关于粘性导数的几个性质的探讨     

汪元伦 《绵阳师范学院学报》2004,23(2):19-21

M .G .Crandall等人在文 [1]中给出了函数的粘性导数的概念。在这个概念的基础上我们讨论了函数的粘性导数的上 (下 )导集的几个性质 :在函数可微点处的性质、闭凸性质、与C1类函数的和的性质、与C2 类函数的差在严格局部极大 (小 )值点的性质。  相似文献   

几个重要积分不等式     

丁玉敏 《蒙自师范高等专科学校学报》1995,(2)

从简单的代数不等式ab~≤a+b/2出发,通过变形,观察,猜想,用极限思想得出并证明了一些新的积分不等式。  相似文献   

Implicit knowledge of general upper secondary school in a bridge-building project     

Annette Rasmussen  Karen Andreasen 《Ethnography and Education》2016,11(3):316-330

Bridge-building activities are practiced widely in the education systems of Europe. They are meant to bridge transitions between lower and upper secondary school and form a mandatory part of the youth guidance system in Denmark. By giving pupils the opportunity to experience the different educational context of upper secondary school, bridge-building activities are meant to facilitate their decision-making on educational paths, but also to attract more and new groups of pupils. However, the premises of the inherent differences of educational contexts and of pupils’ lacking knowledge of upper secondary education can be questioned. In this ethnographic case study of a bridge-building project in a rural area in Denmark, we analyse the implicit knowledge of the general upper secondary school, as it is practiced in a bridge-building project, and how it is experienced by the pupils on the background of their prior knowledge. The analysis is theoretically informed by especially the code concepts of Basil Bernstein.  相似文献   

非线性n阶微分方程多点边值问题     

姜波  刘颖 《沈阳教育学院学报》2003,5(4):99-102

用上、下解方法研究了n阶非线性微分方程k点边值问题y(n)=f(t,y(n-2),y(n-1))y(i)(di)=ai(i=0,1,…,n-3),g(y(n-2)(t1),y(n-1)(t1))=0,h(y(n-2)(tk),y(n-1)(tk))=0(1)　　　解的存在性、唯一性。其中tj∈R,j=1,2,…,k;t1相似文献   

一类特殊矩阵特征值的绝对扰动上界     

孔祥强 《巢湖学院学报》2011,13(3):5-7

利用矩阵的奇异值分解和矩阵的计算技巧研究了Hermite矩阵特征值的扰动界,得到了Hermite矩阵特征值的绝对扰动上界,对以往的结果进行了改进,并推广了Wielandt-Hoffman定理。  相似文献   

Capturing teacher priorities: Using real-world eye-tracking to investigate expert teacher priorities across two cultures     

《Learning and Instruction》2019

Classroom teaching is complex. In the classroom, teachers must readily attend to disruptions and successfully convey new tasks and information. Outside the classroom, teachers must organise their priorities that are important for successful student learning. In fact, differing gaze patterns can reveal the varying priorities that teachers have. Teacher priorities are likely to vary with classroom expertise and can conceivably change with culture too. Therefore, the present study investigated expertise related and cultural teacher priorities by analysing their gaze proportions. To obtain this data, 40 secondary school teachers wore eye-tracking glasses during class time, with 20 teachers (10 expert; 10 novice) from the UK and 20 teachers (10 expert; 10 novice) from Hong Kong. We analysed gaze proportions during teachers' attentional (i.e., information-seeking, e.g., teacher questioning students) and communicative (i.e., information-giving, e.g., teacher lecturing students) gaze. Regardless of culture, expert teachers' gaze proportions revealed prioritisation of students, whereas novice teachers gave priority to non-instructional (i.e., not students, teacher materials, or student materials) classroom regions. Hong Kong teachers prioritised teacher materials (e.g., whiteboard) during communicative gaze whereas UK teachers prioritised non-instructional regions. Regarding culture-specific expertise, with Hong Kong experts prioritised teacher materials more than UK experts who, in turn, did so more than UK novices. We thus demonstrate the role of implicit teacher gaze measures as micro-level indicators of macro-level and explicit aspects of instruction, namely teacher priority.  相似文献   

黄河上游兰西城市群人口时空特征多维透视     

罗君  石培基  张学斌 《资源科学》2020,42(3):474-485

明确区域人口时空演化特征,有助于推动人口高质量集聚。本文以多源数据为基础,采用人口重心、标准差椭圆、人口分布结构指数、人口-土地一致性系数、空间自相关分析和GIS空间统计分析等方法,从城市群整体、县、乡（镇）和栅格尺度对兰州—西宁城市群人口时空特征进行分析,得出以下结论：①兰西城市群人口呈现规模小、流动性弱、城镇化水平低、人口和城镇化率小幅缓慢增长等基本特点。②人口重心略微西移,人口分布“西北—东南”走向的空间格局基本稳定,呈“核心—外围”式空间结构,兰州、西宁和临夏是3个人口集聚中心,其中兰州市显现出人口集聚的“虹吸效应”。甘青两片人口分布格局存在差异,甘肃片区人口密度中南部高、北部低,青海片区人口以西宁为中心向其他县域“圈层”递减。③海拔是影响兰西城市群人口垂直分布格局的主要地形因素,人口分布的高程梯度效应和河谷盆地集聚指向明显,人口主要集中在海拔低于2400 m的中海拔河谷盆地内。多尺度、多视角的研究结论及相应的对策建议,可为区域人口空间优化布局提供科学依据。  相似文献   

复合式训练影响青少年下肢爆发力的meta分析     

翟华楠  周彤 《武汉体育学院学报》2020,54(10):65-71

目的：运用元分析的方法检验复合式训练对青少年下肢爆发力影响的干预效果,检验并提出最优的运动干预方案。方法：运用STATA 15.1和Review Manager 5.3对纳入的10篇文献和301名被试者通过设置抗阻类型、抗阻强度、间歇时间、训练频率和训练周期等5个调节变量进行亚组分析,采用固定效应模型进行整体效应、异质性、发表偏倚性检验。结果：（1）复合式训练对跳跃类运动表现的影响效应量d0.36,对短跑类运动表现的影响效应量d-0.51,两者达到中等效应且具有统计学意义;（2）本研究纳入的10篇文献异质性较低,间歇时间、训练频率和训练周期的对跳跃类和短跑类运动表现影响的效应量有一定差别。结论：（1）复合式训练能够显著提升青少年跳跃类和短跑类运动表现;（2）抗阻训练选择等张收缩、强度70%1RM以下、小于3分钟的间歇时间、在4~8周内选择每周1-2次的复合式训练能够对青少年运动表现有较好的提升;（3）围绕青少年人群开展的复合式训练较为缺乏,后续研究应加强理论与实践研究。  相似文献   

4周下肢间歇负压干预对优秀赛艇运动员心率变异性和儿茶酚胺的影响     

董徽徽  高炳宏 《上海体育学院学报》2020,(4):78-83

目的探讨下肢间歇负压干预对赛艇运动员心率变异性(HRV)相关指标和儿茶酚胺的影响。方法将国家赛艇队的14名运动员分为试验组和对照组,试验组运动员每周用间歇负压干预5 d,持续4周,对照组无其他干预方式。试验期间均对2组运动员进行HRV相关指标和儿茶酚胺的测试。结果试验前2组运动员各指标均无统计学差异。开始干预后2组的变化如下:①在时域指标中,试验组正常窦性R-R间期标准差(SDNN)在第3周时高于对照组(P<0.05)。②在频域指标中,试验组高频(HF)值在第2周和第3周时高于对照组(P<0.05),而其高频与低频比(LF/HF)在第1、3和4周时低于对照组(P<0.05)。③2组儿茶酚胺组内、组间比较均无统计学差异,但试验组儿茶酚胺下降程度比对照组高。结论4周的间歇负压干预对运动员自主神经系统功能的恢复有明显促进作用,对儿茶酚胺的分泌也具有抑制趋势;这有利于降低运动员心脏负荷,促进运动后的生理恢复。  相似文献   

The effects of a calf pump device on second half performance of a simulated soccer match in competitive youth players     

S. Béliard  J. Cassirame  G. Ennequin  G. Coratella  N. Tordi 《Journal of sports sciences》2019,37(6):708-716

During soccer matches, performance decrements have been reported that relate to both physical abilities and technical skills. To investigate the effects of low-frequency electrical stimulation LFES (VeinoplusSport®, Ad Rem Technology, France) administered during half-time recovery on performance alterations during the second half. Twenty-two highly trained young players undertook a soccer-match simulation (SAFT⁹⁰). During half-time, they were randomly assigned to LFES group or Placebo group. Each half was split into 3 bouts of 12 minutes. Following each bout, maximal strike speed (MSS), sprint test (ST), maximal sprint accelerations (MA) and metabolic power (MP) were determined in both groups. Arterial (AF) and venous flows (VF) were measured at rest and at the end of half-time. LEFS group exhibited beneficial effects on performance compared to the Placebo group with a likely effect for MSS, ST, MA, and a possible effect for MP. AF and VF increased statistically more in LEFS group compared to Placebo group. The use of specific calf-pump LFES during half-time of a youth simulated soccer match attenuated the decrease in performance during the second half compared to Placebo group. This effect is most marked at the beginning of the second half with regards to explosive parameters.  相似文献