Frequency Offset Estimation Algorithm of High-Order M-APSK Modulation Signal Based on DFT

How to accurately compensate the Doppler shift is the main challenge for broadband satellite terminals. In this paper, a frequency offset estimation algorithm based on frequency domain window function iterative peaking search is proposed with high-order M-APSK signal models, considering both algorithm complexity and estimation accuracy. The variance of the new algorithm is derived mathematically, and performance curve compared with Cramer-Rao Lower Bound (CRLB) is also simulated under various SNR (signal-to-noise ratio). The effectiveness of new method is verified by simulations.

     

转化植物甾醇产22-羟基-23, 24-双降甾-1, 4-二烯-3-酮(HPD)工程菌株的构建及发酵培养基优化

22-羟基-23, 24-双降甾-1, 4-二烯-3-酮（HPD）作为一种重要的甾体药物中间体,是合成很多皮脂类药物的原材料。通过在分枝杆菌（Mycobacterium neoaurum DSM 1381）体内过表达3-甾酮-Δ1脱氢酶（KstD）基因,Mycobacterium neoaurum DSM 1381Z菌株发酵液中HPD的产量由71%提高到84%。在单因素选择的基础上,以产物HPD的产量作为衡量指标,利用响应面方法优化发酵培养基,建立各个因素之间变化的二次回归方程。结果表明,最合适的发酵培养基组成条件是玉米浆9 g/L、硝酸钠1.8 g/L、葡萄糖6 g/L、磷酸氢二钾2 g/L。此条件下5 g/L的植物甾醇,HPD的产量可达3.73 g/L,HPD的产量比原始菌株提高了大约2.7倍,具备潜在的工业化应用价值。     

粉末化猪脂的研制

本文介绍了粉末化猪脂的优点及研究概况，讨论了制造粉末猪脂适应的工艺过程，工艺参数，感观性状，理化指标等，制得了洁白，松散，颗粒细小的粉末猪脂，它具有较普通猪油更长的贮藏期，可以应用于面点，冰淇淋及方便汤料等食品中，是一种新型的食品原料。