2014“高教社杯”全国大学生数学建模竞赛颁奖仪式在海军航空工程学院青岛校区举行

<正>2014年12月20日,2014"高教社杯"全国大学生数学建模竞赛颁奖仪式暨工作会议在海军航空工程学院青岛校区隆重举行。全国大学生数学建模竞赛组委会主任、复旦大学李大潜院士,海军航空工程学院政委龚理华少将,山东省教育厅宋承祥副厅长,高等教育出版社林金安副总编辑,中国科学院袁亚湘院士,全国大学生数学建模竞赛组委会副主任、专家组组长、浙江大学陈叔平教授等160余人出席了颁奖仪式。颁奖仪式由全国组委会秘书长、清华大学谢金星教授主持。颁奖仪式上,学院龚理华     

2014全国大学生数学建模竞赛“高教社杯”获奖感言

<正>尊敬的各位领导、老师,亲爱的同学们:大家好!室外数九隆冬,室内春意阵阵。在这温暖如春的颁奖仪式现场,我的内心既高兴又激动。让我高兴的是,我能参加"高教社杯"全国大学生数学建模竞赛;让我激动的是,自己能作为获奖者的代表在此发言。我是来自信阳师范学院数学与信息科学学院2012级的学生程双泽,我们能获得今年的高教社杯,是和无数人的关心和帮助分不开的。所以我想真诚地对他们说声-谢谢。感谢全国数学建模竞赛组委会及所有为数学建模付出心血的领导和老师们,是你们为全国广大学子提供了一个展现自我风采的平     

Stability of hyperbolic manifolds with cusps under Ricci flow

We show that every finite volume hyperbolic manifold of dimension greater than or equal to 3 is stable under rescaled Ricci flow, i.e. that every small perturbation of the hyperbolic metric flows back to the hyperbolic metric again. Note that we do not need to make any decay assumptions on this perturbation.     

Toughness and failure of heat resistant steel before and after hydrogenation

Fracture toughness of heat-resistant steel can be increased by a preliminary thermomechanical loading called warm pre-stressing (WPS). The procedure creates a plastic deformed area around the crack tip and hence allows larger service loads to be tolerated by the cracked specimen. It is shown that a hydrogenation in the preloading stage decreases the fracture toughness of material.Investigations are also presented of the applicability of physical and mechanical approaches for the prediction of cleavage stress of materials after preliminary plastic deformation (PPD) effects and hydrogenation. Different schemes of the plastic deformation and influence of hydrogenation are considered in the preloading stage to provide different levels cleavage stress of steel 15Kh2MFA.     

Geometrical disorder of the fronts of a tunnel-crack propagating in shear in some heterogeneous medium

A statistical analysis of the deformation of the fronts of a tensile tunnel-crack propagating in fatigue in some medium with spatially varying Paris constant was recently performed, with special emphasis on the evolution of the power spectra and correlation functions of the fluctuations of the fronts around reference straight lines. This study is extended here to coplanar propagation (along a weak plane) of a tunnel-crack loaded in mode 2+3. The results are rather similar to those previously obtained for mode 1. In particular, just like for tensile loadings, there is an effect of gradual selection in time of Fourier components of the fluctuations of the fronts of large wavelength. One novelty, however, is that for shear loadings, the fronts no longer tend to become symmetrical in time, so that correlations between crack front fluctuations at two points are higher for points located on the same front than for points located on distinct ones.     

Effect of surface character of filler particles on rheology of heat-set whey protein emulsion gels

Small-deformation and large-deformation rheological properties of heat-set whey protein emulsion gels containing active and inactive filler particles have been investigated using a controlled stress rheometer. The results suggest that the contributions to the gel network are quite different for pure protein gels and emulsion gels having similar storage moduli. An emulsion gel containing inactive filler has a larger phase angle due to the energy dissipation at the ‘slippery’ droplet surface under the influence of the applied shear stress. The large-deformation rheology of the heat-set protein gel has behaviour intermediate between that for an entropic biopolymer gel and that for a particle gel. Emulsion gels containing active or inactive fillers behave more like typical particle gel systems.     

Structure and mechanical behavior of nylon 6 fibers filled with organic and mineral nanoparticles. II. In situ study of deformation mechanisms

This study reports on the in situ characterization of the deformation mechanisms at room temperature of polyamide 6 (PA6) fibers filled with hyperbranched molecules or montmorillonite (MMT) platelets. A small‐angle X‐ray scattering study shows that the stretching and sliding of the microfibrils takes place concomitantly in the first stage of elastic loading of as‐spun and partially drawn fibers. In the second stage of loading, which is basically plastic, sliding turns out to be the main process of deformation, accompanied by a significant reduction in the microfibril radius. Fibers drawn close to their maximum draw ratio only display the deformation process of microfibril stretching. This in situ study also reveals subtle features of the reversible processes of deformation that could not be detected from ex situ experiments reported previously. A thickening of the crystal blocks in the microfibrils takes place under stress and disappears upon unloading, indicating that some reversible strain‐induced molecular ordering occurs in the amorphous layers close to the crystal surface. The tentative mechanical modeling enabled a characterization of the components of the fibers: the stiffness of the microfibrils appears to be insensitive to the presence of the particles that are excluded in the interfibrillar regions. The presence of HB molecules clearly increases the stiffness of the interfibrillar regions owing to a physical crosslinking effect. Moreover, it seems that the stiffness improvement of the drawn MMT‐PA6 fiber lies in a greater capability of chain unfolding in the interfibrillar amorphous region. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2633–2648, 2004     

DECAY RATE OF SAINT-VENANT END EFFECTS FOR PLANE DEFORMATIONS OF PIEZOELECTRIC-PIEZOMAGNETIC SANDWICH STRUCTURES

This paper is concerned with the decay of Saint-Venant end effects for plane deformations of piezoelectric （PE）-piezomagnetic （PM） sandwich structures, where a PM layer is located between two PE layers with the same material properties or reversely. The end of the sandwich structure is subjected to a set of self-equilibrated magneto-electro-elastic loads. The upper and lower surfaces of the sandwich structure axe mechanically free, electrically open or shorted as well as magnetically open or shorted. Firstly the constitutive equations of PE mate- rials and PM materials for plane strain are given and normalized. Secondly, the simplified state space approach is employed to arrange the constitutive equations into differential equations in a matrix form. Finally, by using the transfer matrix method, the characteristic equations for eigen- values or decay rates axe derived. Based on the obtained characteristic equations, the decay rates for the PE-PM-PE and PM-PE-PM sandwich structures are calculated. The influences of the electromagnetic boundary conditions, material properties of PE layers and volume fraction on the decay rates are discussed in detail.     

平面应变不可压缩橡胶圆柱的大变形

针对一类新的橡胶材料应变能函数，推导了受内压作用下不可压缩橡胶圆柱的大变形公式，给出了位移、应力的解析表达式（用积分形式表示）。建立了适用于分析非线性不可压缩橡胶材料的罚有限元列式，算例表明：位移与应力能很好地与理论解吻合，并提出了控制计算稳定的方法，特别是详细地讨论罚因子的选取及对计算结果的影响。