弹性有限长度杆在轴向应力波传播和反射过程中的屈曲     

徐新生  刘书田  郭杏林 《商丘师范学院学报》1996,(Z4)

讨论弹性有限长度杆端部受冲击载荷作用，在轴向应为波传播和反射过程中的动态屈曲问题．利用扰动方程的解、端部支承条件和应力波反射前后波阵面相容条件得到了动态屈曲的分叉条件，临界载荷和屈曲模态．数值结果表明：临界载荷有多个分支且随时间增加而降低；由于应力波在端部的反射，使临界载荷进一步下降．这个结果就解释了实验中的一些现象．  相似文献   

Fuzzy Comprehensive Assessment Method to Determine Tectonic Stress Patterns     

张海  戚蓝  郝彩哲  郭磊 《天津大学学报(英文版)》2007,13(6):462-468

The tectonic stress patterns were determined by a fuzzy comprehensive assessment method. Data of in-situ survey and fault information were utilized in the method. First, by making pressure and tension in the directions of along-river, cross-river, shear clockwise, and shear counterclockwise , 26 types of tectonic stress patterns were presented. And the stress vector of each pattern was obtained with FE software by taking unit displacement as boundary load. Then, by taking the 26 types of tectonic stress patterns as index set and 3 main stresses as factor set and choosing various operators, comparison of directions of computational stress vector and survey stress vector was made and the most possible tectonic stress pattern was obtained. Taking the 26 types of tectonic stress patterns as index set and strike angle as factor set, comparison of relationships between formation of fault and tectonic stress was made,and the tectonic stress patterns were assessed with known fault information. By summarizing the above assessment results, the most impossible tectonic stress pattern was obtained . Finally an engineering case was quoted to validate that the method is more feasible and reliable than traditional empirical method.  相似文献   

幼儿教师工作压力与生活满意度的关联性研究          下载免费PDF全文

许颖 《宁波大学学报(教育科学版)》2020,(6):117-122

摘要:采用问卷调查法对511名幼儿教师进行调查,考察幼儿教师工作压力与生活满意度之间的关联,探讨心理资本和工作倦怠在其中的序列中介效应。结果表明:（1）幼儿教师工作压力、心理资本、工作倦怠、生活满意度两两显著相关;（2）幼儿教师工作压力对生活满意度的直接预测作用不显著,但分别通过心理资本、工作倦怠的独立中介作用以及二者的序列中介作用间接预测生活满意度。研究结果提示不仅要重视缓解幼儿教师的工作压力,降低工作倦怠,还要从提升幼儿教师心理资本、发挥个体资源的保护性作用等途径缓解工作压力对幼儿教师生活满意度的不利影响。  相似文献   

仿生种植牙应力分布的有限元分析     

王宗篪  庄国铭  赖森财  谢培庆  黄庆杰  黄跃 《三明学院学报》2002,19(4):1-3

以上颌中切牙为解剖学基础 ,提出了仿生种植牙模型。相同载荷分别作用于天然牙、仿生牙及骨性结合种植牙模型 ,用二维有限元法计算得到牙周膜和仿生牙周膜的应力分布 ,对三种模型骨界面上的应力分布进行了比较研究  相似文献   

Teacher self-efficacy moderates the relations between imposed pressure from imposed curriculum changes and teacher stress     

David W. Putwain  Nathaniel P. von der Embse 《教育心理学》2019,39(1):51-64

Based on the Job Demands-resources (RD-R) model, the aim of the current study was to examine how pressure arising from imposed curriculum changes and teacher self-efficacy relate to perceived stress in teachers. Participants (839 teachers working in English schools) completed an online survey that contained questions about demographics, self-reported pressure from imposed curriculum changes, teacher self-efficacy, and perceived stress. Pressure from imposed curriculum changes was positively, and teacher self-efficacy negatively, related to perceived stress. Teacher-self efficacy moderated relations between pressure from imposed curriculum changes and perceived stress. High teacher self-efficacy was associated with lower perceived stress, relative to low teacher self-efficacy, when pressure from imposed curriculum changes was low. The differential advantage offered by high self-efficacy declined as pressure from imposed curriculum changes increased.  相似文献   

论英语节奏     

王守芳 《临沂师范学院学报》2001,23(2):118-120

阐述了英语节奏的特点，论述了英语节奏与词重音、句重音、重音规整性，音长、元音的音质、语调和语言的可理解性三者之间的相互关系和影响。提出了掌握英语节奏的正确方法。  相似文献   

不同品种黄瓜幼苗光合机构对盐胁迫的响应   总被引：26，自引：0，他引：26  

钱琼秋  魏国强  朱祝军  李娟 《科技通报》2004,20(5):459-463

研究了盐胁迫(0、25、50mmol／L)对不同品种黄瓜幼苗生长、光合作用和叶绿素荧光的影响．结果表明，盐胁迫，尤其是高浓度NaCl(50mmol／L)的胁迫，显著降低黄瓜幼苗生长量、叶绿素含量、光系统Ⅱ光合电子传递量子效率(φPSⅡ)、净光合速率(Pn)、气孔导度(Gs)以及气孔限制值(Ls)，同时显著提高叶片相对电导率、丙二醛、脯氨酸含量和细胞间CO2浓度(Ci)，光系统Ⅱ的光化学效率(Fv／Fm)变化不大．盐胁迫对耐盐黄瓜‘津研4号’幼苗生长的影响小于盐敏感黄瓜‘津绿4号’，这可能与耐盐黄瓜在盐胁迫下较高的净光合速率、光系统Ⅱ光合电子传递量子效率和较低的丙二醛(MDA)含量、相对电导率有关。  相似文献   

非协调轴对称杂交应力元单元刚度矩阵的准确建立     

田炯  田宗漱 《中国科学院研究生院学报》1994,(1)

给出新型三类用理性杂交模式、根据一种修正的Ｈｅｌｌｉｎｇｅｒ－Ｒｅｉｓｓｎｅｒ原理、建立高精度非协调轴对称实体旋转有限元时，其单元刚度矩阵的准确计算式。  相似文献   

Effects of osmotic stress on antioxidant enzymes activities in leaf discs of P<Subscript>SAG12</Subscript>-<Emphasis Type="Italic">IPT</Emphasis> modified gerbera     

Lai QX  Bao ZY  Zhu ZJ  Qian QQ  Mao BZ 《Journal of Zhejiang University. Science. B》2007,8(7):458-464

Leaf senescence is often caused by water deficit and the chimeric gene PSA612-1PT is an auto-regulated gene delaying leaf senescence. Using in vitro leaf discs culture system, the changes of contents of chlorophylls, carotenoids, soluble protein and thiobarbituric acid reactive substance （TBARS） and antioxidant enzymes activities were investigated during leaf senescence of PSA612-1PT modified gerbera induced by osmotic stress compared with the control plant （wild type）. Leaf discs were incubated in 20%, 40% （w/v） polyethylene glycol （PEG） 6 000 nutrient solution for 20 h under continuous light [ 130 μmol/（m^2·s）]. The results showed that the contents of chlorophylls, carotenoids and soluble protein were decreased by osmotic stress with the decrease being more pronounced at 40% PEG, but that, at the same PEG concentration the decrease in the transgenic plants was significantly lower than that in the control plant. The activities of superoxide dismutase （SOD）, catalases （CAT）, ascorbate peroxidase （APX）, guaiacol peroxidase （GPX） and dehydroascorbate reductase （DHAR） were stimulated by PEG treatment. However, the increases were higher in PSA612-IPT transgenic plants than in the control plants, particularly at 40% PEG treatment. Lipid peroxidation （TBARS content） was increased by PEG treatment with the increase being much lower in transgenic plant than in the control plant. It could be concluded that the increases in the activities ofantioxidant enzymes including SOD, CAT, APX, GPX and DHAR were responsible for the delay of leaf senescence induced by osmotic stress.  相似文献   

碱胁迫对叶片延迟发光的实验研究   总被引：1，自引：0，他引：1  

王红梅 《实验技术与管理》2011,(10):52-55

选用绿宝石喜林芧叶片为材料,用BPCL型微弱发光测量仪测量了叶片经高浓度NaOH溶液处理后的延迟发光情况。结果发现:同一个叶片随着处理时间的延长,其延迟发光最初值和最后100s的光子数都先有一个小幅度的上升,然后又迅速下降;不同的叶片在相同的处理时间下,随着NaOH质量分数的增加,延迟发光最初值和最后100s的光子数都呈现上升的趋势,NaOH质量分数越大,上升得越快,随着处理时间的延长,上升的趋势变得越来越缓,最后各曲线越来越接近,且趋于平稳。整个实验表明,延迟发光可以规律性地反应碱胁迫对叶片的伤害程度,这为生物物理方法测量外界胁迫对叶片的影响提供了参考。  相似文献