Flowfield of a helicopter submerged inlet with power output shaft

The submerged inlet is an attractive configuration for advanced helicopters due to its high stealth performance and low external drag.In this paper,a submerged ...     

Photoinduced Resistance Change in an Oxygen-Deficient La 0.9 Sr 0.1 MnO 3-δ Thin Film

Photoinduced resistance change （ △ R/R） in an oxygen-deficient La0.9Sr0.1MnO3-δ thin film is studied. At room temperature, the resistance change of about 30% and response time of about 75 ns are observed under the illumination with a 532nm laser pulse of 7ns and light power of 750mW. It is also found that △ R/R changes with the light power. The phenomena are explained in terms of the photoinduced hole carriers and localized insulator-to-metal transition, which may have potential applications in optoelectronic devices.     

Measurement and analysis of fission rates in a spherical mockup of uranium and polyethylene

Measurements of the reaction rate distribution were carried out using two kinds of Plate Micro Fission Chamber （PMFC）. The first is a depleted uranium chamber and the second an enriched uranium chamber. The material in the depleted uranium chamber is strictly the same as the material in the uranium assembly. With the equation solution to conduct the isotope contribution correction, the fission rate of 238U and 235U were obtained from the fission rate of depleted uranium and enriched uranium. Then, the fission count of 238U and 235U in an individual uranium shell was obtained. In this work, MCNP5 and continuous energy cross sections ENDF/BV.0 were used for the analysis of fission rate distribution and fission count. The calculated results were compared with the experimental ones. The calculation of fission rate of DU and EU were found to agree with the measured ones within 10% except at the positions in polyethylene region and the two positions near the outer surface. Because the fission chamber was not considered in the calculation of the fission counts of 238U and 235U, the calculated results did not agree well with the experimental ones.     

Magnetically separated and N,S co-doped mesoporous carbon microspheres for the removal of mercury ions

Magnetically separated and N, S co-doped mesoporous carbon microspheres (N/S-MCMs/Fe₃O₄) are fabricated by encapsulating SiO₂ nanoparticles within N, S-containing polymer microspheres which were prepared using resorcinol/formaldehyde as the carbon source and cysteine as the nitrogen and sulfur co-precursors, followed by the carbonization process, silica template removal, and the introduction of Fe₃O₄ into the carbon mesopores. N/S-MCMs/Fe₃O₄ exhibits an enhanced Hg²⁺ adsorption capacity of 74.5 mg/g, and the adsorbent can be conveniently and rapidly separated from wastewater using an externalmagnetic field. This study opens up new opportunities to synthesize welldeveloped, carbon-based materials as an adsorbent for potential applications in the removal of mercury ions from wastewater.     

土壤/沉积物中重金属元素分析的前处理技术研究进展

概述了近年来土壤/沉积物样品中重金属元素分析的前处理技术,包括电热板法、微波消解法、高压密闭消解法和碱熔法等,对各种前处理方法的优缺点进行了比较,并对土壤/沉积物样品中重金属元素的前处理技术研究方向进行了展望。     

2-溴-4,4'-二硝基-3'-二甲基锍-2'-联苯酚内盐的合成、结构及性质的研究

在胺存在下,3,7-二硝基二苯并溴五环硫酸氢盐与二甲基亚砜反应生成2-溴-4,4'-二硝基-3'-二甲基锍-2'-联苯酚内盐(3).3的X射线晶体结构分析数据表明其分子具有内盐结构但酚氧负离子的负电荷是部分离域的,分子内两苯环所成的两面角为117.3°.3在熔解时发生重排及热分解分别生成2-溴-2'-甲氧基-3'-甲硫基-4,4'-二硝基联苯(6)及3,7-二硝基-4-甲硫基-二苯并呋喃(7).3与盐酸反应生成相应的锍盐(8).     

(±)-Shegansu B,Gnetuhainin F, (±)-Maackin A与(±)-Cassigarol E的全合成

对四种天然二聚二苯乙烯类化合物Shegansu B (1), Gnetuhainin F (1a), Maackin A (2)以及Cassigarol E (3)的全合成进行了研究. 以3,5-二羟基苯甲酸(4)为起始原料, 经六步反应制得异丹叶大黄素(13)和白皮杉醇(14), 在HRP/H₂O₂酶催化氧化体系中, 13和14分别进行自身的氧化偶联得到各自的二聚产物. 首次完成了1a, (±)-2和(±)-3的全合成, 并以较文献报道为高的氧化偶联产率合成了(±)-1.     

氨甲蝶呤在Co/GC离子注入修饰电极上电化学行为及其应用研究

氨甲蝶呤在0.1mol/LHAc-NaAc(pH=4.96)缓冲溶液中,用Co/GC离子注入修饰电极进行伏安测定,得到一良好的还原峰,峰电位为-0.95V(vs.SCE).峰电流Ip与氨甲蝶呤的浓度在2.2×10^-7～8.8×10^-6mol/L范围内呈线性关系。检出限为1.1×10^-8mol/L.建立了测定氨甲蝶呤的新方法,可用于实际样品的测定,回收率在98.9%～106.2%之间。用线性扫描和循环伏安法研究了体系的电化学行为及电极反应机理。实验表明,氨甲蝶呤的还原为不可逆吸附过程,并伴随两个电子和两个氢离子参与电极反应。用俄歇电子能谱(AES)和X射线光电子能谱(XPS)等表面分析技术对Co离子注入修饰电极的表面元素组成及深度分布等进行测定,表明Co离子确被注入到玻碳表面。扫速对催化效率的影响实验证明体系存在催化作用。     

线型脲醛树脂的半结晶模板化作用

酸性条件下硅溶胶体系中尿素和甲醛聚合反应会产生脲醛树脂-氧化硅杂化沉淀. 沉淀的质量随有机组分比例的增加而增加, 当尿素和甲醛物质的量比≥1.0时生成沉淀的量为恒定最大值. 红外分析表明杂化材料在3348, 1635, 1572和784 cm^－1处产生了可被归结为线型结构(—[NHCONHCH₂]_n—)的特征吸收. XRD分析表明这种线型分子可形成氢键(C＝O…H—N)导向型的半结晶. 微分热重和XRD结果证明结晶物种在290 ℃完全分解. SEM表征显示半结晶杂化沉淀以三维网络结构为特征, 具有层状结晶的各向异性, 其初级粒子即使在室温下干燥也容易开裂. 随着反应时间的延长、酸性的增加或无机组分量的相对增加杂化粒子变得更加致密. 液氮吸附结果证明沉淀焙烧后所得氧化硅材料的结构具有层状孔结构性质, 其比表面积、孔尺寸和孔体积可以达到510 m²/g, 14.3 nm和1.68 cm³/g. 改变反应体系的酸性和反应组分配比等条件可以方便地控制杂化材料的结构.     

球壳粒子悬浮系模型化研究——内部相参数对介电谱影响的数值模拟

在Hanai理论基础上对球壳粒子悬浮系的介电模型进行了模拟研究,通过用C++的复数类对理论公式的程序化,建立了介电谱的介电参数与体系内部相参数的关系.所得的解析解可方便地模拟介电弛豫谱依不同相参数的变化曲线,计算并分析了内部参数对介电谱的模式以及介电参数的影响因素.