Mechanical properties and constitutive behaviors of as-cast 7050 aluminum alloy from room temperature to above the solidus temperature

The mechanical properties and constitutive behaviors of as-cast AA7050 in both the solid and semi-solid states were determined using the on-cooling and in situ solidification approaches, respectively. The results show that the strength in the solid state tends to increase with decreasing temperature. The strain rate plays an important role in the stress–strain behaviors at higher temperatures, whereas the influence becomes less pronounced and irregular when the temperature is less than 250°C. The experimental data were fitted to the extended Ludwik equation, which is suitable to describe the mechanical behavior of the materials in the as-cast state. In the semi-solid state, both the strength and ductility of the alloy are high near the solidus temperature and decrease drastically with decreasing solid fraction. As the solid fraction is less than 0.97, the maximum strength only slightly decreases, whereas the post-peak ductility begins to increase. The experimental data were fitted to the modified creep law, which is used to describe the mechanical behavior of semi-solid materials, to determine the equivalent parameter f_GBWL, i.e., the fraction of grain boundaries covered by liquid phase.     

钢管混凝土梁柱节点受剪承载力计算模型分析

为了研究钢管混凝土梁柱节点受剪承载力,对钢管混凝土梁柱节点的剪切破坏机理进行了深入的讨论,分别对核心区混凝土、钢管以及加强环对节点的抗剪贡献进行了分析,提出了考虑轴压力、柱端弯矩、梁端竖向剪力等因素的梁柱节点受剪承载力计算模型,通过实例验证了公式的合理性。     

Mechanism research on arsenic removal from arsenopyrite ore during a sintering process

The mechanism of arsenic removal during a sintering process was investigated through experiments with a sintering pot and arsenic-bearing iron ore containing arsenopyrite; the corresponding chemical properties of the sinter were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The experimental results revealed that the reaction of arsenic removal is mainly related to the oxygen atmosphere and temperature. During the sintering process, arsenic could be removed in the ignition layer, the sinter layer, and the combustion zone. A portion of FeAsS reacted with excess oxygen to generate FeAsO₄, and the rest of the FeAsS reacted with oxygen to generate As₂O₃(g) and SO₂(g). A portion of As₂O₃(g) mixed with Al₂O₃ or CaO, which resulted in the formation of arsenates such as AlAsO₄ and Ca₃(AsO₄)₂, leading to arsenic residues in sintering products. The FeAsS component in the blending ore was difficult to decompose in the preliminary heating zone, the dry zone, or the bottom layer because of the relatively low temperatures; however, As₂O₃(g) that originated from the high-temperature zone could react with metal oxides, resulting in the formation of arsenate residues.     

一类非线性泛函微分方程多个正周期解的存在性

用A Very-Henderson不动点定理考虑一类带有时滞的泛函微分方程多个正周期解的存在性问题,得到此类方程存在多个正周期解的充分条件,并获得了这些正周期解的一些性质。在现有研究的基础上,推广了此类泛函微分方程的形式,放宽了存在多个正周期解这一结论成立的条件,扩大了正周期解存在性证明的适用范围。     

基于Markov模型的松嫩平原西南部土地盐碱化预测研究

摘要：以松嫩平原西南部土地盐碱化典型区之一的吉林省大安市为研究对象,该区土地盐碱化的主要动态变化因子是草地、耕地、水域、林地与盐碱地之间的转化,采用时间尺度为12年的1989年和2001年两期遥感影像,结合野外调查、各种图件和文字资料,利用GIS软件人机交互式解译提取大安市盐碱地、草地、耕地、水域、林地信息,获取统计数据,并以此为基础利用马尔柯夫模型预测和分析大安市未来10年土地利用格局的演化。结果表明。在保持当前人为干扰条件不变的情况下,2010年该区盐碱化土地面积占上述5种土地利用类型总面积的比例将达到38．67％,2015年将达到40．75％,土地盐碱化严重。因此,这一问题不容忽视,必须采取有效措施,维护该区生态环境的健康发展。图2,表4,参12。     

基于深度学习的白光-热成像双通道图像识别系统设计

为解决无人机图像自动识别系统对大视场角下小目标的识别准确率及实时性问题,利用深度学习卷积神经网络对热成像-白光联合图像进行目标识别。设计了一种针对具有温度特征的目标物识别系统以及双通道目标候选提名图像识别算法。充分利用热成像图中目标热源特征的HSV值,将目标物从热成像图中进行筛选、分割。通过Canny算子勾勒目标物轮廓,并标记出目标物大致区域,导入白光图像提取含有目标物的有效图像信息。利用YOLO V2算法对候选图像内目标物进行识别。通过实验表明,提出的双通道目标候选提名图像识别算法具有可行性与实用性,能够在大视场环境下对小目标进行精准快速识别,满足无人机机载系统简易、实时和准确性要求。     

苦地丁抗炎,镇痛作用的实验研究

中药苦地丁粗粉混悬液及水煎液对大白鼠新鲜鸡蛋清所致的急性炎症（足跖肿胀法）和由二甲苯所致的急性炎症（小鼠耳廓炎症法）均有明显的抗炎作用。（Ｐ＜０．０１～０．０５）。并对小鼠热板法和冰醋酸所致的扭体实验有抑制作用（Ｐ＜０．０１～０．０５）。说明该药具有镇痛作用和抗炎症作用。     

胶体刻蚀技术简介及其应用探索

近年来,具有特殊功能的微观图案化表面引起了人们浓厚的研究兴趣,并被广泛应用于微反应器、生物传感器、微电子器件、光学器件以及生物界面等领域。在众多微观图案化表面的构筑方法中,胶体刻蚀技术备受人们关注。本文对胶体刻蚀技术的进展及其应用进行了综述,并对其发展趋势进行了展望。     

分布式流处理系统中基于位置感知的操作共享优化算法

针对流数据规模大、 基本数据处理操作有重叠等特点, 提出一种基于位置感知的操作共享优化算法. 假设操作预先分配了计算节点资源, 在保证流处理实时性和动态性的基础上, 利用多个流数据作业间拓扑结构和操作功能的相似性, 基于DAG图匹配方法建立操作共享备选集; 以输出带宽为约束条件, 建立一个操作共享收益优化
问题模型, 解决了流处理过程中传统操作共享方法对集群的输出带宽影响考虑不充分的问题. 仿真实验结果表明, 该方法较原有算法更充分地考虑了计算节点制约因素, 并提高了共享收益, 从而可有效地节省系统计算资源.     

新型拉伸电磁矢量传感器的两维高精度波达方向估计

较之传统的共点电磁矢量传感器,拉伸电磁矢量传感器能够显著降低阵元间互耦,且非共点结构在硬件设计上更易于实现。但是现有拉伸电磁矢量传感器无法实现阵列的两维孔径扩展,导致了两维波达方向估计精度较差。针对此问题,提出一种新型的拉伸电磁矢量传感器。该阵列结构由单个拉伸电磁矢量传感器和单个电偶极子组成。利用单个拉伸电磁矢量传感器提供一维孔径扩展,再利用垂直于该拉伸电磁矢量传感器的单个电偶极子实现另一维的孔径扩展。针对该两维孔径扩展阵列,提出一种矢量叉积算法与相位干涉法相结合的算法来获取两维波达方向的高精度估计。所提阵列在降低互耦的同时,利用电磁矢量传感器提供的极化分集与两维孔径扩展带来的空间分集,使得两维波达方向估计精度大大提高。