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三种2°视场消大气色散主焦点改正器 被引量:1
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作者 徐文莉 王亚男 《天文学报》 CSCD 北大核心 1993年第2期165-172,共8页
本文给出了为中国的2.16米望远镜设计的三种消大气色散主焦点改正器。视场为2°,可产生的最大色散为6"。三种结构均给出非常好的成象成量。主光线与光轴的夹角也很小。工艺上没有特别困难的问题。这些设计不仅可用于2.16米望远... 本文给出了为中国的2.16米望远镜设计的三种消大气色散主焦点改正器。视场为2°,可产生的最大色散为6"。三种结构均给出非常好的成象成量。主光线与光轴的夹角也很小。工艺上没有特别困难的问题。这些设计不仅可用于2.16米望远镜,对其它大望远镜也是很有意义的。 展开更多
关键词 光学望远镜 改正器 光学 设计
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Improved Sinusoid Analysis and Post-Processing in Parametric Audio Coding
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作者 周宏 陈健 《Journal of Shanghai Jiaotong university(Science)》 EI 2003年第2期163-168,共6页
This paper proposed improvements to the low bit rate parametric audio coder with sinusoid model as its kernel. Firstly, we propose a new method to effectively order and select the perceptually most important sinusoids... This paper proposed improvements to the low bit rate parametric audio coder with sinusoid model as its kernel. Firstly, we propose a new method to effectively order and select the perceptually most important sinusoids. The sinusoid which contributes most to the reduction of overall NMR is chosen. Combined with our improved parametric psychoacoustic model and advanced peak riddling techniques, the number of sinusoids required can be greatly reduced and the coding efficiency can be greatly enhanced. A lightweight version is also given to reduce the amount of computation with only little sacrifice of performance. Secondly, we propose two enhancement techniques for sinusoid synthesis: bandwidth enhancement and line enhancement. With little overhead, the effective bandwidth can be extended one more octave; the timbre tends to sound much brighter, thicker and more beautiful. 展开更多
关键词 parametric audio coding SINUSOID POST-PROCESSING
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