基于季节冻土微观结构特征的神经网络冻胀率仿真预测

为了寻求基于宏观-微观物理参数间接得到季节冻土冻胀率的途径,根据现有技术手段容易测试到土的性质参数,利用BP神经网络法对季节冻土冻胀率进行预测.选取微观孔隙参数及结构单元体参数各4个、外部条件参数3个共11个参数,建立季节冻土冻胀率神经网络预测模型.结果表明:在33个检验样本中,误差最大为0.19,最小为0.00,有4个样本的误差在0.1～0.19之间,其他样本误差都在0.05以下,占总样本数的88%,说明模型能反映冻胀变化的基本趋势.因此,文中建立的基于11个宏观微观物理参数的BP神经网络冻胀率预测模型是可行的.

The control and optimization of macro/micro-structure of ion conductive membranes for energy conversion and storage

Ion conductive membranes(ICMs)are frequently used as separators for energy conversion and storage technologies of fuel cells,flow battery,and hydrogen pump,because of their good ion-selective conduction and low electronic conductivity.Firstly,this feature article reviews the recent studies on the development of new nonfluorinated ICMs with low cost and their macro/micro-structure control.In general,these new nonfluorinated ICMs have lower conductivity than commercial perfluorinated ones,due to their poor ion transport channels.Increasing ion exchange capacity(IEC)would create more continuous hydrophilic channels,thus enhancing the conductivity.However,high IEC also expands the overall hydrophilic domains,weakens the interaction between polymer chains,enhances the mobility of polymer chains,and eventually induces larger swelling.The micro-scale expansion and macro-scale swelling of the ICMs with high IEC could be controlled by limiting the mobility of polymer chains.Based on this strategy,some ef ficient techniques have been developed,including covalent crosslinking,semi-interpenatrating polymer network,and blending.Secondly,this review introduces the optimization of macro/microstructure of both perfluorinated and nonfluorinated ICMs to improve the performance.Macro-scale multilayer composite is an ef ficient way to enhance the mechanical strength and the dimensional stability of the ICMs,and could also decrease the content of per fluorosulfonic acid resin in the membrane,thereby reducing the cost of the perfluorinated ICMs.Long side chain,multiple functionalization,small molecule inducing micro-phase separation,electrospun nano fiber,and organic–inorganic hybrid could construct more ef ficient ion transport channels,improving the ion conductivity of ICMs.

耳蜗感音机理研究及临床应用

听力损失与耳聋疾病已严重威胁人类健康和影响人们的生活质量。耳是人体中重要的感觉器官,耳蜗是人耳关键的感音结构,受限于其复杂精密且位置隐蔽,导致实验研究存在诸多难以克服的困难,迄今为止诠释耳蜗感音机理仍是医学的重要难题。因此,融合数学、力学、生物和医学的多学科交叉原理,建立真实有效的耳蜗结构生物力学模型,深入研究耳蜗的感音机理,为听力修复和临床治疗提供理论基础是许多科学家关注的焦点。本文总结了当前耳蜗感音机理及临床应用研究现状,指出当前尚存在的问题,并对今后的研究工作进行展望。

Progressive failure analysis of composite structure based on micro- and macro-mechanics models

Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stress distribution of the composite structure is calculated by commercial finite element software. According to the macro-stress, the damaged point is found and the micro-stress distribution of representative volume element is calculated by finite-volume direct averaging micromechanics(FVDAM). Compared with the results calculated by failure criterion based on macro-stress field(the maximum stress criteria and Hashin criteria) and micro-stress field(Huang model), it is proven that the failure analysis based on macro- and micro-mechanics model is feasible and efficient.

Structure of Macro- and Trace Elements Status Observed in Residents of Magadan Town

The authors aimed the study at examining macro- and trace elements content in elderly people of the 1 period of middle age （21-35） residing in Magadan town to assess the content of 25 trace elements in hair samples on individual and population levels by atom-emission spectrometry with inductively-bonded argon plasma. It turned out that the majority of surveyed subjects were characterized by deformation of element status demonstrated by excess and deficit of the basic essential elements of different degrees of manifestation. Deficit of Co （68% of surveyed people）, Mg （67%）, Ca （64%）, Cu （47%）, K （46%）, Zn （44%）, I （41%）, Na （33%）, P （27%） and Se （24%） was typical for female subjects as well as excess of Si （28%）, Zn （22%） and P （20%）. Male residents were characterized by deficit of Co （81%）, Ca （66%）, Mg （65%）, I （50%）, Cu （37%）, K and Na （27%） and excess of Zn （41%）. In individual cases it was noted excess concentration of nominally essential and toxic elements in both examined groups. They were： A1, As, Cd, Li, Ni, Pb, Sn, V and B. While analyzing of medians of chemical concentration it was stated reliable sex-related differences （P 〈 0.05）： content of Ca, Mg and Mn was higher in hair samples of women, and content of As, B, Cd, Cr, K, Li, Na, P, Pb and V, on the contrary, was higher in male samples.

Multiscale approach to micro/macro fatigue crack growth in 2024-T3 aluminum panel

When two contacting solid surfaces are tightly closed and invisible to the naked eye, the discontinuity is said to be microscopic regardless of whether its length is short or long. By this definition, it is not sufficient to distinguish the difference between a micro- and macro-crack by using the length parameter. Microcracks in high strength metal alloys have been known to be sev- eral centimeters or longer. Considered in this work is a dual scale fatigue crack growth model where the main crack can be mi- cro or macro but there prevails an inherent microscopic tip region that is damaged depending on the irregularities of the micro- structure. This region is referred to as the ＂micro-tip＂ and can be simulated by a sharp wedge with different angles in addition to mixed boundary conditions. The combination is sufficient to model microscopic entities in the form of voids, inclusions, precipitations, interfaces, in addition to subgrain imperfections, or cluster of dislocations. This is accomplished by using the method of ＂singularity representation＂ such that closed form asymptotic solutions can be obtained for the development of fa- tigue crack growth rate relations with three parameters. They include： （1） the crack surface tightness o-＊ represented by Cro/Cr~ = 0.3-0.5 for short cracks in region I, and 0.1-0.2 for long cracks in region II, （2） the micro/macro material properties reflected by the shear modulus ratio/1＂ （=,L/micro/]-/macro varying between 2 and 5） and （3） the most sensitive parameter d＊ being the micro-tip characteristic length d＊ （=d/do） whose magnitude decreases in the direction of region I ---~II. The existing fatigue crack growth data for 2024-T3 and 7075-T6 aluminum sheets are used to reinterpret the two-parameter da/dN=C（AK）n relation where AK has now been re-derived for a microcrack with surfaces tightly in contact. The contact force will depend on the mean stress ~m or mean stress ratio R as the primary parameter and on the stress amplitude era as the secondary parameter.