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结合具有航天任务背景的轨道设计问题,开展问题导向式教学,激发学生主动学习热情,让学生在动手实践中学习基于轨道力学理论知识的轨道设计方法,是培养学生轨道设计能力的有效途径.本文介绍了对轨道力学问题导向式教学的措施,以及逐步培养学生轨道设计能力的轨道设计问题案例.选取的轨道设计问题与教学过程中的理论知识紧密联系,循序渐进,... 相似文献
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Two new lanthanide coordination polymers [Ln(C 5 H 2 N 2 O 4)(H 2 O) 2 (C 2 O 4) 0.5 ] n nH 2 O (Ln=Ce III (1) or Pr III (2);C 5 H 2 N 2 O 4=imidazole-4,5-dicarboxylate anion;C 2 O 4=oxalate anion) have been synthesized and structurally characterized by single-crystal X-ray diffraction,elemental analyses and IR spectrum.Both compounds crystallize in monoclinic,space group P2 1 /c with a=7.5225(3),b=17.2416(6),c=8.6089(3),β=110.9610(10)°,V=1042.68(7)3,Z=4,C 6 H 8 N 2 O 9 Ce,M r=392.26,D c=2.499 g/cm 3,μ(MoKα)=4.414 mm 1,F(000)=752,the final R=0.0167 and wR=0.0412 for 1;a=7.4973(3),b=17.2113(8),c=8.5729(4),β=110.9440(10)°,V=1033.14(8)3,Z=4,C 6 H 8 N 2 O 9 Pr,M r=393.05,D c=2.527 g/cm 3,μ(MoKα)=4.764 mm 1,F(000)=756,the final R=0.0192 and wR=0.0455 for 2.X-ray diffraction analyses reveal that the lanthanide cations in compound 1 or 2 are linked by imidazole-4,5-dicarboxylate and in situ generated oxalate anions via Ln-O and Ln-N covalent bonds to form two-dimensional layered networks.The successful synthesis of compound 1 or 2 also indicates a crystallographic confirmation for the decomposition of curcumin to form oxalate anion under solvothermal conditions. 相似文献
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临床观察了60例特发性少弱精症患者使用补肾调肝方治疗后精液质量、精液微量元素锌的改变。60例患者精液密度、精液活力在治疗前后分别为(59.40±54.95)×10~6/mL、(85.48±75.58)×10~6/mL(P<0.05);(38.78±28.11)%、(47.10±28.74)%(P<0.05)。治疗前后精液锌含量分别为(1.79±1.20)mmol·L~(-1)、(1.96±1.07)mmol·L~(-1)。经计算,t值等于2.397,大于t_(0.05)(60),即P<0.05,治疗前后锌元素的差异有显著性意义。 相似文献
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