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Cationic ring-opening copolymerization of 1, 4-anhydro-2, 3-O-isopropylidene-α-D-ribo-pyranose (AIRP) with 1,4-anhydro-2,3-di-O-benzyl-α-D-ribopyranose (ADBR) preparedfrom D-ribose was studied. Copolymerization using SbCl_5 or BF_3 OEt_2 as catalyst atlow temperature gave stereoregular (1→4)β-D-ribofuranan (C-1 and C-4 ring cleavagesee Scheme 1) or (1→5) α-D-ribofuranan (C-1 and C-5 ring cleavage) respectively. Theeffects of catalysts, reaction time and temperatures on yield and stereoregularity of the ob-tained polymers were studied. Polymers were characterized by molecular weight, ~1HNMR,~(13)CNMR and optical rotation. 相似文献
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为了研究横向效应增强型侵彻体(penetrator with enhanced lateral effects, PELE)侵彻金属靶板破碎效应的相似规律,选取PELE的壳体破碎长度和靶后破片散布半径作为衡量PELE破碎效应的两个物理参量,基于量纲理论对PELE破碎效应问题进行相似分析,应用AUTODYN软件开展了4组相似模型数值模拟,并进行了两组相似模型验证试验。研究结果表明:通过相似理论分析,确定了PELE破碎效应满足严格的几何相似律。在800~2 000 m/s撞击速度范围内,归一化处理的壳体破碎长度和靶后破片散布半径数值模拟结果及试验结果与几何尺寸无关,仅随撞击速度的提升呈线性增长,从而证明了PELE侵彻金属靶的破碎效应满足几何相似律。 相似文献