Self‐regulation during e‐learning: using behavioural evidence from navigation log files

The current paper examined the relationship between perceived characteristics of the learning environment in an e‐module in relation to test performance among a group of e‐learners. Using structural equation modelling, the relationship between these variables is further explored in terms of the proposed double mediation as outlined by Ning and Downing. These authors initially proposed that motivation and self‐regulation strategies are mediators between the perception of the learning environment and performance. In our replication and extension study, we substituted self‐reported self‐regulation with behavioural indicators of self‐regulation using navigation log files and focused on test‐taking rather than general motivation. We proposed that navigational patterns captured using log files can also help deduce self‐regulation in e‐modules and provide information in the absence of self‐reports. Path analyses provide partial support for our navigational hypotheses and the model. Implications of our results for the use of e‐module data and conclusions based on navigation are discussed.     

Pressure drop for single and two‐phase flow of non‐newtonian liquids in helical coils

New experimental results on pressure loss for the single and two‐phase gas‐liquid flow with non‐Newtonian liquids in helical coils are reported. For a constant value of the curvature ratio, the value of the helix angle of the coils is varied from 2.56° to 9.37°. For single phase flow, the effect of helix angle on pressure loss is found to be negligible in laminar flow regime but pressure loss increases with the increasing value of helix angle in turbulent flow conditions. On the other hand, for the two‐phase flow, the well‐known Lockhart‐Martinelli method correlates the present results for all values of helix angle (2.56‐9.37°) satisfactorily under turbulent/laminar and turbulent/turbulent conditions over the following ranges of variables as: 0.57 ≤ n′ ≤ 1; Re′ < 4000; Re_l < 4000; Re_g < 8000; 8 ≤ x ≤ 1000 and 0.2 ≤ De′ ≤ 1000.     

车辆出行轨迹调查分析中的丢点轨迹还原

针对利用车牌照生成车辆出行轨迹过程中由于车牌遗漏而产生的丢点轨迹问题, 提出一种丢点轨迹还原方法。首先建立一次可达网络模型来描述调查点之间直接可达关系, 并构建轨迹还原解集; 考虑时距相符程度、路径模式匹配程度、路径曲折度指标, 构造轨迹的效用函数, 利用逼近理想解排序的TOPSIS法进行轨迹还原解集决策, 得到最优的还原解。通过一个丢点轨迹示例进行了实验分析, 结果表明, 该方法可以得到满意的丢点还原解。     

坦克装甲车辆用橡胶履带板的研究开发

探讨了坦克装甲车辆用橡胶履带板（ＴＴＲＰ）的损坏摸式及其机理，从胶料配合，性能测试等方面评 ＴＴＲＰ的研究开发进展，并对我国ＴＴＲＰ的研究提出了建议。     

基于单轴速率转台的角速度传感器标定方法

针对传统的标定方法标定成本高且对北向基准的要求严格等问题,提出了一种用单轴速率转台作为标定设备的光纤陀螺捷联航姿系统标定方法。对光纤陀螺组合的误差进行建模,将光纤陀螺捷联航姿系统安装于单轴速率转台上,使光纤陀螺捷联航姿系统的3个陀螺轴向分别朝下进行标定实验,由此标定出3只光纤陀螺的零偏、标度因数和安装失准角共12个误差参数。通过对标定精度进行分析,验证了该方法的可行性,其标定成本低且不需要北向基准,具有一定的工程应用价值。     

晃动基座下捷联惯导的抗干扰自对准算法

针对捷联惯导(SINS) 晃动基座下, SINS 难以快速实现自对准的问题, 提出SINS 的抗干扰自对准算法. 该算法通过将初始对准问题转化为Wahba 求解问题来消除角运动干扰的影响; 利用惯性坐标系重力矢量和晃动干扰加速度的频率特点, 通过设计低通滤波器对比力在惯性坐标下的投影进行滤波来消除线振动干扰的影响. 仿真结果表明, 该算法不需要进行粗对准, 能够在角运动干扰和线振动干扰同时存在的情况下快速实现自对准.

     

脂肪族二异氰酸酯的生产状况及技术进展

综述了脂肪族二异氰酸酯（ADI）生产状况及技术进展,着重介绍了美国、西欧、日本以及中国的市场情况,并对ADI的生产技术发展趋势和市场前景进行了展望.     

用于高速旋转载体的惯性导航系统设计

针对高速旋转载体的实际应用情况,采用了无陀螺捷联惯性导航技术方案,快速精确测量载体的姿态、速度和位置信息。无陀螺捷联惯导系统采用加速度计来解算载体相对惯性系的角速度,从而代替角速度陀螺仪,提高了系统的高过载的适应能力。首先推导了一种基于六加速度计配置方式力学编排方程,分析了加速度计精度、杆臂长度以及时间等因素对角速度误差产生影响,最后仿真分析了加速度计精度对惯导系统的定位精度的影响,为系统设计提供理论依据。     

基于材料非线性的海洋柔性立管防弯器有限元分析

建立海洋柔性立管防弯器三维有限元模型,研究聚氨酯材料非线性对防弯器弯曲性能的影响．通过算例对比不同材料属性的计算结果,发现不考虑材料非线性的计算结果与理论分析结果吻合较好．试验结果表明考虑防弯器材料非线性的立管最大曲率比不考虑材料非线性的小10％．因此,在防弯器详细分析时很有必要考虑材料非线性．     

Cold Crystallization of PLLA Studied by Simultaneous SAXS and WAXS

Summary: The cold crystallization process of initially amorphous poly(L ‐lactic acid), PLLA, with two different molecular weights, during a heating at 2 °C/min, was investigated by DSC and time‐resolved simultaneous SAXS and WAXS, using synchrotron radiation. Equatorial scans of the isotropic 2D‐SAXS patterns showed that the average Bragg long period (L_B) of PLLA samples was approximately constant with the development of cold crystallization up to a temperature that corresponded to a melt/re‐crystallization process that took place before the nominal melting peak seen by DSC. L_B values were found to be higher for the high molecular weight material. This was in accordance with the higher melting temperature observed in the high molecular weight PLLA that implied the existence of thicker lamellae. WAXS results showed that the molecular weight did not apparently affect the crystal form and the final degree of crystallinity of PLLA. The Avrami parameters from WAXS and DSC were consistent, showing that the non‐isothermal cold crystallization of the two PLLA samples corresponded mainly to a three‐dimensional growth, although an imperfect crystallization process was involved at early times. The crystallization rate of PLLA, observed both by WAXS and DSC, decreased with increasing molecular weight.

SAXS profiles of PLLA2 as a function of temperature. The inset shows the 2D‐SAXS pattern obtained at 180 °C.