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51.
We consider finite horizon Markov decision processes under performance measures that involve both the mean and the variance of the cumulative reward. We show that either randomized or history-based policies can improve performance. We prove that the complexity of computing a policy that maximizes the mean reward under a variance constraint is NP-hard for some cases, and strongly NP-hard for others. We finally offer pseudopolynomial exact and approximation algorithms. 相似文献
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根据衍射光栅的标量理论,计算并讨论了金透射光栅在软X波段衍射效率对光栅厚度和占宽比的依赖关系.结果表明,选择合适的光栅槽深和占宽比,高达 21.9%的衍射效率可能被获得,远高于振幅型光栅的+1级衍射效率10.14%.通过全息光刻与电镀转移技术制作的位相型金透射光栅由300nm的聚酰亚胺薄膜支撑,光栅槽深200nm,占宽比为0.55,周期为1μm,面积为20mm×5mm.在国家同步辐射装置上,测得其+1级透射衍射效率在波长λ=7.425nm时获得最大值,约为16%.
关键词:
透射位相光栅
全息光刻
电镀 相似文献
55.
A systematic study of various metal trifluoromethanesulfonates as efficient catalysts in the regioselective reductive ring opening of benzylidene acetals is described, including the effects of solvents, reducing agents, and temperature. These catalysts are found to be effective in cleaving the 4,6‐O‐acetal rings of hexopyranosides at either O4 or O6, respectively. When used in conjunction with a 1 M solution of BH3·THF in THF without extra addition of any solvent, it affects the ring fission at the O6 position to generate the corresponding primary alcohols, whereas O4‐opening takes place in acetonitrile in the presence of dimethylethylsilane as the reductant leading to the secondary hydroxyl derivatives in high selectivity and yields. These methodologies can be applied to a wide range of substrates containing various functional groups. 相似文献
56.
Fang‐Che Hsueh Chi‐You Tsai Chien‐Chen Lai Yi‐Hung Liu Shie‐Ming Peng Sheng‐Hsien Chiu 《Angewandte Chemie (International ed. in English)》2020,59(28):11278-11282
We have prepared NHC‐CuI complexes with a rotaxane structure and used them as sterically sensitive catalysts for one‐pot sequential copper‐catalyzed azide/alkyne cycloadditions in solutions containing all of the coupling partners premixed in unprotected form. Most notably, a photolabile and sterically encumbered complex first catalyzed the coupling of a less bulky azide/alkyne pair; after removing the protective macrocyclic component from the rotaxane structure, through irradiation with light, the exposed dumbbell‐shaped NHC‐CuI complex catalyzed the second click reaction of a bulkier azide/alkyne pair. Using this approach, we obtained predominantly, from a single sealed pot, a bis‐triazole product (84 %) from a mixture of two sterically distinct azides and a diyne. 相似文献
57.
软X射线平焦场光栅光谱仪是等离子体诊断的重要仪器,其核心光学元件全息平焦场光栅通常采用非球面波记录光路制作,因此光栅条纹存在弯曲的现象.光栅条纹的弯曲会影响光谱成像质量,从而影响系统的光谱分辨率.记录光路的优化,只保证光栅子午面的线密度分布,因此优化的记录光路并不是惟一的,所以在保证子午面的线密度分布的同时能制作具有不同弯曲程度条纹的光栅.针对应用于0.8—6 nm的全息平焦场光栅,利用光线追迹方法分析了不同弯曲程度条纹光栅的光谱成像,发现采用柱面反射镜制作的接近于直条纹的光栅具有较好的光谱成像质量.相对于弯曲条纹的光栅,接近于直条纹的光栅理论光谱分辨率有明显的提高,入射波长为3 nm时,光谱分辨率从626提升到953,入射波长为5 nm时,光谱分辨率从635提高到1222. 相似文献
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59.
Xiaoyong Gao Qinggeng Lin Hongliang Feng Yongsheng Chen Shie Yang Jinhua Gu Weiqiang Li Jingxiao Lu 《Applied Surface Science》2009,255(16):7268-7272
Effect of 5.0% diluted NH4Cl aqueous solution was comparably investigated on the postdeposition surface texture of the as-deposited smooth aluminum-doped zinc oxide (AZO) films by direct current pulse reactive magnetron sputtering (DCP-sputtering) and direct current reactive magnetron sputtering (DC-sputtering). The as-deposited AZO films by DCP-sputtering showed an effective surface texture for light trapping upon the etching of 5.0% diluted NH4Cl solution, while the as-deposited AZO films by DC-sputtering demonstrated an obscure surface texture upon the same etching treatment. The different result might be attributable to a big difference in film strain and film compactness. The formation of interstitial Zn, interstitial Al and grain boundary is the key to realize effective surface texture for the as-deposited AZO films. 相似文献
60.
Tsing-Hai Wang Wen-Chun Yeh Shih-Chin Tsai Yi-Lin Jan Shi-Ping Teng 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(3):607-612
We have examined the working diameter of capillary columns with diameter of 5, 7, 10 and 20 mm. These modified capillary columns
were carefully filled with local Taiwan laterite (LTL). The porosity and density of these packed columns was 0.51±0.02 g/g
and 1.27±0.05 g/cm3, respectively. The diffusion experiments were then carried out in synthetic groundwater with Cs loading of 0.1mM at room
temperature. Experimental results have shown that the diffusion profiles of modified capillary columns fit Fick’s second law
very well. This result revealed that the working diameter of a capillary column can be expanded to at least to 20 mm without
affecting the validity of the derived diffusion coefficients. Among these columns, the ones with 5 mm diameter show the most
consistent results of the derived K
d
, apparent and effective diffusion coefficients. Although the derived distribution and effective diffusion coefficients slightly
decrease as the diameter of these columns increases due to the increase of the solid/liquid ratio. These values are still
informative of the Cs diffusion in local Taiwan laterite. Moreover, our results clearly demonstrate the potential of using
“modified capillary method” to study the diffusion behaviors of concerned radionuclide because columns with large diameter
enable the filling with more versatile geological substances. 相似文献