基于Schiff碱反应的新型碳量子点制备及其影响因素研究

通过简便水热合成方法,以戊二醛(GA)与3-氨丙基三甲氧基硅烷(APTMS)的Schiff碱反应制备了新型碳量子点。该碳量子点为直径2~7 nm的球体,激发波长为350 nm时,最大发射峰位于400 nm,量子产率为13.6%。实验表明,碳量子点的最佳制备条件是APTMS与GA的量比为1∶2,在180℃下加热8 h。碳量子点在p H=6.0磷酸缓冲液中的荧光强度最大,且荧光强度随测定温度(273~303 K)的升高而降低。     

高校实验资产内部竞价配置机制及效率研究

采用内部竞价的方法,对高校实验资产进行配置,通过机制的设计,在多方博弈的过程中,使讲真话是竞标者的最优策略,从而实现资源的最优配置,提高资源的使用效率,促进实验资源的良性发展,达到社会效益最大化.     

Preliminary shielding analysis for the CSNS target station monolith

The construction of the China Spallation Neutron Source （CSNS） has been initiated at Dongguan,Guangdong,China.In spallation neutron sources the target station monolith is contaminated by a large number of fast neutrons whose energies can be as large as those of the protons of the proton beam directed towards the tungsten target.A detailed radiation transport analysis of the target station monolith is important for the construction of the CSNS.The analysis is performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method.Successful elimination of the primary ray effects via the two-dimensional uncollided flux and first collision source methodology is also illustrated.The dose at the edge of the monolith is calculated.The results demonstrate that the doses received by the hall staff members are below the required standard limit.     

2, 6-二甲氧基-2-嘧啶氧基-N-芳基苄胺衍生物的酸催化Smiles重排反应动力学

研究了酸催化下的2, 6-二甲氧基-2-嘧啶氧基-N-芳基苄胺衍生物Smiles重排反应的动力学,考察了盐酸的初始浓度、溶剂、反应温度和取代基对反应速率的影响。结果表明,盐酸的初始浓度增加,重排反应速率加快;在单一溶剂中反应速率的顺序为:甲醇>乙醇>二甲基亚砜>乙腈,而在甲醇/水(1:1, V/V)的混合溶剂中反应速率明显增加,其表观反应速率常数(k_obs)值是甲醇溶剂中的5.27倍;在25-45 ℃温度范围内,各衍生物的反应速率随着温度的升高而加快,其活化能(73.99-76.92 kJ·mol^-1)、活化焓(71.57-74.38 kJ·mol^-1)及Gibbs自由能(81.51-85.77 kJ·mol^-1)数值相近,仅活化熵(-24.38 --47.11 J·K^-1·mol^-1)有一定的差别;取代基常数和表观速率常数之间呈现一定的线性关系,环上吸电子基团的存在有利于反应速率的提高;实验验证了反应机理的合理性。     

中学化学教学中的追求简便

以化学用语、化学计算的发展为例,论述了追求简便是化学学科发展的重要推动力。如果教师给予正确的引导,合理追求简便将成为学生创新的不竭动力。以化学教学中2个简化不当的例子说明,过度追求简便会束缚学生的思维,阻碍教学研究的发展与兴盛。     

大气CO2反演的地表反射率影响分析与比值反演方法

近红外波段空基大气CO₂反演是一个病态问题,地表特征的不确定性是其重要的影响因素之一。针对大气CO₂高精度反演的需求,研究了地表反射率两大不确定性因素对大气CO₂反演的影响程度,提出了比值光谱法对这种影响进行校正。比值光谱法中CO₂无吸收通道(off-line)的选择至关重要,通过比较和分析多种off-line通道的选择方法,发现多通道多点平均法因多数据平均可降低随机误差的优势,获得的off-line通道对应的反演精度最高,而且离散程度也小。比值光谱法结合多通道多点平均法选取出的off-line通道对地表反射率的不确定性影响有明显的校正效果,有利于大气CO₂反演精度的提高。     

用于温室气体反演的云检测算法

高分五号卫星同时搭载了温室气体探测仪(GMI)和大气多角度偏振探测仪,两者在云检测方面各有优势,但是均存在局限。提出了一种基于两者数据的协同云筛选新算法以提高温室气体反演中的云筛选效率。利用该算法检测了全球16d在轨实测数据中的77581个GMI观测点,筛选出晴空观测点9508个,占比为12.26%。利用融合后的中分辨率成像光谱仪云掩模和卷云反射率数据集,验证了该算法进行云检测的正确率,得到陆地上和海洋上的云检测正确率分别为92.93%和81.91%。     

硬质合金表面Ti系涂层退除后的界面性能研究

采用电弧离子镀技术(AIP)在YW2合金基体表面制备了TiAlN涂层,通过化学方法退除基体上的涂层,分析了硬质合金表面退除涂层后和镀覆涂层前成分和元素存在形态的变化。发现当样品在30%H₂O₂、草酸钾COOK(1.5mol·L-1)、缓蚀剂葡萄糖酸钠GA和NaOH,V_NaOH溶液∶V_30%H2O2∶V_COOK溶液=1∶1∶1,45 ℃时,45 min可以退除涂层,肉眼未观察到基体表面受腐蚀。涂层退除后样品表面光亮,呈现合金未镀覆涂层前颜色。通过对退镀后YW2基体和基体镀覆涂层前的表面XPS定性及定量分析发现,退除涂层后,基体表面W元素结合能和N元素主峰结合能与XPS结合能与参照表上对应结合能变化很小,元素的价态没有发生变化;镀覆TiAlN涂层时扩散到合金浅表层的Al,Ti,N元素,造成表面Al,Ti,N元素含量较镀覆涂层前增加,结合能位置偏移,形成AlN和TiN,有利于重新镀覆的涂层与合金基体的结合。     

Investigation on the relationship between overpressure and sub-harmonic response from encapsulated microbubbles

Sub-harmonic component generated from microbubbles is proven to be potentially used in noninvasive blood pressure measurement. Both theoretical and experimental studies are performed in the present work to investigate the dependence of the sub-harmonic generation on the overpressure with different excitation pressure amplitudes and pulse lengths. With4-MHz ultrasound excitation at an applied acoustic pressure amplitude of 0.24 MPa, the measured sub-harmonic amplitude exhibits a decreasing change as overpressure increases; while non-monotonic change is observed for the applied acoustic pressures of 0.36 MPa and 0.48 MPa, and the peak position in the curve of the sub-harmonic response versus the overpressure shifts toward higher overpressure as the excitation pressure amplitude increases. Furthermore, the exciting pulse with long duration could lead to a better sensitivity of the sub-harmonic response to overpressure. The measured results are explained by the numerical simulations based on the Marmottant model. The numerical simulations qualitatively accord with the measured results. This work might provide a preliminary proof for the optimization of the noninvasive blood pressure measurement through using sub-harmonic generation from microbubbles.