TIG 熔修对焊接接头海水腐蚀疲劳性能的影响

对经过 TIG 熔修的海上平台用钢(A537)的板状焊接接头进行了海水腐蚀疲劳试验。试验条件是:加载频率0.2Hz,应力比 R=-1,海水温度20°±1℃,阴极保护电位-850mV±30mV,SCE。就平均寿命来说,TIG 熔修试件的海水腐蚀疲劳寿命为原始焊缝(as-welded)试件寿命的四倍至六倍,并且随应力范围的降低而差别增大.在自由腐蚀条件下,TIG 熔修试件的寿命也比原始焊缝试件的寿命长得多。

弹塑性材料中孔洞成核、发展及应力场

采用Bermin的孔洞成核的局部应力准则以及Euler坐标系下大应变有限元方法,分析了平面应变条件下二相粒子与基体在三种不同的界面结合强度下的宏观材料的力学行为.

生物力学——进展和趋向

<正> 今天,生物力学的发展似乎进入了一个新的时期。它有什么特点?未来如何?这是一个引人关注的问题。要回答这个问题,回顾一下它的过去是必要的。 生物力学的发展大体可分三个时期。 Ⅰ.“前学科”时期 生命现象中力学问题的研究由来已久,可以追溯到亚里士多德.但成为一门独立的学

简化Navier-Stokes方程组(SNSE)的几个精确解

对不可压二维驻点流、三维驻点流和旋转圆盘附近的流动等三种流动情况,本文给出简化Navier-Stokes方程组(SNSE)及其精确解。表明:文献[1]理论的SNSE的精确解,在三种流动情况下均与完全Navier-Stokes方程组(NSE)的精确解完全一致;文献[3]SNSE的精确解的速度解与完全NSE精确解的速度解一致,但压力解在三种流动情况下均与完全NSE精确解的压力解不同。文献[3]SNSE精确解给出的压力分布相对与完全NSE精确解给出的压力分布的最大相对误差为100％。

交流电磁流体直接发电的粘性影响

<正> 本文在磁雷诺数不作任何限制的条件下,对直管感应式发电器(图1)计算了粘性对电参数和流场的影响,并着重探索各种因素对功率因子的影响。

Legislação sobre livro e leitura

Apresenta a legislação sobre o livro e a leitura. Reúne as normas jurídicas que tratam da política nacional do livro e da leitura; da preservação do patrimônio bibliográfico; dos direitos autorais e proteção da propriedade intelectual; da regulamentação da profissão de bibliotecário e das datas comemorativas e homenagens cívicas ao livro.

关于动脉血流线性理论的基础

用量纲分析方法分析了动脉脉冲血流线性理论的基础.结论是:1.目前流行的线化条件不适于动脉血流.正确的线化条件应为,或.据此,线性理论适于中等动脉;对主动脉,用以分析压力一流量关系及脉冲波传播特性尚可,不能用来求速度分布.这和实验研究的结论吻合.2.与流动迁移惯性力相比,压力径向梯度的作用是次要的.故在线化条件下考虑径向压力梯度的影响是不必要的.最后用Lou的有限幅度位移模型和最简流动方程给出了解,所得波速公式和计及时一样。

Gain saturation in gas flow and chemical lasers

A theoretical model for gain saturation in gas flow and chemical lasers is presented. The theory is applicable to all possible numerical values of τ/τc, where τ is the characteristie flow time for the flowing gas to move across the laser action region and τc is the characteristic collision relaxation time. The saturation effects of the convection and the "source flow" of the inverted population are revealed. A general relation of gain coefficient and some new gain saturation laws are obtained. For the special case of τ/τc1, the present theoretical results agree with the experimental results on the "anomalous" saturation phenomena in the supersonic diffusion HF chemical laser determined recently by Gross and Coffer[8]. The theory also agrees with the measured results of saturation intensity varying with τ/τc in gas flow CO2 lasers[7]. For the special case of τ/τc1, the present theory is consistent with both the standard theory[1] for gas lasers where the gas has no macroscopic motion and the known gain saturation theory[2-5] for gas flow and chemical lasers.

采动影响下覆岩垮落过程的数值模拟

应用岩层破断过程分析SFPA2D系统 ,分析了采动影响下覆岩破坏的动态发展过程。数值模拟再现了上覆岩层离层、弯曲、沉降、开裂直至冒落的全过程 ,以及采动工作面推进过程中逐步演化的应力场和应变场。根据数值模拟的结果 ,初步探讨了覆岩破断机理 ,指出覆岩的破断特征受分步开挖引起的应力重新分布及其损伤积累以及岩梁的非均质性的影响。

A note on collusion sustainability with optimal punishments and detection lags

In this note we characterize optimal punishments with detection lags when the market consists of n oligopolistic firms. We extend a previous note by Colombo and Labrecciosa (2006) [Colombo, L., and Labrecciosa, P., 2006. Optimal punishments with detection lags. Economic Letters 92, 198-201] to show how in the presence of detection lags optimal punish- ments fail to restore cooperation also in markets with a low number of firms.