四线的

Part four will prove the following 4 theorems : theorem 1 :the curvature and torsion of the locus of foot point of the perpendicular line between the origin and the tangent line of the cylindrical spiral remains to be function t , but not trigonometric function t .

第四部分证明四个定理分别为定理1 由坐标系原点至圆柱螺线的切线所引垂线的垂足的轨迹曲率和挠率仍为t的函数，但不是t的三角函数。

But with its variety and specialization , three-axial non-instaneous envelope method had not meet needs. So four-axial non -instaneous envelope method was set forth firstly in this article, which is based on three-axial non-instaneous envelope and spiral rod compressor rotator speciality.

然而随着螺杆应用范围的扩展，螺杆型线不断复杂化、多样化，三自由度无瞬心包络铣削法已不能满足部分型线的加工要求，为此本文在三自由度无瞬心包络铣削法的基础上，针对螺杆压缩机阴阳转子的特性，在国内首次提出四自由度无瞬心包络铣削螺旋曲面的新方法，赶超国际螺旋曲面加工技术水平，具有重要的理论和现实意义。

The reason of unbalanced load voltage for station transformer in 220 kV substation was analyzed,the important influence of null line wirings in three-phase four-wire system on three-phase load voltage balancing was explained,and put forward a kind of simple,visual and practical vector analysis method.

分析一220kV变电站站用变压器负荷电压不平衡的原因，说明了三相四线制中的零线接线准确与否对负荷三相电压平衡性的重要影响，并提出了一种简单、直观的实用矢量图分析方法。

Compensating devices have developed from Synchronous Adjustive Phasic Device, Static Var Compensator to Advanced Static Var Generator nowadays. Today, Trinomial Three Lines pattern Static Var Generator is grown up. But the anisomerous problem becomes more and more serious.

目前用于三相三线制的静止无功发生器已经较为成熟，但随着不对称负荷问题的日益突出，对零线电流的补偿显得十分重要，这就要求使用三相四线制的静止无功发生器。

Four examples exist from four separate conflicts that call into question the efficacy of non-BAI interdiction: Operation Strangle (Italy, 1944); Operations Strangle and Saturate (Korea, 1951-52); French interdiction efforts against Vietminh supply lines, 1952-54; and the long and arduous campaign against the Ho Chi Minh trail network over a decade later.

有四个分别发生在四个没有关联的冲突中的例子可以提出对非BAI遮断的质疑：绞杀战（意大利，1944）；绞杀行动与饱和轰炸（朝鲜，1951-52）；1952年-54年法国人对越盟补给线的遮断努力；以及十年之后针对'胡志明小道'长期而又艰难的轰炸行动。

And a screwy algorithm based on digital image from mono-view is presented. This algorithm needs the four-region sign with the screwy boundary labeled on the surface of columniform targets. Then the length of the intersecting lines of the object's axis and the screwy boundary are gained by means of digital image processing, such as gray histogram balancing, Susan edge detection and Hough transform. Finally, the object's rolling angle is accurately gotten in shooting range.

该方法通过在圆柱形目标表面涂上边界为螺旋线的四区域标志，综合运用直方图均衡化、Susan边缘检测以及Hough变换等数字图像处理技术，从光测图像中得到各个时刻目标中轴线与螺旋线的相交线段的长度，由此可高精度测出空间目标的滚转角，从而有效地解决了靶场试验中空间目标滚转角的测量难题。

The paper discuss the main circuit and control circuit structure of the active power filter, according to the main circuit divided into two different kinds of structure that are four-phase convertor and three-phase convertor, this paper do deep research on each work theory and control circuit, provide each control method and DC side voltage control method.

论文讨论了在三相四线制系统中有源电力滤波器主电路及控制电路的构成，就主电路分别为四相变流器和三相变流器两种不同结构方式的工作原理和相应的控制电路进行了深入的研究，提出了各自的控制方法以及相应的直流侧电压控制方法。

When we imagined the fourth dimension, it was as if we were treating the entirety of three-dimensional space in a particular state as a single point, and drawing a fourth-dimensional line to another point representing space as it is in a different state.

当我们想象第四维的时候，我们将整个第三维想象成了一个点，然后画一条四维的线。

Then we find out the exact bounded wave solutions for WBK equation in chapter four. According to the theory of dynamical system, we investigate the explicit exact traveling wave solutions of nonlinear wave equations by using the characters of the closed trajectory connecting equilibrium points and the relations between obits and traveling waves.

在对系统进行定性分析、了解了系统所有可能解的大致形态的基础上，论文第四章给出了WBK方程的精确有界解，应用动力系统理论，利用连接平衡点的闭轨线的特点结合轨线与行波之间的对应关系来研究非线性波方程行波解的有界性及精确的显式表达式。

Four years of university life is my life, this small section of the line, is a sparkling period, which includes a sweat and post-harvest, in order to draw my life-line to play a crucial role.

四年的大学生活是我人生这条线上的一小段，是闪闪发光的一段，它包含了汗水和收获，为我划平人生的线起着至关重要的作用。

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。