Investigation of different influences on the fatigue behaviour of industrial rubbers

Load conditions used typically for fatigue life investigations can differ strongly from the conditions for real rubber products. For example, the frequency of the laboratory measurements is increased and the product load curve is simplified to a sine. In this paper, industrial rubber blends (SBR/BR/NR blends) under tension–compression load are used. First, the influence of a higher frequency (5 Hz) compared to the product relevant frequency (1 Hz) is investigated. A higher frequency does not influence the fatigue life but certainly the sample temperature and material behaviour. This is further investigated by varying the ambient temperature for 1 Hz measurements and the strain rate. Second, a non-sinusoidal wave form depicting the product loading case is selected. The load oscillates between tension and compression with dwell periods in every cycle. The results are comparable to those of a sine wave with the same frequency.     

Traveling wave solutions in the mathematical model of blood coagulation

Under normal conditions, blood coagulation provides an effective protective mechanism preventing bleeding in case of vessel damage. Details of its functioning are of particular importance since any blood coagulation disorders lead to severe physiological aggravations. Multiple experimental and computational studies demonstrate the thrombin concentration distribution to determine the spatio-temporal dynamics of clot formation. Propagating from the injury site with constant speed, thrombin concentration profile can be modeled with a traveling wave solution of the system of partial differential equations describing main reactions of the coagulation cascade. In the current study, we derive conditions on the existence and stability of such solutions and provide an analytic approach of their wave speed estimation.     

Fast color transfer from multiple images

Color transfer between images uses the statistics information of image effectively.We present a novel approach of local color transfer between images based on the simple statistics and locally linear embedding.A sketching interface is proposed for quickly and easily specifying the color correspondences between target and source image.The user can specify the correspondences of local region using scribes,which more accurately transfers the target color to the source image while smoothly preserving the boundaries,and exhibits more natural output results.Our algorithm is not restricted to one-to-one image color transfer and can make use of more than one target images to transfer the color in different regions in the source image.Moreover,our algorithm does not require to choose the same color style and image size between source and target images.We propose the sub-sampling to reduce the computational load.Comparing with other approaches,our algorithm is much better in color blending in the input data.Our approach preserves the other color details in the source image.Various experimental results show that our approach specifies the correspondences of local color region in source and target images.And it expresses the intention of users and generates more actual and natural results of visual effect.     

Error propagation model for microscopic magnetic resonance elastography shear-wave images

Microscopic magnetic resonance elastography is a high-resolution method for visualizing shear waves and assessing the biomechanical viscoelastic properties of small biological samples. In this work, we used error propagation to develop a simple analytical model that relates the signal-to-noise ratio of MR magnitude images to the variance in shear-wave maps collected using gradient-echo and spin-echo phase-contrast pulse sequences. Our model predicts results for shear-wave images in phantoms, which match the experimentally observed phase variance within 8%. This model can be used to optimize MR pulse sequences for elastography studies, as well as other phase-difference techniques in MRI.     

Induced explode-decay dromions in the (2 + 1) dimensional nonisospectral nonlinear Schrödinger (NLS) equation

In this paper, we have identified a novel method of inducing localized solutions in the (2+1) dimensional nonisospectral nonlinear Schr?dinger (NLS) equation by utilising the freedom in the system. The new class of localized solutions includes induced dromions, lump dromions, dipole dromions etc. The amplitude of the localized solutions generated is found to explode or decay with time. We have also brought out the interaction of induced dromions.     

空间管路振动频率计算的精确传递矩阵法

考虑了流体定常压力和流速，建立了空间管系振动及声传播的传递矩阵法。该方法可计算空间管系的频率、模态及动力响应。用该方法对典型耐压管路频率计算与解析解对比表明该方法是正确的。     

Hierarchical Nacre Mimetics with Synergistic Mechanical Properties by Control of Molecular Interactions in Self‐Healing Polymers

Designing the reversible interactions of biopolymers remains a grand challenge for an integral mimicry of mechanically superior biological composites. Yet, they are the key to synergistic combinations of stiffness and toughness by providing sacrificial bonds with hidden length scales. To address this challenge, dynamic polymers were designed with low glass‐transition temperature T_g and bonded by quadruple hydrogen‐bonding motifs, and subsequently assembled with high‐aspect‐ratio synthetic nanoclays to generate nacre‐mimetic films. The high dynamics and self‐healing of the polymers render transparent films with a near‐perfectly aligned structure. Varying the polymer composition allows molecular control over the mechanical properties up to very stiff and very strong films (E≈45 GPa, σ_UTS≈270 MPa). Stable crack propagation and multiple toughening mechanisms occur in situations of balanced dynamics, enabling synergistic combinations of stiffness and toughness. Excellent gas barrier properties complement the multifunctional property profile.     

Tensile,fatigue and thermomechanical properties of poly(ethylene-co-vinyl acetate) nanocomposites incorporating low and high loadings of pre-swelled organically modified montmorillonite

The production of exfoliated polymer/clay based nanocomposites is crucial to obtain an actual benefit of nanoscale reinforcement in the polymer matrix. In this project, the production of exfoliated polymer/clay nanocomposite was aimed through the use of poly(ethylene-co-vinyl acetate) (EVA) copolymer as matrix and organically modified montmorillonite (O-MMT) as nanofiller. The research work involved the use of pre-swelled technique through magnetic stirring and ultra-sonication to obtain more readily exfoliated and dispersed O-MMT nanofiller for EVA nanocomposite production. The aims were to allow the improvement in O-MMT exfoliation and dispersion when the nanofiller was incorporated in high loading (greater than 3 wt%) into the copolymer. The original and pre-swelled O-MMTs were employed to produce the EVA/O-MMT nanocomposites with 1, 3, 5, 7 and 9 wt% nanofiller by melt compounding technique. The results of TEM, tensile and fatigue tests, XRD, FTIR and DMA proved that the pre-swelling technique applied on the O-MMT before melt compounding with the EVA copolymer can bring positive impact to the performance of the nanocomposite. As opposed to the original O-MMT, the pre-swelled O-MMT has the ability to improve the tensile toughness, cyclic stability and storage modulus of the EVA copolymer even when high O-MMT loading (7 wt %) was employed. Improvement in the EVA - O-MMT interactions in the nanocomposite system was postulated to be the main reason for such observations.     

浅海内孤立波动态传播过程中声波模态强度起伏规律

内孤立波是一种常见于浅海海域的非线性内波,具有振幅大、周期短和流速强等特点,它通过扰动水体中的温盐分布使声速剖面产生明显的距离依赖性,进而影响水下声传播特性.内波自生成后通常以1 m/s量级的速度传播,运动的内波使声传播路径上的声波模态能量在空间和时间上剧烈起伏.本文定义模态强度为模态系数模值(模态幅度)的平方,并用其衡量各阶模态所含声能量的大小.文中基于耦合简正波理论,推导了内波运动时声波模态强度起伏的表达式,将模态强度表征为振荡项和趋势项的线性叠加.以往的工作大多局限于单独从时域或频域研究内波运动时声波模态强度的时变规律,本文则结合短时傅里叶变换在时频平面上揭示了模态强度的起伏机理.理论推导和数值仿真均表明内孤立波使各阶声波模态之间发生能量交换,即模态耦合.内波的动态传播进一步引起模态干涉,这种干涉效应表现为模态强度中的振荡项并使模态强度随时间快速起伏.受模态剥离效应(不同阶模态之间衰减系数的差异)的影响,趋势项的幅度随时间不断变化,进而对模态干涉引起的振荡叠加了时变的偏置.模态强度的整体走势和振荡项中各频率分量振幅的时变特征均与模态衰减密切相关.同时,本文使用深度积分声强作为总接...