The Inflationary Solutions with O(2,2) Duality Symmetry in String Cosmologies

The low energy duality string model is investicated in time-dependent metric, torsion, dilaton background fields and potential fields, the inflationary solutions for string cosmologies are obtained when the space-time dimension is D = 3. It is found that the new cosmological solutions can be generated through O(d, d) duality transformations.     

On the Klein–Gordon Equation in Higher Dimensions: Are Particle Masses Variable?

We consider ways to generalize the 4D Klein–Gordon equation of particle physics to higher dimensions. The most promising approach implies that the mass which appears in the 4D relation is a term in the source-free 5D relation. We check this explicitly for the case of exact solitonic and cosmological solutions of the Kaluza–Klein equations. In general, particle masses are variable; but are constant for the Schwarzschild and late-universe cases, in agreement with data from the solar system and astrophysics. Our results have significant implications for cosmology, and can easily be extended to 10D superstrings, 11D supergravity and higher dimensions.     

Shock and traveling wave phenomena on an externally damped, non-linear string

We examine the propagation of shocks and traveling wave phenomena on a one-dimensional string that is executing finite-amplitude, transverse vibrations in a resisting medium. As part of our study, we develop an approach that allows us to describe, albeit approximately, the evolution and propagation of a shock front using analytical methods. In addition, exact traveling wave solutions, one of which involves the Lambert W-function, of the string's equation of motion are determined and analyzed. Lastly, a possible new form of the solution to the linearized problem is presented and extensions and other applications of the present work are briefly discussed.     

有机过氧化物的热自燃性小药量评价法

有机过氧化物的热自燃性小药量评价法;有机过氧化物;热自燃危险性;自加速分解温度;微量量热仪     

New method for geometric nonlinear analysis of large displacement drill strings

Introduction Drillstringsina3Dlargedisplacementwellboreareusuallyregardedas3Dcurved beamswithlargedisplacementandlargerotationbutwithsmallstrain,thus,therelationship betweenstressandstrainislinear.Thedeformationofdrillstringscanbecomposedoftwo parts:oneiscalledtheinitialdeformationcausedwhentheaxisofthedrillstringisdeformed fromitsstraightconfigurationtothepositioncoincidentwiththewellaxis,involvinglarge rotationsandwiththeimplicationoffiniterotationalproblem.Theotheristhedeformation fromthew…     

变速度轴向运动粘弹性梁的动态稳定性

研究速度变化的轴向运动粘弹性梁在亚谐波共振及组合共振范围内的参数振动．通过平均法,在运动参数激励频率为2倍固有频率或为两阶固有频率之和附近时得到了自治的常微分方程组．在参数激励频率和激励振幅平面上,可以找到由于共振而产生的失稳区域,并应用数值方法验证了理论推导结果的正确性．分析了粘弹性阻尼,速度和预紧张力对失稳区域的影响．粘弹性阻尼使得共振失稳区域减小,而速度和预紧张力使共振失稳区域在频率-振幅平面上发生漂移．     

Gravitational scattering of massless scalars in QFT and superstring theory

In this paper we perform the calculation of the gravitational scattering amplitude for 4 massless scalars in quantum field theory and Type II superstring theory. We show that the results agree, providing an example of how gravity is incorporated in the superstring theory. During the calculation we quantize gravitational action to derive graviton propagator and interaction vertex with massless scalar. We also calculate general 3‐point and 4‐point scattering amplitudes in SST for open and closed massless strings in NS sector.     

Self-Similar Solutions of Fracture Dynamics Problems on Axially Symmetry

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一种新的岩石非线性黏弹塑性蠕变模型研究

为了克服传统元件组合模型不能描述岩石蠕变过程中非线性特征的缺陷,首先根据加速蠕变阶段的应变和应变率随蠕变时间急剧增大的特点,建立黏塑性应变与蠕变时间的指数函数关系并提出非线性黏塑性体．将该非线性黏塑性体与广义Burgers蠕变模型串联,建立可以描述岩石全蠕变过程的非线性黏弹塑性蠕变模型,根据叠加原理得到一维应力状态下的轴向蠕变方程．然后基于塑性力学理论指出岩石三维蠕变本构方程建立过程中的不足之处,并给出非线性黏弹塑性蠕变模型合理的三维蠕变方程．最后采用不同应力水平下砂岩轴向蠕变试验对模型合理性进行验证,结果表明：拟合曲线与试验曲线吻合度较高,所建蠕变模型能够很好地描述砂岩在不同应力水平下的蠕变变形规律,尤其对加速蠕变阶段的非线性特征描述效果很好,验证了模型的合理性．     

隔水管弯曲对钻柱振动影响的计算与分析

海洋油气资源钻探中隔水管的弯曲对钻柱振动以及钻进特性有特别的影响。为得到隔水管弯曲对钻柱振动的影响规律,对南海已钻深水井使用非线性有限元软件建立全井钻井数值计算模型,研究获得了不同垂深时隔水管弯曲对钻柱振动特性的影响规律。研究表明:隔水管弯曲会加剧钻柱的振动,钻柱振动加剧会导致钻井能耗上升、钻头切削能力下降并且会加快钻柱疲劳;当隔水管的弯曲达到某临界值,钻柱与隔水管间的接触力会陡增;井口的钩载越大,隔水管弯曲带来的井口钩载波动量越大;井越深,隔水管弯曲对全井钻柱最大弯矩和钻头切削能力的影响越小。