Guar gum was modified by the cross-linking in order to improve its properties and broaden its applications. The technology conditions for preparing the cross-linked guar gum were explored by using guar gum as the raw materials, phosphorous oxychloride as a cross-linking agent, sodium hydroxide as a catalyst and ethanol as a solvent. The effects of the reaction temperature, reaction time, amount of phosphorous oxychloride and pH on the sedimentation volume of the crosslinked guar gum were investigated. On the basis of one-factor-at-a-time design, the response surface methodology was used to optimize the process parameters of the cross-linking. The order for influencing the guar gum cross-linking from primary to secondary was as follows: the amount of phosphorous oxychloride, reaction time, reaction temperature and pH. The best reaction conditions for preparing the cross-linked guar gum were: the amount of phosphorous oxychloride 1.2%, reaction time75 min, reaction temperature 33 ℃, pH 11.5. The sedimentation volume of the cross-linked guar gum was 1.03 mL under the optimal conditions.

In order to study the weldability of AZ31 magnesium alloy,AC tungsten inert gas welding (TIG) was conducted for the AZ31 magnesium alloy plate. The microstructure of the welding seam was analyzed using x-ray diffractometer,scanning electron microscope and optical microscope. In addition,the hardness and ultimate tensile strength of the samples obtained with different welding current were determined. The results show that with an increase in welding current,the formability of welding seam becomes worse and the grains get coarsed. At the same time,both gas porosity and crack are easy to generate,which will reduce the properties of the joint. The microstructure of the welding seam is composed of α-Mg matrix and β-Al12Mg17phase. It is also noted that the welding current significantly influences the shape of molten pool and the welding quality of welding joint.

本文以我国9所高校本科288名日语专业学生为对象,对当前大学生学习日语的兴趣进行了调查。通过调查可知,日语专业学生学习日语途径多样化,其中,网络自主学习是同学们课堂之外学习日语的主要途径,相对于课本等相对滞后的学习内容而言,网络学习打破了传统教育模式时间和空间条件的限制,更有利于培养学习兴趣,并具有开放性、交互性、协作性及自主性等特点,是传统学校教育功能的有益延伸。

Through analyzing the features of welding technical design in the manufacturing process of metal bellows,the common methods which were applied to metal bellows welding was summarized.The expert system of metal bellows welding technology based on Visual Basic 6.0-based development platform was designed and developed.The designed theory of main function for the system was emphasized.The methods and the structure of system database were realized.Through entering accurate or vague material name,inputting the thickness and melding method in choice,the system will get the accurate and reasonable result of welding technical parameter by the way of intelligent judgment,comparison,analysis and calculation.Ultimately,the result displayed in form of welding procedure sheet,which can be read by the users.The system not only makes the welding technology from complex to simple,but also offers a scientific foundation for setting a man-hour quota and improving the management.Finally,it achieves the standardization and optimization in the process of metal bellows welding technology.