声速

Numerical results demonstrated that there are three kinds of the instability for the under-expanded supersonic jets according to their shock cell structure patterns:(1) the regular reflection shock cell with a single shear layer,(2) the Mach reflection shock cell with two shear layers and (3) the curved Mach stem with a relatively high expansion ratio.

计算结果表明欠膨胀超声速射流的失稳机制根据射流激波结构的特征可分为3种失稳模式：具有规则反射激波结构和单一剪切层特征的射流不稳定性；带有马赫反射激波结构和双剪切层特征的射流不稳定性；具有弯曲马赫杆和高度欠膨胀射流的不稳定性。

Secondly, supersonic combustion research is reviewed. Then, investigation for scramjet engine model is summarized.

其次是超声速燃烧方面的研究及模型超燃冲压发动机研究。

Part two: both numerical and experimental investigation on the cold flow field of a model dual-combustor scramjet.

超燃冲压发动机是一种新型的吸气式动力装置，在高超声速飞行器上有重要的应用前景。

In addition to measurements of conventional dynamic parameters o n a model surface,an optical observation method was employed,which directly reco rded self-luminosity of high temperature gas induced by a two-dimensional mode l in high enthalpy flow and combustion radiation.Hypersonic flow fields passing over a sharp strut including fuel injection were displayed and recorded with a high-speed CCD camera.A phenomenon of supersonic diffusive combustion under fre e boundary condition was observed.

实验除测量常规流场参数和模型表面的动态参数外，主要使用二维实验模型，利用高温气体的自发光和燃烧伴随的发光现象，采用高速摄影技术来观测燃烧现象，记录到高焓流场中叠加燃料喷射和燃烧的流场，观察到自由边界条件下扩散控制的超声速燃烧现象。

The sound velocity is one of the most important acoustic parameter in ocean sonar.

声速是海洋声呐测量中最重要的声学参数之一。

The signal fluctuations, the impact of temperature on the speed of sound reasons, ultrasonic ranging system ranging accuracy improved much more restricted, This also affected the ultrasonic ranging system in a number of precision applications demanding occasions, the problem of great practical significance Research

由于信号起伏、温度对声速的影响等原因，超声测距系统测距精度的提高受到很大的限制，这也影响到了超声测距系统在一些精度要求较高的场合的应用，所以这个问题的研究有很大的现实意义。问题补充：翻译软件译的就不要再贴上来了！

The experimental results agree with the accepted value of the speed of sound in air, i.e.

实验得出的结果与在空气中的声速的认可值，即

The frequency, wave length, and speed of sound are closely related.

频率，波长和声速三方面是密切相关的。

When did the first measurement of the speed of sound take?

第一次测量声速是在什么时候？

Objective To study the relationship between bone markers and bone speed of sound in women of different ages.

目的 观察绝经前后不同年龄妇女的骨超声声速和骨代谢生化指标的变化情况及相互关系。

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。