莫来石纤维多孔陶瓷的制备与性能

对纤维多孔陶瓷的制备及性能进行了研究。在制备纤维多孔陶瓷时,采用酸性磷酸铝A23(P/Al原子比为2 3)作粘结剂,所制备的多孔陶瓷在各方面都具有优良的性能。如导热系数λ(22℃)为0.0529W/m.℃、热膨胀系数α为4.75×10-6/℃、孔隙率为96.22%、容重为0.1142 g/cm3等。在环保、节能领域具有广泛的应用前景和重要的社会及经济意义。     

高校教师的隐性流失

本文分析了当前高校教师的隐性流失的严重性及流失形式的多样性,认为这种现象严重浪费了教育资源,影响了教学质量,毒化了校园环境和社会环境,必须采取坚决措施才能取得成效,制止流失.     

3,5-二氯苯甲酸的合成

考察了在以邻氨基苯甲酸为原料，三氯化铁为催化剂，X为溶剂，直接通氯氯化，再经重氮化合物3，5－二氯苯甲酸的工艺过程中，物料配比，反应湿度等反应条件对收率的影响，确定了合成的适宜条件，通过此合成工艺，产品的收率可达85％以上。     

丙交酯的合成

以DL－乳酸为原料在催化剂存在下，加热、减压脱水合成了DL－丙交酯，研究了温度、压力、反应时间等反应条件对丙交酯产率的影响，用IR等分析测试仪器对丙交酯进行了表征。     

Allelopathic Potential and Chemical Constituents of Volatile Oil from Ageratum conyzoides

Fresh leaves and volatile oil of the important weed Ageratum conyzoides in south China were highly inhibitory to seedling growth of various cultivated crops, especially in an adverse habitat. The constituents of the volatile oil were analyzed by GC-MS. Eleven components were identified and six main components, precocene I, precocene II, 3,3-dimethyl-5-tert-butylindone, -caryophyllene, -bisabolene, and fenchyl acetate, were isolated by means of column chromatography. Precocene I, precocene II, -caryophyllene, and 3,3-dimethyl-5-tert-butylindone inhibited seedling growth of acceptor plants. Inhibitory activity of the volatile oil was more intense than that of the pure components. Fenchyl acetate and -bisabolene have no inhibitory activity, but when mixed with precocene II, they increased the inhibitory activity to growth of acceptor seedling plants. Experiments show that allelopathic synergism exists among allelochemicals of Ageratum conyzoides.     

一种结合主题模型的推荐算法

针对传统协同过滤推荐算法存在的冷启动、数据稀疏以及相似度度量的准确性问题,基于LDA主题模型对文本隐式主题挖掘的有效性和KL散度在主题分布相似性度量的准确性,提出了结合LDA主题模型的矩阵分解推荐算法。首先,利用改进的LDA算法输出项目-主题分布,并用困惑度作为主题数设置的修正函数;然后分别基于余弦相似度和KL散度计算得到项目相似度矩阵,将得到的相似度矩阵结合原评分训练集输出预评分,再将预评分填充到训练集;最后将训练集输入ALS矩阵分解算法得到推荐结果。通过MovieLens数据集的实验结果表明,该算法在不同隐式参数设定下均能得到比ALS推荐算法以及更小的预测误差,并且最优预测误差小于传统推荐算法。该实验说明了通过集成LDA主题模型的ALS算法效果要优于其他推荐算法。     

Volume phase transition of polyelectrolyte gels in dimethyl sulfoxide/ tetrahydrofuran mixtures

Copolymer gels were prepared from 2-(acrylamido)-2-methylpropanesulfonic acid (AMPS), N,N-dimethylacrylamide (DMAA, comonomer) and N,N′-methylenebis(acrylamide) (BIS). The mole fraction of AMPS were 0.2674 and 0.4318, respectively, with the same BIS mole fraction of 0.013. These gels with counterions H⁺, Na⁺, and K⁺ were swollen at 25°C in mixtures of dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF). A volume phase transition was observed at the THF volume fraction of about 0.58, indicating that the volume phase transition in a polyelectrolyte gel occurs when the medium polarity decreases sufficiently for ion-pair formation. On changing the counterion, the fraction of DMSO in the solvent mixture which is required to initiate swelling decreases in the order Na⁺, H⁺, and K⁺, the same as for counterion condensation in identical gels.     

Consolidation of Nano-Sized TiN Powders by Spark Plasma Sintering

Nano-sized TiN powders with an average particle size of 19 nm were synthesized via a new method, reduction–nitridation reaction in liquid ammonia. A consolidation procedure using spark plasma sintering (SPS) was used, and a dense TiN ceramic (>98% of theoretical) with mean grain size of 100–150 nm was obtained at 1380°C. The influence of sintering temperature on grain growth and microstructural evolution was also discussed.     

Carbon-encapsulated Fe nanoparticles from detonation-induced pyrolysis of ferrocene

Carbon-encapsulated Fe nanoparticles with size between 5 and 20 nm were synthesized via a picric acid-detonation-induced pyrolysis of ferrocene, which is characterized by a self-heating and extremely fast process. The nanoparticles exhibit well-constructed core-shell structures, with bcc-Fe cores and graphitic shells. The graphitic shells can protect effectively the cores against the attack of HNO₃ solution. The formation of the core-shell nanoparticles can be selectively controlled by adjusting the composition of the picric acid-ferrocene mixture, which determines C/Fe atomic ratio of the reaction system. The core-shell nanoparticles are preferably formed at low C/Fe atomic ratios, while tubular structures are formed at high C/Fe ratio. The possible pathway for the carbon-encapsulated Fe nanoparticles formation is discussed briefly.     

Synthesis of polystyrene end-capped with pyrene via reversible addition-fragmentation chain transfer polymerization

A novel benzodithioate compound with a pyrene structure in the R group, pyrenylmethyl benzodithioate (PMB) was synthesized. Using PMB as the chain transfer agent (CTA), the RAFT polymerizations of styrene with AIBN as an initiator were carried out in different reaction conditions. The results indicated that PMB was an effective CTA for the RAFT polymerizations of styrene with the “living”/controlled characteristics. The structures of the obtained polymers were characterized by ¹H NMR. The results showed that majority of the polymer chains contained the pyrene moiety in the chain end. The enhanced fluorescence property in CHCl₃ solution was observed. The chain-extension experiments of the obtained polystyrene (PS) with the monomers of styrene and methyl acrylate were successfully carried out.