有机抛光液中磷酸浓度的定量测定

有机抛光液的成分分析 ,对于调整抛光液的组成 ,控制抛光具有十分重要的意义。抛光液的分析方法很多 ,但是对于不同组成的抛光液的成分分析 ,要采用不同的分析方法 ,这样才能获得可靠的分析结果。否则 ,将给分析结果带来较大的误差 ,甚至使分析无法进行。例如 ,在采用磷钼酸铵沉淀法测定有机抛光液中磷酸浓度的方法时 ,由于柠檬酸的存在 ,使分析结果产生很大误差。本文采用镁混合剂法测定有机抛光液中磷酸的浓度 ,硫酸和柠檬酸等物质的存在对分析不产生影响。1　试剂镁混合剂 :称取 Mg Cl2 · 6H2 O2 .75g及氯化铵52 .5g加水稀至 50 0 ml…     

热分析法观测Na2CrO4熔点

在现有文献中收录的Na2CrO4熔点数据各不相同，有792℃、392℃，两者相差400℃左右。利用热分析法观测Na2CrO4熔点，确定其熔点应为792℃。并且在419．6℃存在着一个可逆的固－固相变，转变焓为148．6J.g^-1。     

数学试卷中的二次根式

2004年全国各地中考教学试题中有很多关于二次根式问题的考题,这类考题源于课本,别于课本,能很好的考查对知识的掌握及应用能力.现将这类试题归类解析如下,供同学们参考:     

近红外光谱结合非线性模式识别方法进行牛奶中掺假物质的判别

以287例上海及上海周边地区牧场的生鲜奶作为真奶样本集组成3个真奶样品集合,配制了526例含有糊精(或淀粉)+三聚氰胺(或尿素、或硝酸铵)的掺假牛奶形成6个不同种类的假奶样品集合,其中糊精、淀粉在掺假奶中的含量为0.15%~0.45%;硝酸铵、尿素和三聚氰胺的含量分别为700~2 100, 524~1 572与365.5~1 096.5 mg·kg-1,以保证掺假奶中凯氏定氮法测得的蛋白含量不低于3%。所有样本的近红外光谱均经过标准正态变换(SNV)预处理。将3个真奶样品集合和6个假奶样品集合进行不同的组合并对其采用改进与简化的K最邻近结点算法(IS-KNN)和改进与简化的支持向量机法(ν-SVM)建立了判别糊精、淀粉、三聚氰胺、尿素、硝酸铵这5类掺假物质的近红外判别模型,探寻掺假物质的浓度与识别正确率之间的关系。结果表明IS-KNN和ν-SVM两种方法对含三聚氰胺、尿素、硝酸铵的掺假牛奶的平均判别正确率分别在49.55%~51.01%,61.78%~68.79%与68.25%~73.51%区间波动,说明在该研究的掺假物浓度范围内,很难用近红外模型良好区分不同类型伪蛋白的掺假奶;IS-KNN和ν-SVM两种方法对含淀粉的掺假牛奶的判别正确率分别为92.33%与93.66%、对含糊精的掺假牛奶的平均判别正确率分别为77.29%与85.08%。从整体结果上来看ν-SVM法进行建模判别的结果大部分优于IS-KNN法进行建模判别的结果。对判别正确率与样品中掺假物质的含量水平分析表明近红外光谱结合非线性模式识别方法能良好地区分掺假奶中含量较高(0.15%~0.45%)的糊精和淀粉,而对含量偏低的三聚氰胺等伪蛋白的判别效果不佳,说明近红外光谱技术不适于鉴别牛奶中含量低于0.1%的掺假物质。     

催化光度法测定电镀废水中微量锌(Ⅱ)

痕量锌 ( )对 H2 O2 氧化铬黑 T(EBT)的褪色反应有强的催化作用 ,且与锌 ( )量线性相关。据此建立了测定痕量锌 ( )的分光光度法。在 p H 4 .75的 HAc- Na Ac缓冲溶液和 OP存在下 ,有色溶液的最大吸收波长为 5 30 nm,方法检出限为 0 .70μg/ L ,锌 ( )量在 0— 0 .2 0 mg/ L范围内符合比耳定律 ,加标回收率为 99.2 %— 10 5 .3%之间。本法可测定电镀废水中的微量锌 ( )。     

Improvement of laser damage thresholds of fused silica by ultrasonic-assisted hydrofluoric acid etching

Polished fused silica samples were etched for different durations by using hydrofluoric(HF) acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared(IR) spectrometer, respectively. The laser induced damage thresholds(LIDTs) of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.     

波前编码显微物镜景深扩展的研究

为了解决传统显微物镜景深与分辨率的矛盾,采用波前编码的方法,设计研究了波前编码的10倍显微物镜,结合传统光学设计软件,采用基于MTF一致性的相位板参数的优化方法,实现了在像面附近一定范围内系统的点扩散函数一致性;此外,还设计了扩展三次相位编码板的10倍显微物镜,比较了采用两种不同相位板系统的焦深扩展的效果,结果显示三次相位板的焦深扩展效果较好,可以将传统10倍显微物镜的焦深扩展15倍。成像模拟仿真结果显示滤波后的编码像在±15倍焦深范围内成像清晰,从而扩大了系统的景深。     

Energetics of He and H Atoms in W–Ta Alloys: First-Principle Calculations

Properties of various defects of He and H atoms in W-Ta alloys are investigated based on density functional theory. The tetrahedral interstitial site is the most configured site for self-interstitial He and H in W and W-Ta alloys. Only a single He atom favors a substitutional site in the presence of a nearby vacancy. However, in the coexistence of He and H atoms in the presence of the vacancy, the single H atom favors the tetrahedral interstitial site(TIS) closest to the vacancy, and the He atom takes the vacancy center. The addition of Ta can reduce the formation energy of TIS He or H defects. The substituted Ta affects the charge density distribution in the vicinity of the He atom and decreases the valence electron density of the H atoms. A strong hybridization of the H s states and the nearest W d state s exists in W_(53)He_1 H_1 structure. The sequence of the He p projected DOS at the Fermi energy level is in agreement with the order of the formation energy of the He-H pair in the systems.     

Evolutionary Prisoner's Dilemma Game Based on Pursuing Higher Average Payoff

We investigate the prisoner＇s dilemma game based on a new rule： players will change their current strategies to opposite strategies with some probability if their neighbours＇ average payoffs are higher than theirs. Compared with the cases on regular lattices （RL） and Newman-Watts small world network （NW）, cooperation can be best enhanced on the scale-free Barabasi-Albert network （BA）. It is found that cooperators are dispersive on RL network, which is different from previously reported results that cooperators will form large clusters to resist the invasion of defectors. Cooperative behaviours on the BA network are discussed in detail. It is found that large-degree individuals have lower cooperation level and gain higher average payoffs than that of small-degree individuals. In addition, we find that small-degree individuals more frequently change strategies than do large- degree individuals.     

用极谱法研究酸性大红GR与环糊精超分子体系

本文用线性扫描二阶导数极谱法研究了酸性大红与各种环糊精的超分子体系;测定了它们的包结常数和包结比,比较了它们的包结能力,初步探讨了影响包结能力大小的可能因素。