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哥德巴赫猜想哥德巴赫猜想,世界近代三大数学难题之一.哥德巴赫是德国一位中学教师,也是一位著名的数学家,生于1690年,1725年当选为俄国彼得堡科学院院士.1742年,哥德巴赫在教学中发现,每个不小于6的偶数都是两个素数(只能被和它本身整除的数)之和.如6=3+3,12=5+7等等.在1742年6月7日给欧拉的信中,哥德巴赫 相似文献
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Probing the improved stability for high nickel cathode via dual-element modification in lithium-ion 下载免费PDF全文
Fengling Chen 《中国物理 B》2022,31(7):78101-078101
One of the major hurdles of nickel-rich cathode materials for lithium-ion batteries is the low cycling stability, especially at high temperature and high voltage, originating from severe structural degradation, which makes this class of cathode less practical. Herein, we compared the effect of single and dual ions on electrochemical performance of high nickel (LiNi0.88Mn0.03Co0.09O2, NMC) cathode material in different temperatures and voltage ranges. The addition of a few amounts of tantalum (0.2 wt%) and boron (0.05 wt%) lead to improved electrochemical performance. The co-modified LiNi0.88Mn0.03Co0.09O2 displays an initial discharge capacity of 234.9 mAh/g at 0.1 C and retained 208 mAh/g at 1 C after 100 cycles at 45 ℃, which corresponds to a capacity retention of 88.5%, compared to the initial discharge capacity of 234.1 mAh/g and retained capacity of 200.5 mAh/g (85.6%). The enhanced capacity retention is attributed to the synergetic effect of foreign elements by acting as a surface structural stabilizer without sacrificing specific capacity. 相似文献
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陈一帆 《广东微量元素科学》2017,24(4)
目的研究分析替硝唑联合盐酸左氧氟沙星对慢性盆腔炎患者的临床治疗价值。方法选取2015年9月至2016年9月期间在江西省共青城市人民医院治疗的90例慢性盆腔炎患者作为研究对象,采用随机数字表法将90例患者分为观察组和对照组,每组各为45例,评价两组治疗效果,评价指标包括治疗有效率和不良反应发生率。结果观察组患者治疗有效率比对照组高,两组数据比较差异有统计学意义(P0.05);观察组患者不良反应发生率比对照组低,两组数据比较差异有统计学意义(P0.05)。结论替硝唑联合盐酸左氧氟沙星对慢性盆腔炎患者的临床治疗价值较高,值得推荐采纳。 相似文献
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Enhancement of electrochemical performance in lithium-ion battery via tantalum oxide coated nickel-rich cathode materials 下载免费PDF全文
Fengling Chen 《中国物理 B》2022,31(5):58101-058101
Nickel-rich cathode materials are increasingly being applied in commercial lithium-ion batteries to realize higher specific capacity as well as improved energy density. However, low structural stability and rapid capacity decay at high voltage and temperature hinder their rapid large-scale application. Herein, a wet chemical method followed by a post-annealing process is utilized to realize the surface coating of tantalum oxide on LiNi0.88Mn0.03Co0.09O2, and the electrochemical performance is improved. The modified LiNi0.88Mn0.03Co0.09O2 displays an initial discharge capacity of ~ 233 mAh/g at 0.1 C and 174 mAh/g at 1 C after 150 cycles in the voltage range of 3.0 V-4.4 V at 45℃, and it also exhibits an enhanced rate capability with 118 mAh/g at 5 C. The excellent performance is due to the introduction of tantalum oxide as a stable and functional layer to protect the surface of LiNi0.88Mn0.03Co0.09O2, and the surface side reactions and cation mixing are suppressed at the same time without hampering the charge transfer kinetics. 相似文献
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