钙钛矿锰氧化物为基体的二相复合体低场室温高磁电阻研究

综述了国内外对钙钛矿锰氧化物为基体的二相复合体低场磁电阻研究现状,提出了钙钛矿锰氧化物低场室温高磁电阻实现的新途径。     

组合磁光光纤光栅的磁场敏感性分析

磁光光纤光栅是一种具有磁光效应的特殊光栅,可直接用于本征型的磁场传感或通过磁控的方式实现可调光子信息处理。该文采用分段均匀模型分析了几种组合磁光光纤Bragg光栅中左右旋圆偏振光的偏振相关损耗对磁场的敏感性,计算表明,均匀磁光光纤光栅的中心区段对磁场最为敏感。提出了一种比均匀磁光光栅更加灵敏的F-P型组合光栅传感结构,可更好地用于较弱磁场下偏振相关损耗的检测。     

微流量智能电磁流量计的研究

根据电磁流量计的基本原理,对其微流量测量技术进行了研究。文中提出了一种运用等效坎截面法的变器结构设计,并对相应的权重函数和阻力损失进行了计算。通过对几种信号处理方法的比较,选择了较佳的基线信号处理方法。在此基础上,围绕单片机展开设计,实现了仪表的智能化和有效的功能。根据流量计栓定规程对样机进行实液标定的结果表明,样机设计达到了预期效果。     

外部经济、企业分工与产业集聚

从资源共享、专业化生产、交易成本的节约、创新利益四个方面分析了产业集聚的经济动因;采用超边际分析方法建立了企业分工模型,并在此基础上推演出产业集群的自组织演化模型。认为外部经济是产业集聚的经济动因,企业分工协作关系的产生和深化则是产业集群形成和发展的关键。     

企业并购理论论纲

企业并购作为现代企业资本经营的有效形式 ,是市场经济的产物 ,是现代经济中资本优化配置的最重要形式 ,也是实现企业发展战略的经济选择的一种途径。企业并购作为资本市场上的一种交易 ,与一般商品买卖或资金拆借不同 ,其内容、形式、过程都较商品市场或资金市场上的交易复杂得多。本文拟就企业并购的动因、基本原则和财务评价予以探讨和研究。文章共分四个部分 :一、引言 :主要是界定企业并购的意义 ;二、企业并购的动因分析 :经济协同效应 ;财务协同效应 ;企业发展的战略动机。三、企业并购的基本原则 :综合效益最大化原则 ;系统化原则 ;创新原则 ;谨慎性原则。四、企业并购的财务评价 :并购目标企业的价值评估 (资产评估法、收益法、贴现现金流量法 ) ;企业并购的成本分析 ;企业并购的风险分析。     

带传动装置的振动研究

对带传动装置的振动进行了实验研究,测试了在不同带轮偏心配置及不同转速下带轮的纵向振动,发现带轮偏心造成的离心力和由变频调速 引起电机的随时间震荡的电磁转矩是造成振动的主要原因。     

Sex differences in the development of mild cognitive impairment and probable Alzheimer’s disease as predicted by hippocampal volume or white matter hyperintensities

This study examined biological sex differences in the development of mild cognitive impairment (MCI) and probable Alzheimer’s disease (AD) development as predicted by changes in the hippocampus or white matter hyperintensities. A secondary data analysis of the National Alzheimer’s Coordinating Center Uniform Data Set was conducted. We selected samples of participants with normal cognition at baseline who progressed to MCI (n = 483) and those who progressed to probable AD (n = 211) to determine if hippocampal volume or white matter hyperintensities (WMH) at baseline predicted progression to probable AD or MCI and whether the rate of progression differed between men and women. The survival analyses indicated that changes in hippocampal volumes affected the progression to probable AD (HR = 0.535, 95% CI [0.300–0.953]) only among women. White men had an increased rate of progression to AD (HR = 4.396, CI [1.012–19.08]; HR = 4.665, 95% CI [1.072–20.29]) compared to men in other race and ethnic groups. Among women, increases in hippocampal volume ratio led to decreased rates of progressing to MCI (HR = 0.386, 95% CI [0.166–0.901]). Increased WMH among men led to faster progression to MCI (HR = 1.048. 95% CI [1.011–1.086]). Women and men who were older at baseline were more likely to progress to MCI. In addition, results from longitudinal analyses showed that women with a higher CDR global score, older age at baseline, or more disinhibition symptoms experienced higher odds of MCI development. Changes in hippocampal volumes affect the progression to or odds of probable AD (and MCI) more so among women than men, while changes in WMH affected the progression to MCI only among men.     

Modelling columnarity of pyramidal cells in the human cerebral cortex

For modelling the location of pyramidal cells in the human cerebral cortex, we suggest a hierarchical point process in that exhibits anisotropy in the form of cylinders extending along the z-axis. The model consists first of a generalised shot noise Cox process for the xy-coordinates, providing cylindrical clusters, and next of a Markov random field model for the z-coordinates conditioned on the xy-coordinates, providing either repulsion, aggregation or both within specified areas of interaction. Several cases of these hierarchical point processes are fitted to two pyramidal cell data sets, and of these a final model allowing for both repulsion and attraction between the points seem adequate. We discuss how the final model relates to the so-called minicolumn hypothesis in neuroscience.     

W型六角铁氧体的研制

采用化学共沉与高温助熔相结合的工艺制备了 W 型六角晶系铁氧体—Ba(Zn_(1-x)CO_x)_2Fe_(16)O_(27)。对不同烧结温度,其物相组成的变化,比饱和磁化强度σ、磁晶各向异性场 H_A~θ随 Co~(2+)取代值 x 的变化以及晶粒形貌进行了测试和分析。结果表明:在烧结温度1250℃,保温0.5h 的条件下,测得纯相 W 型材料;当 x=0.45左右时,Ba(Zn_(1-x)Co_x)_2Fe_(16)O_(27)的磁矩从优方向由单轴过渡到平面。     

用TEMcell进行电磁兼容性测试的理论与实践

讨论了横电磁波小室（ＴＥＭｃｅｌｌ）在电磁兼容性测量中的应用，着重讨论应用ＴＥＭｃｅｌｌ测量受试设备的辐射干扰特性的理论基础和测量技术。就原理上而言，电磁泄漏源是电气小的，且可用三个等效的正交电偶极矩和三个等效的正交磁偶极矩来描述，通过测量确定这些组合偶极矩的振幅和相位。给出了实测结果。