Compactifications whose remainders are zero dimensional and retract

LetX be a locally compact non compact space. Necessary and sufficient conditions forfX/X to be a retract offX are given wherefX is the Freudenthal compactification ofX. LetX be a locally compact and zero dimensional space,m be any cardinal number andJ be a set with cardinalitym. It is proved thatX has a dyadic family of powerm if and only if there exist and compactificationY ofX such thatY/X=2 ^J andY/X is a retract ofY.     

Reconsidering extra time-like dimensions

In this study we reconsider the phenomenological problems related to tachyonic modes in the context of extra time-like dimensions. First we reconsider a lower bound on the size of extra time-like dimensions and improve on the conclusion in the literature. Next we discuss the issues of spontaneous decay of stable fermions through tachyonic decays and disappearance of fermions due to tachyonic contributions to their self-energies. We find that the tachyonic modes due to extra time-like dimensions are less problematic than the tachyonic modes in the usual 4-dimensional setting because the most troublesome Feynman diagrams are forbidden once the conservation of momentum in the extra time-like dimensions is imposed.     

Magnetic Texturing of Xenon-Irradiated Iron Films Studied by Magnetic Orientation Mössbauer Spectroscopy

Modifications of magnetic properties upon heavy-ion irradiation have been recently investigated for films of ferromagnetic 3d-elements (Fe, Ni, Co) and alloys (permendur, permalloy), in relation to changes of their microstructure. Here we report on Xe-ion irradiation of a highly textured iron film prepared via pulsed-laser deposition on a MgO(100) single crystal and containing a thin ⁵⁷Fe marker layer for magnetic orientation Mössbauer spectroscopy (MOMS). We compare the results with those obtained for a polycrystalline Fe/Si(100) sample produced by electron evaporation and premagnetized before Xe-irradiation in a 300 Oe external field. Characterization of the samples also included magneto-optical Kerr effect (MOKE), Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD).     

Polymer electrolyte membranes based on p‐toluenesulfonic acid doped poly(1‐vinyl‐1,2,4‐triazole): Synthesis,thermal and proton conductivity properties

Throughout this work, the synthesis, thermal as well as proton conducting properties of acid doped heterocyclic polymer were studied under anhydrous conditions. In this context, poly(1‐vinyl‐1,2,4‐triazole), PVTri was produced by free radical polymerization of 1‐vinyl‐1,2,4‐triazole with a high yield. The structure of the homopolymer was proved by FTIR and solid state ¹³C CP‐MAS NMR spectroscopy. The polymer was doped with p‐toluenesulfonic acid at various molar ratios, x = 0.5, 1, 1.5, 2, with respect to polymer repeating unit. The proton transfer from p‐toluenesulfonic acid to the triazole rings was proved with FTIR spectroscopy. Thermogravimetry analysis showed that the samples are thermally stable up to ～250 °C. Differential scanning calorimetry results illustrated that the materials are homogeneous and the dopant strongly affects the glass transition temperature of the host polymer. Cyclic voltammetry results showed that the electrochemical stability domain extends over 3 V. The proton conductivity of these materials increased with dopant concentration and the temperature. Charge transport relaxation times were derived via complex electrical modulus formalism (M*). The temperature dependence of conductivity relaxation times showed that the proton conductivity occurs via structure diffusion. In the anhydrous state, the proton conductivity of PVTri1PTSA and PVTri2PTSA was measured as 8 × 10^?4 S/cm at 150 °C and 0.012 S/cm at 110 °C, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1016–1021, 2010     

INTRODUCTION TO THE 7TH TEACHING COMPETITION OF YOUTH FACULTY OF FUNDAMENTAL MECHANICS COURSES

阐述了教育部高等学校力学基础课程教学指导分委员会举办的全国高校第七届基础力学青年教师讲课比赛的基本情况、本届讲课比赛的特点、讲课比赛中反映出的问题及其改进的建议。希望通过本文的介绍,让国内各高校教师了解本届讲课比赛以及比赛中反映出的问题,为进一步办好讲课比赛、提高我国基础力学课程的教学水平和质量提供参考。     

Batch process monitoring and its application to polymerization systems

Slight changes in raw material properties or operating conditions during critical periods of operation of batch and semi-batch polymerization reactors may have a strong influence on reaction mechanism and impact final product quality. Online process monitoring, fault detection, fault diagnosis, and product quality prediction in real-time ensure safe reactor operation and warn operators about excursions from normal operation that may lead to deterioration in product properties. Multivariate statistical process monitoring and quality prediction using multiway principal components analysis and multiway partial least squares have been successful in detecting abnormalities in process operation and product quality. When abnormal process operation is detected, fault diagnosis tools are used to determine the source cause of the deviation. Illustrative case studies are presented via simulated polyvinyl acetate polymerization.     

超重力作用下软材料薄膜失稳的有限元分析

软材料在自然界和工业应用中无处不在,其显著特点是对外界刺激极其敏感,相对于传统材料其弹性模量更小,容易发生表面形态的失稳现象．现有研究主要把光、声、电等作为诱导材料失稳的因素进行研究,而重力往往作为常量考虑．本文通过有限元模拟,建立超重力作用下环向受限的圆柱状软材料薄膜失稳模型,探究了薄膜材料的密度、厚度、半径、剪切模量等材料和几何参数对失稳临界超重力和临界失稳模态的影响．结果表明,触发薄膜失稳的超重力随薄膜厚度和密度增大而减小,随剪切模量增大而增大,随着薄膜半径增大快速减小并迅速趋于常数．另外,当径厚比R/H较小时,无量纲临界超重力随着径厚比增大而单调减小,但当径厚比R/H大于3 时,此量为一个常数．超重力作用下软材料的临界失稳模态与密度、剪切模量等参数无关,随径厚比R/H增大,临界失稳模态波数增大、波长减小．     

Direct computation of higher-order propagation modes using the imaginary-distance beam propagation method

In this paper we present an extension to the standard method of eigenmode-extraction using the imaginary-distance beam propagation method. We show that it is possible to directly extract higher-order propagation modes of arbitrary shaped waveguide structures by propagating the field along the imaginary axis when the parameters are chosen in an appropriate manner. This method requires an assumption of the propagation constant of the eigenmode. In many cases this value can be determined using fast approximate techniques like the effective index method. Additionally, the approximate mode shape may be introduced as a starting condition and can further accelerate the extraction of the eigenmode. The overall number of propagation steps needed to extract multiple eigenmodes is then significantly smaller than in the case when extracting the modes sequentially with the former method.