Direct synthesis of electrorheological suspension containing salt of poly(methacrylic acid) and its electrorheological effect

Colloidal suspensions containing salts of poly(methacrylic acid) which exhibit high electrorheological (ER) activity were synthesized by inverse emulsion polymerization. Factors influencing the ER effect were studied. The results showed that maximum yield stress occurred at optimum amounts of both polymeric stabilizer and crosslinking agent used in the inverse emulsion polymerization as well as a certain water content of the particles, while yield stress increased with electric field strength, average diameter of the particles below 0.9 μm, or the molar ratio of the salt to the acid. The ER activity for the suspensions containing different monovalent counter ions decreased in the following order: Li⁺ > Na⁺ > K⁺ > NH₄⁺. The phenomena were discussed with the ionic polarization mechanism. © 1995 John Wiley & Sons, Inc.     

接受理论视角下的儿童文学翻译

接受理论的基本观点对儿童文学翻译研究也具有一定的启发和借鉴作用:译者在翻译的过程中不仅要尊重原文和原作者.也要尊重译文的目标语读者--儿童,充分考虑儿童读者的期待视野,从而实现原文与译者期待视野、译文与儿童读者期待视野之间的视野融合.     

Facile synthesis of uniform hollow hematite sub-micro spheres with controllable shell thickness

A simple method was developed to prepare the uniform hematite hollow submicro-spheres with controllable structure and different diameter based on monodisperse poly(styrene-co-acrylic acid) [P(St-co-AA)] particles. The structure and formation mechanism of the hollow spheres were investigated in detail. The control mechanism of shell thickness was also discussed. The results indicated that the shell thickness and coarseness of the synthesized core-shell hematite hollow spheres could be tuned simply by the surface carboxyl content of the P(St-co-AA) particles. This method provided a new approach for the structure control in the preparation of hollow spheres. A Brunauer-Emmett-Teller (BET) test shows that the prepared hollow spheres have large surface areas which were decreased along with the increase of the diameter. The magnetic properties of the as-obtained hematite hollow spheres were investigated. The result showed that the coercivity and saturated magnetization were increased along with the increase of the shell thickness, and the remanent magnetization was increased along with the decrease of the diameter.     

短纤维/弹性体复合材料的研究 Ⅲ涤纶短纤维与再生胶/聚乙烯复合材料研究

本工作探索了再生胶/高密度聚乙烯硫化共混体(RTPV)与涤纶短纤维(SF)复合材料(SFRTPV)的制备与性能,讨论了制取该复合材料的密炼法动态硫化工艺(D)和开炼法静态硫化工艺(S),SF与RTPV的增粘体系和效果,SF组份作用及SF—RTPV的挤出加工性能。     

基于高精度流线生成的交互流场可视化

高效准确的流线绘制一直是流场可视化的重要研究内容,流线可以对流场的重要特征进行有效的稀疏表示,但流线需要长期的粒子追踪过程及大量的积分计算,在面向大规模流场可视化时时间效率较低,需要高性能计算设备进行辅助计算.本文通过设计一种基于深度学习的高精度流线生成算法,将初始的低精度流线快速映射为稠密的高精度流线,可以在较短的时间内快速生成可靠的流线可视化结果,并在此基础上设计了交互式实时流场可视化系统,涵盖了流场的特征检测,属性关联分析,信息论分析等,帮助用户快速了解流场数据,找到自己感兴趣的区域进行后续进一步深度分析,避免了获取过多冗余数据,同时优化了分析工作的效率,满足用户对于流场结构,特征属性等多维度进行关联分析的需求.     

基于多季相Sentinel-2影像的白洋淀湿地信息提取

白洋淀湿地是华北平原上重要的浅水湖泊湿地,对雄安新区绿色发展具有重要的生态价值。对白洋淀高度异质化的景观格局进行分类,能够为白洋淀湿地资源的遥感监测提供指导意义。针对湿地季节变化的特点,对白洋淀每个季节选取一期具有代表性的Sentinel-2影像,采用分类与回归树（CART）、支持向量机（SVM）、随机森林（RF）3种常用的机器学习分类器对15种季相组合实验方案进行分类,分析不同季相遥感影像及其组合对白洋淀湿地信息提取的优劣。结果表明：相较于使用单一季相影像分类,多季相影像的组合能够显著提高分类精度,春&夏季相组合能够得到最优的分类效果,相对单季影像总体分类精度提高了10.9%~25.5%,Kappa系数提高了0.09~0.29;SVM分类器的分类表现较为稳定,能够得到最高的平均分类精度,CART分类器在处理高维特征的能力不如随机森林和SVM;不同特征类型对湿地信息提取的贡献度从高到底依次是红边光谱特征、传统光谱特征、缨帽变换特征、主成分分析特征、纹理特征。实验成果能为湿地信息的遥感识别提供依据。     

面向隐私保护联邦学习的医学影像目标检测算法

联邦学习技术是一种新型多机构协同训练模型范式,广泛应用于多领域,其中模型参数隐私保护是一个关键问题.针对CT影像综合性病灶检测任务,提出隐私保护的联邦学习算法.首先部署松散耦合的客户端-服务器架构;其次在各客户端使用改进的RetinaNet检测器,引入上下文卷积和后向注意力机制;最后完成联邦训练.各客户端使用局部更新策略,采用自适应训练周期,局部目标函数中加入了限制项;服务器使用自适应梯度裁剪策略和高斯噪声差分隐私算法更新全局模型参数.在DeepLesion数据集上的消融分析说明了算法各部分的重要性.实验结果表明,改进的RetinaNet检测器有效地提升了多尺度病灶的检测精度.与集中数据训练模型范式相比,联邦学习所得模型性能略低(mAP分别为75.33％和72.80％),但训练用时缩短近38％,有效地实现了隐私保护、通信效率和模型性能的良好权衡.     

Machine-learning-aided precise prediction of deletions with next-generation sequencing

When detecting deletions in complex human genomes,split-read approaches using short reads generated with next-generation sequencing still face the challenge that either false discovery rate is high,or sensitivity is low.To address the problem,an integrated strategy is proposed.It organically combines the fundamental theories of the three mainstream methods(read-pair approaches,split-read technologies and read-depth analysis) with modern machine learning algorithms,using the recipe of feature extraction as a bridge.Compared with the state-of-art split-read methods for deletion detection in both low and high sequence coverage,the machine-learning-aided strategy shows great ability in intelligently balancing sensitivity and false discovery rate and getting a both more sensitive and more precise call set at single-base-pair resolution.Thus,users do not need to rely on former experience to make an unnecessary trade-off beforehand and adjust parameters over and over again any more.It should be noted that modern machine learning models can play an important role in the field of structural variation prediction.     

基于Pushover方法的大跨度悬挑钢梁结构的弹塑性分析

本文以某实际工程为例,采用静力弹塑性分析方法,通过SAP2000进行Pushover分析,研究大跨度悬挑梁在地震作用下的结构抗震性能。通过在多遇和罕遇地震荷载作用下对结构的顶点位移、层间位移角以及塑性铰发展过程的研究,分析其抗震性能。同时研究不同悬挑长度对结构抗震性能的影响规律并提出相应的加固措施,可为今后类似结构的设计与抗震分析提供参考。     

Microstructure and properties of cement foams prepared by magnesium oxychloride cement

Microstructural features including pore size distribution, cell walls and phase compositions of magnesium oxychloride cement foams (MOCF) with various MgO powders and water mixture ratios were studied. Their influences on compressive strength, water absorption and resistance of MOCF were also discussed in detail. The experimental results indicated that moderate and slight excess MgO powders (MgO/MgCl₂ molar ratios from 5.1 to 7) were beneficial to the formation of excellent microstructure of MOCF, but increasing water contents (H₂O/MgO mass ratios from 0.9 to 1.29) might result in opposite conclusions. The microstructure of MOCF produced with moderate and slight excess MgO powders could enhance the compressive strength, while serious excess MgO powders addition (MgO/MgCl₂ molar ratios = 9) would destroy the cell wall structures, and therefore decrease the strength of the system. Although MOCF produced with excess MgO powders could decrease the water absorption, its softening coefficient was lower than that of the material produced with moderate MgO powders. This might be due to the instability of phase 5, the volume expansion and cracking of cell walls as immersed the sample into water.