Effects of Bed Load Movement on Mean Flow Characteristics in Mobile Gravel Beds

The effects of bed-load movement on mean flow characteristics were experimentally investigated using particle image velocimetry (PIV). The gravel beds associated with open-channel flow are hydraulically rough, and two types of grain with different median diameters were used. The flow field and bed load motion images were simultaneously obtained via the particular experimental setup. The mass of sediment particles instantaneously moving on the bed, i.e., the sand-wave, was observed in the experiment. It was found that the sand-waves have an average friction angle of 11.2° and heights ranging from 2.2 d ₅₀ to 3.8 d ₅₀. The mean velocity profiles on the mobile bed can also be represented with logarithmic distribution with deviations occurred in the near wall region. Based on the Schultz–Grunow formula, a modified equation is developed in this study to better express the flow resistance factor in terms of the Reynolds number and the ratio of flow depth to roughness height.     

换装行人重识别研究进展

行人重识别旨在建立目标行人在多个无交叉覆盖监控区域间的身份联系,在智慧城市、司法侦查和监控安全等领域具有重要应用价值。传统行人重识别方法针对短时间跨度场景,依赖行人外观特征的稳定不变性,旨在克服光照差异、视角变化和物体遮挡等挑战。与之不同,换装行人重识别针对长时间跨度场景,除受限于上述挑战还面临换装带来的外观变化问题,是近几年的一个研究难点和热点。围绕换装行人重识别,本文从数据集和解决方法两个方面综述国内外研究进展,探讨面临的挑战和难点。首先,梳理并比较了当前针对换装行人重识别的数据集,从采集方式、行人及样本数量等方面分析其挑战性和面临的局限性。然后,在简单回顾换装行人重识别发展历史的基础上,将其归纳为基于非视觉传感器的方法和基于视觉相机的方法两类。针对基于非视觉传感器的方法,介绍了深度传感器、射频信号等在换装行人重识别中的应用。针对基于视觉相机的方法,详细阐述了基于显式特征设计与提取的方法、基于特征解耦的方法和基于隐式数据驱动自适应学习的方法。在此基础上,探讨了当前换装行人重识别面临的问题并展望未来的发展趋势,旨在为相关研究提供参考。     

N,N,N'''',N''''-四丁基-3-氧-戊二酰胺辐解机理的研究

计算了N，N，N’，N’-四丁基-3-氧-戊二酰胺（N，N，N’，N’-tetrabutyl-3-oxa-pentanediamide，TBOPDA）中各个原子的电荷分布，根据电荷分布情况讨论了TBOPDA中有关化学键的相对稳定性和可能断裂几率，认为TBOPDA中化学键的辐照稳定程度为C-O〈C-H〈C-N〈C-C。理论推测的结果与相关辐解产物的产额顺序基本一致。     

N，N-二乙基羟胺与Np(Ⅵ)氧化还原反应动力学研究

研究了ＮＨＯ３介质中，Ｎ，Ｎ－二乙基羟胺还原Ｎｐ（Ⅵ）的动力学性能和行为。通过考究还原剂浓度和酸度等条件对Ｎｐ（Ⅵ）动力学过程的影响，确定了反应的动力学速率主程为－ｄｃ（Ｎｐ（     

Y形铁氧体波导锁式开关设计

本文用保角变换和变分法相结合,算出Y形退磁铁氧体结的谐振频率,还算出开关各部分的阻抗变化。这些计算都为x,Ka波段的开关所证实。     

1,1—二甲基肼应用于U,Np分离的研究

应用１，１－二甲基肼进行了Ｕ，Ｎｐ分离的单级实验和模拟ＰＵＲＥＸ流程１Ａ槽工艺的串级试验，实验结果表明，降低酸度，提高还原剂１，１－二甲肼浓度，延长还原时间，有利于抑制水相中Ｎｐ的萃取，也有利于从含Ｕ，Ｎｐ的３０％ＴＢＰ－煤油溶液中还原洗涤Ｎｐ。在８级萃取，６级洗涤的１Ａ槽中级试验中，β（Ｎｐ／Ｕ）可达４．６×１０＾４。     

650t/h桥式卸船机卷筒装置故障分析及其改进措施

综合分析了我单位650t/h桥式卸船机起升开闭减速机卷筒装置的结构特点,对出现的一些故障进行分析研究。采用新型联轴器,同时改进卷筒结构,并规范操作技能和加强点检定修等措施来提高卷筒装置的安全可靠性。     

Experimental study on flow behavior at open channel confluences

Channel confluences are common in natural rivers and hydraulic engineering, and the flow behavior at confluences becomes very complex because of the interaction between the tributary and the main river. In this study, the experiments were performed in a combined flume with a 30° angle between the main and tributary flume located at Sichuan University. The velocity was measured by using a three-component acoustic Doppler velocimeter (ADV) over a grid defined throughout the junction region. Based on the analysis of the velocity at the confluence, the distinctive characteristics of a channel confluence flow may be divided into several zones including a zone of separation immediately downstream of the junction branch channel, the maximum and minimum velocity regions at the upstream and downstream in the confluent channel, and a shear plane developed between the two combining flows downstream of the confluent channel. In addition, secondary circulations in different directions at the higher and lower velocity zones are observed as well. Translated from Journal of Sichuan University (Engineering Science Edition), 2006, 38(2): 1–5 [译自: 四川大学学报 (工程科学版)]     

平面波在任意磁化方向旋磁媒质中传播时的极化特性

在铁氧体基片平面电路和发射天线中必须研究平面波在任意磁化方向旋磁媒质中的传播。这时平面波的特征波为ＴＥ波,其磁通密度、磁场、电通密度、电场的极化是不相同的,磁场的极化方向为左、右椭圆极化。     

线性插值框架下矩阵步态识别的性能分析

针对现有的步态周期检测方法检测效果不佳以及行走速度变化对步态识别性能有很大影响的问题,提出的基于矩的步态周期检测方法中,Zernike矩需要人体居中、尺度归一的前期预处理过程,而伪Zernike矩具有能描述运动图像的特点,它可以避免人体居中、尺度归一等处理,以便直接测试步态的周期性.根据行走时的两帧之间的特征取决于前一帧和后一帧的特征,提出了基于线性插值的矩阵步态识别算法框架,并且将投影特征、Hough变换特征、Trace变换特征和Fan-Beam映射特征应用在CASIA(B)步态库上,验证了框架的有效性,为解决步态识别问题带来新的方法与思路.这种基于线性插值的矩阵步态识别特征本质上是一种权值不同的能量形式.