参数曲线

These curves contain a shape parameter which can adjust the softness of curve and have the same continuity with the original B-spline. In succession, using the positive conditions of Bernstein polynomial to find a range in which the shape parameter takes its value so as to make the corresponding interpolating curves monotonicity-preserving and C~2 continuous.

利用奇异混合的思想构造出一类带有形状参数的多项式样条曲线，即均匀α-B样条曲线，在无需反求方程组、迭代过程和最值求解的情况下就能轻松做到插值给定的点列；它含有形状参数α，这就增加了曲线的柔性，同时又和原B样条曲线具有相同的参数连续性。

Secondly, in our methods, the essential geometry of the image single axis geometry may be specified by six parameters and this may be estimated from one conic and one fundamental matrix (a total of 12 parameters) or may be minimally estimated from two conics (a total of 10 parameters).

本文证明了单轴旋转运动的不变量可以通过一个基本矩阵和一条二次曲线来确定，在这种情况下，由于基本矩阵的自由度为7，二次曲线的自由度为5，所需确定的参量个数仅为12，大大减少了不变量的计算量；本文同时证明单轴旋转运动的不变量可以通过最少两条二次曲线来确定，在这种情况下所需确定的参量个数仅为10，该方法是目前同类算法中参数最少的；本文提出了用多条二次曲线求解单轴旋转运动的不变量的最大似然估计算法，其所需确定的参量个数为6+2n，其中n为二次曲线的个数，该公式更深刻地反映了二次曲线与不变量的参数关系。

The macroscopic rheological parameters and microstructure parameters were closely related, it is helpful to explain the essence of multiple rheological properties through the analysis of which the wax evolution process and microstructure of the crude oil which is waxy and high viscosity; the yield time of gelled waxy crude oil monotone increases along with the decreasing of rate of shear (the time of stress effect prolonged), there was power function relationship between them, it can be expressed with ; when adding diesel oil to Sudan crude oil, dilute proportion bigger the eccentricity degree of paraffin particles were bigger too, that was to say the symmetry of wax crystal was better, the wax crystal form fabric more hardly when the intermolecular interaction was smaller; in the light of macroscopica, the fall extent of the abnormity temperature, solidifying point and viscosity could be larger along with the accretion of dilute proportion, as a result, it's rheological properties could be improved.

SD原油析蜡点为94℃，析蜡高峰为50～30℃，异常点为40℃；其蜡晶颗粒细小、对称性差，所以具有较大的比表面能，容易形成联生、联锁结构；损耗角曲线与储能模量曲线或损耗模量曲线的交点所对应的温度与原油凝点或倾点温度非常接近，大约在39℃左右；也就是说，含蜡原油粘弹特性曲线的交点可以表征其流动性；原油宏观流变参数与微观结构参数密切相关，原油析蜡过程及蜡晶微观结构分析有助于诠释易凝高粘原油多重流变特性的本质；胶凝含蜡原油的屈服时间随剪切速率的降低而单调增加，二者显然存在幂函数关系，可用关系式描述；当SD原油加柴油稀释处理时，稀释比越高，蜡晶颗粒的偏心度也越大，亦即蜡晶对称性越好，分子间作用力越小，蜡晶颗粒越不易形成结构，宏观表现为异常点、凝点及表观粘度等流变参数下降的幅度越大，流动性越好。

Based on the example of turbine reverse engineering , the general procedure that can be used to translate the physical object into CAD datum by Surfacer software is determined in this paper1 By going deep into the vector of point-cloud , it's parametrization can be gained by adopting the precept of accumulating chordal parametrization1 According to the principle of const ructing curve using the least square method , the high quality-curve can be gained by modifying curve's parameter1 This paper also empha2sizes on some methods about processing point-cloud , const ructing curve and const ructing surface1 And it can provide several methods to const ruct high quality2CAD model for mould machining1

此栏目为免费论文，可自行复制获取，如需要其他完整论文，可点击论文范文查找摘要本文就涡轮反求造型的实例，采用Surfacer 软件规划出由实物转化为工程CAD 资料的一般流程。在深入分析点云数据的矢量方向基础上，采用积累弦长参数化方案实现点云的参数化；根据最小二乘法曲线拟合原理，修改曲线参数获得高品质曲线；并重点论述了点云处理、曲线生成、建构曲面的方法，为模具加工提供了建构高品质CAD 模型的有效途径。

In this paper,the rational approximation of the offset curve of Bézier curves is obtained when a polynomial of symmetric power basis is used to approximate the norm of parametric speed of Bézier curves.

等距曲线逼近技术的关键在于参数速度的逼近，文章用S幂基多项式逼近平面Bézier多项式曲线的参数速度模长，得到Bézier多项式曲线的等距曲线的有理逼近曲线，所得有理多项式逼近曲线与等距曲线在端点处能够达到高阶插值。

As the complete characteristic curves of reversible pump turbine are often used to calculate the instantaneous parameters, this paper studies the characteristic curve and the wicket closure and opening law in pumped storage plants.Chapter 1 presents the importance and the necessity of this study and reviews the previous related research on hydraulic transient process and valve regulation in pumped storage plants.Chapter 2 analyzes the six collected characteristic curves of reversible pumped turbine and studies their diversification from the point of view of specific speed. The six collected discharge and moment curves with maximum efficiency have been fitted to piecewise continuous curves. This curve-fitting procedure is listed.Chapter 3 takes Liyang Pumped storage plant as an example and analyzes the effect of different characteristic curves on regulation guarantee parameters and the variety of its trochoid during the same operation status.Chapter 4 takes three pumped storage plants with different heads as examples and studies the characteristic of coordinated closure with wicket gate and ball valve and its effect on dynamic pressure in the spiral case, inlet pressure in the draft tube and the rise of rotating speed.Chapter 5 summarizes this paper and point out what should be done in the future research.

由于在过渡过程分析计算中，需要频繁利用可逆式机组的全特性曲线推求机组的瞬时参数，所以本文就特性曲线及关闭规律问题进行了研究，其主要内容如下：第1章，指出本文研究的意义和目的，回顾前人对水力过渡过程、抽水蓄能电站及阀调节的研究成果，在此基础上提出本文的研究内容；第2章，针对收集到的六套特性曲线，从比转速的角度出发来研究可逆式机组特性曲线的变化规律；并对六套曲线的最高效率流量和力矩曲线进行分段拟合，得到各分段函数的具体形式，再通过举例说明最高效率曲线的拟合步骤；第3章，以溧阳抽水蓄能电站为实例，分析讨论不同比转速特性曲线对调保参数造成的影响及对于相同工况其轨迹线的变化；第4章，结合高、中、低三水头段抽水蓄能电站，在导叶直线关闭的基础上，研究导叶与球阀协联关闭规律的特点及对蜗壳动水压力、尾水管进口压力及转速上升造成的影响；第5章，总结全文，提出今后研究的重点和方向。

Based on the theories of rheology, Non-Newtonian Fluid Mechanics, petroleum chemistry, crystallography and pipeline technology etc. and sampling Huabei crudes, experimental indexes and programmes are drew out, integrating the oil properties and parameter analysis; in terms of the macro analysis of continuum mechanics, substantial experiments are conducted with HAAKE RS600 rotational rheometer and the rheological equation as well as the viscosity-temperature equation are further developed with tested rhrogramme and viscosity-temperature curve, respectively. Beased on the researches on thixotropic mechanism and thixotropy fluid property, hysteresis loop curve, structure failure and viscosity build-up curve as well as shear stress decrement curve for one type oil are first present in this paper. According to the theoretical researches and testing results, a novel thixotropy equation with τ=τ_∞e~ pattern, which is of hi-accuracy, few parameter and simplicity, is developed. Considering the influence of various parameters on rheological behaviour, depressant adding condition is optimized and experimental evaluation on BEM-5P is conducted, which further unrip its mechanism on the Huabei crude. A corresponding viable pipe transportion programmel is also recommended.

本文基于原油流变学、非牛顿流体力学、石油化学、结晶学、原油管输工艺学等理论，以华北原油为研究对象，结合原油物性及实验影响因素分析，制定出实验研究的评价指标及实验方案；从连续介质力学宏观分析的角度，利用HAAKE RS600高端旋转流变仪开展了大量的室内实验，并运用微观研究方法，测定了油样的流变曲线和粘温曲线，建立了流变方程和粘温方程；通过对触变性机理和触变性流体特征的研究，首次对华北原油测定出滞回环曲线、结构破坏与恢复粘时曲线、剪切应力裂降过程曲线，并在理论研究和实验结果的基础之上，建立了能定量描述含蜡原油剪切应力裂降过程的新型三参数触变模式τ=τ_∞e~b/(t+c，该模型具有精度高、参数少、实验简便且适用性强的特点；通过对含蜡原油流变性的影响因素理论研究，开展了加剂条件优选及BEM-5P降凝剂室内评价实验，进一步揭示了降凝剂对华北原油作用机理，在此基础之上，提出了华北原油管输的可行性方案。

Based on the theories of rheology, Non-Newtonian Fluid Mechanics, petroleum chemistry, crystallography and pipeline technology etc. and sampling Huabei crudes, experimental indexes and programmes are drew out, integrating the oil properties and parameter analysis; in terms of the macro analysis of continuum mechanics, substantial experiments are conducted with HAAKE RS600 rotational rheometer and the rheological equation as well as the viscosity-temperature equation are further developed with tested rhrogramme and viscosity-temperature curve, respectively. Beased on the researches on thixotropic mechanism and thixotropy fluid property, hysteresis loop curve, structure failure and viscosity build-up curve as well as shear stress decrement curve for one type oil are first present in this paper. According to the theoretical researches and testing results, a novel thixotropy equationwith τ=τ_∞e~ pattern, which is of hi-accuracy, few parameter and simplicity, is developed.Considering the influence of various parameters on rheological behaviour, depressant adding condition is optimized and experimental evaluation on BEM-5P is conducted, which further unrip its mechanism on the Huabei crude. A corresponding viable pipe transportion programmel is also recommended.

本文基于原油流变学、非牛顿流体力学、石油化学、结晶学、原油管输工艺学等理论，以华北原油为研究对象，结合原油物性及实验影响因素分析，制定出实验研究的评价指标及实验方案；从连续介质力学宏观分析的角度，利用HAAKE RS600高端旋转流变仪开展了大量的室内实验，并运用微观研究方法，测定了油样的流变曲线和粘温曲线，建立了流变方程和粘温方程；通过对触变性机理和触变性流体特征的研究，首次对华北原油测定出滞回环曲线、结构破坏与恢复粘时曲线、剪切应力裂降过程曲线，并在理论研究和实验结果的基础之上，建立了能定量描述含蜡原油剪切应力裂降过程的新型三参数触变模式τ=τ_∞e~b/(t+c，该模型具有精度高、参数少、实验简便且适用性强的特点；通过对含蜡原油流变性的影响因素理论研究，开展了加剂条件优选及BEM-5P降凝剂室内评价实验，进一步揭示了降凝剂对华北原油作用机理，在此基础之上，提出了华北原油管输的可行性方案。

When t=1/2, Path of the C-curves and H-curves ofdegree two and three are lines, but not for the Path of degree four, weneed more about the control polygon. Paths are commonly curves. Butthe reference [38] pointed out that they can closely be approximated bylines. By this method we can get a C-curve passing a given point easily.

一般情况下，C曲线族的Path也是曲线，文献[38]以三次C曲线为例，提出用直线进行近似，应用这一方法，我们可以简洁的求出过一定点的C曲线，只要给定的点在C曲线族的范围内，则可以首先求出过这一点的C曲线族的Path，然后可以确定过这一点的C曲线的形状参数α，以及曲线参数t.H曲线的情况与C曲线类似。

In consideration of the chain grate stoker with steam capacity of 20t/h,based on experimental testing data,a fast modeling with step input,was set up by calculating transfer function on step response curve,gets model parameters on "two-point method" on the first,and then modifies those parameters with "curve fitting method" through MATLAB/SIMULINK software,proves that the combination of "two-point method" and curve fitting mothod...

对阶跃响应曲线先采用&两点法&得出模型参数，再采用&曲线拟合法&对模型参数进行修正，从而实现系统动态特性建模。着重讨论了针对阶跃响应曲线，在&两点法&建模的基础上，进一步采用在MATLAB/SIMULINK软件环境下&曲线拟合法&对模型进行修正，发现&两点法&与&曲线拟合法&相结合的方法可以更准确地对系统进行建模。此方法可为锅炉燃烧优化设计、热力系统仿真研究提供热工对象理论模型，也可用于控制系统调试时控制参数的预选择。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。