力学研究中"大数据"的启示、应用与挑战

大数据在全世界发展迅猛, 应用成效显著.大数据独特的思维和方法, 为科学研究与探索提供了全新的范式.力学研究中,高时空分辨率、多参数同步观测与高精度、大规模模拟手段的发展,为力学大数据的发展提供了契机,大数据、机器智能方法的应用正呈现快速上升趋势.本文旨在分析大数据思维方法在力学研究中的应用, 及其启示与挑战.首先从大数据资源、大数据科学及大数据技术3个层面分析了大数据的内涵及研究态势,概括了国内外政府及组织机构的大数据发展规划.而后对比分析了力学思维方法与大数据思维方法的特点,指出两者的本质区别在于数据使用方式的不同而带来的范式差异:大数据采用数据驱动模型替代力学中的偏微分方程组以描述问题,在复杂系统的分析、预测中优势显著.回顾了大数据方法在材料性能预测、材料本构建模、湍流建模、结构健康监测及试验力学等方面的最新研究进展,以及动态数据驱动与数字孪生等大数据驱动的建模模拟新范式.总结了大数据在力学研究中应用的3种方式, 即驱动已有模型改进,挖掘复杂隐含的规律, 以及替代已有的理论方法等. 最后,建议以力学研究为主体和牵引, 大数据与力学双驱动,推动大数据与力学交叉形成理论与方法突破、及学科发展新方向.      

CHARACTERIZATIONS AND RELATIONSHIPS BETWEEN OUTDOOR AND INDOOR BIOAEROSOLS IN AN OFFICE BUILDING

1.IntroductionBioaerosolsaremicroorganismsorparticles,gases,vapors,orfragmentsofbiologicalorigin(i.e.,aliveorreleasedfromalivingorganism)thatexistintheair.Bioaerosolsareeverywhereintheenvironment.Underfavorableconditions,bioaerosolsareabletogrowandpropagateonavarietyofbuildingmaterialsandindoorsurfaces,causingindoorairpollution.Therefore,owingtotheirubiquitouspresenceinnature,bioaerosolsasapollutionsourcearealmostinevitableinarangeofenclosedenvironmentsandincommunityair(Kodama&McGee,1986;Lig…     

基于微面有效应力矢量的各向异性屈服准则

基于微面模型，定义损伤变量为微面上有效承载面积的减少. 将Kachanov的一维有效 应力概念推广到三维，提出微面有效应力矢量的概念. 根据微面的有效应力矢量，将无损材 料的宏观应力张量及不变量与微面应力矢量的积分关系拓展到有损材料，得到了有损材料的 宏观有效应力张量及其不变量与宏观名义应力张量、微面面积损伤组构张量之间的关系. 将 无损材料的以应力张量不变量表示的Drucker-Prager准则推广到有损材料，建立了含缺陷 材料的各向异性屈服准则. 对有损材料，宏观有效应力张量与Murakami的有效应力张量具 有相同的形式，各向异性强度准则与Liu等提出的扩展Hill准则有相同的形式，当不考虑 静水应力对屈服的影响时，它与Hill准则具有相同的形式.     

THERMODYNAMIC AND PARTICLE-DYNAMIC STUDIES ON SYNTHESIS OF SILICA NANOPARTICLES USING MICROWAVE-INDUCED PLASMA CVD

1. Introduction1.1 Silica nanoparticles and synthesis methods Silica (SiO2) nanoparticles are widely used in industry asan active filler for polymer reinforcement, a rheologicaladditive in fluids, a free flow agent in powders, and anagent for chemical mechanical polishing during IC (inte-grated circuit) fabrication (Sniegowski & de Boer, 2000).Silica powder is also used for producing silicon carbide(Koc & Cattamanchi, 1998) or opaque silica aerosols (Leeet al., 1995). Many methods can …     

OFDMA中继系统中基于QoS保证的资源分配算法

研究了 OFDMA 中继下行链路通信系统中的动态资源分配问题,提出了一种可以保证用户最低 QoS 需求的资源分配算法.首先在简化资源优化问题的过程中,采用等功率分配方法以降低算法复杂度,然后通过拉格朗日松弛优化方法推导出了子载波分配和中继选择最优解,并在此基础上引入用户速率权衡因子,根据速率权衡因子越大的用户,越具有选择子载波和中继的优先权这一准则进行子载波分配和中继选择.仿真结果表明:新算法能够获得较高的系统容量,同时也能很好地保证不同用户的最低速率需求.     

Synthesis and gelation behaviors of five new dimeric cholesteryl derivatives

Five new diacid amides of di-cholesteryl L-glycinates were designed and prepared.The compounds with linkers containing 0,1, 2,3,or 4 methylene units are denoted as 1,2,3,4,and 5,respectively.Their gelation behaviors in 25 solvents were tested as novel low-molecular-mass organic gelators(LMOGs).It was shown that the length of the linker connecting the two-cholesteryl residues in a gelator plays a crucial role in the gelation behavior of the compound.1 gels 11 of the 25 solvents tested at a concentration lowe...     

Two New Diterpene Alkaloids from the Roots of Spiraea japonica var. Acuta

Spiraea japonica L. (Rosaceae) is widely distributed in Yunnan Provence, P. R. China. Previous chemical investigations on S. japonica and its varieties have led to the report of 7 new atisane-type diterpenoids and 38 new diterpene alkaloids of atisine- and hetisine-type1-11. This paper describes the isolation and structure elucidation of two new diterpene alkaloids named spiratines A and B (1-2). Their structures were elucidated on the basis of 1D and 2D NMR experiments (HMQC, HMBC, 1…