Calculating method of contact stress for non-circular gears     

LI Ji-qiang  LIU Zhong-ming  YAN Shi-dang 《重庆大学学报(英文版)》2015,14(1):19-24

According to Hertz theory, the difference of contact stress for non-circular gears and equivalent gears is compared in the paper, a calculating method of contact stress for non-circular gears by using equivalent gears is researched, and computing formulas of power and rotation speed for equivalent gears are deduced. A numerical simulation of contact stress for non-circular gears has also been conducted based on the finite element method. By the comparison of fitting curves, the feasibility of using equivalent gears instead of non-circular gears to calculate the contact stress is testified.  相似文献   

Chlorogenic acid prevents acetaminophen-induced liver injury: the involvement of CYP450 metabolic enzymes and some antioxidant signals     

Chun Pang  Yu-chen Sheng  Ping Jiang  Hai Wei  Li-li Ji 《Journal of Zhejiang University. Science. B》2015,16(7):602-610

Chlorogenic acid (CGA), a polyphenolic compound, is abundant in fruits, dietary vegetables, and some medicinal herbs. This study investigated the prevention of CGA against acetaminophen (AP)-induced hepatotoxicity and its engaged mechanisms. CGA reversed the decreased cell viability induced by AP in L-02 cells in vitro. In addition, CGA reduced the AP-induced increased serum levels of alanine/aspartate aminotransferase (ALT/AST) in vivo. The effect of CGA on cytochrome P450 (CYP) enzymatic (CYP2E1, CYP1A2, and CYP3A4) activities showed that CGA caused very little inhibition on CYP2E1 and CYP1A2 enzymatic activities, but not CYP3A4. The measurement of liver malondialdehyde (MDA), reactive oxygen species (ROS), and glutathione (GSH) levels showed that CGA prevented AP-induced liver oxidative stress injury. Further, CGA increased the AP-induced decreased mRNA expression of peroxiredoxin (Prx) 1, 2, 3, 5, 6, epoxide hydrolase (Ephx) 2, and polymerase (RNA) II (DNA directed) polypeptide K (Polr2k), and nuclear factor erythroid-2-related factor 2 (Nrf2). In summary, CGA ameliorates the AP-induced liver injury probably by slightly inhibiting CYP2E1 and CYP1A2 enzymatic properties. In addition, cellular important antioxidant signals such as Prx1, 2, 3, 5, 6, Ephx2, Polr2k, and Nrf2 also contributed to the protection of CGA against AP-induced oxidative stress injury.  相似文献   

盐胁迫对大豆POD、SOD和CAT同工酶的影响     

何庆元  向仕华  吴萍  王松华  李正鹏  祝嫦巍  张晓红 《安徽科技学院学报》2015,(3):10-13

采用1/2浓度Hoagland营养液培育法中不同浓度(0.000、0.050、0.075、0.100和0.125 mol/L)的Na Cl溶液处理V2期苗期大豆,待大豆生长至V3期,分析不同浓度盐胁迫对大豆生长以及POD、SOD和CAT同工酶的影响。结果表明:Na Cl浓度越高,大豆生长受到的抑制越大,而POD、SOD和CAT的活性在Na Cl浓度在0.050 mol/L有一定的增加,但增加到0.075 mol/L后,酶的活性降低。在0.075和0.100mol/L的Na Cl浓度诱导出了新的POD同工酶谱带,而0.125 mol/L Na Cl使SOD同工酶的2条谱带消失。  相似文献   

中厚及厚煤层煤柱灾害长钻孔松动爆破防治技术研究     

徐涛 《鸡西大学学报》2011,(12):50-51

通过对长钻孔松动爆破技术研究,形成完整的长钻孔松动爆破技术,并运用其对中厚及厚煤层开采留设的煤柱进行处理,改变煤柱受力状态,消除由于煤柱引起的集中应力、冲击矿压、采空区自燃等矿井灾害是解决中厚及厚煤层开采遗留问题的有效技术手段。  相似文献   

水杨酸对铅胁迫下玉米幼苗生理特性的影响     

李红侠  韩雪飞 《滁州学院学报》2011,13(5):60-62

以玉米种子为试验材料,采用砂培法研究了水杨酸(SA)对铅(Pb2+)胁迫下玉米种子的萌发、叶绿素含量、MDA含量、POD活性、等方面的影响。结果表明:低浓度的SA≤80mg/L时,能促进铅胁迫下玉米幼苗的生长,表现为玉米种子的发芽率增大,幼苗根长的增加,叶绿素含量增大,MDA的含量降低,POD活性升高,等。当SA浓度为60mg/L～80mg/L,Pb2+≤1mg/L时,SA对Pb2+的解毒效应最明显,当SA浓度为100mg/L,Pb2+为8mg/L时,SA与Pb2+协同迫害幼苗的生长。  相似文献   

基于实证的中小学生学业质量分析报告——以江苏连云港市为例     

顾长明 《考试研究》2011,(6):13-21

中小学生学业质量是教育教学质量的重要组成部分,连云港市义务教育阶段学生学业质量监测与问卷实证数据的分析,反映出中小学学业质量整体达标率、优分率较好,学生基础知识与基本技能较为扎实,教与学方式发生深刻变化,学校办学行为进一步规范。同时,该报告也反映出学生解决问题能力不高、区域内质量不均衡、教师教学策略与本体知识缺失、学业质量背景环境不理想等问题。为此,本文提出要发挥质量监测功能、引领教学行为跟进、研发学业质量标准、推进教育现代化创建和完善质量监测反馈系统等建议,以引导学生、教师、学校、社会树立正确的教育观、教学观、评价观和质量观。  相似文献   

中小学教师信息技术应用能力现状及培训建议   总被引：1，自引：0，他引：1  

张屹  马静思  周平红  范福兰  白清玉 《中国电化教育》2015,(1)

信息技术能力已成为信息化社会教师必备的专业能力,2014年6月,教育部颁布了《中小学教师信息技术应用能力标准(试行)》,开启了中小学教师新一轮信息技术应用能力提升培训。为了了解现阶段中小学教师信息技术应用能力水平,为能力提升培训的实施提供依据。该文以湖北、河南、安徽和广西四个省市中35个市区的414名中小学教师为调研对象,从标准的角度对其信息化应用能力现状开展较为全面的调研。结果表明中小学教师应用信息技术优化课堂教学能力的达标情况优于转变学习方式的能力。根据测评结果对中小学教师信息应用能力培训提出建议,也为我国推进信息化环境下教师队伍的建设提供借鉴。  相似文献   

AtHsfAla 对拟南芥幼苗在干旱中生理指标的影响     

谭越  何承忠  郭丽红 《昆明师范高等专科学校学报》2015,(3)

以过量表达 AtHsfAla 及 AtHsfAla 基因沉默的转基因植株为材料,通过控制土壤水分进行干旱处理,结果显示,过量表达型干旱处理后的存活率最大,而基因沉默型最小,表明 AtHsfA1a 能增强植物的抗旱性。为了从生理水平研究 AtHsfA1a 提高抗旱性的机制,研究发现过量表达型的叶片相对含水量和叶绿素含量最高,而沉默型最低。不同基因型植株的 H2 O2和 MDA 的含量正好相反,说明 AtHsfA1a 通过保护细胞膜而减小细胞所受氧化伤害来提高抗旱能力。  相似文献   

Parental perspectives and challenges in inclusive education in Singapore     

Meng Ee Wong  Kenneth K. Poon  Sarinajit Kaur  Zi Jia Ng 《Asia Pacific Journal of Education》2015,35(1):85-97

Relatively little work has focused on inclusive education in Singapore. This study examines the experiences and perceptions of parents whose children with disabilities are attending mainstream secondary schools in Singapore. Data was drawn from interviews with 13 parents of children with mild disabilities. Our findings reveal that parental perspective on inclusive education in Singapore is not only about classroom support but also reflects a deeper concern about whether their children with disabilities will emerge from school as contributing individuals in society. While parents strive to effectively include their children with disabilities in mainstream classrooms, there were dichotomies in their (1) understanding of disabilities, (2) expectations of school support, and (3) expectations for their child with disabilities. Given that academic and social prowess is a critical prerequisite to have a shot at entering the meritocratic Singapore society, the tension parents experience is to gauge a reasonable amount of pressure to exert on their children, the school and themselves as they assert their children's educational entitlements within an imperfect but evolving state of inclusion.  相似文献   

Equity in opportunity-to-learn and achievement in reading: A secondary analysis of PISA 2009 data     

《Studies in Educational Evaluation》2015

Using data from PISA 2009, the present study investigates firstly how equally students are exposed to opportunities to improve their reading skills (OTL) depending on the school they are enrolled in, and secondly the links between OTL in reading and achievement at the school level. A multidimensional within-item IRT is used to model the OTL. The intraclass correlation of both OTL dimensions issued from the IRT analysis – reading fiction and reading non-continuous tasks – is high, especially in differentiated education systems, showing an unequal exposure to OTL in reading according to the school. Robust correlations between the two OTL dimensions and reading achievement are observed at the school level. In addition, the results of a multilevel regression analysis show that a substantial proportion of the between-school variance in reading can be explained by OTL and by the school social intake. The proportion of between-school variance explained jointly by OTL and social intake is higher in differentiated education systems than in comprehensive ones.  相似文献