共查询到18条相似文献，搜索用时 387 毫秒
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根据杂交应力理性模式，基于一种修正的Hellinger－Reissuer原理，建立了具有一个无外力斜边的杂交应力元，其应力场由无边界面力在非协调位移上所作虚功之和为零的约束条件导出，将这种特殊元与具有一个无外力圆弧边的杂交应力元联合，可有效地分析具有倒圆角V型槽孔板的应力集中，并可提供远较一般假定位移及一般假定应力元准确的孔边应力分布。 相似文献
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根据Ｈｅｌｌｉｎｇｅｒ－Ｒｅｉｓｓｎｅｒ原理，建立了一种具有一个无外力圆形边界的特殊杂交应力元，其应力场准确满足弹性力学平衡方程、协调方程及无外力圆弧上的边界条件。根据修正的Ｈｅｌｌｉｎｇｅｒ－Ｒｅｉｓｓｎｅｒ原理，建立了另一种具有一个无外力直边界的特殊杂交应力元，其应力场在元上变分满足平衡方程，但准确满足无外力直边上的边界条件。数值算例表明：特殊假定应力元与一般假定位移元这两类元联合，能十分有效地进行纵向倒圆槽孔板的应力集中分析。 相似文献
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应用假设应力杂交元的方法,导出了一个八节点的实体元。此元具有二个平行的表面及一个无外力自由的园柱表面。引用园柱坐标、以使所假设的应力场满足平衡方程及固柱边界面无外力的条件。当退化至平面应力状态时,此应力场也满足协调方程。一些算例证实这种特殊元在分析具有固孔实体时的优越性。 相似文献
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应用杂交应力模式导出新的特殊实体元,这种元具有两个平行表面及一个无外力圆柱面.以圆孔矩形板、圆孔方块等作为算例,评价了不同的元,并选出一种相对最佳的应力场.将以上结果与8节点实体杂交应力特殊元、一般杂交应力元及假设位移元等结果对比,明显看出现在的元.给出远较以上各类元准确的应力集中系数及应力分布. 相似文献
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偶应力问题的非协调元分析 总被引：2，自引：0，他引：2
从偶应力弹性体势能泛函的驻值条件出发,得到了偶应力理论中非协调元体系的能量相容原理。基于其常应力(常偶应力)分片检验条件的强形式,对平面四结点单元的非协调试探内函数进行了优化,提出了一种稳定有效的非协调元方法。有限元列式中,微转动和宏观转动相等的约束条件通过罚因子的形式引入。分析了含中心圆孔的无限平板,在单轴拉伸以及纯剪状态时,偶应力的存在对孔周应力集中的影响。算例表明,该单元计算效率高,精度好,即使在材料本征长度很小时,仍然能够得到相当理想的结果 相似文献
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本文描述了无网格伽辽金法的基本原理及其一些特点，该法只需结点信息，不需要划分单元；并应用具体算例将无网格法计算结果与弹性力学精确解作比较，计算表明无网格伽辽金法具有较高的精度。 相似文献
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边的聚类系数是用来度量复杂网络中两个结点的紧密程度的,被广泛的应用于识别网络模块。本文介绍了如何利用SQL及相关函数来求解边的聚类系数。 相似文献
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在公路建设中，为了预防或降低震陷的危害，除了加强抗震设施外，通过数值计算来估算震陷量，具有一定的社会效益与经济效益。通过有效应力等效线性动力反应分析，运用等价结点力法分析了高速公路软粘土路基震陷随地震最大加速度的变化趋势，建立了震陷同路堤高度、软土动模量系数、饱和重度、遭遇的竖向与水平向地震加速度放大系数之比和水平向地震系数等因素的相关关系式。 相似文献
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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
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以体外循环手术作为创伤应激模式，采用放射免疫法测定了１６例低温麻醉体外循环手术者围术期７个时段的血浆ｃＡＭＰ、ｃＧＭＰ值，探讨其在应激状态下的变化及临床意义．发现随机体承受创伤刺激，特别是对心脏的手术操作及体外循环转流刺激强度的增减，ｃＡＭＰ及ｃＧＭＰ呈相应的变化．表明在体外循环手术这种特定的创伤模式下，对血浆环核苷酸的动态监察可作为病人机体、特别是心脏应激反应强度的一个综合参考指标 相似文献
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《Information processing & management》2022,59(6):103064
Occupational stress has a significant adverse effect on workers’ well-being, productivity, and performance and is becoming a major concern for both individual companies and the overall economy. To reduce negative consequences, early detection of stress is a key factor. In response several stress prediction methods have been proposed, whose primary aim is to analyse physiological and behavioural data. However, evidence suggests that solutions based on physiological and behavioural data alone might be challenging when implemented in real-world settings. These solutions are sensitive to data problems arising from losses in signal quality or alterations in body responses, which are common in everyday activities. The contagious nature of stress and its sensitivity to the surroundings can be used to improve these methods. In this study, we sought to investigate automatic stress prediction using both surrounding stress data, which we define as close colleagues’ stress levels and the stress level history of the individuals. We introduce a real-life, unconstrained study conducted with 30 workers monitored over 8 weeks. Furthermore, we propose a method to investigate the effect of stress levels of close colleagues on the prediction of an individual’s stress levels. Our method is also validated on an external, independent dataset. Our results show that surrounding stress can be used to improve stress prediction in the workplace, where we achieve 80% of F-score in predicting individuals’ stress levels from the surrounding stress data in a multiclass stress classification. 相似文献
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低钾胁迫对不同基因型杂交水稻氮代谢的影响 总被引：5，自引：0，他引：5
通过在低钾胁迫下对杂交水稻耐低钾基因型威优３５及不耐低钾基因型汕优６号的比较研究,表明低钾胁迫会显著增加不耐低钾基因型植株地上部分的氮含量和叶片总游离氨基本酸含量,降低籽粒粗蛋白含量,显著影响叶片脯氨酸含量的变化;而对耐低钾基因型的影响较小。低钾胁迫还引起两基因型其它主要游离氨基酸的不同变化,籽粒产量也有明显差异,说明耐低钾基因型水稻在氮代谢方面具有特异性。 相似文献
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H.B. Maris 《Journal of The Franklin Institute》1947,244(1):27-62
The equations of equilibrium in a stress field as given by Lamé are compared with those given by Cauchy. The (P ? Q and P ? R) terms of the Lamé equations identified by the new words detend and double detend are invariant for any point in a stress field. The principal stresses are defined as real stress components. The terms of the Cauchy equations are considered as imaginary force components. Real and imaginary stress and force components are differentiated by the differences between ray vectors, as for example a force which has only one real value and direction, and diffuse vectors, as for example a gradient, which has a real value in any direction. Shear is differentiated from detend value by its variation with the direction in which it is taken. Shear is found to be an imaginary component of force parallel to a plane.The photoelastic equidetend (isochromatic) and isoclinic maps of a plane stress field define, for any point, a gradient triangle with the three maximum gradients, Δ(P ? Q) ΔP and Δ ? Q, for its sides. Five quantities, the detend (P ? Q), the ratio of the detend to its gradient (r4), the ratio (r3) of the isoclinic normal ds3 to the stress axis direction change along its length dα, the direction of the equidetend normal (θ) and the orientation of an isoclinic line (ω) with reference to a principal stress direction, determine each gradient triangle. Five equations which define elements of the gradient triangle in terms of the five measurable quantities, are developed. Definition of the triangle can be complete with two of the five measurable quantities or two of the five equations omitted. Graphic integration of principal stress changes along any line in a stress field can be made by plotting the line straight and measuring the area swept out by the normal projections, along the line, of the sides of the gradient triangle, after it has been rotated through 90 degrees.Properties of the gradient triangle are used to solve several symmetrical stress problems and to integrate along two lines through a stress field. 相似文献
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Ronald E. Mickens 《Journal of The Franklin Institute》1983,316(3):273-277
We extend to difference equations the classical method of harmonic balance. We show that the method can be used to obtain an approximation to the periodic solutions of a special class of second-order nonlinear difference equations containing a small parameter. Two examples illustrating the method are presented. 相似文献