Normal compression wave scattering by a permeable crack in a fluid-saturated poroelastic solid

A mathematical formulation is presented for the dynamic stress intensity factor (mode I) of a finite permeable crack subjected to a time-harmonic propagating longitudinal wave in an infinite poroelastic solid. In particular, the effect of the wave-induced fluid flow due to the presence of a liquid-saturated crack on the dynamic stress intensity factor is analyzed. Fourier sine and cosine integral transforms in conjunction with Helmholtz potential theory are used to formulate the mixed boundary-value problem as dual integral equations in the frequency domain. The dual integral equations are reduced to a Fredholm integral equation of the second kind. It is found that the stress intensity factor monotonically decreases with increasing frequency, decreasing the fastest when the crack width and the slow wave wavelength are of the same order. The characteristic frequency at which the stress intensity factor decays the fastest shifts to higher frequency values when the crack width decreases.

Huangqi Guizhi Wuwu Decoction suppresses inflammation and bone destruction in collagen-induced arthritis mice

Objective:Rheumatoid arthritis(RA)is a chronic inflammatory and destructive arthritis,characterized by inflammatory infiltration and bone destruction.Huangqi Guizhi Wuwu Decoction(HGWD)is traditional Chinese medicine,which has been applied in the treatment of RA in clinical.The aim of this study was to investigate the therapeutic effect of HGWD on collagen-induced arthritis(CIA)mouse model.Methods:DBA/1J female mice were used to establish the collagen-induced arthritis(CIA)model.HGWD was administered intragastrically once a day for four weeks starting on the 22nd day after the first immunization.The body weight,hind paw thickness and clinical score were measured every five days.Gait analysis,histopathological staining,enzyme-linked immunosorbent assay(ELISA),ultrasound imaging and micro-computed tomography imaging were performed to determine the effects of HGWD treatment on inflammation and bone structure in this model.Moreover,Real-time PCR and Western blot analysis were used to detect inflammatory factors mRNA and protein levels after HGWD intervention in RAW 264.7 cells.Results:HGWD attenuated symptoms of arthritis,suppressed inflammatory synovium area and the serum levels of inflammatory factors,inhibited joint space enlargement in the knee and ankle joints,reduced numbers of osteoclasts,protected bone destruction,as well as improved motor function.HGWD decreased the expression of mRNA for inflammatory factors and the protein expression levels of p-NF-rB and IL-17.Conclusion:These results suggested that HGWD suppresses inflammation,attenuates bone erosion and maintains motor function in collagen-induced arthritis mice.

含随机指向狭缝流体饱和岩石中的弹性波

波致扩散被认为是引起地震波频散和衰减的主要原因之一,它也可以看作是弹性波遇夹杂通过模式转换产生的散射慢纵波.本文将流体饱和孔隙介质中狭缝对弹性波的散射问题归结为位错密度的积分方程,结合散射问题的严格数学解和Foldy-Lax均匀化格式,建立了含随机指向狭缝流体饱和岩石的等效黏弹性模型.为消除求解积分方程耗时较长、不便于反演应用的缺点,本文基于散射远场的低、高频渐近解,利用分支函数近似法建立了背景岩石弹性和渗透率、孔隙流体性质、狭缝参数以及频率与等效黏弹性模量的简单显式函数关系.研究表明,在波致扩散主导的频段内,横波具有与纵波同量级的速度频散和衰减.横波衰减随流体体积模量增加而单调增加,而纵波先增加、后降低.此外,低频纵波速度对流体体积模量敏感,而横波速度对流体模量变化不敏感,说明含裂缝孔隙介质中同样满足流体替代方程.流度主要影响纵横波的峰频,这与定向狭缝的情况相同.本文模型克服了双孔模型不能预测横波速度频散和衰减的局限性,所得结论为联合利用纵、横波特性提取岩石裂缝参数和流体性质提供了理论基础.

改进的求解裂纹问题中指数函数对偶积分的倍数因子积分法

裂纹问题通常可归结为对偶积分方程,可通过将位移积分方程展开为类Chebyshev多项式或Jacobi多项式形式的级数来求解.通过构造一个适定的线性代数方程组来确定展开系数的施密特倍数因子积分法是最受欢迎的方法之一.然而,由于线性方程组的矩阵元素是从二重积分计算出来的,施密特方法的数值计算效率较低.本文提出了一种改进方法来构造线性方程组,以便有效地确定展开系数.改进技术是在将某些倍数因子应用于牵引积分方程,然后在“源”区域上积分得到的方程后发展起来的.该操作将矩阵元素简化为单重积分.文章通过数值算例证明了此方法的计算精度高,且效率高.尤其该方法只需要施密特方法计算时间的1/5左右.因此该方法可以用于代替施密特方法并有望在解决裂纹问题中发挥作用.