二次曲线

Abstract］ Objective To describe the shape of the planar space of the corneal anterior surface of children with emmetropia by using a conic section, and then to plot the changes in asphericity on 36 meridians to deduce the formulae of the three-dimensional shape of the corneal anterior surface.

目的 通过二次曲线方程来描述正视儿童角膜前表面的二维空间形态，根据各子午线非球面性的变化规律推导出其三维形态的数学表达式及非球面性变化规律表达式。

Conics or smooth 3D B-spline curve can be drawn freely and quickly.

并在点云表面高效地绘制出二次曲线或者平滑的B样条曲线。

By using the Graham scanning for the convex hull extraction and fitting these convex hull points with the conics,roots of the conics are regarded as points we need.

采用格雷厄姆扫描法对包络进行凸壳提取，并用二次曲线拟合凸壳点，计算出拟和曲线的根。

When the generation cost function is quadratic curve,the new bargaining is compared with the former one.

比较了发电费用曲线为二次曲线时新的定价方式与已有定价方式的关系。

There are three curve types: linear, secondary curve and interpolation method.

曲线类型具有：线性、二次曲线、插值法。

The numbers of new cases and the rate of incidence of malaria can be predicted by the quadratic forecast model of population and the logarithmic curve model of new cases. The general trend of malaria are gradually decreasing in Chongqing municipal.

运用人口数的二次曲线模型和疟疾新发病例的对数曲线模型能够较好的预测疟疾发病数和发病率，总体来看重庆市疟疾动态的总趋势是持续下降的。

Result The population and new case of malaria can be predicted by the quadratic forecast model of population and logarithmic curve model of new case in Chongqing municipal. The prediction range of population is from 3113112 to 3368928, and the range of the new cases rate of incidence of malaria is from 126 to 134 in 2002 year. These two numbers are consistent with actual number of population and new cases, which are 31309038 and 130, respectively.

结果 重庆市人口数的二次曲线模型和疟疾新发病例的对数曲线模型能够对重庆市人口数和疟疾新发病例数进行预测，2002年重庆市人口数预测范围为3113112~3368928人，新发病例数范围为126~134例；分别与实际的人口数（31309038人）和病例数（130例）基本吻合。

The effects of different plant densities on flag leaves chlorophyll content,SOD activity and MDA content after anthesis in stronggluten wheat interplanted in paddyfield were studied.

本试验在江苏淮北地区设计不同密度试验，研究其对稻田套播强筋小麦花后剑叶叶绿素含量、SOD酶活性和MDA含量的影响，结果表明：随花后生育进程推移，叶绿素含量呈下降趋势，且随密度增加，下降幅度增大；花后单茎干物质积累量和单茎籽粒产量亦随密度增加而下降，二者呈极显著负相关；随花后生育进程推移，剑叶SOD酶活性呈单峰曲线变化，可用二次曲线方程模拟，在花后1416 d达峰值，且随密度增加峰值出现时间提前，峰值数值呈先上升再下降的变化特征；随花后生育进程推移，剑叶MDA含量呈上升的变化特征，且随密度增大，数值变大；花后35 d剑叶SOD酶活性与花后单茎干物质积累量和单茎籽粒产量呈极显著正相关，而MDA含量与花后单茎干物质积累量和单茎籽粒产量则呈显著或极显著负相关。

Projective transformation of curved surface and plane intersecting line are completed based on vector algebra,adopting space coordinate transforming method.

方法基于向量代数，采用空间坐标变换方法，建立了圆锥面与平面相交中截交曲线的形成特点，讨论了二次曲线的构成的数学原理。

During the whole growing period of tobacco plant, the change of evapotranspiration showed a single–peak curve. The evapotranspiration and soil evaporation increased. as soil water content increased.Tobacco water consumption of tobacco was related to yield through a binomial function.

随土壤含水量增加，烤烟各生育时期的耗水量和棵间蒸发量增大，全生育期内烤烟的耗水量呈单峰曲线，耗水量与烟叶产量呈二次曲线关系。

It has been put forward that there exists single Ball point and double Ball points on the symmetrical connecting-rod curves of equilateral mechanisms.

从鲍尔点的形成原理出发，分析对称连杆曲线上鲍尔点的产生条件，提出等边机构的对称连杆曲线上有单鲍尔点和双鲍尔点。

The factory affiliated to the Group primarily manufactures multiple-purpose pincers, baking kits, knives, scissors, kitchenware, gardening tools and beauty care kits as well as other hardware tools, the annual production value of which reaches US$ 30 million dollars.

集团所属工厂主要生产多用钳、烤具、刀具、剪刀、厨具、花园工具、美容套等五金产品，年生产总值3000万美元，产品价廉物美、选料上乘、质量保证，深受国内外客户的青睐