涂料用支化型饱和聚酯树脂的合成及表征

采用溶液缩聚的方法,以对苯二甲酸、间苯二甲酸、己二酸、新戊二醇、一缩二乙二醇和1,1,1-三羟甲基丙烷(TMP)为原料,合成了一类新型的涂料用支化型饱和聚酯树脂。介绍了合成工艺及原材料的选择。通过红外光谱分析、X-射线衍射、热重分析和差热分析等测试其结构、形态和热性能。结果表明,合成的涂料用支化型饱和聚酯树脂的热稳定性较高。     

芦山地震中大跨空间结构主要破坏模式及数值分析

为探究短边距混凝土网架平板支座的受力机理和破坏模式,分别针对不同混凝土边距以及不同钢底板开孔形式共3个平板支座缩尺试件进行拟静力试验。对平板支座试件的破坏模式、滞回曲线、混凝土柱上层箍筋应变进行分析。试验结果表明：采用规范中对抗剪锚筋混凝土边距的建议长度,不能避免支座混凝土边缘破坏发生,但是混凝土柱上层箍筋对混凝土边缘的约束作用明显,并且采用开长孔钢底板并合理设计开孔长度,能有效推迟甚至避免发生混凝土边缘破坏。     

Modeling tree root diameter and biomass by ground-penetrating radar

Roots play a key role in ecosystem functioning as they transfer water and nutrients from soil to plants.Traditional methods for measuring roots are labor-intensive and destructive in nature,which limits quantitative and repeatable assessments in longterm research.Ground-penetrating radar(GPR) provides a non-destructive method to measure plant roots.Based on the superiority of GPR with 2 GHz frequency,we developed a new,practical method to estimate root biomass.First,average root matter density was measured ...     

Oscillation propagation features of the atmosphere around the Qinghai-Xizang Plateau during the spring season of typical strong and weak monsoon years

The interaction between the low-frequency atmospheric oscillation(Madden-Julian Oscillation,MJO) and the diabatic heating over the Qinghai-Xizang Plateau(QXP) from March to June is analyzed.The results show that there are respectively two and one wave trains around the QXP during the onset of the South China Sea monsoon in strong and weak monsoon years.The locations and strength of the wave train propagation differ between the strong and weak monsoon years.Because diabatic heating of the QXP prevents the lo...     

我国项目管理的现状分析与对策

本文对项目管理的意义和现状进行了分析,对我国项目管理中存在的问题进行了探讨,并提出了针对性的建议。     

标杆管理的精髓及其应用的探讨

本文从理论的视角对标杆管理的精髓进行了探讨,从实践的结果对标杆管理在电力勘察设计行业及其企业中的应用进行了分析,对应用中出现的主要问题提出了建议。     

On Weakly Semicommutative Rings

A ring R is said to be weakly scmicommutative if for any a, b ∈ R,ab ＝ 0 implies aRb (∈) Nil(R), where Nil(R) is the set of all nilpotcnt elements in R.In this note, we clarify the relationship betveen weakly semicommutative rings and NI-rings by proving that the notion of a weakly semicommutative ring is a proper generalization of NI-rings. We say that a ring R is weakly 2-primal if the set of nilpotent elements in R coincides with its Levitzki radical, and prove that if R is a weakly 2-primal ring which satisfies α-condition for an endomorphism α of R (that is, ab ＝ 0 (→) aαα(b) ＝ 0 where a, b ∈ R) then the skew polynomial ring R[x; α]is a weakly 2-primal ring, and that if R is a ring and I is an ideal of R such that I and R/I are both weakly semicommutative then R is weakly semicommutative.Those extend the main results of Liang et al. 2007 (Taiwanese J. Math., 11(5)(2007),1359-1368) considerably. Moreover, several new results about weakly semicommutative rings and NI-rings are included.     

双重分离全自动控制空气分离器工作过程分析

讨论分析双重分离全自动控制空气分离器的工作过程及影响因素。     

甲醇储罐开车前的化学清洗

报道了某一煤化工项目中甲醇储罐及连接管线的清洗实践。     

酯化法合成丙酮酸乙酯的研究

论述了以丙酮酸、乙醇为原料,离子交换树脂作催化剂,催化合成丙酮酸乙酯的新工艺。考察了催化剂种类、用量、原料配比、反应时间以及催化剂使用次数等因素对酯化率的影响,确定了催化剂种类和最佳工艺条件。结果表明,732强酸性离子交换树脂具有良好的催化活性和选择性,可多次重复使用,酯化率可达85.7%,产品质量符合国家标准。