Non-Linear response of a long,discontinuous fiber/melt system in elongational flows

The authors investigated the transient elongational behavior of a highly-aligned 600% volume fraction long, discontinuous fiber filled poly-ether-ketone-ketone melt with a computer-controlled extensional rheometer at 370°C. Prior experiments at controlled strain rate and stress produced _E ⁺ (t, ) and ^– (t, _E) similar to a shear dominated flow of a non-linear viscoelastic fluid. Stress relaxation following steady extension showed nonlinear effects in the change in stress decay rate with increasing strain rate. Continuous relaxation spectra showed a shift in the spectral peak to smaller values of with increasing strain rate. The Giesekus nonlinear constitutive relation modeled the elongation and stress relaxation with shearing rate at the fiber surface set by a strain rate magnification factor. Suitable for elongation, the model produced insufficient shift in the stress relaxation spectrum to account for the large change in stress decay rate exhibited in the experiments.English alphabet a _r aspect ratio of the fibers or l/d - A ₀ initial uniform cross-section area of the specimen - d fiber diameter - f fiber volume fraction - H() relaxation spectrum found by the method of Ferry and William l length of the fiber - L(t) time function specimen length - L ₀ initial specimen length - r radial coordinate across the shear cell - R _i fiber radius and inner cell dimension - R _o outer cell radius - t time in s - t _max duration of the extension - T _g glass transition temperature of the polymer - v velocity of the moving end of the test specimen - x axial position where is calculated Greek alphabet nonlinearity parameter in the Giesekus relation - axial mass distribution along the specimen major axis - shear strain rate - strain tensor - ₍₁₎ first convected derivative of the strain tensor - ₍₂₎ second convected derivative of the strain tensor - average strain at the end of extension as determined from - extension strain rate - average extension strain rate determined from - ^– transient strain rate under controlled stress, creep, test - _E elongational viscosity - _Eapp apparent elongational viscosity determined from - _E ⁺ transient elongational viscosity - ₀ zero shear rate viscosity - relaxation parameter - ₁ relaxation parameter in either Jeffrey's or Giesekus fluid - ₂ retardation parameter in either Jeffrey's or Giesekus fluid - _max relaxation value at which 99.9% of the H spectrum had occurred - _p relaxation value at which H reaches a maximum - volumetric composite density - _E elongational stress - _E ⁺ transient elongational stress - _E ^– controlled elongational stress, creep stress - _E ^y peak elongational stress in controlled experiment - shear stress at surface of the fiber in a shear cell - _yx simple shear component of the strain rate tensor - stress tensor - ₁ first convected derivative of the stress tensor     

Facile Synthesis of Thiol‐Functionalized Long‐Chain Highly Branched ROMP Polymers and Surface‐Decorated with Gold Nanoparticles

The synthesis of thiol‐functionalized long‐chain highly branched polymers (LCHBPs) has been accomplished in combination of ring‐opening metathesis polymerization (ROMP) and thiol‐Michael addition click reaction. A monotelechelic polymer with a terminal acrylate and many pendent thiol groups is first prepared through adding an internal cis‐olefin terminating agent to the reaction mixture immediately after the completion of the living ROMP, and then utilized as an AB_n‐type macromonomer in subsequent thiol‐ene reaction between acrylate and thiol, yielding LCHBPs as the reaction time prolonged. Au nanoparticles are then covalently conjugated onto the surface of thiol‐functionalized LCHBP to fabricate novel hybrid nanostructures, which is shown as one interesting application of such functionalized metathesis polymers. This facile approach can be extended toward the fabrication of novel nanomaterials with sophisticated structures and tunable multifunctionalities.

     

Long range effect in ion-implanted GaAs

Abstract

New experimental data are presented which indicate the change of defect centers concentration in GaAs at macroscopic (up to millimeters) distances from the implanted regions edge. These data were obtained by locally exited cathodoluminescence, by observation of photoconductivity detected locally by contactless MW technique, by conductivity, DLTS and Raman spectroscopy measurement. Interpretation of the mechanism of long range effect is presented.     

衍射型长程大型非球面轮廓测量仪

分析了基于衍射准直技术的f-θ系统的特点，在此基础上提出了一种新型长程面形仪用以实现对大型非球面光学表面，特别是同步辐射中掠入射光学元件的高精度轮廓测量。成功地研制了样机，目前新型长程面形仪样机的纵向扫描范围可达370mm，分辨率优于0．25μrad，单点稳定性小于0．7μrad/200s，全程测量精度可达1．14μrad，全长扫描的重复精度为0．09μrad。样机测试结果表明，新型长程面形仪轮廓测量方案能够胜任对第三代及后继同步辐射光源中各种非球面光学元件的轮廓测量任务。     

Modified WKB transmission for fusion

In the optical model (OM) approach for fusion, absorption of flux occuring beyond the barrier position is presented in detail at low energies. It has been shown that the OM transmission can be well approximated as a sum of the WKB transmission and a long range absorption (LRA) contribution. Owing to absence of LRA, the fusion predictions of coupled channel codes based on transmission approach like the CCFUS code, do not agree with the predictions of complete coupled reaction channel (CRC) calculations based on OM approach using the code FRESCO. The CCFUS code with a modified transmission which includes LRA contribution is shown to be consistent with the CRC results using FRESCO. The static deformation of the colliding nuclei strongly influences the fusion imaginary potential and therefore the deep sub-barrier fusion cross sections.     

Nonlinear instability of wavetrain under influences of shear current with varying vorticity and air pressure

Under the assumption of weak shear current with varying vorticity in water and weak air pressure the Zakharov theory is extended to include the effects of vorticity and air pressure on the modulation of water waves. This new equation is used to examine the influence of current and wind on the Benjamin-Feir sideband instability and long-time evolution of wavetrain. As strength of the current increases the bandwidth is found broadened, and the maximum growth rate of sidebands decreased. Periodic solution of sidebands in the presence of current is indicated, which means that shear current does not affect the downshift of wave spectrum peak. Energy input by imposing the air pressure leads to the enhancement of the lower sideband, which is in agreement with the finding of Hara and Mei (1991). The project supported by the National Natural Science Foundation of China     

子孔径拼接技术在长平晶计量中的应用研究

研究子孔径拼接在长平晶测试中的应用。讨论了子孔径拼接的基本原理,建立了子孔径拼接模型,确定了进行长平晶拼接测试的基本算法。根据最小二乘法的基本原理,编制了子孔径拼接数据处理程序,通过使用该程序,可以有效地修正测试过程中产生的倾斜量。进行了长平晶拼接检测实验,拼接结果与全孔径检测结果进行了比较,结果表明,该程序能够满足长平晶的检测要求。     

关于光学速调管长波长辐射的分析

由波荡器渡越辐射公式和电子通过wiggler边界产生的长波长辐射公式, 解析给出了电子通过光学速调管时产生的长波长辐射公式. 根据基本的电动力学公式数值计算出合肥同步辐射装置光学速调管的长波辐射, 并将其结果与解析公式的结果进行比较. 计算合肥同步辐射装置的光学速调管和弯转磁铁在红外波段范围内辐射的强度和通量, 表明光学速调管有很好的性能.本文说明, 光学速调管不但可以用来进行相干谐波的试验研究, 也可以兼用作储存环中的红外辐射光源.     

THE SPATIAL DISPERSION THEORY OF EXCESS CONDUCTION LOSS IN NORMAL METALS AT SUB-MILLIMETER WAVELENGTHS

On using the spatial dispersion theory, we have developed a rigorous model for analyzing excess conduction loss in normal metals. We have used the model to account excess conduction loss and dissect the discrepancies between excess conduction loss measurements and classical theoretical predictions in normal metals for sub-millimeter wavelengths. Our analysis shows that the conductivity is not only frequency but also wave vector dependent. We demonstrate good quantitative agreement with the published experimental data for the room temperature excess conduction loss of normal metals for sub-millimeter wavelengths.