Preparation of V-doped TiO_2 Photocatalysts by the Solution Combustion Method and Their Visible Light Photocatalysis Activities

A series of nanocrystalline V-doped （0.0-3.0 at.%） TiO2 catalysts have been successfully prepared by the one-step solution combustion method using urea as a fuel. The obtained powders were characterized by XRD, SEM, Raman, XPS and UV-Vis DRS. The effects of V doping concentration on the phase structure and photocatalytic properties were investigated. XRD, Raman, and XPS show that V doping diffuses into TiO2 crystal lattice mainly in the form of V5＋ and causes a phase transition from anatase to mille. V doping can widen the light absorption range of TiO2, with the absorption threshold wavelength shifting from 425 to 625 nm. The photocatalytic activity of V-doped TiO2 powders were evaluated by the photocatalytic degradation of methyl orange （MO） under visible light irradiation. It is found that V doping enhances the photoeatalyilc activity under visible light irradiation and the optimal degradation rate of MO is about 95.8% with 1.0 at% V-doped TiO2.

Effects of Mechanical Alloying Parameters on the Microstructures of Nanocrystalline Cu-5 wt% Cr Alloy

Nanocrystalline Cu-5 wt%Cr alloy powders were fabricated by mechanical alloying （MA）, The effects of MA processing parameters on the crystallite size, solid solubility, and microstructures of the Cu- 5 wt%Cr alloys were investigated including type and size distribution of the grinding medium and ball-topowder weight ratio （BPR）. The results show that the crystallites were refined effectively and solid solubility of Cr in Cu was extended when heavier ball and higher BPR were adopted. The maximum solubility is extended up to 5.6 at% （namely 4.6 wt%） Cr in Cu by use of a combination of large and small size WC-Co balls with BPR of 30：1. A Cn-5 wt%Cr supersaturated solid solution alloy bulk is obtained by spark plasma sintering the as-milled powders at 900 ℃ for 5 min.

高中生自我认同与社会适应的关系:同伴信任的中介作用

采用自我认同量表、信任量表和青少年社会适应状况量表调查福建某高中855名学生,探讨高中生自我认同对社会适应的影响以及同伴信任在这两者间的中介作用。结果表明,自我认同、同伴信任和积极适应两两正相关,高中生同伴信任在自我认同与积极适应中起到部分中介作用,其中介的解释度是13.5%,而自我认同、同伴信任分别和消极适应负相关;高中生同伴信任在自我认同与消极适应中起到部分中介作用,其中介的解释度是8.5%。

Preparation and Arc Erosion Characteristics of Ultrafine Crystalline CuCr50 Alloy by MA-SPS

The ultrafine crystalline CuCr50（Cr 50 wt%） alloys were fabricated by a combination of mechanical alloying and spark plasma sintering process. The effects of milling time on crystallite size and solid solubility of the CuCr50 composite powders were investigated. The results showed that crystallite size of powders decreases gradually and solid solubility of Cr in Cu was extended with increasing milling time. The minimal crystallite size about 10 nm and the maximum solid solubility about 8.4 at%（i e, 7 wt%） were obtained at 60 h. The microstructure of ultrafine crystalline CuCr50 alloy was analyzed by SEM and TEM, which contains two kinds of size scale Cr particles of 2 μm and 50-150 nm, distributing homogeneously in matrix, respectively. The arc erosion characteristics of ultrafine crystalline CuCr50 alloy were investigated by the vacuum contact simulation test device in low D.C. voltage and low current（24 V/10 A）. A commercial microcrystalline CuCr50 alloy was also investigated for comparison. Experiments indicate that the cathode mass loss of ultrafine crystalline CuCr50 contact material is higher than that of microcrystalline CuCr50 material, but its eroded surface morphology by the arc is uniform without obvious erosion pits. While the surface of microcrystalline CuCr50 contact is seriously eroded in local area by the arc, an obvious erosion pit occurred in the core part. Therefore, the ability of arc erosion resistance of ultrafine crystalline CuCr50 alloy is improved compared to that of microcrystalline CuCr50 material.

浅谈我国医学信息检索课程研究的现状、热点与趋势

以中国知网数据库为数据来源,运用CiteSpace知识图谱软件,对1984—2022年发表的医学信息检索课程研究文献进行可视化分析。研究共纳入918篇文献,研究发现,我国医学信息检索课程研究可分为探索阶段、发展阶段和稳定阶段,研究热点聚焦在混合式教学模式改革、循证医学、信息素养等主题,未来研究需适度拓宽研究领域,促进医学信息检索课程研究向更深更高层次发展。