of robot walking in the unstructured environments. The coordinated movement relationship between the body and the leg mechanism is presented. The stability of quadruped robot with spinning gait is analyzed based on the center of gravity( COG) projection method. The effect of different body bending angle on the stability of quadruped robot with spinning gait is mainly studied. For the quadruped robot walking with spinning gait,during one spinning gait cycle,the supporting polygon and the trajectory of COG projection point under different body bending angle are calculated. Finally,the stability margin of quadruped robot with spinning gait under different body bending angle is determined,which can be used to evaluate reasonableness of spinning gait parameters.

Hydrogenation of bilayer graphene： A small twist makes a big difference

The effect of twist angle on the hydrogenation of bilayer graphene （BLG） is systematically explored by density functional theory （DFT） calculations. We found that a twist between the upper and lower layers of the graphene BLGs, either big or small, interferes with the formation of inter-layer C-C covalent bonds and this leads to strong resistance to hydrogenation. In addition, the electronic properties of stable, hydrogenated twisted BLG with different twist angles and degrees of H coverage were investigated. This study paves the way to the selective functionalization of BLG for various applications.

Spatial distribution, seasonal variation and regionalization of PM_(2.5) concentrations in China

In order to provide scientific support to policy makers in the regulation of PM2.5 pollution in China, it is important to accurately assess the current status, spatiotemporal characteristics and regionalization data for this air pollutant. An analysis of the pollution status of PM2.5 was conducted using daily averaged mass concentration data recorded in 74 cities in 2013 and 161 cities in 2014. The rotated empirical orthogonal function(REOF) method was applied to analyze this data. Results showed that the average annual PM2.5 concentration in urban areas of China is 62.2±21.5 ?g/m3, and that the distribution is spatially heterogeneous. The North China Plain, middle and lower Yangtze River Plain, Sichuan Basin and Guanzhong Plain had relatively high annual PM2.5 concentrations compared with the southeast coastal region, the Tibetan Plateau and the Yungui Plateau. PM2.5 mass concentrations tended to be higher in winter than in summer, however, the data for many cities showed a small peak in concentrations from May to July. An analysis of the spatial correlation of PM2.5 indicated a significant influence of topographic conditions. A lower correlation was observed where terrain features varied greatly. Based on the results of the REOF analysis and topographic characteristics, ten regions were identified in mid-eastern China, which could be considered as basic pollution prevention divisions for PM2.5; these include the North China Plain region, Pearl River Delta region, Jianghuai Plain region, middle Yangtze River Plain region, Northeast Plain region, Jiangnan coastal region, Sichuan Basin region, Qiantao Plain region, Guanzhong-Central Plain region and Yungui Plateau region. Seasonal variations in the regionalization data were observed, especially for the North China Plain and Pearl River Delta regions. Among the ten regions identified in this study, the North China Plain, Guanzhong-Central Plain, middle Yangtze River Plain and Jianghuai Plain had relatively high PM2.5 mass concentrations in comparison with the others. Therefore, these regions should be considered as the key regions to target in developing PM2.5 pollution prevention strategies. This study improves the present understanding of the spatial distribution, seasonal changes and regional status of PM2.5 pollution in China and helps establish possible control strategies for the reduction of this air pollutant.