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81.
82.
在电学实验的创新设计类问题中,常常涉及到滑线变阻器的分压线路和限流线路。本文对滑线变阻器的分压线路和限流线路的特性作一较系统的分析,对涉及到此类问题的实际工作具有指导意义。 相似文献
83.
84.
A rapid and simple as well as sensitive inductively coupled plasma mass spectrometry (ICP-MS) method for the determination
of cobalamin is described. Cobalamin in human urine and medicine tablet solutions was converted on-line into free cobalt ions
in acid medium, the cobalt ions were then detected by ICP-MS. Cobalamin was determined by measuring the increase of integral
counts per second intensity, which was linear over the cobalamin concentration range of 1.0 × 10−10 g mL−1 to 8.0 × 10−5 g mL−1, and the limit of detection was 0.05 ng mL−1 (3σ). At the pump rate of 30 rotations per minute, one analysis cycle of cobalamin, including sampling and washing, could be
accomplished in 0.5 min with the relative standard deviations of less than 5 %. The proposed procedure was applied successfully
in monitoring cobalamin in human urine without any pretreatment process and in rapid determination of cobalamin in multivitamin
tablets. 相似文献
85.
Piaoping Yang Chunxia Li Wenxin Wang Zewei Quan Shili Gai Jun Lin 《Journal of solid state chemistry》2009,182(9):2510-2520
Rare-earth ions (Eu3+, Tb3+) doped AMoO4 (A=Sr, Ba) particles with uniform morphologies were successfully prepared through a facile solvothermal process using ethylene glycol (EG) as protecting agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra and the kinetic decays were performed to characterize these samples. The XRD results reveal that all the doped samples are of high purity and crystallinity and assigned to the tetragonal scheelite-type structure of the AMoO4 phase. It has been shown that the as-synthesized SrMoO4:Ln and BaMoO4:Ln samples show respective uniform peanut-like and oval morphologies with narrow size distribution. The possible growth process of the AMoO4:Ln has been investigated in detail. The EG/H2O volume ratio, reaction temperature and time have obvious effect on the morphologies and sizes of the as-synthesized products. Upon excitation by ultraviolet radiation, the AMoO4:Eu3+ phosphors show the characteristic 5D0–7F1–4 emission lines of Eu3+, while the AMoO4:Tb3+ phosphors exhibit the characteristic 5D4–7F3–6 emission lines of Tb3+. These phosphors exhibit potential applications in the fields of fluorescent lamps and light emitting diodes (LEDs). 相似文献
86.
Chun Yang Piaoping Yang Wenxin Wang Shili Gai Jun Wang Milin Zhang Jun Lin 《Solid State Sciences》2009,11(11):1923-1928
Europium doped hydroxyapatite (Eu:HAp) nanosized particles with multiform morphologies have been successfully prepared via a simple microemulsion-mediated process assisted with microwave heating. The physicochemical properties of the samples were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra, and the kinetic decays, respectively. The results reveal that the obtained Eu:HAp particles are well assigned to the hexagonal lattice structure of the hydroxyapatite phase. Additionally, it is found that samples exhibit uniform morphologies which can be controlled by altering the pH values. Furthermore, the samples show the characteristic 5D0–7F1–4 emission lines of Eu3+ excited by UV radiation. 相似文献
87.
Density functional theory (DFT) calculations have been performed to elucidate the reaction mechanism of hydrosilylation of carbonyl compounds catalyzed by high-valent rhenium(V)-di-oxo complexes ReO2I(PR3)2 (R = Me, Ph). The calculations suggest that the most favorable mechanism involves the rate-determining dissociative [2 + 2] addition of the Si-H bond across a Re=O bond to form a Re(V) hydrido siloxy intermediate; this is followed by carbonyl coordination, reduction of the carbonyl, rearrangement, and final intramolecular nucleophilic attack from the alkoxy group to the silyl center (dissociative retro-[2 + 2] addition). It was also found that the additional oxo ligand in the ReO2I(PR3)2 complexes promotes the [2 + 2] addition across the rhenium-oxo bond both kinetically and thermodynamically, as compared to the neutral rhenium(V)-mono-oxo complex ReOCl3(PMe3)2. The effect of different silanes on the [2 + 2] addition barriers is also studied. 相似文献
88.
To reduce quantization error, preserve the manifold of local features, distinguish the ambiguous features, and model the spatial configuration of features for Bag-of-Features (BoF) model-based human action recognition, a novel feature coding method called spatially regularized and locality-constrained linear coding (SLLC) is proposed. The spatial regularization and locality constraint are involved in the feature coding phase to model the spatial configuration of features and preserve their nonlinear manifold. The action recognition experimental results on benchmark datasets show that SLLC achieves better performance than the state-of-the-art feature coding methods such as soft vector quantization, sparse coding, and locality-constrained linear coding. 相似文献
89.
Fisher信息是估计理论中的重要概念,最近发现与量子信息中的纠缠判据具有密切联系.非旋波近似条件下,Dicke模型经典相空间表现为混沌动力学特征.本文详细考察了Dicke模型描述的光与物质相互作用系统中量子Fisher信息和自旋压缩动力学特性.结果表明:在短时瞬态情况下,无论初态处于规则区域还是混沌区域系统均表现为纠缠性质;但在长时稳态情况下,初态处于规则区域时系统纠缠消失,而初态处于混沌区域时系统则一直存在纠缠.通过与系统自旋压缩动力学性质相比较,发现量子Fisher信息可以更有效地刻画量子混沌.进一步考察初态处于规则和混沌区域时系统密度矩阵和纯度的动力学演化特性,发现混沌导致系统退相干现象发生,说明量子Fisher信息对混沌更敏感. 相似文献
90.
Shen Yu Ying-Xi Liu Xiu-Zhen Sun Ying-Feng Su Ying Wang Yin-Zhe Gai 《Acta Mechanica Sinica》2014,30(2):250-258
In the present study, we reconstructed upper airway and soft palate models of 3 obstructive sleep apnea-hypopnea syndrome(OSAHS) patients with nasal obstruction. The airflow distribution and movement of the soft palate before and after surgery were described by a numerical simulation method. The curative effect of nasal surgery was evaluated for the three patients with OSAHS. The degree of nasal obstruction in the 3 patients was improved after surgery. For 2 patients with mild OSAHS, the upper airway resistance and soft palate displacement were reduced after surgery. These changes contributed to the mitigation of respiratory airflow limitation. For the patient with severe OSAHS, the upper airway resistance and soft palate displacement increased after surgery, which aggravated the airway obstruction. The effcacy of nasal surgery for patients with OSAHS is determined by the degree of improvement in nasal obstruction and whether the effects on the pharynx are beneficial. Numerical simulation results are consistent with the polysomnogram(PSG) test results, chief complaints, and clinical findings, and can indirectly reflect the degree of nasal patency and improvement of snoring symptoms, and further,provide a theoretical basis to solve relevant clinical problems. 相似文献