四级的

I plant the production of high-purity quartz sand mining on their own quartz stone from the processing of raw materials, we have a unique purification technology and techniques, will quartz in potassium, sodium feldspar, mica and other metal ions from the exact chemical products Purity, physics, and optical properties of the 34 crystal-standard in the country is a unique product, and formed a large-scale production line the cause of 5,000 tons of annual output.

我厂生产的高纯石英砂是以自己开采的石英石为原料加工而成的，我们采用独特的提纯技术和工艺，将石英中的钾、钠长石，云母及其它金属离子分离确实产品的化学纯度、物理、光学性能达到三四级水晶石的标准，在国内属独一无二的产品，并形成了大规模的事业生产线年产量5000吨。

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。