Turkish Preservice Primary School Teachers' Science Teaching Efficacy Beliefs and Attitudes Toward Science: The Effect of a Primary Teacher Education Program

The main purpose of this study was to investigate the effectiveness of a primary teacher education program in improving science teaching efficacy beliefs (personal science teaching efficacy beliefs and outcome expectancy beliefs) of preservice primary school teachers. The study also investigated whether the program has an effect on student teachers' attitudes toward science. Data were collected by administering the “Science Teaching Efficacy Beliefs Instrument” and “Attitudes toward Science Scale” to 282 preservice primary teachers (147 freshmen, 135 seniors). Statistical techniques such as means and t‐test were used to analyze the data. Results of the study showed that the primary teacher education program has a medium positive effect on science teaching efficacy beliefs of the primary preservice teachers (t = 4.791, p = .000) and that there were no gender differences in terms of efficacy beliefs. Results also indicated that preservice primary teachers' attitudes toward science were moderately positive and differ by class level. Fourth‐year preservice teachers' attitudes toward science were found to be significantly more positive than the first years (t = 5.494, p = .000). There were no gender differences in attitudes toward science.     

利用低能质子束产生高强度放射性束流

加拿大TRIUMF实验室利用¹¹C成功验证了一种产生高强度(～10⁸ions/s)放射性束流的方法. 该方法不同于普通在线同位素分离方法, 它利用了13MeV的低能强流质子束, 可以产生一系列核天体物理实验感兴趣的高强度放射性束流.     

Competition between ferroelectric and flexoelectric polarization in freely suspended smectic films

We report a detailed ellipsometric study of freely suspended films of chiral liquid-crystal compounds possessing smectic-A and smectic-C phases. In the temperature region between the smectic-A - smectic-C bulk and surface transitions, a discontinuous reconstruction of the tilt profile across the film is observed in the presence of a constant d.c. electric field. Comparison of the measured ellipsometric quantities with values calculated from model tilt profiles reveals a competition between a structure possessing a homogeneous tilt direction and large ferroelectric polarization and a structure with opposite tilt direction in the two film halfs and large flexoelectric polarization. Received 21 October 1998     

聚合物孔材料的合成与应用

近年来,有关聚合物孔材料的合成及应用研究日趋活跃,已成为现代材料学研究领域的一大热点。本文分别对微孔、介孔和大孔聚合物孔材料的主要合成方法,如胶态晶体模板法、Track-eteh膜模板法、悬浮聚合法和超临界快速降压法等方法,以及聚合物孔材料在传感器材料的合成、化学分离等领域的应用进展情况进行了综述。     

基于Add-drop型微环谐振腔的硅基高速电光调制器设计

相比于传统的All-pass型微环谐振腔硅基电光调制器, Add-drop型微环谐振腔可提供更多的设计自由度, 使调制器在不改变杂质掺杂浓度的情况下就能在调制带宽和消光比性能上获得均衡考虑. 本文设计了基于Add-drop型微环谐振腔的高速、且在低调制电压下实现大消光比的硅基电光调制器, 所用微环谐振腔的半径仅仅为20 μm. 重点分析了直波导与微环谐振腔的耦合对调制器性能的影响, 发现较小的Drop端耦合系数有利于消光比的提高, 但是不能同时达到最佳的调制带宽, 因此设计上存在一个带宽和消光比性能上的折中考虑. 根据优化设计的结果进行了实际器件的制作和测试. 静态光谱测试表明, 在3 V反向偏置电压的作用下, 调制器的消光比最大可达12 dB. 动态电光响应测试中, 在仅仅1.2 V的信号幅值电压下测得了8 Gbps数据传输速率的清晰眼图. 关键词： 电光调制器 绝缘体上的硅 微环谐振腔 载流子色散效应     

Prolongation of solutions of measure differential equations and dynamic equations on time scales

In this paper, we prove the results on existence and uniqueness of the maximal solutions for measure differential equations, considering more general conditions on functions f and g by using the correspondence between the solutions of these equations and the solutions of generalized ODEs. Moreover, we prove these results for the dynamic equations on time scales, using the correspondence between the solutions of these last equations and the solutions of the measure differential equations.     

低阶煤热萃取物与瘦煤共炭化焦炭的微观结构及显微强度研究

以众唯瘦煤作为主炼焦煤,大同长焰煤萃取物作为添加剂,进行共炭化处理制备坩埚焦。利用偏光显微镜法定量研究焦炭光学显微组分,获得焦炭的各向异性指数(DRAS);采用XRD及分峰拟合的方法研究了焦炭的微晶粒径(L_c)、芳香缩合度(I_a)、石墨化度(g);利用Raman光谱结合分峰拟合的方法研究了焦炭中理想石墨微晶含量(I_g)。对所得焦炭的光学显微组分进行定量分析发现:大同长焰煤热解萃取产物的添加对共炭化焦炭的光学显微组分有显著的影响,利用偏光显微镜法计算出焦炭的DRAS与XRD和Raman计算的焦炭微晶参数呈现很好一致性。并且,焦炭的显微强度与其微观结构关联性极大。     

有机污染物在碳纳米管吸附的定量结构-性质关系

对一系列共59个芳香性分子进行了HF/6-31G^*水平上的结构优化,并在优化结构上进行了分子静电势及其导出参数的计算,应用多元线性回归方法建立了碳纳米管吸附有机污染物的平衡常数与分子结构间的定量关系. 结果表明,分子表面静电势参数（V_min、σ₊² 和ΣV_ind⁺）结合分子表面积（S）和最低空轨道能级（ε_LUMO）可以很好地用于构建碳纳米管吸附的定量结构-性质关系（QSPR）模型. 模型中引入的参数均具有明确的物理意义,其合理性可以从污染物与碳纳米管或水分子间相互作用的角度进行解释. 模型的稳定性和预测能力经“留一法”和Monte Carlo 交叉验证法进行了确证. 本文亦采用支持向量机（SVM）、最小二乘支持向量机（LSSVM）和高斯过程（GP）等三种方法建立了上述参数与碳纳米管吸附性质的非线性模型. SVM和LSSVM模型表现出强的拟合能力,但预测能力明显不如其他模型. GP模型无论是拟合能力还是预测能力都是最佳,但并没有明显地优于线性模型,说明对本文研究体系而言,其分子结构与性质间的关系主要以线性形式存在.