一种改进的劳仑茨一劳仑兹公式

我们已经推导出一个电介质方程，在方程中电介质的密度能够由介电常数算出。麦克斯威关系是联系非极性电介质的介电常数ε和折射系数ｎ的表达式。利用麦克斯威关系，我们把这个非极性电介质方程推广到光频区域并获得相应公式，这个公式是在电介质的密度和折射系数之间建立了联系。我们把它称为一种改进了的劳仑茨一劳仑兹方程，也就是本文中的方程（７）。方程（７）中有三个参量，它们能够通过和实验数据进行比较来确定。氢是最常见的电介质物质，它有完善的实验数据，其中包括密度和介常数。仲氢的方程（７）中的参量值通过和实验数据比较而求得，并把它们列在文中方程（９）中。方程（１０）是关于仲氢的改进了的劳仑茨一劳仑兹方程的形式。从方程（９）我们能够确定平均极化率和分子半径。氢的平均极化率为０．３９８×１０－２４ｃｍ３，分子半径为２．０４×１０－８ｃｍ。它们和实验值是同一数量级。这样，首次由折射率来求得分子半径。另一方面，仲氢的密度可以由公式（１０）来计算。在密度范围从０．００２ｇ／ｃｍ３到０．０９６ｇ／ｃｍ３区域内，计算结果是极好的。它和实验值的偏差小到只有１０－６数量级。然而，由著名的Ｂｏｅｔｔｃｈｅｒ公式和劳仑茨—劳仑兹方程计算的结果，和实验?

“靡室劳矣”注释再探

古代汉语和古代文学等相关教材都收录《诗经.卫风》中的名篇《氓》。长期以来,人们对《氓》中"靡室劳矣"句的解释纷纭。本文立足诗句中关键词语的释义,结合诗歌的具体语境,对已有的常见注释进行了分析,提出了对此诗句理解为"不以室家之务为劳"的具体例证。

三青团与劳劳纠纷:以1947年信和案为中心的考察

抗战胜利后,上海三青团为扩展组织,将发展对象转向职业青年。为争取青年工人的信任,三青团采取多种方式为工人发声,包括介入劳劳纠纷。但三青团此举目的并非维护工友权益,而是借此掌握工人、控制工会。但三青团对劳劳纠纷的参与引发上海总工会的不满。1947年,双方围绕信和纱厂工会纠纷,展开争夺信和工会及工人的博弈。三青团、总工会、上海市政府等方面在其中的参与,体现了上海支团战后的发展路径及三青团在地方政治的困境。

Fatigue behavior and life prediction of A7N01 aluminium alloy welded joint

Fatigue characteristics of A7N01 aluminium alloy welded joint were investigated and a fatigue crack initiation life-based model was proposed. The difference of fatigue crack initiation life among base metal, weld metal and heat affected zone (HAZ) is slight. Furthermore, the ratio of fatigue crack initiation life (Ni) to fatigue life to failure(Nf) is a material dependent parameter, 26.32%, 40.21% and 60.67% for base metal, HAZ and weld metal, respectively. Total fatigue life predicted using the presented model is in good agreement with the experimental data and that using Basquin’s model. The observation results of fatigue fracture surfaces, using scanning electron microscope (SEM), demonstrate that fatigue crack initiates from smooth surface due to welding process for weld metal, blowhole in HAZ causes fatigue crack initiation, and the crushed second phase particles play an important part in fatigue crack initiation in base metal.

Fatigue behavior of friction stir spot welded AZ31 Mg alloy sheet joints

The fatigue behavior of friction stir spot welded （FSSW） AZ31 magnesium alloy sheet joints was investigated by tension- compression of fatigue test. The results suggest that all the fatigue failures occur at the stir zone of the FSSW AZ31 sheet joints, and all cracks initiate at the stir zone outer edge between the upper and lower sheet. When the cycle force equals 1 kN, the crack propagates along the interface of heat-affected zone and thermo-mechanical zone, simultaneously across the direction of force; while the cycle force equals 3 kN, the crack propagates along the diameter of stir zone and shear failure occurs finally. Moreover, the transverse microsections indicate that there is a tongue-like region at the outer edge of stir zone between the two AZ31 sheets, and the direction of tongue-like region is toward outside of the stirred zone and all fatigue cracks initiate at the tongue-like region.

Corrosion fatigue behavior of epoxy-coated Mg-3Al-1Zn alloy in gear oil

The corrosion fatigue behavior of epoxy-coated Mg-3Al-1Zn alloy in gear oil was investigated. The corrosion and the fracture surfaces after fatigue test were analyzed by scanning electron microscopy(SEM) and the corrosion compositions were measured by energy-dispersive spectrometry(EDS). The fatigue properties and the crack initiation mechanisms of the specimens before and after epoxy coating treatment were discussed. The results indicate that the fatigue limit after epoxy coating treatment in gear oil is higher than that of the uncoated specimens. The epoxy coating is an excellent way to prevent direct contact between the Mg-3Al-1Zn alloy and surrounding environments. The mechanical properties of the epoxy coating layer are lower than that of magnesium alloy, which is the main reason for the fatigue crack initiation on the epoxy coating layer. In addition, the gear oil lubrication could lead to the flaking off of the epoxy-coated layer.

Influence of high-speed milling parameter on 3D surface topography and fatigue behavior of TB6 titanium alloy

High-speed milling of titanium alloys is widely used in aviation and aerospace industries for its high efficiency and good quality.In order to optimize the machining parameters in high-speed milling TB6 titanium alloy,experiments of high-speed milling and fatigue were conducted to investigate the effect of parameters on 3D surface topography and fatigue life.Based on the fatigue fracture,the effect mechanism of surface topography on the fatigue crack initiation was proposed.The experiment results show that when the milling speed ranged from 100 m/min to 140 m/min,and the feed per tooth ranged from 0.02 mm/z to 0.06 mm/z,the obtained surface roughness were within the limit（0.8 μm）.Fatigue life decreased sharply with the increase of surface equivalent stress concentration factor.The average error of fatigue life between the established model and the experimental results was 6.25%.The fatigue cracks nucleated at the intersection edge of machined surface.

A model of continuum damage mechanics for high cycle fatigue of metallic materials

A non-linear continuum damage model was presented based on the irreversible thermodynamics framework developed by LEMAITRE and CHABOCHE. The proposed model was formulated by taking into account the influence of loading frequency on fatigue life. The parameters H and c are constants for frequency-independent materials, but functions of cyclic frequency for frequency-dependent materials. In addition, the expression of the model was discussed in detail at different stress ratios （R）. Fatigue test data of AlZnMgCu1.5 aluminium alloy and AMg6N alloy were used to verify the proposed model. The results showed that the model possesses a good ability of predicting fatigue life at different loading frequencies and stress ratios.

GIGACYCLE FATIGUE BEHAVIOR OF CAST ALUMINUM IN TENSION AND TORSION LOADING

An improved understanding of fatigue behavior of a cast aluminum alloy（2-AS5U3G-Y35）in very high cycle regime is developed through the ultrasonic fatigue test in axial and torsion loading.The new developed torsion fatigue system is presented.The effects of loading condition and frequency on the very high cycle fatigue（VHCF）are investigated.The cyclic loading in axial and torsion at 35 Hz and 20 kHz with stress ratio R=-1 is used respectively to demonstrate the effect of loading condition.S-N curves show that the fatigue failure occurs in the range of 105—1010 cycles in axial or torsion loading and the asymptote of S-N curve is inclined,but no fatigue limit exists under the torsion and axial loading condition.The fatigue fracture surface shows that the fatigue crack initiates from the specimen surface subjected to the cyclic torsion loading.It is different from the fatigue fracture characteristic in axial loading in which fatigue crack initiates from subsurface defect in very high cycle regime.The fatigue initiation is on the maximum shear plane,the overall crack orientation is on a typical spiral 45° to the fracture plane and it is the maximum principle stress plane.The clear shear strip in the torsion fatigue fracture surface shows that the torsion fracture is the shear fracture.

飘逸潇洒 深邃隽永——简论秦似的散文艺术

在沉甸甸的、厚重的四卷(150万字)的《秦似文集》中,散文作品占了相当重要的页码。秦似先生是以创作杂文著称于世的,他的杂文创作的光辉成就,已经理所当然地载入了中国现代文学的灿烂史册;那针砭时弊的犀利笔锋,常常令人们精神为之一振,鼓起鞭挞丑恶,抨击劣迹的勇气。相比而言,秦似的散文比之杂文篇幅则少一些,艺术风格也迥然相异。因此,读他的散文,人们仿佛被带进了自然清新、朴素雅淡的艺术天地,那飘逸潇洒的气质,深邃隽永的韵味,使你感受到“象苹果饱含着果汁一样”的美的享受。秦似的散文同样闪耀着不凡的艺术才华。

Fatigue reliability quantitative analysis of cement concrete for highway pavement under high stress ratio

In order to obtain the change law of the fatigue reliability of cement concrete for highway pavement under high stress ratios, first, the probability densities of monotonic random variables including concrete fatigue life are deduced. And then, the fatigue damage probability densities of the Miner and Chaboche-Zhao models are deduced. By virtue of laboratory fatigue test results, the fatigue damage probability density functions of the two models can be obtained, considering different stress ratios. Finally, substituting load cycles into them, the change law of cement concrete fatigue reliability about load cycles can be acquired. The results show that under the same stress ratio, with the increase in the load cycle, the fatigue reliability declines from almost 100% to 0% gradually. No matter under what stress ratio, during the initial stage of the load action, there is always a relatively stable phase for fatigue reliability. With the increase in the stress ratio, the stable phase gradually shortens and the load cycle corresponding to the reliability of 0% also decreases. In the descent phase of reliability, the higher the stress ratio is, the lower the concrete reliability is for the same load cycle. Besides, compared with the Chaboche-Zhao fatigue damage model, the Miner fatigue damage model is safer.

Fatigue behavior of aluminum stiffened plate subjected to random vibration loading

Vibration tests were carried out on three types of stiffened aluminum plates with fully clamped boundaries under random base excitation. During the test, the response of the specimens was monitored using strain gauges. Based on the strain history, the accumulation of fatigue damage of the stiffened plates was estimated by means of the rainflow cycle counting technique and the Miner linear damage accumulation model in the time domain. Utilizing the change of natural frequencies, a nonlinear model was fitted for predicting the fatigue damage of plate and then the foregone failure criterion of 5% reduction in natural frequency is improved. The influence of section and spacing of the stiffeners on the vibration fatigue behavior of the aluminum plate was investigated. The results show that the fatigue life of aluminum plate increases with adding either T or L section riveted stiffeners. With the same cross-sectional area of stiffener, the T section stiffened plate shows longer fatigue life than L section stiffened plate. Meanwhile, the vibration fatigue life also shows great sensitivity to the spacing between the stiffeners.

论李白的五言绝句

李白诗集中有五言绝句九十三首(包括个别存疑之作),虽不能说是字字精绝,首首玑珠,但绝大部分都是绝妙的短章。它有自己突出的特色,表现了诗人的独诣的韵味。历代诗论家对李白的五言绝句虽则赞不绝口,其实是有许多保留和偏见的。譬如《诗薮》的作者胡应麟,虽然说:“太白五七言绝,字字神境,篇篇神物”,“太白五言绝自是天仙口语”。又说;“五言绝二途:摩诘之幽玄,太白之超逸”。这些评价都是很高的,但纵观他对李白五言绝句的全部评价,就可以发现他,恐怕是慑于李白的盛名,有些地方,不免有违心之谈。他在同一部著作中就说:“太白五言,如《静夜思》、《玉阶怨》等,妙绝古今,然亦齐、梁体格。他作视七言绝句,觉神韵小试,缘句短,逸气未舒耳”。这段话与前面的话,分明是有抵牾的。它有两层意思:其一是说,李白五言绝句。犹是齐梁体格,没有在继承前人的基础上形成自己独特的艺术风格,

简论审美过程中的“移情”

在人类审美活动中,大量存在着如下事实:“感时花溅泪,恨别鸟惊心”,“摆酒问春春不语,黄昏却下潇潇雨”,“徘徊枝上月,空度可怜霄”,“红梅不屈服,树树立风雪”,等等。自然景物在人看来有了思想、感情、性格、行动和生命。这种现象,美学家称之为“移情”,认为这是人在观照或欣赏事物时产生“移情作用”的结果。

Numerical study of fatigue damage of asphalt concrete using cohesive zone model

In order to investigate the fatigue behavior of asphalt concrete, a new numerical approach based on a bi-linear cohesive zone model （CZM） is developed. Integrated with the CZM, a fatigue damage evolution model is established to indicate the gradual degradation of cohesive properties of asphalt concrete under cyclic loading. Then the model is implemented in the finite element software ABAQUS through a user-defined subroutine. Based on the proposed model, an indirect tensile fatigue test is finally simulated. The fatigue lives obtained through numerical analysis show good agreement with laboratory results. Fatigue damage accumulates in a nonlinear manner during the cyclic loading process and damage initiation phase is the major part of fatigue failure. As the stress ratio increases, the time of the steady damage growth stage decreases significantly. It is found that the proposed fatigue damage evolution model can serve as an accurate and efficient tool for the prediction of fatigue damage of asphalt concrete.

Experimental study on mechanical properties of dowel bar embedded in concrete under fatigue loads

To investigate the mechanical properties of a dowel action under fatigue loads, nine reinforced concrete specimens were fabricated, and the monotonic and fatigue loadings were performed on these specimens, respectively. All of these specimens were divided into two series. Six specimens in SeriesⅠwith different bar diameters of 12, 20 and 25 mm were subjected to monotonic loads and were used to confirm the ultimate bearing capacity. The remaining three specimens in Series Ⅱ were subjected to fatigue loads and were designed to investigate the attenuation character of dowel action and the fatigue failure modes. The test results show that the accumulated fatigue damage due to fatigue loads can reduce the ultimate bearing capacity of specimens. With the increase in fatigue loads, the failure mode can transform to fatigue rupture of the dowel bar under the serviceability loading state,i. e. 55% of the monotonic capacity. The fatigue life is determined by the fatigue properties of steel and concrete.Based on the test data, the failure process of dowel action can be divided into two stages： the accumulation of fatigue damage and the fatigue rupture of dowel bar.

PRE-CORROSION FATIGUE NOTCH FACTOR

The notched and smooth specimens of aluminum alloy LC4CS soaked in EXCO solution for different time are tested under the constant amplitude cyclic loading to obtain S-N curves and fatigue notch factors with different pre-corrosion time. By analyzing the corrosion process of LC4CS specimens in EXCO solution, the influ- ence mechanism of corrosion on fatigue notch factor is expounded. Then, a two-parameter model used to describe the change of corrosion fatigue notch factor with time is established and verified by experiment. The results show that the pre-corrosion fatigue notch factor of LC4CS material decreases at first and then increases with the increasing pre-corrosion time. The inflection point appears at the beginning of denudation stage.

管理十忌

因工作关系,我与经理们接触的机会不少,深知经理们的苦衷。我发现,企业有很多主管,整天劳劳碌碌,结果还是弄得下属怨声四起。效率不高。特别是有些年轻经理缺乏学习机会,无法体验管理技巧,在一系列的挑战面前屡遭失败。因此,想就我所见所闻,针对管理中的一些问题谈淡自己的看法。

A fatigue life prediction method of rolling bearing under elliptical contact elastohydrodynamic lubrication

In order to more accurately predict the contact fatigue life of rolling bearing, a prediction method of fatigue life of rolling bearing is proposed based on elastohydrodynamic lubrication （EHL）, the 3-paameter Weibull distribution ad fatigue strength. First,the contact stress considering elliptical EHL is obtained by mapping film pressure onto the Hertz zone. Then,the basic strength model of rolling bearing based on the 3-parameter Weibull distribution is deduced by the series connection reliability theory. Considering the effect of the type of stress, variation of shape and fuctuation of load, the mathematical models of the 尸 -tS-TV curve of the minimum life and the characteristic life for rolling bearing are established, respectively, and thus the prediction model of fatigue life of rolling bearing based on the 3-paameter Weibull distribution and fatigue strength is further deduced. Finally, the contact fatigue life obtained by the proposed method ad the latest international standard （IS0281： 2007） about the fatigue life prediction of rolling bearing are compared with those obtained by the statistical method. Results show that the proposed prediction method is effective and its relative error is smaier than that of the latest international standard （IS0281： 2007） with reliability R 〉 0. 93.

Nonequilibrium Statistical Modeling of Fatigue Crack Growth Behaviour

In order to study the influence of microstructural texture on the growth of short fatigue cracks in metals, the nonequilibrium statistical theory of fatigue fracture correlating a microscopic mechanism with the macroscopic properties is modified to take into consideration the microstructural features of a material, thereby allowing a rationalisation of the experimental data of short fatigue crack growth and long fatigue crack growth. The nonequilibrium statistical theory thus developed relates the growth of cracks with a dislocation mechanism to simulate short fatigue crack growth with the long fatigue crack growth behaviour and predicts the fatigue crack growth rates throughout the fatigue lifetime. The results is finally compared with that of other fatigue theories.