利用锁定放大器测量低电阻和高电阻

利用锁定放大器能够测量湮没在噪声中的信号的特点,采用低频交流伏安法,在0.5Vrms和0.5mArms条件下,实现了对几十mΩ级低电阻和数百MΩ级高电阻的测量,测量误差在1%左右。     

阴阳离子聚氨酯/羟基磷灰石复合微球的制备及其自组装

分别以2,2-双羟基丙酸(DMPA)和N-甲基二乙醇胺(MDEA)作扩链剂,采用自乳化法成功制备出带有正、负电荷的阳、阴离子聚氨酯/羟基磷灰石(PU/HA)微球,并考察HA的复合比例对微球形貌、理化性能的影响。在此基础上,通过微球间的静电作用力,将制备出的阴、阳离子复合微球自组装形成凝胶体系,并对其力学性能进行探究。SEM、ζ电位和激光粒度结果显示成功制备出具有一定形貌的带电微球,其中当扩链剂含量为15%(n/n)、HA含量为10%(w/w)时,微球形貌较佳且粒度分布均匀;X射线衍射、热分析结果表明,微球确为一定比例的HA与PU复合产物;自组装体系的流变学测试结果表明,微球组装后的产物呈类凝胶状态,具有较高的弹性模量,并有一定的可注射性。同时,骨髓间充质干细胞(BMSCs)可在组装材料表面粘附、铺展,生长良好。     

丁二酸酐修饰啤酒废酵母菌吸附阳离子染料的研究

以戊二醛为交联剂,用丁二酸酐修饰啤酒废酵母菌表面制成新的生物吸附剂(简称修饰酵母菌).研究发现,修饰酵母菌吸附阳离子染料的性能明显优于未修饰酵母菌.实验结果表明,在室温、溶液的pH=4.0～8.0、吸附时间1 h的条件下,修饰酵母菌能有效吸附亚甲基蓝和中性红.吸附模式以Langmuir单分子层化学吸附为主.修饰酵母菌对...     

降低度量计算突出直观想象——新课标湖北卷对文科立体几何内容的考查研究

1 引言 立体几何的内容是高中数学的重要组成部分,《普通高中数学课程标准(实验)》(以下简称"课标")对立体几何的教学作了重大的结构调整和教学要求改变."课标"中的立体几何定位于培养和发展学生的几何直观能力、空间想象能力和推理论证能力等,在处理方式上,与以往按照点、线、面、体从局部到整体展开几何内容的方式不同,"课标"按照从"整体—局部—整体"的原则展开,突出直观感知、操作确认、思辨论证、度量计算等探索研究几何的过程.其内容分层设计和分科要求,文理两科共同学习必修《数学2》中的"立体几何初步",主要是通过直观感知、操作确认,获得几何图形的性质,并通过简单的推理发现、论证一些几何性质,对于进一步的论证与度量则放在选修《数学2-1》"空间向量与立体几何"中用向量方法处理[1][2][3][4],并只要求理科学生学习和掌握.     

耗散腔中Λ型原子与光场Raman相互作用体系的线性熵

为了研究耗散腔中原子与光场Raman相互作用体系中子系统间的熵交换,利用超算符方法通过对系统主方程求解,讨论了光场强度、腔的耗散系数及原子两能级的Stark位移对线性熵的影响.结果表明：光场越强,光场与其它子系统进行熵交换的时间越长|腔耗散系数越大,熵交换时间越短|改变两能级间的Stark位移使原子和场之间的耦合增强,而系统的耗散系数不变,此时,系统的熵交换加快且其稳态值变小.     

Tunable Fano resonances and plasmonic hybridization of gold triangle–rod dimer nanostructure

A gold dimer structure consisting of a notched triangle nanoslice and a rectangle nanorod is proposed to produce distinct Fano resonance. Owing to the coupling between the dipole plasmon mode of the nanorod and the dipole or quadrupole plasmon mode of the nanoslice, the extinction spectrum with a deep Fano dip is formed and can be well fitted by the Fano interference model for different geometry parameters. In addition, Fano resonance of the gold dimer nanostructure also intensely depends on the polarization direction of incident light. Moreover, Fano resonance of the triangle–rod trimer is also analyzed by adding another nanorod into the former dimer and exhibits the splitting of plasmonic resonant peak in high order coupling modes. The plasmonic hybridizations in these nanostructures have been analyzed for revealing the physical origin of the Fano resonance.     

近红外光谱技术的结缕草种子发芽率研究

根据收获的年份和地点的差异收集37份结缕草种子,其发芽率分布在58.5%～92%的范围,并按照3∶1的比例将其划分为校正集和检验集,使用近红外光谱技术和定量偏最小二乘法分析其发芽率。结果表明,采用的光谱范围为6 000～7 000 cm-1,主成分个数取6时,校正集的决定系数为90.73%,相关系数为0.986 6,平均绝对误差为7.64%,标准差为9.80,而检验集则分别为91.80%,0.987 2,6.98%和9.47。使用不同的建模样品来检验该方法建模的准确性,两组样品集决定系数均超过90%,校正标准差和预测标准差控制在10.00附近,平均绝对误差达到8.00%的水平。     

Supercritical CO<Subscript>2</Subscript> assisted preparation of open-cell foams of linear low-density polyethylene and linear low-density polyethylene/carbon nanotube composites

The open-cell structure foams of linear low-density polyethylene (LLDPE) and linear low-density polyethylene (LLDPE)/multi-wall carbon nanotubes (MWCNTs) composites are prepared by using supercritical carbon dioxide (sc-CO₂) as a foaming agent. The effects of processing parameters (foaming temperature, saturation pressure, and depressurization rate) and the addition of MWCNTs on the evolution of cell opening are studied systematically. For LLDPE foaming, the foaming temperature and saturation pressure are two key factors for preparing open-cell foams. An increase in temperature and pressure promotes both the cell wall thinning and cell rupture, because a high temperature results in a decrease in the viscosity of the polymer, and a high pressure leads to a larger amount of cell nucleation. Moreover, for the given temperature and pressure, the high pressurization rate results in a high pressure gradient, favoring cell rupture. For LLDPE/MWCNTs foaming, the addition of MWCNTs not only promotes the cell heterogeneous nucleation, but also prevents the cell collapse during cell opening, which is critical to achieve the open-cell structures with small cell size and high cell density.     

生活中的几种有机反应趣闻

研究生物体及生命现象是有机化学的深远研究意义之一。本文介绍了一些日常生活中的有机反应趣闻。1屁弹虫的武器当屁弹虫遇到情况时会迅速射出有毒的雾弹,能够在4min内发射29次,射程可达30cm。这种雾弹是如何产生的呢?原来,在其腹部有一对囊状分隔室,储藏有对苯二酚和过氧化氢,     

加权Bloch空间上复合算子的线性组合

设λi(i=1,...,N)是一列非0的数,D是一维复平面C的开单位圆盘,φi(i=1,...,N)是D的解析自映射,本文研究了定义在加权Bloch空间上复合算子线性组合∑i=1NλiCφi、的紧致性.