基于自适应直角网格的二维全速势方程有限体积解法A finite volume method for 2D Full-Potential equation on adaptive Cartesian grids

为满足亚声速和跨声速飞机概念设计中快速气动计算的需求,研究和发展一种基于自适应直角网格的非线性全速势方程有限体积解法。要点如下。（1）在几何自适应直角网格的基础上,使用结合单元融合的网格切割算法处理物面边界,提出一种修正非贴体切割网格的方法。（2）采用隐式格式结合GM RES算法求解该非线性位流方程,针对流场的自适应来捕捉激波。（3）采用镜像法处理物面边界处的无穿透条件,并提出解析的方法来修正镜像单元的值。（4）针对直角网格的特点,提出在库塔线上插入库塔单元的方法施加库塔条件。NACA0012翼型绕流的算例结果表明,该方法用于亚声速和跨声速气动计算能得到令人满意的结果,且自动化程度高、收敛速度快。     

侵彻引信炸点精确控制技术

为了实现侵彻弹药的高效毁伤,硬目标侵彻引信必须完成最佳炸点识别和起爆控制任务。对比研究了两类炸点精确控制方案:一类是基于侵彻深度经验公式,另一类是基于侵彻引信记录装置中的高g值加速度计测量信息。前者的精度完全依赖于先验信息,而后者的精度则取决于冲击加速度的精确测量和控制算法的实时解算。给出了基于伪自相关的空穴识别算法。冲击加速度信号自乘实现调频脉冲压缩,再通过低通滤波即可提取出平滑的侵彻信号包络线。进一步,详细推导了实时计算侵彻深度的积分算法。利用数学仿真的侵彻两层钢靶和实测的侵彻五层混凝土靶冲击加速度进行了算法验证。空穴识别算法能够准确识别出侵彻介质的层数,而冲击加速度的双积分与弹体实际位移保持一致,相对误差约3%。     

蜂窝遮弹层抗弹丸侵彻实验研究

为研究蜂窝遮弹层的抗弹丸侵彻性能,采用15 mm弹体对六边形单元蜂窝遮弹层结构进行了侵彻实验研究。实验结果表明,同钢筋混凝土遮弹层相比,蜂窝遮弹层的破坏仅发生在弹靶接触的六边形单元内,且破坏面积较小,同时弹体在侵彻蜂窝遮弹层过程中易发生偏航现象。应用应力波传播理论分析了实验结果,主要是六边形单元对其内的混凝土约束作用及其自身阻隔作用,使混凝土抗压强度和弹体在侵彻过程中受到的阻力增大,从而减小了弹体的破坏效应。     

复合材料层合板单搭胶接力学性能检测技术与分析

胶接工艺缺陷对单搭胶接接头的拉伸剪切性能有着重要的影响。为了研究不同单搭接胶接层厚度对不同材质复合材料层合板胶接性能的影响规律,通过喷水穿透法超声C扫描对试样的剪切区域进行无损检测,并分别采用1mm、2mm、4mm的胶层厚度,以碳纤维/玻璃纤维复合材料层合板为被粘物,进行单搭胶接拉伸剪切性能试验。检测及试验结果表明:当胶层厚度h1mm时,对于相同材料的被粘物,胶层厚度越大,试件胶接接头剪切强度越小;相同的粘接剂厚度,以碳纤维增强复合材料板为被粘物的试件胶接接头剪切强度大于以玻纤增强复合材料板为被粘物的试件胶接接头强度;胶粘剂与碳纤维被粘物表面的润湿效果要优于胶粘剂与玻纤被粘物表面的润湿效果。     

Bearing splitting and near-surface source ranging in the direct zone of deep water

Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a bearing-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz–360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The bearing-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally,the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.     

Application of a Low Transition Temperature Mixture for the Dispersive Liquid–Liquid Microextraction of Illicit Drugs from Urine Samples

The use of psychoactive substances is a serious problem in today’s society and reliable methods of analysis are necessary to confirm their occurrence in biological matrices. In this work, a green sample preparation technique prior to HPLC-MS analysis was successfully applied to the extraction of 14 illicit drugs from urine samples. The isolation procedure was a dispersive liquid–liquid microextraction based on the use of a low transition temperature mixture (LTTM), composed of choline chloride and sesamol in a molar ratio 1:3 as the extracting solvent. This mixture was classified as LTTM after a thorough investigation carried out by FTIR and DSC, which recorded a glass transition temperature at −71 °C. The extraction procedure was optimized and validated according to the main Food and Drug Administration (FDA) guidelines for bioanalytical methods, obtaining good figures of merit for all parameters: the estimated lower limit of quantitation (LLOQ) values were between 0.01 µg L⁻¹ (bk-MMBDB) and 0.37 µg L⁻¹ (PMA); recoveries, evaluated at very low spike levels (in the ng-µg L⁻¹ range), spanned from 55% (MBDB) to 100% (bk-MMBDB and MDPV); finally, both within-run and between-run precisions were lower than 20% (LLOQ) and 15% (10xLLOQ).     

融合抽象层级变换和卷积神经网络的手绘图像检索方法

针对人工设计的描述子（HOG、SIFT等）在基于手绘的图像检索（Sketch Based Image Retrieval,SBIR）领域的局限性,提出了一种融合抽象层级变换和卷积神经网络构建联合深度特征描述子的手绘图像检索方法.首先,提取常规图像的边缘概率图,在此基础上进行不同抽象层级的图像变换,将抽象层级变换图像输入到深度神经网络并提取不同隐层的输出向量,最后,联合不同隐层的输出向量作为手绘图像检索的特征描述子（即联合深度特征描述子）.在Flickr15k数据库上对本方法进行了实验验证,结果表明：融合抽象层级变换和联合深度特征描述子的检索效果相较HOG、SIFT等传统方法有显著提高.本方法从图像预处理和特征描述子构建2个方面,对SBIR问题进行了改进,具有更高的准确率.     

基于4MAT系统开发促进知识深层理解的学习策略

基于4MAT系统开发了组织策略、模式再认策略和系列动作学习策略,为教师帮助不同学习风格的学生提供参考,当把这些学习策略应用于课堂时,可以促进学生对知识的深层理解。     

离子热法合成磷酸盐微孔材料研究进展

离子液体具有传统溶剂无法取代的优良性能,其在制备无机微孔材料等领域显示出广阔的应用前景.近年来,采用离子液体或低共熔混合物作为反应溶剂的离子热合成发展迅猛.本文对离子液体进行了较系统的介绍,就离子热法合成磷酸铝、金属取代磷酸铝、过渡金属磷酸盐微孔材料的研究进展进行了综述,并对离子热法合成其他微孔材料及离子热合成面临的挑战做出了展望.     

聚碳酸酯弹丸穿甲实验与数值模拟

利用空气炮为加载设备,开展了不同头部形状聚碳酸酯弹丸的穿甲实验,获得了弹体穿甲时靶板 的变形时间历程曲线及弹靶相互作用时间,观察到不同弹体在穿甲过程中产生的断裂、内部损伤及头部塑性 变形等失效特征。采用光塑性方法,分析了截锥型聚碳酸酯弹丸穿甲后的变形特征,通过用户子程序将DSGZ 模型引入商用有限元程序,对截锥型聚碳酸酯弹丸的穿甲过程进行了数值模拟,获得了不同时刻聚碳酸 酯弹丸应力分布及靶板的变形特征,模拟结果与实验结果吻合较好。