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101.
Abbas Niknejad G.H.Liaghat H.Moslemi Naeini A.H.Behravesh 《Acta Mechanica Solida Sinica》2010,23(4):353-360
In this paper, a theoretical formula is presented to predict the instantaneous folding force of the first fold creation in square and rectangular columns under axial loading.The rectangular column is a small and single model of honeycombs with square or rectangular cells.Calculations are based on the analysis of the Basic Folding Mechanism (BFM).For this purpose, sum of the dissipated energy rate under bending around horizontal and inclined hinge lines and the dissipated energy rate under extensional deformations was equal to the work rate of the external force on the structure.The final formula obtained in this research, reasonably predicts the instantaneous folding force of single-cell square and rectangular honeycombs instead of the average value.Finally, according to the calculated theoretical relation, the instantaneous folding force of the first fold creation in a square column was sketched versus folding distance and compared to the experimental results, which showed a good correlation. 相似文献
102.
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104.
Yiu‐Ting R. Lau Lu‐Tao Weng Kai‐Mo Ng Chi‐Ming Chan 《Surface and interface analysis : SIA》2010,42(9):1469-1475
The effect of film thickness on the structural conformation of the surfaces of the amorphous state, edge‐on lamellae and flat‐on lamellae of a semiflexible polymer, poly(bisphenol‐A‐etheroctane), was investigated by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) with the aid of principal component analysis (PCA). PCA results empirically indicate that a structurally regular polymer surface was obtained with the formation of the flat‐on lamellae from the amorphous state at a low degree of supercooling. A higher concentration of end group and cilium ion fragments, which are indicative of free chain ends, was observed on the edge‐on lamellar surfaces than on the amorphous and the flat‐on lamellar surfaces. This finding was attributed to the fact that the lateral surface of the edge‐on lamellae contains many growth fronts, leaving behind a large number of uncrystallized chain remnants on the surfaces. Structural disorder was facilitated on both edge‐on and flat‐on lamellar surfaces as the film thickness decreased. Hence, this PCA study offers new insights into the nonequilibrium nature of polymer crystals and the mechanism of polymer crystallization in thin and ultrathin films. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
105.
Marek Kossowski 《Annals of Global Analysis and Geometry》2002,21(1):19-29
Using C
-singularity theory, we describe natural conditions on nonimmersivemappings of a compact orientable 2-manifold into Euclidean 3-space (e.g., theexistence of a global limiting tangent bundle). These conditions are weaker thanthose of caustic theory and imply that the image is a CW-complex. In general, the domainmanifold is not homeomorphic to the image CW-complex. We then adapt classical methods to this setting. (This adaptation is simplified by freely moving betweenthe Gauss, Cartan, and Kozul formulations for surface theory.) As an application,we show that part of the extrinsic topology of the image is determined by the firstfundamental form, i.e., a global `theorem egregium'. 相似文献
106.
Raman longitudinal acoustic mode (LAM) spectra have been obtained during isothermal crystallization from the melt at various temperatures of a poly(ethylene oxide) (PEO) fraction of molecular weight about 3000 and an α,ω-methoxylated fraction (MPEO) derived from it. For both fractions, we find that noninteger fold (NIF) chains are formed in the initial stages of crystallization. With time, and more rapidly at higher crystallization temperatures, the NIF chains transform into integer-fold (IF) structures. The final morphologies of the two fractions are similar, consisting of IF mixed-crystal lamellae composed mainly of extended (E) chains with embedded once-folded (F2) chains. This solid-state transformation from the NIF state may proceed through the F2 state. The effect of hydrogen bonds in the case of PEO is not to change the transformation process but to slow it when compared to MPEO. Comparison with small-angle x-ray scattering (SAXS) data indicates that in both cases the NIF chains are tilted to the lamellar surface and that the tilt from perpendicular eventually disappears as IF chains form at the later stages of crystallization. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1117–1126, 1997 相似文献
107.
周树昂 《应用数学和力学(英文版)》1990,11(3):215-237
The overall mechanical and electrical behaviors of elastic dielectric composites are investigated with the aid of the concept of material multipoles. In particular, by introducing a statistical continuum material multipole theory, the effects of the electric-elastic interaction and the microstructure (size, shape, orientation,...) of inhomogeneous particles on the overall behaviors of the composites can be obtained. A basic solution for an ellipsoidal elastic inhomogeneity with electric polarization in an infinite elastic dielectric medium is first given, which shows that classical Eshelby ’s elastic solution is modified by the presence of electric-elastic interaction. The overall macroscopic constitutive relations and their overall macroscopic material parameters accounting for electroelastic interaction effect are then derived for the elastic dielectric composites. Some quantitative calculations on the problems with statistical anisotropy, the shape effect and the electric-elastic interaction are finally given for dilute composites. 相似文献
108.
在γ脉冲射线束测量中,束流波形是由许多不同能量的γ粒子叠加而成的,在大气介质传输中,由于γ粒子与空气原子的相互作用,测点的γ能通量强度随时间变化的波形、同源点的γ强度波形相比,在较大测点距离的情况下就会产生畸变。讨论了γ射线在大气中输运的传输函数以及用褶积计算测点γ能通量强度波形的方法,给出了解析表达式,对典型的γ源脉冲波形输运不同距离,计算了大气输运对测量的影响。最后讨论了减小或避免波形畸变的方法。 相似文献
109.
Wind instrumentalists, especially brass players, and singers share common factors, including vocal tract shape, function and pressure, vocal fold opening and closure, breath vector of force and air flow rates. To understand the mechanism and function of the vocal folds with a pathological lesion, it is necessary to visualize the differing interactions of the vocal tract during wind and brass instrument playing and in singing. A school band director, singer, wind and brass instrumentalist, was referred by musician colleagues with intermittent dysphonia, aphonia, and inability to sing high notes. Simultaneous videolaryngoscopy, with and without stroboscopy, and external video examination were documented. An hourglass glottis with a sessile, cystic polyp of the left vocal fold were recorded and studied during phonation and the playing of 3 instruments. The techniques of glottic opening, closure, configuration and function varied with the type of instrument and phonatory function. Singing was adversely affected by the vocal fold polyp but no harmful interaction occurred during wind/brass instrument playing. Down-stream loading in singers is at the laryngeal level and in wind/brass instrumentalists is at the embouchure. Preoperative voice therapy, phonomicrosurgery, and postoperative voice rest followed by voice therapy, succeeded in restoring her combined wind/brass instrumental and singing career. 相似文献
110.
Anne E. Vertigan Deborah G. Theodoros Peter G. Gibson Alison L. Winkworth 《Journal of voice》2006,20(3):466-480
SUMMARY: Chronic cough (CC) and paradoxical vocal fold movement (PVFM) are debilitating conditions. PVFM has been given many labels, including vocal cord dysfunction, Munchausen's stridor, functional inspiratory stridor, nonorganic functional or psychogenic upper airway obstruction, factitious asthma, psychogenic stridor, emotional laryngeal wheezing, and episodic laryngeal dyskinesia. Although CC and PVFM have been considered separate entities in many reports, there is preliminary support for the notion that there may be an underlying link between these two conditions. Speech pathologists have become increasingly involved in the treatment of these patients and therefore need to understand the theoretical background of these disorders, the pathophysiological links between the two, and the impact of voice disorders on these populations. The aim of this article is to review the current literature on CC and PVFM from a speech pathology perspective to provide a model for defining and conceptualizing the disorders and to provide a framework for management and future research. 相似文献