近似圆形的

Researched influence of frequency on characteristic of electromagnetic wave transmission in tunnels, and analyzed characteristic of electromagnetic wave transmission in circular, arches and curved tunnels by method of metal wave guide, and gives approximate formulas of attenuation rate. Main conclusions we obtain are as follows: in circular,rches tunnels, if frequency is higher, attenuation rate is smaller, it is beneficial for EM waves to transmit, in curved tunnel, higher frequency, more attenuation rate ...

研究了频率对井下电磁波传输特性的影响，采用金属波导法分析了圆形、拱形及弯曲隧道中电磁波的传输特性并给出衰减率近似公式，得出主要结论：在圆形和拱形隧道中，频率越高，衰减率越小，越有利于电磁波的传播；在弯曲隧道中，频率越高，衰减率越大，不利于电磁波的传播；通过特性曲线与井下实验数据相比较得出在900MHz左右为井下无线通信系统传输信号最佳频段。

Considering that the left ventricle is roughly a circle, a shape constraint based on circle is adopted for segmentation of the endocardium.

就左室壁内膜的分割而言，考虑到左室壁的形状近似为圆形，引入基于圆形约束的能量项。

In this paper the stress analysis solution of parallel circular tunnels in elastic ground under any coefficient of lateral pressure is derived, and the stress field and displacement field of parallel circular opening subjected to continuous boundary stresses are first solved, and then the ground pressure and the internal force in lining are obtained, using the displacement compatibility equation between linin...

先求得连续洞周边界应力条件下双圆形洞室的应力场和位移场；再利用衬砌和围岩界面位移协调方程，获得平行圆形隧道的地层压力和衬砌内力公式，并可考虑开挖面的三维效应和洞室自由位移等因素。根据结论公式，对隧道间距、地层性质、衬砌厚度等诸因素进行了讨论，得到了单因素的一般规律，在此基础上，提出了平行圆形隧道最小间距的近似方法，并在某工程中予以应用，得到了满意的结果。本应力分析方法在平行圆形隧道的设计和施工中供作参考。

In this paper, Newton iteration formula for computing normal depth and critical depth was put forward by mathematical transformation of uniform flow equation and critical flow equation of circular section tunnel. Then, the relationship between the corresponding central angle and the introduced parameters was analyzed. An approximate formula for angle was obtained according to optimal uniform approximation principle. Using this approximate formula as initial value of iteration formula, a direct formula for calculating normal depth and critical depth of circular section tunnel was established after its first iterative.

该文通过对圆形断面均匀流方程与临界流方程的数学变换，分别得到其正常水深与临界水深的牛顿迭代公式，同时，通过对正常水深与临界水深对应的中心角与引入参数之间关系的分析及数值计算，利用最优一致逼近原理分别得到了正常水深与临界水深对应中心角的近似计算式，并以此近似计算式为初值，用迭代方程进行一次迭代得到了圆形断面均匀流水深与临界流水深的直接计算公式。

According to the situation in permafrost regions, the governing differential equations of heat transfer in frozen zone and unfrozen zone are simplified.

根据冻土地区的实际情况对圆形隧道正冻区和未冻区的热传导方程进行简化，应用无量纲量和摄动技术对简化方程进行求解，给出了圆形隧道冻结过程的近似解析解。

As same as the above-mentioned reason, because theconditions at the inside straight boundary of the binarycomposite material can not be easily satisfied, here, anelastic circular inclusion with large radius is used to replacethe upper half space of the binary composite material, so the〓mary binary composite mater ial problem can be changed〓the scattering problem of a circular elastic inclusion andto the scattering problem of a circular eastic inclusion and〓circular cavity in an infinite space to the steady incident〓wave.

与前面两个问题的理由一样，同样，由于问题中双质复合材料的内部直边界上的边界条件不易解析满足，为此，本文采用了一个半径很大的弹性实夹杂来代替问题中双质复合材料的上半空间部分，而将原来的双质复合材料问题转化成了无限大空间中一圆形弹性夹杂和一圆孔对稳态P波的共同散射问题，根据该问题的特点写出了弹性夹杂内外波场中波函数的一般形式解，利用该问题中夹杂和圆孔处的位移和应力的连续条件，并采用复数傅立叶级数展开技术将其化为一个仅包含问题波函数中未知系数的无穷线性代数方程组，在满足一定计算精度的前提下，通过有限项截断进行近似求解，进而讨论了双质复合材料中圆孔边界处的动应力集中系数随不同入射角、圆孔的不同位置、以及入射波的不同无量纲波数的变化和分布情况。

In the United States, chronic alcoholism and hepatitis C are the most common ones.

在美国，慢性酒精中毒，肝炎是最常见的。

If you have any questions, you can contact me anytime.

如果有任何问题，你可以随时联系我。