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排序方式: 共有277条查询结果,搜索用时 15 毫秒
101.
Jinping Tian Xijing Liang Caijiao Zhang Hongjuan Li 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2013,67(5):1-5
The investigation of quantum and classical correlations has mostly concentrated on two-qubit states because the minimization in the classical correlation is quite complicated for high-dimensional states. Thermal quantum and classical correlations are studied for a two-qutrit system with various coupling constants, external magnetic fields, and temperatures as well, where the quantum correlation is described in terms of the quantum discord that has been extensively used in recent literature. The entanglement negativity is calculated for comparison. It is shown that the discord is nonzero whereas the negativity is zero in some ranges of system parameters and temperature. Moreover, the discord is more robust than the entanglement against temperature and magnetic field. However, at lower temperatures all three correlations behave similarly. Those are useful for understanding quantum correlations in high-dimensional mixed states and quantum information processing. 相似文献
102.
103.
B,N-TiO2 photocatalysts were synthesized by boron doping firstly and subsequently nitrogen doping in NH3 at variable temperatures. The effects of the nitrogen doping temperature on the structure and photocatalytic activity of the B,N-codoped TiO2 were investigated. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectrum (DRS), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated with photocatalytic degradation of methyl orange dye (MO) under visible light and UV-visible light irradiation. The results suggested that the boron and nitrogen can be incorporated into the TiO2 lattice either interstitially or substitutionally or both, while the Ti-O-B-N structure plays a vital role in photocatalytic activity in visible light region. The optimal nitrogen doping temperature is 550 °C. Higher temperature may form many oxygen vacancies and Ti3+ species, resulting in the decrease of photocatalytic activity in visible light. 相似文献
104.
Nanoscaled nitrogen doped anatase TiO(2) with dominant (001) facets, which exhibited high photocatalytic activity and excellent photoelectrochemical properties under visible light irradiation, was successfully synthesized by solvothermal treatment of TiN in acidic NaBF(4) solution for the first time. 相似文献
105.
Blind source separation (BSS) is an increasingly popular data analysis technique with many applications. Several methods for BSS using the statistical properties of original sources have been proposed; for a famous case, non-Gaussianity, this leads to independent component analysis (ICA). In this paper, we propose a hybrid BSS method based on linear and nonlinear complexity pursuit, which combines three statistical properties of source signals: non-Gaussianity, linear predictability and nonlinear predictability. A gradient learning algorithm is presented by minimizing a loss function. Simulations verify the efficient implementation of the proposed method. 相似文献
106.
Potassium sodium niobate (KNN) powders were synthesized by a modified sol–gel method, using as starting chemicals potassium carbonate, sodium carbonate, and niobium hydroxide, and, as esterification and chelating agents, respectively, ethylene glycol (EG) and ethylene diamine tetraacetic acid (EDTA)/citrate. The effects of citric acid (CA), EG, and EDTA on the stability of the precursor sol were systemically investigated. The powders and gels were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis-differential scanning calorimetry (TGA-DSC). The results indicated that a stable precursor sol was formed when n(CA):n(Mn+) = 3:1, n(EDTA):n(NH4OH) = 1:3.5, and n(CA):n(EG) = 1:2. The xerogel was calcined at 500–950 °C to prepare the KNN powder. Pure KNN perovskite phase with a cube-like structure was synthesized at 850 °C from the precursor sol for a K/Na molar ratio of 1.2. The formation mechanism of the KNN perovskite phase was also discussed. 相似文献
107.
脱水催化剂的改性对浆态床一步法合成二甲醚的影响 总被引:9,自引:0,他引:9
以Cu(NO3)2为前驱体,以水、丙酮或乙二醇为溶剂,以γ-Al2O3为载体,采用等体积浸渍法制备了用于合成气一步法制二甲醚的脱水-变换双功能催化剂,并对其还原性能、晶态分布、还原态的酸性及催化性能进行了研究. H2-TPR结果表明,以乙二醇为溶剂制备的催化剂上可还原氧化铜的量最多. XRD结果表明,以水为溶剂制备的催化剂上,氧化铜并未完全均匀地分散在氧化铝表面,而是有一部分以单质铜或铜铝化合物的形式存在; 而以丙酮或乙二醇为溶剂制备催化剂时,氧化铜分布均匀. 还原态催化剂NH3-TPD结果表明,以乙二醇为溶剂制备的催化剂上,酸性中心主要集中在弱酸位上. 浆态床搅拌釜中合成反应的结果表明,用氧化铜对脱水催化剂进行改性,能改善催化剂的催化性能,提高CO转化率和产物中二甲醚的选择性,抑制副反应的发生. 非水溶剂的使用对CO转化率没有明显的影响,但可改变催化剂上酸中心的分布,提高二甲醚的选择性,并抑制副反应的发生. 相似文献
108.
Zheng Aifang Chen Jinlong Li Hongjuan He Chiyang Wu Genhua Zhang Yuanguang Wei Heping Wu Ganlin 《Mikrochimica acta》2009,165(1-2):187-194
Microchimica Acta - Water-soluble fluorescent CdTe nanorods (NRs) capped with L-cysteine (Cys) and thioglycolic acid (TGA) were prepared for optical determination of silver ions. These NRs are... 相似文献
109.
Hongqing Chen Hao Yu Yong Tang Minqiang Pan Guangxing Yang Feng Peng Hongjuan Wang Jian Yang 《天然气化学杂志》2009,18(2):191-198
Hydrogen was produced over noble metal (Ir, Ru, Rh, Pd) catalysts supported on various oxides, including γ-Al2O3, CeO2, ZrO2 and La2O3, via the autothermal reforming reaction of ethanol (ATRE) and oxidative reforming reaction of ethanol (OSRE). The conversion of ethanol and selectivites for hydrogen and byproducts such as methane, ethylene and acetaldehyde were studied. It was found that lanthana alone possessed considerable activity for the ATRE reaction, which could be used as a functional support for ATRE catalysts. It was demonstrated that Ir/La2O3 prevented the formation of methane, and Rh/La2O3 encumbered the production of ethylene and acetaldehyde. ATRE reaction was carried out over La2O3-supported catalysts (Ir/La2O3) with good stability on stream, high conversion, and excellent hydrogen selectivity approaching thermodynamic limit under autothermal condition. Typically, 3.4 H2 molecules can be extracted from a pair of ethanol and water molecules over Ir(5wt%)/La2O3. The results presented in this paper indicate that Ir/La2O3 can be used as a promising catalyst for hydrogen production via ATRE reaction from renewable ethanol. 相似文献
110.
Hongjuan Zhang Zhenwei Shi Chonghui Guo Enmin Feng 《Journal of Computational and Applied Mathematics》2009
Blind source extraction (BSE) has become one of the promising methods in the field of signal processing and analysis, which only desires to extract “interesting” source signals with specific stochastic property or features so as to save lots of computing time and resources. This paper addresses BSE problem, in which desired source signals have some available reference signals. Based on this prior information, we develop an objective function for extraction of temporally correlated sources. Maximizing this objective function, a semi-blind source extraction fixed-point algorithm is proposed. Simulations on artificial electrocardiograph (ECG) signals and the real-world ECG data demonstrate the better performance of the new algorithm. Moreover, comparisons with existing algorithms further indicate the validity of our new algorithm, and also show its robustness to the estimated error of time delay. 相似文献