基于改进DeepLabV3+的铣床碎屑图像分割方法

针对铣床碎屑形状不规则导致图像分割中碎屑轮廓不清晰、分割精度低的问题,本文提出一种改进的DeepLabV3+铣床碎屑分割算法。首先在DeepLabV3+的Xcepetion模块中嵌入通道与空间注意力机制(convolutional block attention module, CBAM)模型,优化通道的权重和位置信息,加强碎屑图像区域的特征学习;其次将DeepLabV3+的空洞空间卷积池化金字塔(atrous spatial pyramid pooling, ASPP)模块改为密集连接(dense conolutional network, DenseNet)方式,增大碎屑图像特征点的感受野,提升铣床碎屑图像特征的复用效率;最后在解码过程中采用多尺度自适应特征融合方法,聚合多尺度特征作为解码器的输入特征,提高碎屑图像分割的精度与鲁棒性。实验结果表明,本文算法优于其他分割算法,改进后算法相比DeepLabV3+,像素准确率提高0.026,平均交并比(mean intersection over union,MIOU)提高0.020,F₁值提高了0.013。     

基于深度学习的智能问答系统综述

在科技发达和信息爆炸的时代,如何从海量数据中准确地提取所需信息已成为人们研究的目标.问答系统作为解决此问题的重要途径之一,其主要通过对已有数据信息进行检索和分析,并最终返回问题答案或其他相关信息.近年来,深度学习的革命性发展给问答系统带来了长足的进步,序列到序列的模型,端到端的模型以及最近流行的预训练,都给问答系统留下无限的发展空间,但其仍面临许多挑战.本文首先对问答系统的发展进行简要介绍,接着将问答系统按照3个不同角度进行分类,并对相关数据集、评测指标和各类问答系统的主流技术进行阐述,最后对问答系统面临的问题和未来的发展趋势进行讨论.     

无线通信网络在智能灌溉系统中的应用

农业是一个国家经济发展的命脉,节水灌溉则在农业发展中具有非常重要的作用,特别是对于我国这样的农业大国而言,更是如此。当前,随着我国农业用水量越来越多,而水资源利用率不高等问题的出现,采用先进技术提高农业生产效率就成了迫在眉睫的重要问题。而随着无线通信网络的产生,基于无线通信网络的智能灌溉系统,不仅可以有效提升水资源的利用率,还可以让水资源短缺的问题得到一定程度的缓解,促进农作物产量和质量的提高,降低种植成本,极大地促进了灌溉的有效性与准确性。为此,对无线通信网络在智能灌溉系统中的应用问题进行探究,具有重要的意义和价值。基于此,文中首先对当前智能灌溉系统中无线通信网络技术的应用进行了介绍,之后分别从总体目的、具体目标、基于无线通信技术的智能灌溉系统的总体功能结构、基于无线通信技术的智能灌溉系统设计等方面,阐述了基于无线通信技术在智能灌溉系统中的应用。     

用于测厚和裂纹检测的正交横波电磁超声换能器仿真分析及实验研究

垂直入射的横波在测厚时具有较高的灵敏度,但检测裂纹常需采用斜入射方式,单个换能器无法同时进行这两种检测。该文设计了一种正交横波电磁超声换能器（EMAT）,通过两个蝶形线圈在铝板中激发正交偏振的横波,提出在脉冲回波模式下利用两个线圈接收信号的声时信息和幅值差,同时进行测厚、检测裂纹并确定裂纹方向的方法。建立正交偏振EMAT三维有限元模型,对横波声场与裂纹缺陷的相互作用进行仿真,研究线圈间距、裂纹尺寸对正交声场和信号幅值差的影响。仿真和实验结果表明：正交横波EMAT通过一次检测可以同时实现测厚、裂纹检出及裂纹方向定位,为腐蚀减薄和裂纹等缺陷的在线检测提供了新方法。     

Stress dependence of the creep behaviors and mechanisms of a third-generation Ni-based single crystal superalloy

Elevated temperature creep behaviors at 1100℃ over a wide stress regime of 120–174 MPa of a thirdgeneration Ni-based single crystal superalloy were studied. With a reduced stress from 174 to 120 MPa,the creep life increased by a factor of 10.5, from 87 h to 907 h, presenting a strong stress dependence.A splitting phenomenon of the close-(about 100 nm) and sparse-(above 120 nm) spaced dislocation networks became more obvious with increasing stress. Simultaneously, a_0010 superdislocations with low mobilities were frequently observed under a lower stress to pass through γ'precipitates by a combined slip and climb of two a_0110 superpartials or pure climb. However, a_0110 superdislocations with higher mobility were widely found under a higher stress, which directly sheared into γ'precipitates.Based on the calculated critical resolved shear stresses for various creep mechanisms, the favorable creep mechanism was systematically analyzed. Furthermore, combined with the microstructural evolutions during different creep stages, the dominant creep mechanism changed from the dislocation climbing to Orowan looping and precipitates shearing under a stress regime of 137–174 MPa, while the dislocation climbing mechanism was operative throughout the whole creep stage under a stress of 120 MPa, resulting a superior creep performance.     

Inhibition of G protein-coupled receptor kinase subtypes by Ca2+/calmodulin

G protein-coupled receptor kinases (GRKs) are implicated in the homologous desensitization of G protein-coupled receptors. Six GRK subtypes have so far been identified, named GRK1 to GRK6. The functional state of the GRKs can be actively regulated in different ways. In particular, it was found that retinal rhodopsin kinase (GRK1), but not the ubiquitous betaARK1 (GRK2), can be inhibited by the photoreceptor-specific Ca2+-binding protein recoverin through direct binding. The present study was aimed to investigate regulation of other GRKs by alternative Ca2+-binding proteins such as calmodulin (CaM). We found that Gbetagamma-activated GRK2 and GRK3 were inhibited by CaM to similar extents (IC50 approximately 2 microM), while a 50-fold more potent inhibitory effect was observed on GRK5 (IC50 = 40 nM). Inhibition by CaM was strictly dependent on Ca2+ and was prevented by the CaM inhibitor CaMBd. Since Gbetagamma, which is a binding target of Ca2+/CaM, is critical for the activation of GRK2 and GRK3, it provides a possible site of interaction between these proteins. However, since GRK5 is Gbetagamma-independent, an alternative mechanism is conceivable. A direct interaction between GRK5 and Ca2+/CaM was revealed using CaM-conjugated Sepharose 4B. This binding does not influence the catalytic activity as demonstrated using the soluble GRK substrate casein. Instead, Ca2+/CaM significantly reduced GRK5 binding to the membrane. The mechanism of GRK5 inhibition appeared to be through direct binding to Ca2+/CaM, resulting in inhibition of membrane association and hence receptor phosphorylation. The present study provides the first evidence for a regulatory effect of Ca2+/CaM on some GRK subtypes, thus expanding the range of different mechanisms regulating the functional states of these kinases.     

视线追踪系统中视线估计方法研究

文中提出一种基于瞳孔—角膜反射(PCCR)的视线估计方法(GEMHSSO).针对现有PCCR存在的主要问题:限制使用者头部运动和个体标定问题,提出了一种单相机单光源条件下头部位置的补偿方法,实现了头部位置变化对瞳孔角膜向量影响的解析补偿,并建立一种个体差异的转化模型,进而简化标定过程为单点标定.以此为基础形成一种新的视线估计方法,本方法使精确视线估计的最小硬件要求降低到单相机(未标定)单光源,既不需要繁杂的系统标定,又实现了自然头动视线估计,并且简化用户标定为单点标定.该方法的各个环节都满足实时性要求,为面向人机交互的视线追踪系统提供了有效的解决方案.     

基于STC单片机的机场车辆超速报警系统

采用STC89C52单片机结合LM2596-5.0开关电压调节器、DS12C887时钟芯片、AT24C64串行存储器、74HC595移位寄存器以及接触式IC卡等器件,实现了对机场车辆速度的实时显示以及超速后的自行报警,并将超速情况以数据的形式存储到存储器中,可用IC卡对数据进行读取.该系统通过超速报警来提醒司机减速,从而减少车辆刮碰飞机等事件的发生.