Waterborne acrylic–casein latexes as eco-friendly binders for coatings

The use of casein as renewable resource to produce eco-friendly hybrid latexes has an increasing importance in industrial applications especially for high performance waterborne coatings. This work describes the synthesis of hybrid acrylic–casein latexes by emulsion polymerization of acrylic monomers in presence of varied casein concentration, and in absence of emulsifier which is usually a challenge for preparing stable nanocomposite latexes. The production and microstructure characterization of the casein–acrylic nanoparticles, as well as the properties of the films obtained from the hybrid latexes are here reported. The synthesized acrylic–casein latexes are able to form films with promising properties for a potential application as waterborne bio-based coatings.     

窑灰与粉煤灰复合作为混凝土掺合料的研究

以粉煤灰和窑灰与普通硅酸盐水泥组成的复合体为试验对象，采用新型水泥水化过程测定方法（仪器为非接触式电阻率测定仪）以及水化热测试方法，对粉煤灰一窑灰一水泥的水化过程进行了研究，结果表明：窑灰与粉煤灰有着良好的复合效应，且粉煤灰能有效固化和吸附窑灰中的有害离子，克服过量碱对混凝土的有害作用。通过SEM研究了该浆体微观结构的发展，并测定了砂浆的抗折及抗压强度，结果进一步证明了上述结论。     

高心墙堆石坝填筑标准的试验研究

近期建成的几座高心墙堆石坝的监测资料表明,坝体的分区变形协调性并没有达到设计目标。为此,结合建设中的长河坝300m级心墙堆石坝,开展了坝壳料的室内和现场大型相对密度试验,得到了相应的相对密度指标,并对各分区的填筑标准进行了讨论。结果表明:①由于级配为较好的分形分布、压实性优良,现场堆石区的填筑平均孔隙率达到19%,优于21%的设计指标,但相对密度仅为0.65;②根据规范要求设计的反滤2区、过渡区和堆石区的填筑相对密度在0.96～0.65之间,其压实程度存在明显差异,不易保证坝体各分区的变形协调;③采用与现场压实功能相匹配的室内相对密度试验技术,可解决高心墙坝的反滤料或面板坝的垫层料相对密度大于1的问题;④高坝堆石体的变形控制设计,需要考虑级配效应的影响,宜采用孔隙率和相对密度双控填筑指标。结论可为高堆石坝的设计与建设提供参考。     

错层位巷道布置在煤与瓦斯共采上的应用构想

随着煤矿开采深度和强度不断增加,瓦斯灾害的发生概率也随之增大,煤与瓦斯共采技术逐渐得到重视。本文致力于为提高煤矿瓦斯抽采率,实现高瓦斯矿井安全、高效生产找到更多可能的有效方法。通过对错层位巷道布置开采首采工作面之后其上覆岩层运动特点进行总结分析,试着从改革巷道布置方面着手,将错层位巷道布置与现有煤与瓦斯共采技术结合,从而提出了错层位巷道布置在煤与卸压瓦斯共采上的应用构想。文中做出了相应的预测,认为采用这种方法,比用传统方法抽采瓦斯在安全、经济方面更具优势,需要通过具体工程实践进行验证。     

响应面优化草石蚕多糖提取工艺研究

以草石蚕为原料，研究了草石蚕中多糖提取的工艺条件。在单因素试验基础上，通过响应面试验优化了草石蚕中多糖提取的工艺条件。结果表明，草石蚕中多糖的最佳提取工艺条件为：提取温度79．00℃，提取时间2．82h，乙醇体积浓度81．22％，料液比1g：18．49mL，此条件下草石蚕多糖提取率4．89％。     

High pressure phase equilibria of ethyl esters in supercritical ethane and propane

The high pressure phase equilibria of ethyl esters (ethyl decanoate/caprate, ethyl dodecanoate/laurate, ethyl tetradecanoate/myristate and ethyl hexadecanoate/palmitate) in supercritical ethane and propane have been measured in the temperature ranges 311–358 K (T_R = 1.02–1.17) and 376–409 K (T_R = 1.02–1.11), respectively. The measurements were conducted in a high pressure view cell for ethyl ester mass fractions between 0.015 and 0.65. The results show a generally linear relationship between the phase transition temperature and pressure. No temperature inversions or three phase regions were observed. An increase in hydrocarbon backbone length leads to an increase in phase transition pressure. For ethane as supercritical solvent, this increase is linear. For propane as supercritical solvent, the nature of the increase was not quantified as the magnitude of the increase would be significantly influenced by the experimental measurement error as the observed increase is not very large. Comparison of the phase behaviour of ethyl esters with methyl esters shows very little difference, yet the phase transition pressure of ethyl esters in supercritical ethane and propane is significantly lower than those of the corresponding acids. The phase transition pressure of ethyl esters in ethane and propane is also lower than those in carbon dioxide.     

Measuring the Impact of an Individual Course on Students' Success

Background At the University of Michigan, qualified first‐year students who place out of the first‐semester calculus course may enroll in either the regular second‐semester calculus course or Applied Honors Calculus II. Students who enroll in Applied Honors Calculus II show higher academic performance than students enrolling in the Regular Calculus II. Purpose (Hypothesis ) The study addressed the question: does enrollment in Applied Honors Calculus II have a positive causal impact on subsequent academic performance for engineering students at the University of Michigan? Design /Method We acquired seven years of institutional data for engineering students who entered the University of Michigan from 1996 through 2003 and who qualified to enroll in Applied Honors Calculus II. Using regression analyses, we tested a causal model of impact of Applied Honors Calculus II on four measures of subsequent academic performance: grade in Physics II and average grade in all subsequent physics, mathematics, and engineering courses. Results After controlling for students' personal characteristics and prior academic achievement, the impact of Applied Honors Calculus II on students' academic performance was not statistically significant. In particular Advanced Placement scores accounted for the higher performance observed in Applied Honors Calculus II students. Conclusions We recommend including Advanced Placement scores in models that predict academic performance. Future research should also include measures of socioeconomic status (SES) and explore interactions between SES and academic background. Finally, in evaluations of specific curricula, the treatment effect—measured as treatment group mean minus control group mean, after controlling for covariates—is unlikely to be large if the control group receives high quality instruction.     

广西某难选铅锌矿铅锌分离试验

广西某铅锌矿属铅低锌高、微细粒嵌布的难分离铅锌矿,铅品位为0.88%、锌品位为9.19%。主要含锌矿物为闪锌矿,含铅矿物较复杂,主要为脆硫锑铅矿、硫锑铅矿和方铅矿,且嵌布粒度极微细。为了高效开发利用该矿石资源,对该矿石进行了铅、锌分离回收试验研究。结果表明：在磨矿细度为-0.074 mm占80%的情况下,采用1粗2扫3 精选铅,1粗2扫3 精选锌,铅、锌1次精选尾矿和1次扫选精矿合并返回再磨,其余中矿顺序返回流程处理该矿石,最终获得了锌品位为48.05%、锌回收率为91.13%的锌精矿,以及铅品位为26.63%、锑品位为21.80%、铅回收率为87.46%、锑回收率为86.30%的铅锑精矿,铅锑精矿铅含量较低的原因与矿石中主要含铅矿物脆硫锑铅矿和硫锑铅矿理论含铅量较低、嵌布粒度极微细有关,不适合细磨深选。     

不规则边角煤连续开采设计及回采实践

以显德汪矿1223工作面为工程背景,针对工作面实际情况,分析边角煤地质条件,提出"倒L"形工作面连续开采设计方案并进行回采实践。实践中进行一次工作面对接,三次旋转开采和连续穿越两条老巷,并且通过采取多种有效措施,实现该工作面的安全回采。回采实践表明,"倒L"形工作面连续开采设计方案实现了1223工作面正常回采,减少工作面搬家次数,保证工作面连续推进,节约了成本,提高了经济效益;工作面回采时采取保障措施,及时加强支护并延长超前支护距离,有效控制煤壁片帮和顶板冒顶以及巷道围岩变形;1223工作面的正常回采,扩大了综采的应用范围和适应性,为不规则边角煤资源的回收提供参考。