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81.
Huaijin Zhang Xianlin Meng Changqing Wanga Li Zhu Xuesong Liu Chunming Dong Ruiping Cheng Xunmin Liu Ruihua Wang Shaojun Zhang Y. T. Chow Lianke Sun 《Journal of Crystal Growth》2000,210(4):815-818
In this letter, Nd : Ca4Gd0.275Y0.725O(BO3)3 (Nd : GdYCOB) single crystal with good optical quality and large size has been grown by the Czochralski method. The absorption and fluorescence spectra have been measured. The self-frequency doubling (SFD) laser output of Nd : GdYCOB at 0.53 μm has been demonstrated when a Nd : GdYCOB crystal sample with dimensions of 3 mm×3 mm×7 mm (the phase-matched angle is θ=78.8°, Φ=90°) is pumped by a cw Ti : sapphire laser. 相似文献
82.
Tracking the correct directions of monotonicity in multi-dimensional modeling plays an important role in interpreting functional associations. In the presence of multiple predictors, we provide empirical evidence that the observed monotone directions via parametric, nonparametric or semiparametric fit of commonly used multi-dimensional models may entirely violate the actual directions of monotonicity. This breakdown is caused primarily by the dependence structure of covariates, with negligible influence from the bias of function estimation. To examine the linkage between the dependent covariates and monotone directions, we first generalize Stein’s Lemma for random variables which are mutually independent Gaussian to two important cases: dependent Gaussian, and independent non-Gaussian. We show that in both two cases, there is an explicit one-to-one correspondence between the monotone directions of a multi-dimensional function and the signs of a deterministic surrogate vector. Moreover, we demonstrate that the second case can be extended to accommodate a class of dependent covariates. This generalization further enables us to develop a de-correlation transform for arbitrarily dependent covariates. The transformed covariates preserve modeling interpretability with little loss in modeling efficiency. The simplicity and effectiveness of the proposed method are illustrated via simulation studies and real data application. 相似文献
83.
本文对截止波长为0.85μm的椭芯保偏光纤测试了其传输损耗系数与入射光波长及偏振态的关系。给出了测试原理和实验装置,并分析了实验结果。 相似文献
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用沉淀法、浸渍法和机械混合物焙烧法制备了三组MoO_3-SnO_2催化剂。XDR, IR和ESR等研究表明: MoO_3-SnO_2之间存在明显的相互作用, 两组份间发生电子迁移现象, 导致Mo(Ⅵ)→Mo(Ⅴ)的价态变化, 产生pKa≤+3.3的表面酸位和甲醇选择氧化活性位。制备方法对这种相互作用以及样品的催化性能有明显影响。沉淀法所得样品中MoO_3可溶于SnO_2形成固溶体; 浸渍法则可发生钼离子向SnO_2体相的扩散; 机械混合物焙烧法在一定MoO_3含量下, MoO_3可在SnO_2表面形成近似单层分散。红外光谱中950 cm~(-1)的新吸收谱带可归因于表面上Mo(Ⅴ)=0振动。表面Mo(Ⅴ)位可能是催化剂表面酸位和甲醇氧化的活性中心。没有发现催化剂中Sn~(4+)价态有明显变化。 相似文献
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Weihua Xue Xiaoyun Cheng Jian Fan Huajia Diao Chunming Wang Lei Dong Yi Luo Jiangning Chen Junfeng Zhang 《Tetrahedron letters》2007,48(35):6092-6095
A mild and one-pot protocol for the efficient and stereoselective synthesis of 1,2-trans-aldosyl mercaptans is presented. 相似文献
89.
Science China Mathematics - Variable selection has played an important role in statistical learning and scientific discoveries during the past ten years, and multiple testing is a fundamental... 相似文献
90.
Extracts of the fungus Inonotus obliquus exhibit cytotoxic properties against different cancers; hence, this fungal species has been extensively studied. This study aimed to extract total triterpenoids from Inonotus obliquus using ionic liquids (ILs) and separate potential lactate dehydrogenase (LDH) inhibitors via ultrafiltration (UF)-high-speed countercurrent chromatography (HSCCC). Total triterpenoids from Inonotus obliquus were extracted by performing a single-factor experiment and employing a central composite design via ultrasonic-assisted extraction (UAE) and heat-assisted extraction (HAE). The extract was composed of 1-butyl-3-methylimidazolium bromide as the IL and methanol as the dispersant. Ultrafiltration-liquid chromatography (UF-LC) was used to rapidly scan the LDH inhibitors and betulin and lanosterol were identified as potential inhibitors. To obtain these target compounds, betulin and lanosterol with the purities of 95.9% and 97.8% were isolated from HSCCC within 120 min. Their structures were identified using several techniques, among which IL-HAE was fast and effective. This study reports the extraction of triterpenoids from Inonotus obliquus by IL for the first time. Collectively, the findings demonstrate that UF-LC is an effective tool for screening potential LDH inhibitors from crude extracts of I. obliquus and may help to identify bioactive substances against myocardial infarction, whereas high-purity compounds can be separated via UF-HSCCC. 相似文献