聚丁二酸丁二醇酯合成方法比较研究

以丁二酸、丁二醇为原料,用熔融缩聚法、溶液熔融相结合法两种不同方法合成聚丁二酸丁二醇酯（PBS）。通过对合成方法及合成结果的讨论,比较不同方法之间存在的区别,并分析了溶液熔融相结合方法的优势所在。     

（丁二酸丁二醇酯-co-己内酯）共聚物的合成及性质

采用环境友好的有机钛催化剂,以不同摩尔比的己内酯（CL）对聚丁二酸丁二醇酯（PBS）进行了共聚改性,得到了（丁二酸丁二醇酯/己内酯）共聚物（P（BS-co-CL））.对不同组分比例的共聚物的相对分子质量、化学结构、热性质和降解性能进行了研究.结果发现：得到了数均相对分子质量7万以上的共聚物,分子质量分布范围在2左右;共聚物热分解温度（热失重2%）和PBS相比没有明显的降低,都在300℃以上,共聚物具有较好的热稳定性.降解实验表明共聚物具有更好的生物降解性能.     

新型表面活性剂-辛酸三乙醇胺酯的合成研究

以天然油脂为表面活性剂工业原料,合成具有很高表面活性的辛酸三乙醇胺单醋.通过有机酸作催化剂,酚作溶剂,控制反应温度、压力,提高单酯的产率,使其达到93.6%.     

铜氨纤维制备实验条件的改进

应用氢氧化铜与浓氨水制备铜氨纤维,研究了铜氨溶液、硫酸的温度、溶液的浓度等条件的影响,并与教材中实验方案进行对比.结果表明直接用氢氧化铜与25％的浓氨水制备铜氨纤维成功率高,效果好.该方法更有助于教师课堂教学和学生实验的实施.     

铜氨纤维制备实验条件的优化

铜氨纤维是一种性能优异的"绿色纺织品",作为纤维素性质的拓展,在高中及大学教材里都引入铜氨纤维的制备.通过对铜氨纤维制备实验的条件研究,发现CuSO_4溶液、NaOH溶液的量及二者的比例关系,浓氨水的量、沉淀的处理方式及最终硫酸介质的量及温度,对产品质量都有一定的影响.实验结果表明,用10 mL 15%的CuSO_4溶液与10 mL 25%NaOH溶液反应后,沉淀,静置,抽滤,洗涤,加入浓氨水,得到深蓝色的铜氨溶液;将脱脂棉溶解其中,得到黏稠液,再注入25 mL、 30℃的20%H_2SO_4溶液中拉丝,制得高质量的铜氨纤维.该实验方法简便,现象明显,重复性好,适于学生实验.     

工件表面粗糙度预测实验系统的研制

使用模糊自适应BP算法建立影响表面粗糙度参数与工件表面粗糙度之间的关系模型,依据给定的数据样本对模型进行训练,将训练好的网络进行实际的表面粗糙度预测.采用VB和Matlab语言相结合的方法建立一种实验系统,实现了数据采集和神经网络预测功能.实验结果表明,基于模糊自适应BP算法的工件表面粗糙度预测有一定的准确度.     

用手机实现的几个简单有效的课堂实验

课堂实验借助手机和软件较直观、较精确地实现,其取材简单方便,能增加高中物理课堂实验的可视性与真实性,提高学生参与度,激发学生积极性,提升课堂有效性。     

浅析温度对铜氨纤维实验的影响

<正>一、引言1857年,德国的Schweitzer发现硫酸铜氨水溶液能溶解纤维素,然后纺丝,再用稀酸处理可得再生纤维,这种纤维叫做铜氨纤维。铜氨纤维虽是纤维素纤维中较小的品种,但其优异的耐磨性、手感柔软的特性得到人们的青睐。铜氨纤维采用天然的棉花的短毛制成,是一种对人类、地球生态环境最温和的纤维。铜氨纤维易受     

探究“蚯蚓在什么样的物体表面爬得快”实验方法

“蚯蚓在什么样的物体表面爬得快”是苏教版七年级《生物》第二章第二节的教学实验,日常实验结果常会出现这样的错误：蚯蚓反而在光滑的玻璃表面爬得快。笔者发现在实验中水的用法不同,往往影响实验结果的正确率。为了能保证课堂实验的成功,决定探究出最佳喷水方式的实验方法。     

初中物理实验的有效方法

实验教学是初中物理教学的重要组成部分,涉及力学、热学、声学、光学、电学等内容。让学生参与物理实验知识的学习,激发学生的学习兴趣,将学习知识内化为自己的知识体系,更新物理实验的学习理念和方法技能,从而更好地提高教学效果。     

一种启发式聚类特征选择方法

为了使聚类可以在低维数据空间中进行,提出了一种新的聚类特征选择方法.该方法分3个步骤,每个步骤都在一个wrapper框架中执行.首先,将所有原始特征都按照重要性进行排序,引入一个特征重要性评价函数E(f);然后,顺序地选择特征组成重要特征子集;最后,去除重要特征子集中可能存在的冗余特征.由于是顺序选择特征而不是在巨大的特征子集空间中进行搜索,因此算法效率很高.实验结果表明该方法可以找出有助于聚类的重要特征子集,并且可以去掉那些不利于聚类的特征.     

高级德语精读课程教学法的选择与应用

本文在分析高级德语精读课程教学目标以及课程特点的基础上,以理论分析和案例分析的形式,探讨语法翻译法、直接教学法、听说教学法和任务教学法在高级德语精读课程中的运用。研究结果表明,上述几种教学在实际授课过程中各有优势,根据不同的课程内容和学生能力选择不同的教学方法,可以使得该课程取得良好的授课效果。     

Self‐selection of Simple Computer Activities by Infant School Pupils

Abstract Many activities from the infant class curriculum may be enhanced by realising them in the interactive context of a computer environment. This raises the question of whether young children can make choices among such activities that would reflect an awareness of their difficulty and a motivation to master them. In this research, infant class pupils were provided with software that offered unconstrained opportunities to select a range of related activities and the level of difficulty at which they would be tackled. Choices and response times were automatically recorded over a period of three weeks. These choices remained stable throughout that time and were biased towards the easiest options. There was some improvement in performance although little evidence of choice strategies that could be effective in driving such improvement. There was no evidence of sex differences in frequency of using the computer.     

一种化简二次曲面方程的新方法

利用平面上的坐标轴旋转变换消去两坐标变量的混乘项,再用空间中的移轴变换化简二次曲面方程,得到了化简二次曲面方程的一种新方法,依此方法易见曲面在给定坐标系中的位置。     

结构动力响应分析的一种简便的直接积分法

提出了一种简单且有效的可应用于线性和非线性系统响应分析的直接数值积分方法，并就算法稳定性作了扼要的分析。与一些常用的直接积分方法(如差分法、Wilsonβ及Newmarkβ法等)不同的是：文章提出的方法首先由控制方程计算加速度，然后基于位移、速度和加速度的近似关系式导出位移及速度的计算公式。文中给出了若干个数值算例，其结果表明该方法对于线性和非线性系统的动力响应分析是较为有效的。     

平面简谐波势能的简易分析方法

平面简谐波是理工科专业《大学物理》课程中的重要内容。势能的分析和推导是平面简谐波教学中的难点。本文利用弹性波的传播机理和特征,提出一种简易的分析和推导平面简谐波势能密度函数的方法。此方法可以避开学生陌生和难以理解的一些物理量和概念,因此其可使教学过程大为简化,并便于学生掌握和深刻理解相关内容。     

A simple and effective method for total RNA isolation of appressoria in Magnaporthe oryzae

Appressorium formation is an important event in establishing a successful interaction between the rice blast fungus, Magnaporthe oryzae, and its host plant, rice. An understanding of molecular events occurring in appressorium differentiation will give new strategies to control rice blast. A quick and reliable method to extract total RNA from appressorium is essential for studying gene expression during appressorium formation and its mechanism. We found that duplicate film is an efficient substratum for appressorium formation, even when inoculated with high density conidia. When inoculated with conidia at 1×106ml-1, the percentages of conidium germination and appressorium formation were (97.98±0.67)% and (97.88±0.45)%, respectively. We applied Trizol before appressorium collection for total RNA isolation, and as much as 113.6 pg total RNA was isolated from the mature appressoria at 24 h after inoculation. Functional analysis of two genes, MNH6 and MgATG1, isolated from the cDNA subtractive library, revealed that the quantity of RNA was good enough to construct a cDNA (complementary DNA) library or a cDNA subtractive library. This method may be also applicable for the appressorium RNA isolation of other pathogenic fungi in which conidia differentiate into appressoria in the early stages of host infection.     

Fabrication method of ultra-small gradient-index fiber probe

Fabrication method and device of ultra-small gradient-index （GRIN） fiber probe were investigated in order to explore the development of ultra-small probes for optical coherence tomography （OCT） imaging. The beam- expanding effect of no-core fiber （NCF） and the focusing properties of the GRIN fiber lens were analyzed based on the model of GRIN fiber probe consisting of single-mode fiber （SMF）, NCF and GRIN fiber lens. A stereo micro- scope based system was developed to fabricate the GRIN fiber probe. A fiber fusion splicer and an ultrasonic cleaver were used to weld and cut the fiber respectively. A con- focal microscopy was used to measure the dimensions of probe components. The results show that the sizes of probe components developed are at the level of millimeter. Therefore, the proposed experimental system meets the fabrication requirements of an ultra-small self-focusing GRIN fiber probe. This shows that this fabrication device and method can be employed in the fabrication of ultra- small self-focusing GRIN fiber probe and applied in the study of miniaturized optical probes and OCT systems.     

Modified surface tension model for free surface flow with single-phase lattice Boltzmann method

A single-phase lattice Boltzmann model with modified surface tension is developed in this paper to solve the problem of high-density-ratio free surface flow.The computational efficiency and accuracy are both enhanced.The restriction to the relaxation factor （which needs to be smaller than 1） is circumvented by the new surface tension algebra,due to its rational physical nature compared with the treatment of Xing,Buther and Yang in their paper （Comp.Mater.Sci.,2007,39（2）：282-290）.The proposed stable surface tension scheme is applied to simulate the free deformation of a square droplet with surface tension effect and the process of a droplet impinging on a liquid film.The numerical solution for free deformation of a droplet agrees well with thermodynamic principles,and also achieves high accuracy in comparison with Xing,et al.＇s model.Three typical impinging modes are successfully obtained with the new scheme,and another particular mode found by Wang and Chen is also successfully simulated.The evolutions of liquid crown agree well with the power law related to time.     

光纤通信课程教学方法改革与探索

通过对光纤通信技术教学现状的分析,提出了一些亟需解决的问题,并从教学内容、教学方法和实验教学等方面论述了教学改革措施,以期进一步提高学生分析、解决问题的能力,不断完善知识结构,改善教学质量。