Geometrical optics approach can only calculate the high frequency approach solution of drilling bit vibration source wave equation in non caustic area but it become invalid in caustic area.

由于几何光学法求解钻头震源波动方程的高频近似解有局限性，即在焦散区失效，故只能计算非焦散区的高频近似解。

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Low penetration as well as drilling incidents of high frequency resulted from problems caused by leakage, gas migration, collapsing sticking, well kick, blowout and so forth.

且常发生井漏、气侵、坍塌性卡钻、井涌与井喷等井下复杂问题，导致机械钻速低与钻井事故频发。

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And we have CNC, CJK, Punch press, high-frequency heating machine, argon arc welding machine , drilling machine….

拥有数控车床，冲床，仪表车，锯床，高频电热机。脉冲氩弧焊机，电焊机，钻床等设备。

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