Mindlin second-gradient elastic properties from dilute two-phase Cauchy-elastic composites. Part I: Closed form expression for the effective higher-order constitutive tensor

It is shown that second-order homogenization of a Cauchy-elastic dilute suspension of randomly distributed inclusions yields an equivalent second gradient (Mindlin) elastic material. This result is valid for both plane and three-dimensional problems and extends earlier findings by Bigoni and Drugan [Bigoni, D., Drugan, W.J., 2007. Analytical derivation of Cosserat moduli via homogenization of heterogeneous elastic materials. J. Appl. Mech. 74, 741–753] from several points of view: (i) the result holds for anisotropic phases with spherical or circular ellipsoid of inertia; (ii) the displacement boundary conditions considered in the homogenization procedure is independent of the characteristics of the material; (iii) a perfect energy match is found between heterogeneous and equivalent materials (instead of an optimal bound). The constitutive higher-order tensor defining the equivalent Mindlin solid is given in a surprisingly simple formula. Applications, treatment of material symmetries and positive definiteness of the effective higher-order constitutive tensor are deferred to Part II of the present article.     

Ideomechanics of transitory and dissipative systems associated with length, velocity, mass and energy

Validation of Ideomechanics (IDM) is manifested by removing the inconsistency of applying open system test data to closed system theories. Instead, the available open system test data can be used rightly to determine the physical parameters of the transitional functions defined by the mean values of length (free path), velocity, mass and energy. Multiscaling and size/time effects are considered. Ambiguities are mitigated when energy takes precedent in lieu of the concept of force.Determined directly from IDM is the energy density function from the velocity that can represent the magnitude of the energy sink and source. The formulation involves grouping pairs of variables of opposing poles that can be constructed as ideograms, much like yin-yang of I-Chin. The flow of Chi implicates the arrow of time and irreversibility. Mass activation/inactivation (AIA) is assumed to be related to the expansion/contraction (EXCO) of matter. Inadvertently, physical systems are identified with inhaling and exhaling of energy corresponding, respectively, to direct-absorption and self-dissipation (DASD). They are postulated to be the basic process for determining the integrity of the system.In contrast to Newtonian/Einsteinian mechanics (NEM) that uses field equations for determining the behavior of the whole everywhere for all time, IDM considers the mean behavior at any given size/time scale, however, large and small. Uncertainties are addressed by the scale transitional functions. The new paradigm can be applied to scaling shifting and to construct equivalence relations for open systems and to the use of existing test data free of ambiguities. Classical conservation laws for closed systems are reducible from the equivalence principles of open systems. The same holds for the classical kinetic molecular theory of matter that can be modified to include dissipation.     

中央开耦合槽矩形双间隙谐振腔中的TM高次模

 用解析方法导出了中央开耦合槽矩形双间隙谐振腔中π-TM模式频率的本征方程和特性阻抗的计算公式,分析了耦合槽大小对几种π-TM模式频率和特性阻抗的影响。对TM₃₁₀模的具体计算结果显示,解析方法与模拟方法的计算结果符合得很好,可以用于计算谐振频率和特性阻抗。研究表明,耦合壁的厚度对π-TM模式频率的影响不大,耦合槽的大小和位置对谐振频率影响则较大。同时发现,在TM高次模双间隙腔中,出现了π₁模消失现象。     

硬X射线透射弯晶谱仪

 提出了一种基于圆柱面石英透射弯晶的晶体谱仪,主要用于诊断10～60 keV范围的硬X射线光谱。石英弯晶的曲率半径为112 mm,晶格常数为0.425 6 nm。实验利用Mo靶X射线管作为点光源,晶体与光源距离700 mm,采用成像板作为记录介质,获得了清晰的光谱图像。Mo的两条特征谱线以光轴为中心线对称分布,谱线的位置与理论计算符合得很好。误差分析表明,实际测量值与理论值的偏差主要来源于瞄准精度。     

五种灯盏细辛药材的红外光谱对比分析

本文采用傅里叶红外光谱测试了云南红河洲产五种盏细辛药材的红外谱图,它们的红外光谱的峰形、峰位极相似,只是特征峰的相对强度有变化,从特征峰的峰强比知,虽然有偏差,但很小,表明:除弥勒产的灯盏细辛药材的黄酮类化合物含量偏大外,各产地灯盏细辛药材的质量没有明显差异,结果对灯盏细辛的生产应用、品种选育、栽培技术研究具有一定的指导意义。     

Where is the rudder of a fish？： the mechanism of swimming and control of self-propelled fish school

Numerical simulation and control of self- propelled swimming of two- and three-dimensional biomimetic fish school in a viscous flow are investigated. With a parallel computational fluid dynamics package for the two- and three-dimensional moving boundary problem, which combines the adaptive multi-grid finite volume method and the methods of immersed boundary and volume of fluid, it is found that due to the interactions of vortices in the wakes, without proper control, a fish school swim with a given flap- ping rule can not keep the fixed shape of a queue. In order to understand the secret of fish swimming, a new feedback con- trol strategy of fish motion is proposed for the first time, i,e., the locomotion speed is adjusted by the flapping frequency of the caudal, and the direction of swimming is controlled by the swinging of the head of a fish. Results show that with this feedback control strategy, a fish school can keep the good order of a queue in cruising, turning or swimming around circles. This new control strategy, which separates the speed control and direction control, is important in the construction of biomimetic robot fish, with which it greatly simplifies the control devices of a biomimetic robot fish.     

Time-Dependent Stokes Shift from Solvent Dielectric Relaxation

The Stokes shift response function, which is related to the time dependent solvation energy, is calculated with the dielectric response function and a novel expression of nonequilibrium solvation energy. In the derivation, relationship between the polarization and the dielec-tric response function is used. With the dipole-in-a-sphere model applied to the system coumarin 343 and water as the solvent, encouraging agreement with the experimental data from Jimenez et al. is obtained [Nature 369, 471 (1994)].     

基于狭义相对论转动质量效应的X-ray光谱分析

基于狭义相对论的基本观点,研究了特征X-ray的产生机理,分析了在狭义相对论下转动质量效应对X-ray光谱的影响,导出了一个计算X-ray特征波长的公式,同时对计算推导的特征波长值做了系统的误差分析,得到了相对误差的规律。结果表明,计算推导的波长值与实验的波长值相比是非常的接近的,并且随着原子序数的增加,转动质量效应对特征波长的影响越来越明显,研究结果在实际应用中对分析特征X-ray光谱具有一定的参考意义。     

提高特征光谱法在微量气体监测中灵敏度的研究

为了实现对室内微量有毒气体实时监测,提高基于特征光谱检测方法的测量精度,提出了特征波长过滤窗的方法。将高浓度的待测气体作过滤窗,标准空气作参考窗,气室充待测浓度的待测气体,采用组合测量得到的多组光谱进行差分、相关等数据处理求解气室中待测气体的浓度。实验显示,采用WQF-520-FTIR型红外光谱仪得到癸二酸二丙脂红外吸收谱线主要有四条：3 385.26,3 417.64,5 797.11和8 561.65 nm,分别对应的吸光度为1.520 0,1.542 1,2.431 8和1.352 6。对应的可检测的最小含量为50×10-9,而采用特征波长过滤窗的方法波长位置可实现10-4 nm量级的对准,在确定待测气体含量量级的条件下,可检测的最小含量为5×10-9,灵敏度提高约10倍。该方法具有高灵敏度、无中毒、可实时检测等优点。     

玉米秸秆纤维素和半纤维素NIRS特征波长优选

预处理是提高玉米秸秆生物转化利用效率的有效途径。玉米秸秆经生物炼制转化为生物燃料时,转化率与其原料内的纤维素和半纤维素含量直接相关。为了实现对预处理后玉米秸秆的生物炼制过程的有效调控,提出使用近红外光谱(NIRS)对玉米秸秆的纤维素和半纤维素含量进行快速检测,解决传统化学方法测试速度慢、成本高的问题。为了提高NIRS检测的效率和精度,将遗传算法与模拟退火算法相结合构建遗传模拟退火算法(GSA)用于预处理后玉米秸秆纤维素和半纤维素含量NIRS特征波长优选。GSA算法以NIRS波长点数为码长进行二进制编码,以偏最小二乘法(PLS)回归模型的交叉验证均方根误差为目标函数,结合温度参数设计适应度函数,基于Metropolis判别准则实现扰动解的选择复制,能够在避免早熟的同时有效提高进化后期的搜索效率。采用碱预处理、生物预处理及其相结合的方法对采集的玉米秸秆进行预处理后制备样品120个,并测定其纤维素和半纤维素含量及NIRS。使用7点Savitzky-Golay平滑结合多元散射校正和标准正则变换对光谱进行预处理后,利用Kennard-Stone法按3∶1比例划分校正集和验证集。然后,使用GSA算法对NIRS全谱进行特征波长优选(记为Full-GSA)、对协同区间偏最小二乘法(SiPLS)优选后谱区进行特征波长优选(记为SiPLS-GSA)、对反向区间偏最小二乘法(BiPLS)优选后谱区进行特征波长优选(记为BiPLS-GSA),并使用PLS回归模型和验证集对特征波长优选结果进行评测。Full-GSA以全谱1 557个波长点为基因,执行16次算法,优选出118个纤维素特征波长点和164个半纤维素特征波长点。SiPLS-GSA经SiPLS优选的纤维素和半纤维素谱区波长点数分别为388个和160个,再经GSA进一步优选后得到157个纤维素特征波长点和148个半纤维素特征波长点。BiPLS-GSA经BiPLS优选的纤维素和半纤维素谱区波长点数分别为358个和180个,再经GSA进一步优选后得到130个纤维素特征波长点和153个半纤维素特征波长点。结果表明,通过波长优选,不仅参与建模的波长点数量显著减少,而且回归模型的性能显著优于全谱建模。其中,采用Full-GSA优选的纤维素特征光谱回归性能最佳,采用SiPLS-GSA优选的半纤维素特征光谱回归性能最佳。回归模型验证集的平均相对误差(MRE)分别为1.752 4%和2.020 8%,较全谱建模分别降低了13.636 6%和25.368 4%。基于结合温度参数设计适应度函数的策略构建的GSA具有良好的全局搜索性能,适用于玉米秸秆纤维素和半纤维素含量NIRS特征波长优选。GSA以全谱每个波长点为染色体基因的编码方案适用于NIRS全谱的特征波长优选。GSA同样适用于SiPLS和BiPLS优选后谱区的特征波长优选,能够有效实现优选后谱区的波长点优选。