一种极柱接线端的连接方式及对温升的影响

当前在电网改造升级的推动下,海上油气田对更大容量、更高额定电流的中压开关设备产品需求不断提高.但目前常规中压断路器固封极柱因紧固连接失效常常导致产品无法可靠运行,无法满足大电流产品的热稳定要求.为此,选用一种新型的复合紧固连接形式,并对此进行了数值分析和试验研究.结果 表明这种复合紧固连接具有比常规连接更优异的温升特性表现.     

In vivo quantitative MRI: T1 and T2 measurements of the human brain at 0.064 T

Objective

To measure healthy brain \({T}_{1}\) and \({T}_{2}\) relaxation times at 0.064 T.

Materials and methods

\({T}_{1}\) and \({T}_{2}\) relaxation times were measured in vivo for 10 healthy volunteers using a 0.064 T magnetic resonance imaging (MRI) system and for 10 test samples on both the MRI and a separate 0.064 T nuclear magnetic resonance (NMR) system. In vivo \({T}_{1}\) and \({T}_{2}\) values are reported for white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) for automatic segmentation regions and manual regions of interest (ROIs).

Results

\({T}_{1}\) sample measurements on the MRI system were within 10% of the NMR measurement for 9 samples, and one sample was within 11%. Eight \({T}_{2}\) sample MRI measurements were within 25% of the NMR measurement, and the two longest \({T}_{2}\) samples had more than 25% variation. Automatic segmentations generally resulted in larger \({T}_{1}\) and \({T}_{2}\) estimates than manual ROIs.

Discussion

\({T}_{1}\) and \({T}_{2}\) times for brain tissue were measured at 0.064 T. Test samples demonstrated accuracy in WM and GM ranges of values but underestimated long \({T}_{2}\) in the CSF range. This work contributes to measuring quantitative MRI properties of the human body at a range of field strengths.

     

计及相位影响的间谐波与电压闪变的定量关系研究

电力系统闪变与间谐波存在密切的关系,文中从信号调制理论的角度进一步揭示了两者之间的定量关系。一方面,在充分考虑相位参数的影响下,分析了间谐波叠加在工频信号上所引起的幅度调制和相位调制效应,指出只有发生幅度调制时,间谐波才会引起信号包络的波动。另一方面,从闪变信号的数学模型推导出由调幅波所引起的间谐波参数的定量计算公式。基于MATLAB软件的仿真验证了结论的正确性。     

气温变化对用电负荷影响的分析

以贵阳地区2011年至2012年的用电情况为基础,从气温角度出发,主要对民用负荷用电情况进行分析,找出气温变化对民用负荷的影响规律,可以更好地开展电力需求侧管理工作。     

温度对阀控式铅酸蓄电池的影响分析

研究了阀控式密封铅酸蓄电池在正常工作时的耐环境性问题,即自然环境下温度对蓄电池寿命、容量的影响,对阀控式铅酸蓄电池在使用过程中出现的过热现象进行了分析和探讨,提出了阀控式密封铅酸蓄电池在制造及使用过程中应注意的一些问题,真正意义上提高了蓄电池的使用寿命。     

MRI of ischemic lesions in gerbil brain

Brain temperature was varied during global forebrain ischemia in adult male Mongolian gerbils to produce a graded response to the ischemic insult. The severity of damage in the dorsal hippocampus was then quantified 4 days after the event withT ²-weighted 2DFT images and with histology. Statistically significant correlation was observed between magnetic resonance imaging (MRI) score and brain temperature and between MRI score and the area of the CA region in the dorsal hippocampus measured by histology.     

Segmentation of human brain using structural MRI

Segmentation of human brain using structural MRI is a key step of processing in imaging neuroscience. The methods have undergone a rapid development in the past two decades and are now widely available. This non-technical review aims at providing an overview and basic understanding of the most common software. Starting with the basis of structural MRI contrast in brain and imaging protocols, the concepts of voxel-based and surface-based segmentation are discussed. Special emphasis is given to the typical contrast features and morphological constraints of cortical and sub-cortical grey matter. In addition to the use for voxel-based morphometry, basic applications in quantitative MRI, cortical thickness estimations, and atrophy measurements as well as assignment of cortical regions and deep brain nuclei are briefly discussed. Finally, some fields for clinical applications are given.     

温度、风速对湿度传感器响应时间影响的研究

湿度传感器在实际使用过程中,温度和风速会对湿度传感器的响应时间产生影响。为了研究温度和风速对电容式湿度传感器阶跃响应时间的影响规律,通过分析实验数据发现湿度传感器的响应时间随着温度的升高和风速的增大而逐渐减小,并采用神经网络算法拟合湿度传感器的阶跃响应时间和温度、风速之间的关系,最后对影响机理进行分析研究。     

富氧燃烧技术及其对环境的影响研究综述

富氧燃烧不仅可以使CO:的回收和利用容易进行,还可以有效减少NOx和SO2的排放,同时,还可以有效提高锅炉热效率,是一项高效节能的燃烧方式.对富氧燃烧技术研究现状进行了综述,分析了富氧燃烧的节能特点及其对环境的影响.     

对高压并联电容器组中电容器单元安装间距的研究

通过对各种容量并联电容器,在不同安装间距下的温升研究,确定不同的安装间距对电容器组温升的影响,本项试验研究成果,可作为《并联电容器装置设计规范》修订相关条文的依据,为电容器和电力用户的并联电容器成套装置的设计提供参考。     

对高压并联电容器组中电容器单元安装间距的研究

通过对各种容量并联电容器,在不同安装间距下的温升研究,确定不同的安装间距对电容器组温升的影响,本项试验研究成果,可作为《并联电容器装置设计规范》修订相关条文的依据,为电容器和电力用户的并联电容器成套装置的设计提供参考。     

MRI quality assurance based on 3D FLAIR brain images

Objective

Quality assurance (QA) of magnetic resonance imaging (MRI) often relies on imaging phantoms with suitable structures and uniform regions. However, the connection between phantom measurements and actual clinical image quality is ambiguous. Thus, it is desirable to measure objective image quality directly from clinical images.

Materials and methods

In this work, four measurements suitable for clinical image QA were presented: image resolution, contrast-to-noise ratio, quality index and bias index. The methods were applied to a large cohort of clinical 3D FLAIR volumes over a test period of 9.5 months. The results were compared with phantom QA. Additionally, the effect of patient movement on the presented measures was studied.

Results

A connection between the presented clinical QA methods and scanner performance was observed: the values reacted to MRI equipment breakdowns that occurred during the study period. No apparent correlation with phantom QA results was found. The patient movement was found to have a significant effect on the resolution and contrast-to-noise ratio values.

Discussion

QA based on clinical images provides a direct method for following MRI scanner performance. The methods could be used to detect problems, and potentially reduce scanner downtime. Furthermore, with the presented methodologies comparisons could be made between different sequences and imaging settings. In the future, an online QA system could recognize insufficient image quality and suggest an immediate re-scan.

     

过燃风水平摆动对烟气温度影响的研究

阐述了2×600 MW超临界褐煤锅炉主要设计参数和燃烧器设计参数,通过烟温测量试验分析了不同过燃风摆动角度对高温再热器出口截面烟气温度的影响,评价了水平烟道内烟气速度分布的不均匀性。试验分析结果表明,在相同二次风配风方式前提下,过燃风水平摆动对高温再热器出口截面烟气温度有影响,能消除炉内气流残余旋转,减小炉膛出口左侧、右侧烟温偏差。     

烧结温度对氧化铝陶瓷介质陷阱分布的影响

论文采用等温衰减电流法研究了在不同烧结温度下制备的陶瓷试样的陷阱分布，试验结果表明，烧结温度能够影响到氧化铝陶瓷介质的陷阱分布，微观结构分析表明，不同的烧结温度会导致陶瓷介质不同数量的结构缺陷，从而造成了它们陷阱分布的不同。     

基于ANSYS仿真的温度对洗碗机固频的影响研究及噪声优化

针对洗碗机洗涤模式下低频噪声,发现其峰值随工作温度波动峰值而呈现,研究分析得到其零部件固频与温度的关系,并使用LMS软件进行模态、ODS测试,再使用ANSYS15.0仿真软件,发现内胆100 Hz固频振型图振动强烈且与两倍工频共振,根据分析结果对具体结构进行优化设计,降低了洗碗机的结构共振点噪声13 dB.     

红外测温设备的空间环境影响及防护研究

随着航天器结构与热设计复杂性的提升,结构表面测温工艺实施难度增大,测温区域趋于多元化,对航天器热试验中非接触测温技术的应用需求日益增多。以红外测温设备在真空、高低温环境中的应用为研究对象,对设备热防护方案与装置进行设计,并基于节点网络法对红外测温设备热防护进行仿真分析,通过物理试验验证,该防护装置能够有效实现设备在真空、高低温环境中热防护,确保设备处于正常工作温度区间且其测温算法模型不受影响,测温准确度优于±2℃,满足设备在空间环境试验中的使用需求。     

紫外光交联电缆工艺装备及其对产品性能的影响

该文简要介绍了紫外光辐照交联的基本原理,着重介绍了紫外光辐照交联的工艺装备及其对产品性能的影响。     

温度对电动汽车直流充电机计量性能影响的研究

自电动汽车直流充电机被国家市场监督管理总局列入强制管理的计量器具目录后,其电能计量性能越来越得到社会的关注。直流充电机实际使用环境温度变化范围比较大,温度变化对直流充电机的计量性能有一定的影响。文中结合直流充电机电能计量的工作原理,选取温度作为影响量,利用搭建的温度影响仿真测试平台,测量直流充电机计量单元在不同温度下的计量准确度。分析了直流充电机温度影响规律,提出了基于分段线性插值法的直流充电机计量单元温度补偿模型。实验结果表明,经过温度补偿的直流充电机电能计量准确度得到明显的提高,验证了分段线性插值补偿方法的准确性和适用性。     

电压暂降相位跳变及其对敏感设备的影响研究

电压暂降作为最为严重的电能质量问题之一,已受到国内外专家学者广泛的重视。在电压暂降的特征参数中,除暂降幅值和持续时间外,相位跳变的影响也不容忽视。文中进行了相位跳变研究的必要性分析,给出了相位跳变的计算方法,通过对国内多个地区电能质量监测系统所获取到的暂降事件数据的处理与分析,得到了相位跳变值的分布特征;选取开关电源和交流接触器作为敏感性设备,进行了相位跳变的试验研究,绘制了不同相位跳变值下的电压暂降敏感度曲线。基于上述分析,在电压暂降评估中,将相位跳变作为电压暂降的一个重要特征参数进行研究是非常必要的。