薄片漏斗试样的应变等效换算与Zr-4合金疲劳寿命估算

完成了Zr-4合金薄片漏斗小试样的横向等幅应变疲劳试验;提出了薄片漏斗试样细腰部与薄片等直试样疲劳损伤等效的局部损伤等效假设;基于弹塑性有限元分析,建立了Zr-4合金薄片漏斗小试样横向测试应变向轴向应变转换的应变等效转换模型,该模型考虑了几何效应和泊松效应;结合实验结果,提出了用于Zr-4合金应变疲劳寿命估算的Manson-Coffin(M-C)模型。研究表明:薄片漏斗小试样及其应变等效转换模型可以有效应用于薄片金属材料的低周疲劳试验和寿命估算;国标推荐的应变换算公式应用于薄片漏斗小试样的Zr-4合金疲劳寿命估算会带来很大安全余量。     

Microstructure and corrosion resistance of sputtered TiN coatings on surface of Zr-4 alloy

To improve the oxidation resistance and corrosion resistance of Zr-4 alloy, titanium nitride(TiN) coatings were prepared on the Zr-4 alloy with a TiN ceramic target with different ratios of N_2. Microstructure and high-temperature properties of the TiN coated samples were studied by scanning electron microscopy(SEM), energy dispersive spectrometer(EDS), X-ray diffraction meter(XRD), X-ray photoelectron spectroscopy(XPS), heat treatment furnace and autoclaves, respectively. The x value of the TiN coatings(TiN_x) ranges from 0.96 to 1.33. After the introduction of N_2, TiN coating exhibits a weak(200) plane and a preferred(111) orientation. The coating prepared with an N_2 flow ratio of 15% shows an optimal oxidation resistance in the atmospheric environment at 800 °C. In either 1 200 °C steam environment for one hour, or deionized water at 360 °C and a pressure of 18.6 Mpa for 16 d, the opitimized TiN coated samples have no delamination or spallation; and the gains in the masses of samples are much smaller than Zr-4 alloy. These results demonstrate the effectiveness of the optimized TiN coating as the protective coating on the Zr-4 alloy under extreme conditons.     

剖腹产术后的观察护理

剖腹产的产妇往往心里总有一种恐惧的感觉,既怕伤口感染,又怕子宫收缩欠佳,出血等症。因此我们要做好术后的护理工作一、术后严密观察病情:产妇从手术室回病房后立即测血压、脉搏、呼吸,并查看尿管是否保留通畅。进行输液。每20分钟-30分钟测量生命体征一次。观察产妇的面色、神志、发现异常及时处理。观察阴道出血情况。如有2例产妇,回病房4     

根管治疗实验课中引入根管电测仪的必要性与可行性分析

根管治疗术是牙髓病学课程的重点及难点,也是口腔本科生必须掌握的内容。根管工作长度测量是根管治疗中的一个重要步骤,其准确性对根管治疗的预后影响极大。目前本科生根管治疗实验课中有关根管测量的内容较少。在临床上常用根管电测仪测量根管长度,借助体外模型,根管电测仪也可用于离体牙根管长度的测量。因此,本文分析根管电测仪在根管治疗实验课中应用的必要性及可行性,以便进一步提高根管治疗实验课程的教学效果。     

高超声速风洞进气道流量系数测量精度影响因素研究

进气道是飞行器动力装置的重要组成部分,准确测量进气道流量系数是进气道风洞试验的重要内容。对来流马赫数Ma=4.5,5.0和6.0状态下皮托管进气道开展流量系数测量研究,通过对比理论值和实测值,获取各状态流量系数修正系数。试验结果表明,随着来流马赫数增加,进气道流量系数与理论值偏差较明显,并逐渐增大。超声速风洞试验通常认为测量截面总温与来流总温相等,通过对测量截面总温与来流总温偏差以及测量截面流场畸变情况的分析,判断测量偏差主要是由测量截面总温等于来流总温的假设导致的。在高超声速风洞试验中,由于模型壁面热交换的存在,测量截面总温低于来流总温,进气道流量系数测量时需要进行总温修正,以提高流量测量精度。      

振荡水柱装置波浪水槽试验中用于模拟非线性能量俘获系统的孔口特性(英文)

目的:在振荡水柱装置研究中,通常通过不同的孔口几何特征来改变能量俘获系统的特性,但其具体流动特性却鲜有报道。本文探讨孔口几何特征(形状、尺寸和开孔率等)对流动特性的影响机制,理解影响能量俘获系统特性的关键因素,研究其对振荡水柱装置水动力特性和波能提取的影响规律,并评估波能提取性能指标的有效性。创新点:1.提出了两点测量法来重构振荡水柱腔室内液面;2.建立了孔口流动特性与孔口几何特征的关系式;3.提出了仅测量腔室内气压即可获得波能提取功率的方法;4.该方法可扩展至非二维矩形腔室及斜向波。方法:1.采用不同尺寸狭缝孔和圆形孔来模拟非线性能量俘获系统;2.通过一系列波浪水槽试验,对振荡水柱装置的水动力特性及波能的提取展开研究;3.采用二次损耗系数和收缩系数来描述孔口往复流动特性,并构建其与孔口几何特征的关系;4.通过两点测量法获取振荡水柱腔室内的准确信息;5.评估压力波动系数和液面放大系数作为振荡水柱装置波能提取性能指标的有效性。结论:1.两点测量法能够重建二维矩形振荡水柱腔室内液面的瞬时空间分布,消除了单点法的测量偏差;2.孔口相对厚度及振荡气流对可被视为薄壁的圆形孔的影响可以忽略不计,但对不能视为薄壁的狭缝孔的影响显著;3.本文提出的二次损耗系数经验公式可用于(1)通过孔口几何尺寸设计其流动特性和(2)通过仅测量腔室内气压来计算波能提取功率;4.用作振荡水柱装置的波能提取性能指标时,压力波动系数比液面放大系数更为可靠。     

TCT416型导热系数测试仪的改进

对TCT416型导热系数测试仪进行了改进,并用圆筒法、圆球法和该仪器测量了颗粒耐火材料的有效导热系数,以对其进行检验。实验表明,该仪器可以方便地用于颗粒催化剂材料有效导热系数的测量,大大加快了催化剂的筛选速度,并且扩大了TCT416型导热系数测试仪的测量范围。     

用电子分析天平测量液体的表面张力系数

阐述用电子分析天平测量液体表面张力系数的原理和方法．对液体表面张力系数测量公式进行分析讨论,指出某些文献中所给出的拉脱法测液体表面张力系数实验测量公式存在的问题．     

硅藻土沥青及沥青混合料低温抗裂机理(英文)

对一种基质沥青和3种硅藻土沥青进行了差示热扫描分析,并结合相应的混合料约束试件的温度应力试验分析了硅藻土沥青的低温抗裂机理.结果表明:硅藻土沥青有优于基质沥青的低温性能;玻璃态转化温度可以较好地反映硅藻土沥青的低温性能;玻璃态转化温度与破断温度有较高的相关性.另外还进行了相应的4种沥青混合料的低温弯曲试验、低温压缩试验和收缩系数试验.结果表明:硅藻土沥青混合料的低温性能优于基质沥青混合料;硅藻土沥青混合料临界弯曲应变能密度及压缩应变能密度均大于基质沥青混合料;沥青混合料加入硅藻土后收缩系数降低.在此基础上,从混合料收缩性能和破坏能量2个角度分析了硅藻土沥青混合料的低温抗裂机理.     

基于VB的ANSYS二次开发及其在管道外自然对流换热系数确定中的应用

介绍一种以ANSYS有限元分析软件为基础,结合VB开发语言共同解决管道外自然对流换热系数确定的方法。利用VB语言开发可视化界面,完成对管道温度场分布及管道外自然对流换热系数的确定,降低ANSYS软件的使用难度,方便、快捷地计算出管道外自然对流换热系数,避免了大量迭代分析过程,提高了效率。     

电网等值中CSR法与REI法准确性研究

利用BPA软件以新英格兰39节点系统为算例,分别采用CSR法与REI法对外部系统的网络进行简化等值,并根据简化后系统的稳态和暂态等值效果比较两种方法的准确性。     

美国CSR影响及原因分析

现在美国在基础教育中极力实施的“小班化”(CSR)教学大大提高了学生的学业成绩。本文对美国CSR项目的影响和原因等方面做了分析研究，总结出CSR的实施特点。     

中美教育比较的新视角: 小班化教育 (CSR)境况、焦点论争及方略

“小班化教育”是当今美国所实施的最热门、最有争议的一项教育改革措施，被称为“教学领域的一场革命”。我国当前也正积极探寻小班化教育改革理论与实践。虽然两国在经济文化各方面存在差异．但在小班化教育改革中有许多值得比较研究之处。也产生了一些令人关注的问题，分析与思考这些问题．对我国小班化教育的开展具有一定的积极意义。     

BOOK REVIEW. Development Planning and School Improvement for Middle Managers Co-authors: Marilyn Leask and Ian Terrell,London, UK: Kogan,Page 1997.x + 246 pp. ISBN 0 7494 2038 3

The longitudinal impacts on school change and student achievement of implementing varied Comprehensive School Reform (CSR) models was investigated in 12 elementary schools in diverse geographic locations. Each school was individually matched and compared to a demographically similar control school on measures of school climate, teacher satisfaction, observed classroom teaching methods, and student achievement on a battery of 4 individually administered reading tests. Data were analyzed for all CSR-control school pairs combined and separately for pairs representing 4 different CSR models (Balanced Early Literacy Initiative, Core Knowledge, Direct Instruction, and Success for All). Although results varied across location (rural versus urban) and models on different measures, overall CSR advantages were evidenced for teacher attitudes, school climate, and student achievement. Observations of teaching strategies further revealed their general conformity to the CSR models' pedagogical emphases (e.g., direct instruction, ability grouping, higher order questioning). The implications of the findings are discussed relative to processes of enacting and sustaining educational change using whole-school reform approaches.     

Implementation: Measuring and Explaining the Fidelity of CSR Implementation

Comprehensive school reform (CSR) is only as effective as its implementation. By using data collected for the National Longitudinal Evaluation of Comprehensive School Reform (NLECSR), this article explores the factors that predict CSR model implementation and the ways that CSR model implementation varies. We found little difference in the fidelity of implementation between schools implementing a CSR program and their matched comparison schools, but we found vast differences in the fidelity of implementation between different CSR program implementation keys (the normative guidelines received from CSR program developers on which we based our implementation measures). The fidelity of implementation is predicted by multiple factors, including the CSR program implementation keys, the principal's instructional leadership, the measure of teachers' professional community, and the usefulness of the CSR developers' assistance. The change in implementation is associated with positive change in principal's instructional leadership and usefulness of the CSR developers' assistance.     

Implementation of Comprehensive School Reform and Its Impact on Increases in Student Achievement

This study examined the relationship between the implementation of comprehensive school reform (CSR) and changes in reading and math achievement from 1999 until 2003. Survey data about CSR implementation and school-level achievement data were collected for multiple years from a sample of CSR schools and compared with a sample of matched comparison schools. The sampled CSR schools adopted several promising CSR models. Results revealed that improvement over the years in school-level mathematics and reading achievement of CSR schools was not consistently greater than the improvement for comparison schools. The relationship between implementation of CSR and improvement in student achievement was shown to vary by number of years, level of implementation, and CSR designation. CSR schools experienced the largest increases in student achievement between Years 3 and 5 of implementation. A high level of implementation and comprehensiveness of implementation was weakly associated with a large increase in mathematics and reading achievement relative to the matched comparison school. This relationship also varies by CSR designation.     

Tackling California’s Class Size Reduction policy initiative: an up close and personal account of how teachers and learners responded

This chapter examines some effects of California’s Class Size Reduction (CSR) policy on teachers and pupils in four elementary schools over a two year period using interviews and participant observation. Among the main findings from the interviews, confirmed by the observations, was that while teachers found classes with 20 pupils easier to teach, they did not initially consider the possibility of changing practice in order to maximize the advantages of the smaller classes. In the second year there were slight increases in the amounts of individual attention pupils received, particularly feedback, and teachers expressed greater confidence when making assessments. Pupils’ reactions were generally positive although some expressed the view that in larger classes they got more help from friends. There were several unanticipated effects; for example, some older grade teachers with larger classes expressed resentment because of their higher administrative and marking loads.     

Implications of NCLB Accountability for Comprehensive School Reform

No Child Left Behind (NCLB) accountability mechanisms have the potential to derail comprehensive school reform (CSR) implementation. For those pursuing CSR, the question is how to reconcile the implementation of NCLB accountability mandates with ongoing CSR efforts. Drawing from longitudinal data from a national study of CSR, this article explores this question. Survey data indicate that schools identified for improvement are no more likely to drop their models than are other CSR schools. Moreover, it appears that when CSR schools are identified for improvement, this identification stimulates a higher rate of model implementation than in schools that are not identified under NCLB. Case study interview data revealed that a district variation in stakeholders' awareness and perceptions of NCLB and the interactions of NCLB accountability mechanisms and CSR sustainability.