以非离子表面活性剂为高效催化剂的TEX合成工艺研究

以甲酰胺和质量分数40%的乙二醛为原料,经缩合反应得到1,4-二(甲酰基)-2,3,5,6-四羟基哌嗪(DFTHP),然后在硝硫混酸作用下,合成了4,10-二硝基-2,6,8,12-四氧杂-4,10-二氮杂四环[5.5.0.05,9.03,11]十二烷(TEX),并用FTIR光谱、核磁共振对其结构进行表征。研究了硝硫混酸体积比、硝化反应温度、非离子型表面活性剂种类及用量对TEX收率和纯度的影响。得到最优合成条件为:发烟硝酸与浓硫酸的体积比为4∶3、加样温度45℃、硝化温度55℃、以聚乙二醇400(PEG400)为反应催化剂,且PEG400与DFTHP的质量比为0.15∶1.00,此时TEX收率为59.8%,纯度为99.2%。     

S-07钢在高压充气阀芯中的替代应用研究

目的解决高压充气阀S-03钢渗氮阀芯生产过程中周期长、合格率低、渗氮层开裂和贮存过程中锈蚀及方向漏率超标等问题。方法结合S-03钢渗氮阀芯工艺流程,分析其生产及贮存过程中存在的问题,并提出由S-07钢替代S-03钢渗氮工艺,从防锈、硬度和强度3个方面进行两种材料特性理论分析,同时进行耐蚀性试验、功能性试验、力学环境试验和寿命试验考核。结果 S-03钢渗氮阀芯经历湿热试验20 d后,出现轻微锈蚀,盐雾试验96 h后,锈蚀严重,而同条件下的S-07钢阀芯无锈蚀。S-07钢阀芯经过了功能性试验,x,y,z这3个方向的力学环境试验,动作200次的寿命考核试验后,动作灵活,功能测试合格。结论充气阀阀芯完成了S-07钢替代工艺研究,成功解决了影响充气阀功能的阀芯锈蚀问题和渗氮层开裂问题,同时使生产效率提高了约70%,生产成本降低了约50%。     

絮凝体的分形特征和致密型絮凝体形成

传统混凝条件下形成的随机型絮凝体具有分形特征．其分形维数Df与其密度函数ρ3∝dp^-Kp的指数Kp之间具有Df=3-K，的关系．通过建立分步成长絮凝体模型．讨论了在絮凝过程中逐次导入颗粒间的空隙率对絮凝体密度和构造的影响．模型参数分析的结果进一步证明了分步成长的絮凝体是一个典型的分形，其分形维数取决于空隙率ε和颗粒结合个数m．降低ε或提高m均有利于提高Df，使絮凝体由松散型向致密型过渡．脱水收缩和逐一附着模式是达到这一目的的两种操作模式．前者可以通过延长机械搅拌时间来实现，而后者通过造粒流化床实现．实验结果表明两种方式均能提高形成的球状颗粒的密度．但是前者所形成的团粒依然具有颗粒密度随粒径增大而降低的特点，其分形维数为2．40～2．47；而逐一附着模式所形成的团粒密度基本上与粒径无关．其分形维数接近于3．通过讨论造粒流化床操作条件．并将试验得到的致密型絮凝体密度和常规絮凝体密度进行比较．说明该方法实现逐一附着型絮凝体操作是促使絮凝体致密化的有效途径．     

Fuzzy h-ideals of hemirings

A characterization of an h-hemiregular hemiring in terms of a fuzzy h-ideal is provided. Some properties of prime fuzzy h-ideals of h-hemiregular hemirings are investigated. It is proved that a fuzzy subset ζ of a hemiring S is a prime fuzzy left (right) h-ideal of S if and only if ζ is two-valued, ζ(0) = 1, and the set of all x in S such that ζ(x) = 1 is a prime (left) right h-ideal of S. Finally, the similar properties for maximal fuzzy left (right) h-ideals of hemirings are considered.     

Redefined fuzzy Hv-submodules and many valued implications

This paper considers a relationship between fuzzy sets and algebraic hyperstructures. A generalization of ideas presented by Davvaz [B. Davvaz, Fuzzy H_v-submodules, Fuzzy Sets Syst. 117 (2001) 477-484] and Bhakat and Das [S.K. Bhakat, P. Das, (∈, ∈ ∨ q)-fuzzy subgroup, Fuzzy Sets Syst. 80 (1996) 359-368], is presented. In fact, the main purpose of this paper is to introduce and study a new sort of fuzzy H_v-submodule of an H_v-module called (∈, ∈ ∨ q)-fuzzy H_v-submodules. These fuzzy H_v-submodules are characterized by their level H_v-submodules. The concept of a fuzzy H_v-submodule with thresholds is introduced, and some interesting properties are investigated.     

A revisit to the common mean problem: Comparing the maximum likelihood estimator with the Graybill-Deal estimator

For estimating the common mean of two normal populations with unknown and possibly unequal variances the well-known Graybill-Deal estimator (GDE) has been a motivating factor for research over the last five decades. Surprisingly the literature does not have much to show when it comes to the maximum likelihood estimator (MLE) and its properties compared to those of the GDE. The purpose of this note is to shed some light on the structure of the MLE, and compare it with the GDE. While studying the asymptotic variance of the GDE, we provide an upgraded set of bounds for its variance. A massive simulation study has been carried out with very high level of accuracy to compare the variances of the above two estimators results of which are quite interesting.     

纳米WO3薄膜的制备及其光学性能研究

以钨酸钠为原料，采用溶胶技术结合浸渍镀膜方法制备出WO3薄膜，利用透射电子显微镜、紫外-可见分光光度计、X射线衍射仪对薄膜的性质进行了研究。实验结果表明：草酸浓度的大小对产物粒径和紫外-可见透过光谱特性均有影响，随着草酸浓度的增大，产物的粒径减小，在可见光附近的透过率增大。热处理温度对产物的光透过性有影响，处理温度越高，光透过率越大。     

A new framework for identifying differentially expressed genes

Microarrays have been widely used to classify cancer samples and discover the biological types, for example tumor versus normal phenotypes in cancer research. One of the challenging scientific tasks in the post-genomic epoch is how to identify a subset of differentially expressed genes from thousands of genes in microarray data which will enable us to understand the underlying molecular mechanisms of diseases, accurately diagnosing diseases and identifying novel therapeutic targets. In this paper, we propose a new framework for identifying differentially expressed genes. In the proposed framework, genes are ranked according to their residuals. The performance of the framework is assessed through applying it to several public microarray data. Experimental results show that the proposed method gives more robust and accurate rank than other statistical test methods, such as t-test, Wilcoxon rank sum test and KS-test. Another novelty of the method is that we design an algorithm for selecting a small subset of genes that show significant variation in expression (“outlier” genes). The number of genes in the small subset can be controlled via an alterable window of confidence level. In addition, the results of the proposed method can be visualized. By observing the residual plot, we can easily find genes that show significant variation in two groups of samples and learn the degrees of differential expression of genes. Through a comparison study, we found several “outlier” genes which had been verified in previous biological experiments while they were either not identified by other methods or had lower ranks in standard statistical tests.