太阳能热水器水管自动“空水”装置的教学

1问题的提出观察事物的缺陷,寻找解决方案的一系列发明课题.太阳能热水器已得到普遍的应用,不论是夏天还是冬天,都能给用户提供热水.但太阳能热水器有一个缺点,往往在冬天,水管内的水会结冰,使得太阳能热水器不能应用,甚至水管会被冻爆,特别是冰熔化后,室内自来水及水箱内的水都通过破裂处流出,导致"水灾"的发生,给家庭或邻居造成一定的     

Enhancement of upconversion luminescence of YAlO3:Er3+ by Gd3+ doping

The upconversion luminescences of YAlO3:Er3+ phosphor co-doping with different Gd3+ concentrations are investigated under the excitation of 980- and 532-nm diode lasers. A near ultraviolet upconversion emission at 410 nm is observed in YAlO3 under 532-nm excitation. Moreover, the inactive Gd3+ ions can improve the upconversion intensity efficiently in a certain range of concentration. Under 980-nm excitation, the visible upconversion emissions at 546 and 646 nm are enhanced by about 10 and 8 times at the Gd3+ concentration of 40%, respectively. The upconversion emission at 410 nm under 532-nm excitation is also enhanced by 7 times. The substitution of Gd3+ ions for Y3+ sites changes the local symmetry of Er3+, leading to the improvement of upconversion efficiency.     

Exploration of the sum of flexoelectric coef ficients of nematic liquid crystals

We present a theoretical calculation of the dependence of reflectivity Rpp of the improved fully leaky waveguide geometry,which comprises pyramid,matching fluid,and strongly anchored hybrid aligned nematic liquid crystal(NLC) cell on the internal angle.The calculation is based on the multi layer optical theory and the elastic theory of liquid crystals.For different sums of flexoelectric coefficients e11 and e33,the curve of Rpp moves a distance to the left or the right relative to the case of ignoring the flexoelectric effect and the distance of the movement varies with different flexoelectric coefficients.Consequently,the sum of flexoelectric coefficients can be explored by measuring the distance of the movement.     

毛细管电泳-电化学检测法检测水解植物蛋白调味液中的3-氯-1,2-丙二醇及其应用

运用毛细管电泳-电化学检测法研究了水解植物蛋白液中3-氯-1,2-丙二醇(3-MCPD)含量的测定。探索了3-MCPD检测的最佳电泳条件。以328 μm的铜圆盘电极为工作电极,在电极电位为+0.65 V(参比电极为饱和甘汞电极),检测池缓冲液为0.05 mol/L氢氧化钠,运行缓冲液为30 mmol/L硼砂(pH 9.24)时,3-MCPD能被很好地分离。3-MCPD的线性范围为6.6~200 mg/L,检测限为0.22 mg/L。研究了水解缓冲液的pH值、水解温度、水解时间等因素对3-MCPD水解反应的影响,用毛细管电泳-电化学检测法检测水解反应过程中3-MCPD的含量。结果表明,在pH 8.0的水解缓冲液中,将水解植物蛋白调味液前体于90 ℃条件下恒温加热1 h,能有效地控制3-MCPD的含量在1.0 mg/kg以下,从而达到我国食品安全允许的限量标准。     

Anchoring properties of substrate with a grating surface

The anchoring properties of substrate with a grating surface are investigated analytically. The alignment of nematic liquid crystal (NLC) in a grating surface originates from two mechanisms, thus the anchoring energy consists of two parts. One originates from the interaction potential between NLC molecules and the molecules on the substrate surface, and the other stems from the increased elastic strain energy. Based on the two mechanisms, the expression of anchoring energy per unit area of a projected plane of this grating surface is deduced and called the equivalent anchoring energy formula. Both the strength and the easy direction of equivalent anchoring energy are a function of the geometrical parameters (amplitude and pitch) of a grating surface. By using this formula, the grating surface can be replaced by its projected plane and its anchoring properties can be described by the equivalent anchoring energy formula.     

An improved semi-empirical relationship for cluster radioactivity

An improved semi-empirical relationship for cluster radioactivity half-lives is proposed by introducing an accurate charge radius formula and an analytic expression of the preformation probability.Moreover,the cluster radioactivity half-lives for the daughter nuclei around ²⁰⁸Pb or its neighbors and the ¹²C radioactivity half-life of114Ba are calculated within the improved semi-empirical relationship.It is shown that the accuracy of the new relationship is improved significantly compared to its predecessor.In addition,the cluster radioactivity half-lives that are experimentally unavailable for the trans-lead and trans-tin nuclei are predicted by the new semi-empirical formula.These predictions might be useful for searching for the new cluster emitters of the two islands in future experiments.     

声音传播实验的改进

现行课本上介绍的声音传播实验，要么使用抽气机，使瓶内气体变稀薄；要么使用烧瓶将水烧至沸腾，加盖冷却后使瓶内气体变稀薄．然后，由气体逐渐变稀，传出的声音逐渐减小进行推理，从而得出“声音在真空中不能传播”的结论．此类实验的不足之处是器材较多，实验的时     

一道竞赛题的简证

在“从联想中获得巧思”一文(《数学通报》1991年第3期)中对一道数学竞赛题给出了一种巧妙的解法。现按原文摘录部分如下: “例1 证明:不等式     

表面接枝季铵盐型聚合物的纤维素纤维——灭菌机理研究

以大肠杆菌JM10 5(E .ColiJM10 5)为模拟体系 ,系统研究一种新型聚阳离子型表面接触抗菌材料及其单体的抗菌过程和机理 .采用平板计数法测定该单体的最低抑菌浓度以衡量其抗菌能力 ,采用扫描电镜法和 β 半乳糖苷酶活性考察该单体对大肠杆菌的抑制作用过程及其机理 .分别采用静态和动态吸附法考察聚阳离子型表面接触抗菌材料对大肠杆菌的吸附性能 ,测定吸附在材料表面菌体TTC 脱氢酶的活性和菌体呼吸活性以揭示该材料的抗菌作用机理 ,并采用电镜观察抗菌纤维表面菌体形态随时间的变化 .结果表明 ,聚阳离子型表面接触抗菌材料的单体可导致大肠杆菌细胞壁破裂 ,由此破坏细胞膜并导致细胞凝聚而死亡 .该消毒剂的灭菌过程由吸附和杀灭两步构成 ,前者为快速过程 ,而后者则是慢速过程     

非均匀成核法表面包覆氧化铝的尖晶石LiMn2O4研究

采用高温固相法合成尖晶石LiMn2O4,以非均匀成核方式对其进行包覆氧化铝的表面处理.通过XRD、SEM、粒度分析等技术对表面处理前后的LiMn2O4进行表征,分析了表面处理前后LiMn2O4物理特性的变化,并结合电化学性能测试,研究了表面处理工艺对LiMn2O4电化学容量与循环性能的影响.未经表面处理的LiMn2O4在1 C倍率下初期放电容量为86.5 mA•h•g－1,50次循环充放电后容量衰减26.3％.表面包覆0.5％、1％(w)氧化铝的LiMn2O4在1 C倍率下的初期放电容量分别为96.0、80.1 mA•h•g－1,经过50次循环后,容量分别降低7.0％、5.6％.实验结果表明,表面处理后的LiMn2O4循环性能显著提高,而且随着氧化物含量的增加,循环性能增强,但放电容量降低.