adj. 1.【物理学】双焦点的。 2.(望远镜等)远近两用的。 3.有二重观点的。 短语和例子 a bifocal view 双重观点。 n. 〔pl.〕 双光眼镜，远近视两用眼镜；双焦点透镜。
Example Sentences:
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Lt ' s definitely a modern - day bifocal lens , 这肯定是今天才有的双焦镜片
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Lt ' s definitely a modern - day bifocal lens , 这肯定是今天才有的双焦镜片
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Focusing properties of gaussian beams passing through a bifocal lens 高斯光束通过双焦透镜的聚焦特性
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Third , this dissertation analyzes the complicacy of result size estimation problem for xml structure based query optimization compared to its counterpart in traditionally relational database , and proposes a full - featured result size estimation algorithm for xml query , sxm . for simple path expression query , this dissertation proposes a dynamic synopsis model for xml data based on the concept of f - stable and b - stable , xmap . for complicated path expression query , this dissertation adopts an improved bifocal sampling method for result size estimation 第三，分析了xml结构化查询优化中的查询代价估计问题与传统关系型数据库中的查询代价估计问题的区别，提出了一套完整的xml结构化查询代价估计体系sxm ，包括对简单路径表达进行查询代价估计的动态xml数据统计模型xmap ，对复杂路径表达进行查询代价估计的双焦点例举法，以及对值匹配条件进行查询代价估计的基于小波的多维直方图方法，并能将多种查询表达的查询代价估计结果结合在一起，以给出一个完整的xpath查询的代价估计。
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Detailed numerical results for a pgsm beam passing through a bifocal lens are presented . it implies that the degree of polarization is no longer uniformly polarized in general and propagation - induced polarization changes depend on the beam parameters and system parameters , such as beam coherence parameter 通过对双轴透镜系统进行的数值计算表明， pgsm光束光场的偏振不再是均匀偏振，光束的偏振特性与光束参数和光学系统参数有关，不同相关状态下场点的偏振度不同。
