Highly active sites of low spin FeⅡN4species:The identification and the ORR performance

Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe₃C/C and Fe₂N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH₄/H₂and pure NH₃,respectively.By acid leaching of Fe₂N/C sample,only single sites of FeN₄species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN₄in ORR.A correlation was conducted between the concentration of Fe^ⅡN₄in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin Fe^ⅡN₄ species as highly active sites for the ORR.     

microRNA在亨廷顿病中的研究进展

亨廷顿病(Huntington's disease, HD)是神经退行性疾病(neurodegenerative disorders)中一种单基因遗传病,由亨廷顿基因(the huntingtin gene, HTT)第一个外显子中的CAG三核苷酸序列重复扩增引起,尚无法治愈。HTT编码的蛋白产物被称为亨廷顿蛋白(Huntingtin protein, Htt)。突变亨廷顿蛋白(mutated huntingtin protein, mHtt)容易形成聚集体,具有毒性,导致一系列细胞学异常和神经元功能障碍。microRNA(miRNA)在基因转录后水平调控中起重要作用,其表达的改变与HD病理过程有关,成为治疗HD的潜在生物标志物。近年来,对一些特定miRNA在HD中调控机制及靶基因预测方面的研究可为HD提供潜在的治疗方法。本文就miRNA在HD中的相关研究进展进行综述。     

Na+掺杂对LiNi1/3Co1/3Mn1/3O2结构和电化学性质的影响

采用高温固相法成功制备了不同Na+掺杂浓度的Li_1-xNa_xNi_1/3Co_1/3Mn_1/3O₂锂离子电池正极材料,探究了Na元素掺杂对层状氧化物正极材料结构以及电化学性能的影响。通过X射线粉末衍射仪和扫描电子显微镜表征了材料的结构和形貌,结果表明,当x≤0.3时,样品不会出现其它杂相;当x＞0.3时,样品中会出现NaNi_1/3Co_1/3Mn_1/3O₂的杂相。同时随着掺杂浓度的增加,样品的阳离子混排度逐渐增加。电化学性能结果表明,少量Na+的掺入可以提高LiNi_1/3Co_1/3Mn_1/3O₂在0.2C,0.5C下的放电比容量并增强其循环稳定性,但会损坏材料的倍率性能。     

遮挡人脸表情图像预处理研究进展

对遮挡表情图像的传统预处理、基于重要区域的预处理、基于图像重构和基于深度学习的预处理方法进行总结,阐述了各类方法的基本原理,介绍了常用的表情数据集及其特点,讨论了现阶段存在的问题和未来的研究方向.     

LFSCA-UNet：基于空间与通道注意力机制的肝纤维化区域分割网络

目的 肝纤维化是众多慢性肝脏疾病的常见表现,如不及时治疗可发展为肝硬化甚至引发肝癌。肝纤维化的准确评估对临床治疗和预后评估等至关重要。目前,肝纤维化的诊断通过肝穿活检判断,有创且有并发症危险。为此,基于影像学的无创诊断方法越来越受到关注。本文提出一种基于通道注意力与空间注意力机制改进的用于肝纤维化区域的自动化分割U-Net （liver fibrosis region segmentation network based on spatial and channel attention mechanisms,LFSCA-UNet）。方法 依据Attention U-Net的改进方式,围绕U-Net的跳跃连接结构进行基于注意力的改进,在AG （attention gate）的基础上,加入以ECA （efficient channel attention）模块为实现方式的通道注意力机制,依据加入ECA的位置,LFSCA-UNet分为A、B、C共3个子型。结果 在肝数据集上与其他实验网络进行评估对比,本文提出的LFSCA-UNet网络结构平均Dice系数达到了93.33%,相比原始U-Net的Dice系数提高了0.539 6%。结论 本文方法将空间注意力机制与通道注意力机制进行结合,有效提高了肝纤维化区域的分割精度,对空间注意力模块使用通道注意力模块优化输入和输出,增加了网络的稳定性,提升了网络的整体效果。     

基于BIM技术的装配式建筑设计阶段协同度评估

为评估BIM技术对装配式建筑设计阶段协同能力的影响程度,基于协同论序参量原理,把软件协同、专业协同作为协同度测度模型的一级指标,在一级指标下选取22个序参量分量指标构建协同度模型。结合具体案例,以装配式建筑设计阶段为研究对象,运用专家打分法将测量指标进行更明确的量化,并借助功效函数对构建的指标体系的协同能力进行评估计算。结果表明：由于BIM软件之间数据共享与转换格式的不统一,仍出现了信息丢失、传递效率低的现象;专业协同与理想状态有一定的差距,BIM技术有待完善。     

Novel recognition method for digital modulation signals with Alpha stable noise

The traditional methods for digital modulation signals recognition with Alpha stable distribution noise have the problem of poor performance. In this paper, a novel recognition method for digital modulation signals based on the generalized cumulant and generalized instantaneous phase is proposed to solve this problem. This method extracts the characteristic parameters which are the generalized cumulant and maximum of normalization and center generalized instantaneous phase spectral density based on fractional Fourier transform. And then the minimum mean square error classifier and the threshold are used to achieve modulation recognition of digital modulation signals with Alpha stable distribution noise. Simulation results show that the proposed method has not only better performance but also lower computation complexity than the traditional recognition methods in an Alpha stable distribution noise environment.     

SiC（Cu）／Fe复合材料制备工艺研究

采用非均相沉淀法制得Cu包裹SiC复合粉体，利用粉末冶金和常压烧结制备SiC（Cu）／Fe复合材料。利用Zeta电位仪、XRD，EDS以及SEM等手段对包裹粉体和烧结样品进行了分析。结果表明，采用非均相沉淀法可以得到Cu／SiC复合粉体。包裹后的粉体与原始SiC粉体的表面电位不同，达到了对SiC颗粒表面改性的目的。Cu作为过渡层改善了SiC／Fe的界面相容性，在1050℃烧结的样品只有微量的FeSi或Fe2Si生成，界面反应得到有效控制，获得化学结合的界面，温度过低不能烧结致密，温度过高出现大量缺陷。     

16MnR低合金钢板对接立焊单面焊双面成形工艺与探索

阐述了16MnR低合金钢板-板对接立焊单面焊双面成形的打底焊、填充焊、盖面焊的工艺过程及操作要领.重点讨论了提高单面焊双面成形打底焊质量的措施;强调了焊条伸入坡口的相对深度对打底焊、填充焊和盖面焊焊缝高度的重要影响.     

Comparison of two scaling approaches for the development of biomechanical multi-body human models

Dimensional scaling approaches are widely used to develop multi-body human models in injury biomechanics research. Given the limited experimental data for any particular anthropometry, a validated model can be scaled to different sizes to reflect the biological variance of population and used to characterize the human response. This paper compares two scaling approaches at the whole-body level: one is the conventional mass-based scaling approach which assumes geometric similarity; the other is the structure-based approach which assumes additional structural similarity by using idealized mechanical models to account for the specific anatomy and expected loading conditions. Given the use of exterior body dimensions and a uniform Young’s modulus, the two approaches showed close values of the scaling factors for most body regions, with 1.5 % difference on force scaling factors and 13.5 % difference on moment scaling factors, on average. One exception was on the thoracic modeling, with 19.3 % difference on the scaling factor of the deflection. Two 6-year-old child models were generated from a baseline adult model as application example and were evaluated using recent biomechanical data from cadaveric pediatric experiments. The scaled models predicted similar impact responses of the thorax and lower extremity, which were within the experimental corridors; and suggested further consideration of age-specific structural change of the pelvis. Towards improved scaling methods to develop biofidelic human models, this comparative analysis suggests further investigation on interior anatomical geometry and detailed biological material properties associated with the demographic range of the population.