996 resultados para 229
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采用溶胶-凝胶法制作波导环形谐振腔, 讨论了环形谐振腔器件的传输特性。测量了在不同物质、不同体积分数的挥发性有机化合物(VOC)蒸气气氛下器件的传输光谱的敏感性。结果表明, 谐振波长随甲醇、乙醇、丙醇等醇类化合物, 以及丙酮、甲醛等蒸气体积分数的上升而向长波方向移动, 具有高的灵敏度, 且两者基本呈线性关系。其中, 对丙醇最敏感, 灵敏度达到1.403 pm/10-6。对甲烷和二甲苯也有微弱反应, 但是其灵敏度很低。也测量了水蒸气对传输谱特性的影响。观察到传输谱衬比度对不同挥发性有机化合物物质蒸气的不同敏
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A presente pesquisa trata da formação da teoria da pintura durante o período das Seis Dinastias, que ocupa o período que vai do ano 229 ao ano 589 da era presente. São discutidos quatro teóricos principais: Gu Kaizhi, Zong Bing, Wang Wei e Xie He. Além disto, apresentamos uma tradução diretamente do chinês para os textos de cada um dos autores analisados. No decorrer de nossa análise tentaremos demonstrar os elos de continuidade existentes entre os diversos teóricos, baseando-nos nas evidências textuais. Além disto, enfatizaremos o fato de ser este o período em que se forma a teoria da pintura chinesa. O período inicial da história dessa teoria é o tema desta pesquisa
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170 p.
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光纤激光器以其结构紧凑、转换效率高、易散热和光束质量好等优点正逐渐成为高功率全固态激光器的主要选择。目前,单根光纤激光器的输出功率已经超过千瓦量级,但是由于受受激拉曼散射(SRS)和受激布里渊散射(SBS)等非线性效应的影响,单根光纤激光器的最终输出功率还是受到限制。要在保证光束质量的同时进一步提高输出功率就需要采用相干组束技术。
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研究了Yb2O3浓度对Tm^3+/Yb^3+共掺氧卤碲酸盐玻璃的上转换发光的影响,分析了上转换发光机理。结果发现,通过980nm的激光二极管激发,在室温下同时观察到强烈的蓝光(475nm)和微弱的红光(649nm),分别是由于Tm^3+离子^1G4→^3H6和^1G4→^3F4跃迁产生的;上转换机理分析表明,上转换蓝光和红光都是由于双光子吸收过程。随Yb2O3浓度增加,Yb^3+离子寿命降低,Yb^3+到Tm^3+的能量转移效率增加,上转换蓝光和红光强度先增加,在Yb2O3摩尔比为3时达到最大,然后降低。
Resumo:
The aim of this study was to investigate the historical catch record from the Castle Fishery on the River Derwent over the period 1923 - 1989, to determine if changes had taken place in the composition of the catch and to examine the influence of flow on the performance of the fishery. The River Derwent is situated in West Cumbria, North West England. It flows from its source on Scafell Pike (NGR NY 229 089) westwards discharging into the Irish sea at Workington, a distance of 52 km. Over its length it receives water from an additional 214 km of stream, 5 large lakes and approximately 30 small tarns. The catchment drains a total area of 663 km2. The study concludes that through the time period there was considerable variation in catch between years. The trend was for the catch to increase steadily over the period 1923 - 1958, declining rapidly in 1959, after which catches increased steadily reaching a peak in the mid-sixties, before declining towards the end of the decade. During the seventies and eighties catches remained relatively stable at between 300 - 600 salmon per year until 1988 when over 2000 salmon were reported caught, the greatest number in any year over the study period.
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ZrO2 thin films were deposited bill using an electron beam evaporation technique on three kinds of lithium triborate (LiB3O5 or LBO) substrates with the surfaces at specified crystalline orientations. The influences of the LBO structure on the structural and optical properties of ZrO2 thin films are studied by spectrophotometer and x-ray diffraction. The results indicate that the substrate structure has obvious effects on the structural end optical properties of the film: namely. the ZrO2 thin film deposited on the X-LBO, Y-LBO and Z-LBO orients to m(-212), m(021) and o(130) directions. It is also found that the ZrO2 thin film with m(021) has the highest refractive index and the least lattice misfit.