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聚(L-乳酸-co-衣康酸丁二醇酯)/中空介孔SiO_(2)微球复合薄膜的制备及对草莓包装中微气氛的调控作用 被引量:2
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作者 张家涛 赵文波 +3 位作者 胡健 孙滔 董同力嘎 云雪艳 《高分子材料科学与工程》 EI CAS CSCD 北大核心 2023年第8期91-103,共13页
为改善聚(L-乳酸)(PLLA)薄膜的果蔬平衡气调包装性能,文中首先通过熔融酯化缩聚法将聚衣康酸丁二醇酯(PBI)作为柔性链段引入PLLA中制备PLBI共聚物,进一步通过溶液浇筑法将中空介孔SiO_(2)微球(HMSM)作为气体渗透“通道”填充到PLBI中制... 为改善聚(L-乳酸)(PLLA)薄膜的果蔬平衡气调包装性能,文中首先通过熔融酯化缩聚法将聚衣康酸丁二醇酯(PBI)作为柔性链段引入PLLA中制备PLBI共聚物,进一步通过溶液浇筑法将中空介孔SiO_(2)微球(HMSM)作为气体渗透“通道”填充到PLBI中制备PLBI/HMSM复合膜。探究了软段嵌入、HMSM粒径对复合膜包装性能的影响,并评估了薄膜对草莓包装内气氛的调控作用。结果表明,与PLLA相比,PLBI薄膜的Tg降低了5.4℃,断裂伸长率增加了14.3倍。继续添加质量分数0.9%700 nm的HMSM后,PLBI薄膜的CO_(2)透过率(CDTR)和O_(2)透过率(OTR)分别约为PLLA的2.2倍和3.3倍,而水蒸气透过率有所下降。草莓保鲜结果表明,在3~25 d的贮藏期间,PLBI/HMSM薄膜内的CO_(2)和O_(2)含量分别维持在6.9%~8.0%和3.1%~4.6%,可为草莓提供理想的保鲜微气氛,有效延缓了草莓的枯干和腐烂。 展开更多
关键词 聚乳酸 衣康酸丁二醇酯 中空介孔SiO_(2)微球 断裂伸长率 透气性 平衡气调包装
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Code acquisition method based on wavelet transform filtering
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作者 Chao Wu Luping Xu +1 位作者 Hua Zhang wenbo zhao 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2015年第6期1169-1176,共8页
In order to improve the acquisition probability of satellite navigation signals, this paper proposes a novel code acquisition method based on wavelet transform filtering. Firstly, the signal vector based on the signal... In order to improve the acquisition probability of satellite navigation signals, this paper proposes a novel code acquisition method based on wavelet transform filtering. Firstly, the signal vector based on the signal passing through a set of partial matched filters (PMFs) is built. Then, wavelet domain filtering is performed on the signal vector value. Since the correlation signal is low in frequency and narrow in bandwidth, the noise out-of-band can be filtered out and the most of the useful signal energy is retained. Thus this process greatly improves the signal to noise ratio (SNR). Finally, the detection variable when the filtered signal goes through the combination process is constructed and the detection based on signal energy is made. Moreover, for the better retaining useful signal energy, the rule of selection of wavelet function has been made. Simulation results show the proposed method has a better detection performance than the normal code acquisition methods under the same false alarm probability. 展开更多
关键词 code acquisition wavelet transform FILTERING detection probability.
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