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991.
992.
993.
针对现有的衍射光学元件设计方法只适用于小角度衍射的情况,本文提出了一种基于瑞利-索末菲衍射积分的设计方法,可以用来设计具有大衍射角的衍射光学元件。先对目标光场进行坐标变换和强度调整,再利用改进的Gerchberg-Saxton算法优化得到衍射光学元件的相位分布。分别采用本文方法和原有的基于夫琅禾费衍射积分的方法设计衍射光学元件实现线条结构光和不同角度方框图形的光场重构,结果表明:原有的设计方法只适用于衍射角全角小于25°的情况,当衍射角大于25°时,重构光场会出现显著的枕形畸变和不均匀的强度分布。而本文方法在小角度和大角度衍射下都能重构出准确的衍射角和较为均匀的强度分布. 相似文献
994.
995.
中国科学院近代物理研究所自主研发的ADS注入器Ⅱ第一代高频低电平(LLRF)控制系统,工作频率为162.5 MHz;LLRF系统是由基于I/Q采样的正交解调技术构成的全数字闭环反馈控制系统,其主要功能是实现超导腔腔体电压幅值稳定控制、相位稳定控制与腔体谐振频率控制;LLRF控制系统在液氦温区超导腔上进行了系统稳定度和性能的在线测试,根据实验数据计算得超导腔体电压幅度稳定度为±3.4‰,相位稳定度为±0.3°,腔体表面峰值电场(Epk)能长时间稳定在25.1 MV/m。通过实验测试,检验了LLRF控制系统的性能,并对测试过程中出现的问题进行了分析,为将来超导腔LLRF控制系统运行积累了经验。 相似文献
996.
Amphiphilic diblock copolymer polystyrene-block-poly(ethylene oxide) (PS-PEO) assembled into nonequilibrium bicontinuous structures or mixture of vesicles, bilayers and nanorods upon rapid micellization induced by rapid addition of selective solvent (water) into the PS-PEO solutions in a common solvent (dimethyl formamide) with different concentrations. These kinetically trapped assemblies were unstable and slowly evolved into thermodynamically favorable spheres and vesicles. The addition of non-ionic surfactant Pluronic P123 upon rapid micellization generated novel nanocages and flower-like vesicles. The nanocages spontaneously transformed into tubules capped with vesicles. These novel assemblies are beyond the classic phase diagram of block copolymer self-assemblies, especially for those primarily based on thermodynamics. 相似文献
997.
The First Five‐Membered‐Heterocycle‐Fused Subphthalocyanine Analogues: Chiral Tri(benzo[b]thiopheno)subporphyrazines 下载免费PDF全文
Hong Shang Luyang Zhao Dr. Dongdong Qi Chao Chen Prof. Dr. Jianzhuang Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(49):16266-16272
Two tri(benzo[b]thiopheno)subporphyrazine regioisomers with C3 and C1 molecular symmetry have been isolated from the cyclotrimerization of benzo[b]thiophene‐2,3‐dicarbonitrile as the first five‐membered‐heterocycle‐fused subphthalocyanine analogues. Optical resolution of both regioisomers was achieved by using a chiral HPLC technique, affording the first chiral subphthalocyanine analogues. 相似文献
998.
Calcite Microneedle Arrays Produced by Inorganic Ion‐Assisted Anisotropic Dissolution of Bulk Calcite Crystal 下载免费PDF全文
Xia Long Ruijie Meng Weike Wu Prof. Yurong Ma Prof. Dong Yang Prof. Limin Qi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4264-4272
Besides studies on the mineralization process, research on the demineralization of minerals provides another way to understand the crystallization mechanism of biominerals and fabricate crystals with complicated morphologies. The formation of ordered arrays of c‐axis‐oriented calcite microneedles with a tri‐symmetric structure and lengths of more than 20 μm was realized on a large scale for the first time through anisotropic dissolution of calcite substrates in undersaturated aqueous solution in the presence of ammonium salts. The lengths and the aspect ratios of the calcite microneedles can be tuned by simply changing the concentrations of the ammonium salts and the dissolution time. The shape of the transverse cross sections of the calcite microneedles obtained in the presence of NH4Cl and NH4Ac is almost regularly triangular. The tri‐symmetric transverse cross‐section geometry of the calcite microneedles could be attributed to the tri‐symmetric feature of rhombohedral calcite atomic structures, the synergetic interactions between electrostatic interaction of ammonium ions and dangling surface carbonate groups, and the ion incorporation of halide ions. 相似文献
999.
Solvothermal Transformation of a Calcium Oleate Precursor into Large‐Sized Highly Ordered Arrays of Ultralong Hydroxyapatite Microtubes 下载免费PDF全文
Dr. Bing‐Qiang Lu Prof. Dr. Ying‐Jie Zhu Feng Chen Chao Qi Xin‐Yu Zhao Jing Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):7116-7121
Hydroxyapatite (HAP), a well‐known member of the calcium phosphate family, is the major inorganic component of bones and teeth in vertebrates. The highly ordered arrays of HAP structures are of great significance for hard tissue repair and for understanding the formation mechanisms of bones and teeth. However, the synthesis of highly ordered HAP structure arrays remains a great challenge. In this work, inspired by the ordered structure of tooth enamel, we have successfully synthesized three‐dimensional bulk materials with large sizes (millimeter scale) that are made of highly ordered arrays of ultralong HAP microtubes (HOAUHMs) by solvothermal transformation of calcium oleate precursor. The core–shell‐structured oblate sphere consists of a core that is composed of HAP nanorods and a shell that consists of highly ordered HAP microtube arrays. The prepared HOAUHMs are large: 6.0 mm in diameter and up to 1.4 mm in thickness. With increasing solvothermal reaction time, the HOAUHMs grow larger; the microtubes become more uniform and more ordered. This work provides a new synthetic method for synthesizing highly ordered arrays of uniform HAP ultralong microtubes that are promising for biomedical applications. 相似文献
1000.
采用高温固相法,在还原气氛下制备出Al2O3/蒙脱土:Eu2+光致发光材料。研究了原料配比、烧结温度、保温时间以及激活剂Eu2+的含量对发光性能的影响。实验结果表明:加入蒙脱土后,所制备的样品仍保持Al2O3的架状结构,晶格常数发生变化,晶体产生畸变,使得Eu2+更容易进入到晶格中。荧光光谱分析显示,发射光谱是两个宽峰组成,对应于Eu2+的4f65d→4f7(8S7/2)宽带允许跃迁。发光机制分析认为,宽峰结构由Eu0.92[Al1.76Si2.24O8]新相产生,生成的新相增加了Eu2+的取代格位,形成新的发光中心。因此Eu2+不仅取代了Al2O3八面体中Al的格位,而且取代了蒙脱土层间所吸附的阳离子格位,使样品发光强度提高了220%。 相似文献