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Science China Mathematics - Linear factor models are familiar tools used in many fields. Several pioneering literatures established foundational theoretical results of the quasi-maximum likelihood... 相似文献
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The generalized method of moments (GMM) is a very popular estimation and inference procedure based on moment conditions. When likelihood-based methods are difficult to implement, one can often derive various moment conditions and construct the GMM objective function. However, minimization of the objective function in the GMM may be challenging, especially over a large parameter space. Due to the special structure of the GMM, we propose a new sampling-based algorithm, the stochastic GMM sampler, which replaces the multivariate minimization problem by a series of conditional sampling procedures. We develop the theoretical properties of the proposed iterative Monte Carlo method, and demonstrate its superior performance over other GMM estimation procedures in simulation studies. As an illustration, we apply the stochastic GMM sampler to a Medfly life longevity study. Supplemental materials for the article are available online. 相似文献
3.
Yanyuan Ma Marc G. Genton Emanuel Parzen 《Annals of the Institute of Statistical Mathematics》2011,63(2):227-243
The asymptotic distribution of sample quantiles in the classical definition is well-known to be normal for absolutely continuous
distributions. However, this is no longer true for discrete distributions or samples with ties. We show that the definition
of sample quantiles based on mid-distribution functions resolves this issue and provides a unified framework for asymptotic
properties of sample quantiles from absolutely continuous and from discrete distributions. We demonstrate that the same asymptotic
normal distribution result as for the classical sample quantiles holds at differentiable points, whereas a more general form
arises for distributions whose cumulative distribution function has only one-sided differentiability. For discrete distributions
with finite support, the same type of asymptotics holds and the sample quantiles based on mid-distribution functions either
follow a normal or a two-piece normal distribution. We also calculate the exact distribution of these sample quantiles for
the binomial and Poisson distributions. We illustrate the asymptotic results with simulations. 相似文献
4.
猪胸腺素对带瘤小鼠胸腺细胞及其富含PNA~-和PNA~+细胞淋转反应的研究 总被引:1,自引:0,他引:1
本文报道用~3H-TdR掺入法测定小鼠胸腺细胞及其亚群在有丝分裂原作用下的淋转反应,以及猪胸腹素对带瘤机体免疫功能的影响.实验结果表明,带瘤小鼠胸腺细胞的淋转反应随着瘤龄的增长而逐渐降低.在体外用猪胸腺素与胸腺细胞一起温育,淋转反应有不同程度提高,如先给小鼠腹腔注射猪胸腺素则淋转反应的效果更为显著,说明猪胸腺素对带瘤机体的免疫功能具有积极的调节作用. 相似文献
5.
声子辅助的上转换荧光是固体激光制冷效应的基础. 激光制冷具有体积小、效率高、无振动干扰、无需制冷剂等优势而具有重要应用价值, 探索更多可以实现激光制冷效应的材料是相关领域的重要研究内容. 二维单层过渡金属硫属半导体化合物是直接带隙荧光材料, 其完美的晶格结构、辐射光子提取效率高等特征使其有望成为一种新型激光制冷材料. 以MoSe2和WSe2为例, 本文研究了不同波长激发下样品的上转换荧光, 并通过激光功率依赖性实验和温度依赖性实验证实了该上转换荧光过程的发光机制为声子辅助过程. 相似文献
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The CLST/PTFE/5%GF composite sharply decreases the CTE in both X&Y and Z directions, obtained a promising microwave dielectric material for microwave communication. 相似文献
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冷冻对正常细胞和肿瘤细胞都有不同程度的杀伤力,这已被动物实验及临床实践所证实.目前冷冻医疗和深冷技术已被广泛应用.为了进一步探索冷冻对肿瘤细胞的杀伤效应及其破坏机理,我们对艾氏腹水癌离体细胞冷冻处理后进行培养,计数细胞数量的变化,观察细胞外部形态及亚显微结构的变化,用~3H-TdR掺入培养测定cpm值,观察细胞合成DNA功能,从而说明冷冻对肿瘤细胞的杀伤效应. 相似文献
8.
Lijuan Yang Wenqian Chen Yanmei Chen Wei Liu Tao Lei Lei Li Miaoshui Lin Jian Wu Yanyuan Cao Wu Li Prof. Dr. Yahong Li 《无机化学与普通化学杂志》2012,638(11):1833-1838
The reaction of the aryl‐oxide ligand H2L [H2L = N,N‐bis(3, 5‐dimethyl‐2‐hydroxybenzyl)‐N‐(2‐pyridylmethyl)amine] with CuSO4 · 5H2O, CuCl2 · 2H2O, CuBr2, CdCl2 · 2.5H2O, and Cd(OAc)2 · 2H2O, respectively, under hydrothermal conditions gave the complexes [Cu(H2L1)2] · SO4 · 3CH3OH ( 1 ), [Cu2(H2L2)2Cl4] ( 2 ), [Cu2(H2L2)2Br4] ( 3 ), [Cd2(HL)2Cl2] ( 4 ), and [Cd2(L)2(CH3COOH)2] · H2L ( 5 ), where H2L1 [H2L1 = 2, 4‐dimethyl‐6‐((pyridin‐2‐ylmethylamino)methyl)phenol] and H2L2 [H2L2 = 2‐(2, 4‐dimethyl‐6‐((pyridin‐2‐ylmethylamino)methyl)phenoxy)‐4, 6‐dimethylphenol] were derived from the solvothermal in situ metal/ligand reactions. These complexes were characterized by IR spectroscopy, elementary analysis, and X‐ray diffraction. A low‐temperature magnetic susceptibility measurement for the solid sample of 2 revealed antiferromagnetic interactions between two central copper(II) atoms. The emission property studies for complexes 4 and 5 indicated strong luminescence emission. 相似文献
9.
Y Chen L Li Z Chen Y Liu H Hu W Chen W Liu Y Li T Lei Y Cao Z Kang M Lin W Li 《Inorganic chemistry》2012,51(18):9705-9713
An efficient strategy for the synthesis of a wide variety of coordination complexes has been developed. The synthetic protocol involves a solvothermal in situ metal-ligand reaction of picolinaldehyde, ammonium acetate, and transition-metal ions, leading to the generation of 12 coordination complexes supported by a novel class of substituted 1-pyridineimidazo[1,5-a]pyridine ligands (L1-L5). The ligands L1-L5 were afforded by metal-mediated controllable conversion of the aldehyde group of picolialdehyde into a ketone and secondary, tertiary, and quaternary carbon centers, respectively. Complexes of various nuclearities were obtained: from mono-, di-, and tetranuclear to 1D chain polymers. The structures of the in situ formed complexes could be controlled rationally via the choice of appropriate starting materials and tuning of the ratio of the starting materials. The plausible mechanisms for the formation of the ligands L1-L5 were proposed. 相似文献
10.
Qianqian Guo Chunying Xu Dandan Zhao Yanyuan Jia Xianjuan Wang Prof. Dr. Hongwei Hou Yaoting Fan 《无机化学与普通化学杂志》2012,638(5):868-873
Abstract. Two metal‐organic coordination polymers [Co(bmb)(btc)0.5]n( 1 ) and {[Zn(bmb)0.5(btc)0.5(H2O)] · 0.5bmb · H2O}n ( 2 ) [H4btc = benzene‐1, 2, 4, 5‐tetracarboxylic acid, bmb = 1, 4‐bis(2‐methylbenzimidazol‐1‐ylmethyl) benzene] were prepared under hydrothermal conditions. Single‐crystal X‐ray diffraction indicates that both complexes have a 2D framework structure with (4 · 62) (42 · 62 · 82) topology. Interestingly, the hydrogen bonds in 2 form a fascinating meso‐helix. The catalytic activity of 1 for oxidative coupling of 2, 6‐dimethylphenol (DMP) and the photoluminescence properties of 2 were investigated. Furthermore, the complexes were investigated by IR spectroscopy and thermogravimetric analysis. 相似文献