二次曲线

The paper is devoted to the quartic invariant algebraic curves in quadratic system.

本文在给定参数满足一定的条件下，研究了一类二次系统的四次不变代数曲线系统平衡点的稳定性态，并运用Dulac函数法给出了该系统不存在极限环的充分条件，这一研究在同类问题中具有一定的拓展性。

The analysis show that O-forming is accomplished by bending of subdividing suspend arc,characterized by evolvement of curvature peaks form one to multiple peaks,which have nearly equal peak-to-peak distance.Process loading has corresponding episodic changes,and each episodic curve is similar.Loa...

载荷在成形过程产生相应的阶段性变化，各段位移载荷曲线具有相似性，并且载荷随悬弧的细分明显增加。O成形过程分为4个阶段：U形口合扰、直边弯曲、悬弧二次弯曲和悬弧多次弯曲过程。

The effects of different parameters and cross-sections on axial velocity, the distribution of secondary flow, temperature field, turbulent kinetic energy, wall friction coefficient and wall Nusselt number are analyzed in detail.

详细分析了充分发展的和发展段的湍流管道内，不同截面形状和几何参数对轴向速度分布，截面二次流结构，湍动能，曲线管道摩擦比，温度分布和曲线管道Nusselt系数比等管道流动和传热特性的影响。

The author interpreted the determinant rule of bad measuring data while power system is in stable state, and implemented the smoothing transition of the measuring results of electrical parameters through curve fitting based on least square while the load in power system is in fluctuation in this paper.

本论文阐述了电网稳态情况下的粗差判定准则，并采用基于最小二乘为准则的二次函数曲线拟和来实现电网负载波动情况下电参量测量值的平滑过渡。

According to testing results, the stress-strain curve of the cemented soil stabilized the nanometer silica fume is fitted using a quadratic parabolic curve and expression equation for upward sector of the stress-strain curve is given.

根据试验结果，分析了纳米硅粉水泥土的变形特性，并对其应力应变曲线进行了二次抛物线拟合分析，推导了曲线上升段的表达式。

A new algorithm is presented in this paper for piecewise quadric B-splines curve reconstruction from scattered data in a plane.

基于控制顶点扰动的思想提出了一种新的曲线重构算法，用于构造一条分段二次B样条曲线来逼近平面上的散乱数据点。

The concept of secondary recalescence is outlined. It is pointed out that the inflection point occurred during recalesence stage only indecates the heat requirement for dendrite remelting, while the inflection point resulted from heat release during new phase formation can be regarded as a strict secondary recalescence.

提出在冷却曲线的再辉阶段出现的温度变化拐点，只是表明枝晶熔断过程对热量的需求，只有在快速凝固阶段的冷却曲线上出现的由于新相形成而释放出潜热导致的温度变化拐点才算得上严格意义上的二次再辉。

Thunbergii trees were established, and the sun survivorship curves were drawn with field data. The results showed that in the three plots, the height and basal diameter growth of regenerated young P. thunbergii trees had exponential, linear, and quadratic functional relations with age and the age structure was of spindle, discrete, and pyramid types, respectively. Most of the regenerated young trees were distrbuted at 0.3-1.2 m from their nearest standing trees, and the individuals of the young trees decreased near to or far from the nearest standing trees. Inplots Ⅰ and Ⅲ, the expected average life of regenerated young P. thunbergii trees had a decreasing trend with their increasing age, and the survival number of the population also decreased with increasing population age. The survivorship craves of regenerated young P. thunbergii trees in the two plots approximated to the type of Deevey Ⅱ, indicating that the young P. thunbergii populations in the plots were at stable development stage. The population structure of regenerated young P. thunbergii trees in plot Ⅱ was lesser integral, suggesting that the population was of declining types being related to human disturbance, slope and other environmental factors.

结果表明：(1) 3个样地中幼龄植株高生长、基径生长与年龄均分别呈指数函数、直线和二次函数关系；(2) 3个样地黑松幼龄植株年龄结构存在着明显差异，分别表现为纺锤形、残缺型和金字塔型；(3)幼龄植株主要集中分布在距最近立木0.3~1.2m，离立木越近或越远幼龄植株均逐渐减少；(4)对样地Ⅰ和样地Ⅲ黑松幼龄植株生命表和存活曲线的分析表明，随年龄的增加，黑松幼龄植株生命期望值基本上呈递减趋势，黑松幼龄植株种群存活数也随着年龄的增加而降低；样地Ⅰ和样地Ⅲ黑松幼龄植株种群存活曲线近似于Deevey Ⅱ型，表明2个样地黑松幼龄植株种群处于稳定发展阶段；(5)样地Ⅱ幼龄植株种群结构很不完整，表明该种群属于衰退型，与人为干扰及坡度等有关。

Some specific problems in connection with blade modeling, such as spanning characteristic mesh, interpolation of curve face modeling, precise presentation arc by second order NURBS curve, node interpolation algor...

深入探讨了在叶片构造过程中遇到的剖分网格确定、插值曲面构造、圆弧的二次NURBS曲线精确表示、NURBS曲线节点插入算法及其升降阶等关键性技术问题。

That is,(1),Angle-tuning curve in thex-zplanefor a type II KTP OPG process phase—matched pumped by a1.064μm Nd:YAG beam and(2),Tuning curves for a 532nm pump(second harmonlcof Nd:YAG)for COllinear type II phase matching in thex-y,plane(θ=90°),they-zplaneand thex-zplaneIn addition,from the Sellmeierequations,the walk-off and group velocity dispersion effects were also calculated.

计算得出，(1)Nd：YAG1.064μm泵浦的KTP晶体在x-z调谐面内的II类相位匹配的角度调谐曲线；(2)Nd：YAG二次谐波532nm泵浦的KTP参量器件在x-y，y-z以及x-z调谐面内的II类共线相位匹配的角度调谐曲线。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。