厚壳三维分析的半解析解

本文对座标系三维弹性力学问题采用周向与径向解析,轴向离散的半解析数值方法。通过引入部分解析函数,将三维问题归结为一维离散化方程。这种方法能适应于一大类复杂的弹性力学问题,方法简单,计算工作量少。本文用这方法来分析厚壳的三维变形与应力规律,研究大厚跨比的强厚壳的三维弹性理论解,为建立可靠的强厚壳理论提供依据。     

M′型LuTaO_4∶Eu~(3+)透明闪烁厚膜的制备及性能研究

X射线成像在生命科学和物质微结构分析等许多方面有着非常重要的应用,X射线成像仪器核心部件之一为X射线-可见光转换屏。透明闪烁薄膜是实现高空间分辨率X射线成像的一条有效途径。铕掺杂M′型LuTaO_4是一种性能优越的闪烁材料,其密度高达9.75g·cm~(-3),化学性质稳定,辐照硬度大,有望制备成透明薄膜型高空间分辨率X射线转换屏。以2-甲氧基乙醇为溶剂、PVP为胶粘剂,采用溶胶-凝胶法成功制备出M′型LuTaO_4∶Eu~(3+)透明闪烁厚膜,并对透射率、光致发光、X射线激发发射光谱和空间分辨率等一系列的薄膜性能进行表征。经过8次旋涂之后,膜层均匀、无裂纹,厚度为2.1μm,发光波段的透射率为70%以上,成像空间分辨率达到1.5μm。将厚膜作为X射线-可见光转换屏,成功对果蝇进行了X射线成像,其复眼结构清晰可见。此外,紫外和X射线激发下闪烁膜的发光特性研究表明,该厚膜具有优良的发光性能,已基本满足高分辨率X射线成像的要求,有望在显微X射线成像方面获得很好应用。     

有限厚度圆柱壳热冲击问题的广义热弹性解

针对包含有界边界的轴对称结构受热冲击作用的广义热弹性问题进行了研究分析.基于Lord-Shulman广义热弹性理论(L-S理论),构建了热冲击下有限厚度圆柱壳热弹性响应的广义热弹性模型.借助Laplace(拉普拉斯)变换技术以及Bessel函数的渐进特性,推导了温变载荷作用下,圆柱壳内部位移、温度以及应力场的解析表达式.该表达式不仅可以清楚地揭示热冲击下热波、热弹性波在壳体内部的传播、反射以及叠加的作用过程,更可准确地捕捉到热波、热弹性波波前位置处的阶跃现象,并对热冲击诱发的动态热应力峰值进行有效预测.     

数值积分法求解厚壁筒的动态应力强度因子

用数值积分法求解了厚壁筒表面裂纹的动态应力强度因子，其结果与有限元的计算结果作了比较，表明该方法简单有效，对工程应用极有参考价值     

高超声速飞行器大面积热防护系统的传热数值分析

隔热毡是高超声速飞行器防热系统中重要的组成部分。隔热毡内存在复杂的多种传热形式的耦合,本文详细地分析了隔热结构内导热与辐射的复合换热问题,用光学厚极限法分析了隔热层纤维席内辐射热流。建立了高温绝热毡有效热导率的数值计算模型,分析了温度和压力对传热机制的影响。该模型预测的有效导热系数与试验结果最大误差不超过6%。通过应用数值分析方法得到有效导热系数,建立了防热结构一维瞬态传热模型,该模型结果与瞬态实验结果最大误差为8%。最后还计算出不同厚度隔热毡蒙皮结构的温度响应,并分析讨论了隔热毡厚度对隔热效果的影响。本文研究表明:TPS隔热毡的厚度达到63.3mm后,继续增加尺寸,其隔热效率将明显降低。     

Fabrication of poly(acrylamide) hydrogels with gradient crosslinking degree via photoinitiation of thick polymer system

In this paper, we report on the synthesis of poly(acrylamide) (PAM) hydrogels by photoinitiation with a thick system. The hydrogels exhibited gradient crosslinking density along the light path. Thermogravimetric analyses (TGA) proved the same effects. We investigated some factors affecting the swelling ratio of the hydrogels such as crosslinking agent concentration, photoinitiator concentration, and monomer concentration. The as‐prepared hydrogels might have some potential applications in drug delivery systems and other function materials. Copyright © 2009 John Wiley & Sons, Ltd.     

Torsion-free,Divisible, and Mittag-Leffler Modules

We study (relative) 𝒦-Mittag–Leffler modules, with emphasis on the class 𝒦 of absolutely pure modules. A final goal is to describe the 𝒦-Mittag–Leffler abelian groups as those that are, modulo their torsion part, ?₁-free. Several more general results of independent interest are derived on the way. In particular, every flat 𝒦-Mittag–Leffler module (for 𝒦 as before) is Mittag–Leffler. A question about the definable subcategories generated by the divisible modules and the torsion-free modules, resp., has been left open.     

Mutation Pairs in Abelian Categories

A notion of mutation pairs of subcategories in an abelian category is defined in this article. For an extension closed subcategory 𝒵 and a rigid subcategory 𝒟 ? 𝒵, the subfactor category 𝒵/[𝒟] is also a triangulated category whenever (𝒵, 𝒵) forms a 𝒟-mutation pair. Moreover, if 𝒟 and 𝒵 satisfy certain conditions in modΛ, the category of finitely generated Λ-modules over an artin algebra Λ, the triangulated category 𝒵/[𝒟] has a Serre functor.     

Dynamic stress concentrations in thick plates with two holes based on refined theory

Based on complex variables and conformal mapping, the elastic wave scat- tering and dynamic stress concentrations in the plates with two holes are studied by the refined dynamic equation of plate bending. The problem to be solved is changed to a set of infinite algebraic equations by an orthogonM function expansion method. As examples, under free boundary conditions, the numerical results of the dynamic moment concen- tration factors in the plates with two circular holes are computed. The results indicate that the parameters such as the incident wave number, the thickness of plates, and the spacing between holes have great effects on the dynamic stress distributions. The results are accurate because the refined equation is derived without any engineering hypothese.     

深厚黏土层冻结壁冻结压力实测与数值分析

为了研究深厚黏土层冻结壁冻结压力的变化特征,根据现场实测结果获得冻结压力随温度变化的发展趋势. 结合对现场实测数据的分析和ADINA 有限元法的数值模型,能够很好地模拟人工冻结地层应力场的变化规律,为工程实践提供参考.