特征值问题Wilson元展开及外推的数值实验

对Poisson方程的特征值采用Wilson非协调元进行展开.从其误差展开式,不能确定近似特征值是上界还是下界,但从展开式的形式上可以推测是下界.利用Wilson元,计算方形区域上的Poisson方程的近似特征值,并对数据进行分析,验证了推测是正确的,通过对误差展开式外推,收敛阶数可以从二阶提高到三阶,得到了高精度的解.     

小动物精准放疗系统在小鼠肿瘤放疗模型中的应用

小动物精准放疗系统是专为小动物实验设计的放疗设备,类似于临床放疗系统,广泛用于临床前的放射生物学效应研究、肿瘤放射治疗、放射性药物等领域.特点是在实施放疗前,对小动物进行精确的CT三维成像,应用专门的软件计算受照剂量并制定照射计划,最后使用制定好的计划引导仪器对小动物实施精确的放疗,能够模拟临床放射治疗过程,得到更加贴...     

准南中低阶煤孔径结构全孔径定量综合表征

为研究准南地区中低阶煤孔径结构特征,采集6块中低阶煤样,采用高压压汞、低温液氮吸附和二氧化碳吸附实验分别测试不同煤样的孔径结构,研究不同测试方法之间的衔接孔径,并对准南地区中低阶煤进行全孔径表征.结果 表明,液氮吸附法与高压压汞法平滑过渡衔接应满足阶段体积增量相等,且阶段体积增量与孔径的一阶导数相等,即dV Hg/d ...     

柔性臂坐标测量机热误差建模分析

针对柔性臂坐标测量机的热变形误差问题,为了进一步提高其测量精度,分析了自身发热导致的热误差对测量机精度的影响,布置了相应的温度传感器进行监测.利用BP神经网络建立热变形误差补偿模型,通过模拟退火算法优化权值,加快了收敛速度并解决了神经网络易陷入极小值缺点.通过实验获得样本训练所建模型,进行测量误差补偿验证,结果表明SA-BP模型补偿后误差的平均值相比BP模型减小了0.0129 mm,标准差减小了0.019 mm,验证了所提算法的有效性.     

基于机器视觉和MATLAB/GUI的柚子外观尺寸检测系统

介绍了一种基于机器视觉技术的柚子外观尺寸检测系统.利用CMOS摄像头采集柚子正立图像,通过数字图像处理技术获取柚子的纵径、横径、表面积及体积等外观尺寸参数.借鉴已有球状水果机器视觉检测误差理论,对检测数据进行修正,提高检测精度,并应用Matlab/GUI技术建立柚子外观尺寸测量系统界面.实验表明,检测系统具有较高的检测精度,可满足实际生产中柚子分级精度的要求,且人机交互界面友好,使用操作方便.     

利用Phyphox软件验证机械能守恒定律

Phyphox软件能够方便地采集手机传感器记录的数据,克服实验数据处理繁琐的弊端.文中利用其磁力计功能读出当铁球经过手机传感器区域时磁感应强度发生明显变化的时间,进而利用公式计算动能与势能的变化量验证机械能守恒定律.改进实验能够有效减小误差、缩短处理数据时间,有助于物理实验规律的验证研究.     

美国两年制院校的职业技术教育

美国两年制学院按照其控制方式可以分为公立、私立非盈利和私立盈利性三类。两年制院校职业教育课程与转学课程的分界在以前就是不固定的,现在则越来越灵活了,这样学生较容易在不同的教育轨道之间进行选择。自从帕金斯法案以后,不同机构在职业教育领域的合作成为一种重要的改革趋势,技术准备与副学士学位的衔接计划就是类似的合作模式,目的在于加强两年制职业教育课程与中等教育之间的联系。美国两年制院校多样化的办学模式、灵活的衔接关系等值得我国高职教育借鉴。     

大轴加工误差的测量技术

本文主要阐述三点误差分离理论,讨论了圆度误差测量的基本方程,给出了大轴加工的新方法.适合于车间生产时测量大轴加工误差,先进的测量技术得到了验证,可作为今后类似工件加工测量参考.     

亚像素级激光光条提取及其激光平面标定应用(英文)

为了标定激光平面以实现三维形貌测量,提出一种亚像素级精度激光光条提取算法.该算法包括两侧边检测和中心线提取2个部分.首先,利用基于主成分角的渐进概率霍夫变换检测2条侧边并依赖该两侧边的距离获取光条宽度;然后,应用二维泰勒展式提取具有亚像素级精度的光条中心线并依据重建的三维坐标标定激光平面.实验结果表明,所提算法光条中心提取速度较快,平均约为78 ms/帧,光条平面共面误差较低,限制在0.3 mm以内.因而所提算法能够满足提取光条的两侧边和中心线的需要,且快速可靠、精度高和抗干扰能力强.     

基于生物识别技术的网络身份验证研究

随着计算机网络的发展与普及,从最开始的电子邮件,到现在的博客、电子商务等形式的出现,越来越多的网站需要用户身份的验证.经常输入账号和密码,很不方便.利用生物识别技术进行网络身份的验证更快捷、更方便.本文分析了传统的账号加密码登陆方式的弊端.概括了现有的生物识别技术,提出了将生物识别技术应用于网络身份验证上,从而可以更高效、更安全地进行网络身份的验证.     

Electromagnetic environment around a high-speed railway using analytical technique

A switched-mode unit used in electric locomotive generates a strong high frequency conducted electromagnetic interference (EMI), which radiates electromagnetic energy through railway lines. Evaluation of magnetic field using analytical technique based on contour integral is presented, in order to assess the electromagnetic environment around a high-speed railway. Actual railway multiconductor finitely long overhead lines are represented by an infinitely long single line above two-layered earth, whose characteristic is different from homogeneous earth. Owing to the constraint of the GB/T 24338-2009 and the high frequency investigated (a few MHz), only the magnetic fields are examined. The magnetic fields consist of four components: the direct wave, the ideal reflected wave or image wave, the trapped surface wave, and the lateral wave. The calculation results proved that due to the presence of the trapped surface wave, the magnetic field of the observer point on the interface is strongly influenced, when the line is on or closed to the interface.     

高压P-LDMOS的栅击穿及其改进方法

高压P-LDMOS的失效实验分析表明其沟道区的高峰值电场会导致沟道区的热载流子效应,从而将降低高压P-LDMOS的可靠性.借助半导体器件专业软件Tsuprem-4和Medici的模拟给出了高压P-LDMOS沟道区的电场分布情况,模拟结果显示在沟道区存在2个峰值电场,讨论了产生这2个峰值电场的原因,同时给出了降低这2种峰值电场的有效方法———适当增加沟道的长度和降低沟道区的浓度.实验结果表明采用这2种方法优化得到的高压P-LDMOS的栅击穿电压得到了很大的提高,同时P-LDMOS的可靠性也得以大幅提高.     

Comparing Collective and Personal Professional Theories of Experienced Practitioners

A characteristic of being a professional is the internalisation of the collective professional theory (CPT)—the shared insights of professionals. Problems arise when different opinions stemming from professionals’ personal professional theories (PPTs) obscure a CPT’s content. This study argues that cooperating professionals’ CPTs form a so-called field and can be represented by concept maps. The relations between PPTs, CPTs, and fields are examined for the fields of accountancy and teaching. The results indicate that CPTs are more complex than PPTs, and that the teachers’ field is more diverse than the accountants’ field. These insights are important because socialisation in a field may be fostered if one is aware of CPTs and the surrounding field in relation to one’s PPT.     

表面棱边单元法求解三维电磁场问题

提出了表面棱边单元方法并应用它求解任意形状物体的三维电磁场散色问题.首先根据物体剖分得出表面区域的几何特性,推导出表面棱边单元法的基本公式.该方法保持了普通棱边单元法的基本特性,维持变量的切向分量连续.然后用复合积分方程来模拟普通介质的电磁场散色问题,应用所提出的方法离散积分方程,并且对奇点问题采用特殊的处理方法.最后用该方法计算圆柱体以及四方体的在不同介质条件下的电磁场散色问题,对所得的数值解进行测试,并与其他数值方法解相比较,结果表明该方法行之有效.     

数字式非循环侧抑制网络在联想记忆中的应用

提出了基于侧抑制理论和细胞神经网络(CNN)的数字式非循环侧抑制网络，给出其用于数字图象联想记忆的算法，并给出了仿真结果。     

河南省襀翅目一新记录属种记述

报道了河南叉襀科一新纪录属：球尾叉襀属Sphaeronemoura,并记述了一新纪录种：Sphaeronemoura songshana.该属鉴别特征为颈侧片的内外两侧具有一不分支的腊肠状颈鳃;雄成虫腹端第8背板后缘延伸,略不对称;第10背板在肛上突基部下方形成一个纵向的膜质区,其侧缘通常有尖锐的隆突;肛侧突中叶形成钝圆的突起;肛上突不对称,端部有长的鞭状突出物.雌成虫的鉴别特征为第7腹板前生殖板后缘中部向前明显凹入,后生殖板有2个骨化的侧骨片.该属稚虫尾须念珠状,端部数节逐渐变大,每节具1圈长鬃,鬃间有1簇短的刚毛,为其与近缘属的有效鉴别特征.观察标本保存在河南科技学院昆虫标本馆.     

The Differential Impact of Curriculum on Aptitude Test Scores

A sample of 22, 923 students who had taken the SAT and the GRE General Test was classified by the four general undergraduate fields of study and by sex. The authors performed several analyses to determine the degree of differential impact that sex and field of study might have on GRE-Verbal, GRE-Quantitative, and GRE-Analytical scores after controlling on SAT-Verbal and SAT-Mathematical scores. They found, first, that the correlations of SAT-Verbal with GRE-Verbal scores and SAT-Mathematical with GRE-Quantitative scores were extremely high, .86 in the total sample and ranging from the low to middle .80s in the eight subgroups. The impact of curriculum and sex, after controlling on SAT scores, was found to be low on GRE- Verbal scores but relatively high on GRE-Quantitative scores, with students in heavily quantitative fields enjoying an advantage over their peers in less quantitative fields of study. The impact was moderate on GRE-Analytical scores. Further studies designed to "purify" the fields of study and include only clearly verbal fields and clearly mathematical fields showed small additional impact. An additional study indicated a generally slight effect of the institution attended on GRE-Quantitative scores after controlling for sex, major field of study, and initial ability.     

全序域及半序域

我们给出一个与传统的全序域定义等价的全序域定义,并由此推导出一系列关于全序域的基本命题。顺带地,我们还引入“半序域”——概念,并指出其一些性质。最后,借助于序这个概念,我们将域分为全序域,半序域及Galois域三类。其中前二类的特征为0,而最后一类的特征为各个素数P。     

Cross‐field effects and temporary social fields: a case study of the mediatization of recent Australian knowledge economy policies

This paper utilizes Bourdieu’s conceptual frame to examine the mediatized effects of policy processes concerned with the growth and support of knowledge industries in Australia. These policies span education, science, research and other knowledge industries (such as venture capital firms and intellectual property law). The paper argues that some policy processes are best represented as temporary social fields. The nature of these fields can be described by the kinds of cross‐field effects that they produce. A case study of an Australian knowledge economy policy, The chance to change, and associated policy processes demonstrates the broad analytic capacities of Bourdieu’s conceptual frame for policy analysis, when combined with the concepts of cross‐field effects and temporary social field developed here.     

Double gamers: academics between fields

The field of academia is frequently associated with traditional norms that aim to regulate scholarly activity, especially research. The social web, as another field, is often viewed as challenging long-established conventions with novel knowledge production practices. Hence, the two fields seem to oppose rather than complement each other. Using a Bourdieuian lens, this research examines research participants’ accounts of their approaches to practice on the social web in relation to academia. The paper reports on the habitus dissonance between the two fields, before discussing the effects of the two fields’ competing doxas on individuals’ habitus.