排序方式: 共有56条查询结果,搜索用时 265 毫秒
1.
3.
5月中旬,几乎在我国着手打捞海底沉船“南海一号”的同时,世界著名的沉船打捞公司美国奥德赛海洋探勘公司宣布,他们在一艘古沉船上找到了价值约2.5亿英镑的钱币,但拒绝透露具体的打捞地点和沉船的国籍、名号。随即,西班牙、英国纷纷声明,声称自己是这批财富的合法主人。原来,该公司曾与英国政府签署寻找17世纪战舰“萨克塞斯”号协议,并曾因此申请在西班牙领海勘察的许可证。 相似文献
4.
The barium titano-silicate phosphors doped with Eu3+ were synthesized by high temperature solid state reaction. The structures of as-synthesized samples were characterized by powder XRD. The maximum peaks of emission spectra of Ba2TiSi2O8 and Ba2TiSi2O8∶Eu3+ were respectively located at 450 and 618 nm, coming from the transitions of charge-transfer bands of Ti4+-O2- and forced electric-dipole transition 5D0-7F2 of Eu3+. The luminous mechanisms of Ba2TiSi2O8 and Ba2TiSi2O8∶Eu3+ were suggested. The effects of concentration of Eu3+ on the luminous performance of Ba2TiSi2O8∶Eu3+ were also studied and the results showed that the optimum concentration of Eu3+ was 0.12 mol per mole of matrix. 相似文献
5.
6.
两性树脂解吸动力学的研究──温度对扩散系数的影响 总被引:1,自引:0,他引:1
本文采用浅床法对阳离子在弱酸强碱两性树脂相内的扩散速度进行了研究。发现温度升高 ,其粒内扩散系数增大 ,离子价态越高 ,扩散过程的活化能就越大 ,表明温度的改变对高价阳离子的扩散速度的影响更显著 相似文献
7.
改革开放以来中国学生身体素质发展敏感期变迁趋势研究 总被引:1,自引:0,他引:1
8.
通过二次回归正交设计,实验研究了化学沉淀法净化未经浓缩的革余酸中镁离子的工艺条件,对氟硅酸用量、萃余酸水去除量、反应温度和反应时间四个因子进行了研究。实验结果表明:当氟硅酸用量为95.71g,除水量为80.41g,反应温度为36.02℃,反应时间为45.03min时,可使镁离子去除率达到最佳值,达到生产优等DAP的磷酸要求;实验得到的镁去除率(y)与氟硅酸用量(z_1)、除水量(z_2)、反应温度(z_3)和反应时间(z_4)的模型预测方程为:y= 59.1785-0.541156z_1+0.425071z_2-0.660951z_3-1.635317z_12+1.768750z_1z_2-6.392974z_22+1.768750z_1z_2-6.392974z_22+1.011250z_1z_3-0.978750z_2z_3-0.611140z_32+1.011250z_1z_3-0.978750z_2z_3-0.611140z_32-1.106885z_42-1.106885z_42. 相似文献
9.
A top quark mass measurement scheme near the t production threshold in future e~+e~- colliders, e.g. the Circular Electron Positron Collider(CEPC), is simulated. A χ~2 fitting method is adopted to determine the number of energy points to be taken and their locations. Our results show that the optimal energy point is located near the largest slope of the cross section v. beam energy plot, and the most efficient scheme is to concentrate all luminosity on this single energy point in the case of one-parameter top mass fitting. This suggests that the so-called data-driven method could be the best choice for future real experimental measurements. Conveniently, the top mass statistical uncertainty can also be calculated directly by the error matrix even without any sampling and fitting. The agreement of the above two optimization methods has been checked. Our conclusion is that by taking 50 fb~(-1) total effective integrated luminosity data, the statistical uncertainty of the top potential subtracted mass can be suppressed to about 7 Me V and the total uncertainty is about 30 Me V. This precision will help to identify the stability of the electroweak vacuum at the Planck scale. 相似文献
10.
新时期新疆高校学风建设的调查分析与建议 总被引:1,自引:0,他引:1
学风建设是高等教育改革和发展中一个永恒的主题,优良的学风是保证提高教育质量的重要条件,为更好地把握大学生的学习状况,研究其精神风貌、学习志向、学习热情、学习动机和学习方法等,有针对性地开展学风建设活动,课题组结合新疆医科大学学风状况,调查分析当前新疆高校学风方面存在的问题和原因,并在此基础上提出加强和改进学风建设的对策和建议. 相似文献