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排序方式： 共有218条查询结果，搜索用时 703 毫秒
41.
文中定性分析了用双光束作干涉实验时,由于菲涅尔直边衍射效应对双光干涉的影响。给出用双棱镜产生双光束时菲涅尔衍射现象对干涉影响的分析结果,指出了在此类实验中减少误差的方法 相似文献
42.
David A. Scott 《文物保护研究》2018,63(4):215-235
Nine ancient Egyptian sarcophagi of the twenty-fifth to twenty-sixth dynasty, one Ptolemaic Hawk Mummy, and one Amarna fresco were examined in the collections of the San Diego Museum of Man. Binding media, pigments, wood identification, deterioration and alteration products were identified. The pigment palette represents the basic suite of ancient Egyptian pigments: charcoal black, red ochre, yellow ochre, Egyptian blue, green earth, calcite, and gypsum. In the case of the Hawk mummy, oxammite was identified as a degradation product, together with magnesium phosphate, the first identification of oxammite in ancient artefacts. In a child’s coffin, realgar and orpiment were additionally identified. The binding media for practically all of the coffins studied was confirmed as gum Arabic with only one example of gum tragacanth found from a wall plaque from Amarna. Wood identification showed that Ficus sycomorus had been used, rather than the assumed cedar of Lebanon for coffin manufacture. One unidentified species of shrubby wood was also found. Some of the coffins had been restored, with one having a completely repainted face, in rutile, and the child’s coffin has an attached foot-box with modern screws. Possible indications of ancient reuse were found during the study. 相似文献
43.
A sodium copper formate, first described in 2002, can also form on copper alloys with sodium originating from soda glass hydrolysis. The frequent occurrence (50% of 250 cases of glass-induced metal corrosion) is due to the presence of formaldehyde emissions in storage and its direct reaction to formate in the alkaline surface films. The compound can be produced without the presence of acetate when chalconatronite or metal coupons immersed in soda solution are exposed to formaldehyde vapours. The crystal structure, derived from X-ray powder diffraction, yielded the sum formula Cu4Na4O(HCOO)8(OH)2·4H2O. Except for the absence of acetate in the structure, this is in good agreement with the 2002 publication. To assess which kind of combined glass/metal objects are affected, a number of large museum collections were surveyed. Sodium copper formate was detected as a corrosion product using mainly micro-Raman spectroscopy, for instance, on 18 painted Limoges enamels, eight glass vessels with metal mountings, glass beads on metal wire from 11 bridal crowns, nine Christmas tree balls with wire decoration, 40 pieces of jewellery with glass gems, three daguerreotypes, and one miniature with cover glasses. 相似文献
44.
谢冰 《钦州师专钦州教院学报》2007,22(6):62-65
通过对物理专业师范生关于光衍射知识理解的调查，了解学生对光的衍射知识的掌握情况，探讨影响学生掌握知识的成因，并提出了相应的教改措施． 相似文献
45.
根据菲涅耳-基尔霍夫衍射理论,将高斯光束的高斯振幅分布近似用抛物线代替,推导出高斯光束照射下单缝衍射光场分布的近似解及其成立条件,并通过实验和数值仿真,讨论了衍射光场的基本特性． 相似文献
46.
利用电解还原法制备钾蓝青铜单晶,通过x射线衍射实验分析实验样品结构,得实验中制备的单晶确属钾蓝青铜。 相似文献
47.
基于 Huygens-Fresnel 衍射积分,利用 Hankel 变换算法及球面波因子处理方法,在普通 PC上使用 MFC 编程较好地实现了 Fresnel 衍射的计算机模拟演示。演示中,Fresnel 衍射的输入光强剖面分布、输出光强剖面分布和输出光强影射图样分别随光的传输距离和波长及输入光束半腰的改变而变化,光的传输距离和波长及输入光束半腰分别由三个滚动条分别控制。 相似文献
48.
49.
刘秋武 《内江师范学院学报》2010,25(10):40-41,76
应用基尔霍夫—菲涅耳衍射理论,分析了菲涅耳双棱镜对柱面波的相位调制作用,得到双＂虚光源＂距离和条纹间距等与几何光学一致的结果. 相似文献
50.