APD探测器模块性能及噪声检测

为了实现可见光通信系统的探测器模块微小型化，设计并制作了一款50 cm3的温控APD探测器模块，并对模块的稳定性、温控效果和噪声特性进行了检测。结果表明，APD探测器模块的光电流测量平均相对偏差为0.795%；APD探测器的雪崩增益和响应度随着温度的降低而提高；APD探测器电阻的变化影响负载电阻分压，使得过剩噪声因子的测量值远大于真实值，且会随着入射光功率的增大而增大。可以得出结论:提高反向偏置电压与降低温控温度相配合，更有利于弱光信号检测；检测电路中的负载电阻影响APD探测器噪声特性。     

高效液相色谱法测定地塞米松及有关物质

建立了高效液相色谱法测定地塞米松及有关物质的方法。采用Kromasil 100-5 C_(18)(250 mm×4. 6 mm,5μm)色谱柱,以水和乙腈为流动相,梯度洗脱,流速1. 5 mL/min,检测波长240 nm,柱温40℃,进样量20μL。在上述色谱条件下,地塞米松与1,2-二氢物、16β-甲基环氧物和17-脱氧-21醇等杂质分离效果好,地塞米松在4～480μg/mL范围内线性关系良好,检测限为0. 32μg/mL,1,2-二氢物、16β-甲基环氧物和17-脱氧-21醇在0. 2～4. 0μg/mL范围内线性关系良好,检测限分别为0. 058,0. 063,0. 060μg/mL。方法可用于测定地塞米松及有关物质的含量。     

Kagome晶格中的拓扑平带和量子霍尔效应

本文采用紧束缚模型研究Kagome晶格中的拓扑平带.通过调控交错磁通和次近邻跃迁强度可以得到具有大带隙且Chern数为非零的近平带结构.由于拓扑平带与二维Landau能级的相似性,所以此拓扑非平庸的平带可以产生整数量子霍尔态,再加上相互作用还可能产生分数量子霍尔态.     

Chiral separation abilities of homogeneously synthesized cellulose 3,5-dimethylphenylcarbamates: Influences of degree of substitution and molecular weight

A series of cellulose 3,5-dimethylphenylcarbamates(CDMPCs) with different degrees of substitution(DS) and degrees of polymerization(DP) were homogeneously synthesized in 1-allyl-3-methylimidazolium chloride(Amim Cl). Then, the CDMPCs were coated on silica gel and used as chiral stationary phases(CSPs), and their chiral recognition abilities for seven racemates were evaluated by high performance liquid chromatography. The results showed that DS and DP of CDMPCs had a great influence on chiral recognition abilities of the CSPs. The CSPs with the DS ≈ 1 gives a low chiral recognition to most racemates. On the contrast, the CSPs with the DS ? 2 exhibited high chiral separation abilities. For example, six racemates could be separated on the CSP with CDMPC of DS ≈ 2(CSP-2). Especially, for the enantioseparation of 1-(2-naphthyl) ethanol and Tr?ger's base, CSP-2 gave the highest separation ability in all of CSPs. On the other hand, when the DP of cellulose was in a range from 39 to 220, the chiral separation abilities of CDMPCs increased as the DP increased. This work demonstrates that the structure of cellulose esters such as DS and DP has important effect on their chiral separation ability, and therefore provides a practical method to design and prepare desirable CSPs for different racemates.     

Synthesis and characterization of temperature-sensitive cellulose-graft-poly(N-isopropylacrylamide) copolymers

A new series of cellulose-graft-poly(N-isopropylacrylamide)(cellulose-g-PNIPAM) copolymers were prepared by atom transfer radical polymerization(ATRP) of N-isopropylacrylamide monomers from a cellulose-based macro-initiator, which was homogeneously synthesized in an ionic liquid 1-allyl-3-methylimidazolium chloride(Amim Cl). The composition of cellulose-g-PNIPAM copolymers could be adjusted by altering the feeding ratio and reaction time. The resultant copolymers with relatively high content of PNIPAM segments(molar substitution of PNIPAM ? 18.3) were soluble in water at room temperature. Aqueous solutions of cellulose-g-PNIPAM copolymers exhibited clear temperature-sensitive behavior, and their sol-to-gel phase transition properties were investigated by dynamic light scattering(DLS) and UV measurements. Compared with pure PNIPAM, the cellulose-g-PNIPAM copolymers possessed higher lower critical solution temperatures(LCST) in a range from 36.9 ?C to 40.8 ?C, which are close to normal human body temperature, and could be tuned by adjusting the content of PNIPAM segments in copolymers. Spherical structure of cellulose-g-PNIPAM copolymers formed at temperatures above LCST and its morphology was observed by TEM and SEM. These novel cellulose-g-PNIPAM copolymers may be attractive substrates for some biomedical applications, such as drug release and tissue engineering.     

基于真实情境的初中化学微项目教学实践与反思*——以“溶液的形成”为例

以“溶液的形成”为例进行微项目教学实践,选择学生熟悉的护手霜为主题情境,巧妙设计了“原料分散”“微观探秘”“辨识活动”“对比实验”“感知乳化”等系列微项目活动,通过情境不断地设置认知冲突,引导学生反思、修正并最终形成更完善的概念,在环环相扣的探究活动中使学生自主建构结构化的知识。通过制作“护手霜”将“溶解”和“乳化”串联,感知溶液,感受乳化,感悟人与自然、社会的和谐、可持续发展。     

四氯化碳液相催化加氢制氯仿多元金属催化剂的制备及其催化性能

以贵金属M(=Pd,Pt)为主要活性成分,掺加过渡金属Fe和Ni作为助剂,采取浸渍和氢气还原法制备了椰壳活性炭(ACcs)负载的单元金属(M/ACcs)、二元金属(M-Ni/ACcs、M-Fe/ACcs)和三元金属(M-Ni-Fe/ACcs)系列催化剂;通过CC_l4液相催化加氢制氯仿反应考察了这些催化剂的催化活性和选择性。结果表明,Pd基催化剂的催化活性明显高于Pt基催化剂,但后者对氯仿的选择性优于前者;在前5 h加氢反应时段,两系列催化剂的活性顺序为:Pd-Ni-Fe/ACcsPd-Fe/ACcsPd/ACcsPd-Ni/ACcs和Pt/ACcs≈Pt-Fe/ACcsPt-Ni/ACcsPt-Ni-Fe/ACcs;总体上,引入Fe对于催化性能的改善效果要优于Ni,Ni的单独引入则会不同程度地降低催化活性。综合考量成本、活性和选择性等因素,优选Pd-Ni-Fe/ACcs作为催化剂,在393 K下反应5 h,可实现CC_l497.6%的转化率以及接近100%氯仿的选择性。     

高维线性插值方法及其在3维温度场计算中的应用

通过分析1维和2维线性插值可以推导出任意斜角直线坐标系下n维线性插值的一般计算公式以及有唯一解的条件,这一结论能够应用于三维温度场计算。可以将n维插值问题归结如下:已知n 1维空间中的n 1个点的坐标以及第n 2个点的n个坐标分量xn 2,1,x n 2,2,,xn 2,n,求解该点的第n 1个坐标分量xn 2,n 1。根据线性插值定义,第n 2个点位于前n 1个点所确定的n维超平面上。根据这一条件列写方程、求解方程可得到插值xn 2,n 1。n维插值问题有唯一解的条件是已知的n 1个点在n维空间中构成的多面体的体积不为0。推导过程在斜角直线坐标系中完成,因而结论具有较大普适性。     

用HLLC方法处理运动边界

针对含有运动边界非结构网格点的显式有限体积方法，研究了如何使用HLLC方法处理运动边界条件，计算了活塞拉伸、压缩问题，并和解析解进行了比较．作为应用示例，比较了静止圆柱绕流和静止流场中运动圆柱的绕流情形。结果表明：应用HLLC方法处理运动边界是可行的。     

反演在骨生长方程参数识别中的应用

基于BFGS算法，根据自行设计的动物实验，得到在不同应力环境中，快速生长期大鼠股骨生 长与重建过程中骨密度实测数据，采用反演数值方法，获取了骨生长方程中随时间变化的 生物参数B和K. 通过正演验证，表明所建立的基于BFGS算法的参数识别方法具有较好的 稳定性和较高的识别精度，能够反演出比较切合实际的生物参数数值. 研究表明，反问 题方法是解决生命现象不可测性和未知性问题的有效手段，把反演方法应用到骨生长与重建 等生命现象的研究中，可确定、修正预设的数学模式，为数值量化骨适应生物模型的建立提 供了一条可行的途径.