排序方式: 共有51条查询结果,搜索用时 15 毫秒
41.
采用单晶提拉法成功生长出优质的Gd3+/Yb3+共掺铝酸钇晶体。对晶体的结构、分凝系数、光谱和激光性能进行了表征,结果表明:所生长的晶体空间群为Pnma,属于正交晶系,Yb3+的分凝系数为1.13。从偏振吸收和荧光光谱发现,b偏振方向时,晶体在980 nm处吸收截面为2.14×10-20 cm2,适用于InGaAs 激光二极管泵浦;在1 044 nm处的发射截面为0.39×10-20 cm2,荧光寿命为1.638 ms。此外,对b切向的Gd/Yb∶YAP晶体进行激光实验,在1 μm处实现连续激光输出,斜率效率为23.5%,最大输出功率可达0.51 W。 相似文献
42.
We demonstrate the generation of non-classical photon pairs in a warm ~(87)Rb atomic vapor cell with no buffer gas or polarization preserving coatings via spontaneous four-wave mixing. We obtain the photon pairs with a 1/e correlation time of 40 ns and the violation of Cauchy–Schwartz inequality by a factor of 23±3. This provides a convenient and efficient method to generate photon pair sources based on an atomic ensemble. 相似文献
43.
研究了铋层化合物Sr1+xBi4-xTi4-xTaxO15(x=0—1)陶瓷的介电和铁电特性.研究发现随着x值的增大,材料的居里点由540℃降到30℃左右,但材料始终具有铁电性.对于SrBi4Ti4O15陶瓷施加120kVcm的电场仍无法得到饱和的回线,此时的剩余极化和矫顽场分别约为7μCcm2和73kVcm.对于x=04—05的材料由于它们同时具有较高的居里温度300℃—360℃,较大的剩余极化7—8μCcm2和较小的矫顽场37—47kVcm,因此是一类性能较为优良的铁电材料.
关键词:
居里温度
剩余极化
矫顽场 相似文献
44.
已有土壤有机质的光谱预测模型其适用性受建模样本的采样尺度、土壤类型及光谱参数限制,需要在大尺度及范围上进一步检验适用性,并比较分析不同建模方法的建模效果以寻求适用性更好、精度更高的定量模型.在黑河上游大尺度范围采得225个土壤样品,进行了土壤有机质(SOC)及光谱反射率测定后将样本划分为建模集(180个土样)与验证集(45个土样).将土壤光谱反射率(R)变换处理后得到连续统去除(CR)、倒数(REC)、倒数之对数(LR)、一阶微分(FDR)及Kubelka-Munck变换系数共6种指标,针对建模集分别采用逐步线性回归与偏最小二乘回归方法建立12种光谱指标与SOC的数学模型,并采用验证集进行模型预测效果评价.结果表明:(1)采用逐步线性回归或偏最小二乘回归方法建模,LR指标对SOC变化的解释效果都是最好,是SOC的最优预测因子.(2)基于LR指标建立的SOC模型中,采用偏最小二乘回归模型比逐步线性回归模型的预测精度更好,相较于黑河上游已有的经验模型,偏最小二乘回归法建立的模型的预测效果也更好.(3)采用本实验的225个土壤样品对比验证了黑河上游仅有的SOC模型.该模型的SOC预测值与实测值通过了均值T检验且Pearson相关系数达0.826,表明在局部典型区域建立的SOC预测模型,可以应用到更大尺度上的土壤有机质预测研究. 相似文献
45.
Energy transfer processes between two aggregates in a coupled chromophoric-pigment(protein)system are studied via the standard master equation approach.Each pigment of the two aggregates is modeled as a two-level system.The excitation energy is assumed to be transferred from the donor aggregate to the acceptor aggregate.The model can be used to theoretically simulate many aspects of light-harvesting complexes(LHCs).By applying the real bio-parameters of photosynthesis,we numerically investigate the efficiency of energy transfer(EET)between the two aggregates in terms of some factors,e.g.,the initial coherence of the donor aggregate,the coupling strengthes between the two aggregates and between different pigments,and the effects of noise from the environment.Our results provide evidence for that the actual numbers of pigments in the chromophoric rings of LHCs should be the optimum parameters for a high EET.We also give a detailed analysis of the effects of noise on the EET. 相似文献
46.
THE THERMAL BEHAVIOR OF TWO-COMPONENT PIEZOELECTRIC SINGLE CRYSTAL ALUMINIUM GALLIUM PHOSPHATE Al1-xGaxPO4 下载免费PDF全文
The temperature properties of elastic, piezoelectric and dielectric constants for the single crystal Al0.88Ga0.12PO4 have been studied in detail over a temperature range from 150 to 410K. And two crystal plates with different orientations which have zero temperature coefficient are introduced. As might have been expected, the single crystal Al1-xGaxPO4 is a new kind of materials applicable to the surface acoustic wave devices. 相似文献
47.
在300—20K的温度范围内观测了用丘克拉斯基法生长的Li0.025Na0.975NbO3晶体的介电、铁电和热电特性。介电常数,极化强度和热电性的反常表示该晶体在低温时发生相变。此相变有特别大的热滞(约80K),降温时发生于180K附近,升温时发生于260K附近。测量了晶体的室温结构,指出了可能的低温相点群。观测了热电电荷的时间响应,报道了热电电荷随时间改变符号的特异现象,认为其起因是相变过程中两相共存。
关键词: 相似文献
48.
49.
50.