预警—牙轮防脱落技术的发展方向

提高牙轮钻头防止牙轮脱落的能力，可以显减小牙轮脱落事故的发生率，因而对降低钻井成本以及提高钻头使用效率具有重要意义，综述了国内外牙轮锁紧技术的发展历史和现状，简要介绍了几种典型锁紧结构（钢球结构、卡簧结构、螺纹环结构以及R槽钢球憋卡预警结构等）的工作原理和技术特点。指出牙轮脱落的预警是牙轮防脱落技术的发展方向。分析了牙轮脱落预警的技术关键、难点以及已有预警的优缺点。提出了一种以扭矩显增加、钻速显降低为预警信号的新的牙轮脱落预警技术，并对该技术的预警机理以及研究情况作了简要的分析和阐述，试验证明，该技术能准确监测轴承的磨损状态，在磨损量达到警戒限值时能可靠地自行启动，发出预警信号。     

电磁波探测阻抗的夹杂

利用电磁波探测结构中具有阻抗边界的夹杂 ,是一类典型的逆问题。分别从数学原理及数值计算两个方面探讨了如何求解这类问题。首先建立了求解问题的基本方程 ,分别就正问题和逆问题加以讨论 ,同时构造了一个表达散物特征的指示函数 ,然后利用该函数的性质 ,确定具有阻抗散射物的边界。数值计算使用了 Nystroem方法求解正问题 ,对于不适定的逆问题 ,用 Tikhonov正则化方法     

双波长涂膜CO2传感器涂膜厚度补偿

介绍了对双波长涂膜CO2传感器涂膜厚度差异的补偿算法，该算法能够自动有效地补偿涂膜厚度差异对测量结果的影响．     

相序指示器的最佳参数设计

利用PSpice电路仿真软件,对灯泡指示相序仪中的元件参数进行了全面的扫描分析。依据这些扫描曲线,从理论和工程实用的角度,给出了元件参数的最佳选取范围。研究结果对理解相序仪的本质和正确使用相序仪具有指导作用。     

Development of a subacute ruminal acidosis risk score and its prediction using milk mid-infrared spectra in early-lactation cows

A routine monitoring for subacute ruminal acidosis (SARA) on the individual level could support the minimization of economic losses and the ensuring of animal welfare in dairy cows. The objectives of this study were (1) to develop a SARA risk score (SRS) by combining information from different data acquisition systems to generate an integrative indicator trait, (2) the investigation of associations of the SRS with feed analysis data, blood characteristics, performance data, and milk composition, including the fatty acid (FA) profile, (3) the development of a milk mid-infrared (MIR) spectra-based prediction equation for this novel reference trait SRS, and (4) its application to an external data set consisting of MIR data of test day records to investigate the association between the MIR-based predictions of the SRS and the milk FA profile. The primary data set, which was used for the objectives (1) to (3), consisted of data collected from 10 commercial farms with a total of 100 Holstein cows in early lactation. The data comprised barn climate parameters, pH and temperature logging from intrareticular measurement boluses, as well as jaw movement and locomotion behavior recordings of noseband-sensor halters and pedometers. Further sampling and data collection included feed samples, blood samples, milk performance, and milk samples, whereof the latter were used to get the milk MIR spectra and to estimate the main milk components, the milk FA profile, and the lactoferrin content. Because all measurements were characterized by different temporal resolutions, the data preparation consisted of an aggregation into values on a daily basis and merging it into one data set. For the development of the SRS, a total of 7 traits were selected, which were derived from measurements of pH and temperature in the reticulum, chewing behavior, and milk yield. After adjustment for fixed effects and standardization, these 7 traits were combined into the SRS using a linear combination and directional weights based on current knowledge derived from literature studies. The secondary data set was used for objective (4) and consisted of test day records of the entire herds, including performance data, milk MIR spectra and MIR-predicted FA. At farm level, it could be shown that diets with higher proportions of concentrated feed resulted in both lower daily mean pH and higher SRS values. On the individual level, an increased SRS could be associated with a modified FA profile (e.g., lower levels of short- and medium-chain FA, higher levels of C17:0, odd- and branched-chain FA). Furthermore, a milk MIR-based partial least squares regression model with a moderate predictability was established for the SRS. This work provides the basis for the development of routine SARA monitoring and demonstrates the high potential of milk composition-based assessment of the health status of lactating cows.     

基于深度学习的文本到图像生成方法综述

文本到图像生成方法采用自然语言与图像集特征的映射方式,根据自然语言描述生成相应图像,利用语言属性智能地实现视觉图像的通用性表达.基于卷积神经网络的深度学习技术是当前文本到图像生成的主流方法,为系统地了解该领域的研究现状和发展趋势,按照模型构建及技术实现形式的不同,将已有的技术方法分为直接图像法、分层体系结构法、注意力机...     

大型引水管线施工控制网精度指标的推算与大地网的应用

介绍长距离大口径管线施工控制测量中解决问题的方法。     

肠道微生物与人体健康的关系及其影响因素研究进展

肠道微生物是人体内最复杂和种群数量最多的微生物生态系统,无论是健康或者疾病状态下,人类的生理代谢特性都在时刻受到肠道菌群结构变化的影响.而肠道微生物组成和结构的变化也会影响宿主的健康,因此肠道微生物常被认为是人体的"隐形器官".本文综述了肠道微生物的多样性、肠道微生物的主要生理功能、肠道微生物异常与相关疾病以及影响肠道...     

基于对比学习的心电信号情绪识别方法

现有的机器学习和深度学习在解决基于心电信号的情绪识别问题时主要使用全监督的学习方法。这种方法的缺点在于需要大量的有标签数据和计算资源。同时,全监督方法学习到的特征表示通常只能针对特定任务,泛化性较差。针对这些问题,提出了一种基于对比学习的心电信号情绪识别方法,该方法分为预训练和微调两步。预训练的目的是从未标记的心电数据中学习特征表示,具体为：设计了两种简单高效的心电信号增强方式,将原始数据通过这两种数据增强转换成两个相关但不同的视图;接着这两种视图在时间对比模块中学习鲁棒的时间特征表示;最后在上下文对比模块中学习具有判别性的特征表示。微调阶段则使用带标记数据来学习情绪识别任务。在三个公开数据集上的实验表明,该方法在心电信号情绪识别准确率上与现有方法相比提高了0.21%～3.81%。此外,模型在半监督设定场景中表现出高有效性。     

评价高性能混凝土耐久性综合指标--抗氯离子渗透性及其研究现状

结合国内外高性能混凝土耐久性研究的现状,在近年来基于氨离子渗透的高性能混凝土耐久性预测模型,分析了将抗氯离子渗透性作为评价高性能混凝土耐久性的综合指标的可行性和必要性,对于制定高性能混凝土的耐久性设计规范具有参考意义。