Prediction of the plastic viscosity of self-compacting steel fibre reinforced concrete

Micromechanical constitutive models are used to predict the plastic viscosity of self-compacting steel fibre reinforced concrete (SCFRC) from the measured plastic viscosity of the paste. The concrete is regarded as a two-phase composite in which the solid phase is suspended in a viscous liquid phase. The liquid matrix phase consists of cement, water and any viscosity modifying agent (VMA) to which the solids (fine and coarse aggregates and fibres) are added in succession. The predictions are shown to correlate very well with available experimental data. Comments are made on the practical usefulness of the predicted plastic viscosity in simulating the flow of SCFRC.     

某大桥移梁及加固的设计与施工

介绍了在某铁路小半径曲线改造工程中铁路桥梁移梁及加固改造方案，并针对设计与施工的难点和特点进行了具体阐述，从而为今后类似的工程提供了一些经验和指导。     

Effect of chain architecture on the compression behavior of nanoscale polyethylene particles

Polymeric particles with controlled internal molecular architectures play an important role as constituents in many composite materials for a number of emerging applications. In this study, classical molecular dynamics techniques are employed to predict the effect of chain architecture on the compression behavior of nanoscale polyethylene particles subjected to simulated flat-punch testing. Cross-linked, branched, and linear polyethylene chain architectures are each studied in the simulations. Results indicate that chain architecture has a significant influence on the mechanical properties of polyethylene nanoparticles, with the network configuration exhibiting higher compressive strengths than the branched and linear architectures. These findings are verified with simulations of bulk polyethylene. The compressive stress versus strain profiles of particles show four distinct regimes, differing with that of experimental micron-sized particles. The results of this study indicate that the mechanical response of polyethylene nanoparticles can be custom-tailored for specific applications by changing the molecular architecture.     

Specifications for molded materials used in refractory linings

Basic specifications are formulated for the grain-size composition, binder content, and contents of fibers and rheological additives that favor the formation of a dense and strong structure in molded materials (in the main concrete). The effects are considered on the thermal resistance and cracking resistance. Translated from Novye Ogneupory, No. 2, pp. 43 – 46, February, 2009.     

Crack effects on gas and water permeability of concretes

The relationship between load-induced cracking and concrete permeability is studied. Ordinary concrete (OC) and high-performance concrete (HPC), including steel fiber-reinforced concrete (HPFRC), are used. Two discs, 50 mm-thick slices, cut from 110-220 mm cylindrical specimens are diametrically loaded, as for a normal splitting test. The lateral displacement, also called the crack opening displacement (COD) is monitored for each loading cycle. After unloading, gas and finally water permeability tests are both performed, using constant head permeameter, to compare the influence of the percolating fluid and the COD. Due to the wide range of measured gas flow, Klinkenberg's and Dupuit-Forcheimer's laws are applied to compute the intrinsic gas permeability. Results suggest it increases proportionally to the cube of the COD and it matches water permeability, if only the first water percolating time is considered. The roughness parameter of the cracks induced in each concrete, is compared and discussed.     

Effect of layering pattern on the water absorption behavior of banana glass hybrid composites

Hybridization of Banana fibers with glass fibers has been found to reduce the water absorption behavior of the composites in an earlier work by us. Banana fibers were hybridized with glass and different layering patterns were followed in the preparation of the composites. The effect of the various layering patterns on the water absorption of the composites was studied. It was found that water diffusion occurs in the composite depending on the layering pattern as well as the temperature. In all the experiments, it has been found that composites with an intimate mixture of glass and banana show the maximum water uptake except for temperature of 90°C. At 90°C the maximum water uptake is found to be for composites where there is one layer of banana and another layer of glass. The water uptake follows the same trend as that in all other temperatures till a time span of 4900 min is reached. The kinetics of diffusion was found to be Fickian in nature. The various thermodynamic parameters like sorption coefficient, diffusion coefficient. Enthalpy change, entropy change, and activation energy of the various composites were calculated. From all the calculations it has been concluded that layering pattern is an important parameter which controls the water absorption of the composites. The layering pattern Cg‐b‐g was found to have the lowest water uptake. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

从材料角度探讨影响玻璃钢拉伸性能的诸因素

玻璃钢拉伸强度主要取决于玻璃布经纬向的玻璃纤维和基全树脂的性能以及两者之间的组合状态。本文就组成玻璃钢的三种主要材料；玻璃纤维增强材料、基体树脂浸润分别进行讨论。     

Surface stress and strain fields on compressed panels of corrugated board boxes. An experimental analysis by using Digital Image Stereocorrelation

The complex behaviour of corrugated board packages under compression loading is investigated in this work. Original experimental data are obtained by using a Digital Image Stereocorrelation technique for measuring the displacement and strain fields of the panels’ outer liner of the tested boxes. The stress field is also estimated by accounting for the anisotropic mechanical behaviour of the outer liner, its residual stress state induced by the processing of the corrugated board and the effects of box manufacturing operations and compression. Results show that these fields are extremely heterogeneous on the panels’ surface. Most stressed areas are located along the panels’ edges. The elastic limit of the outer liner is reached quite soon during compression. Box geometry and panel flaps are of primary importance on the observed phenomena. This approach delivers useful information to improve kinematic and constitutive assumptions for buckling and post-buckling models of boxes or thin-walled sandwich structures.     

Natural Language Compression on Edge-Guided text preprocessing

This paper presents Edge-Guided (E-G), an optimized text preprocessing technique for compression purposes. It transforms the original text into a word net, which stores all relationships between adjoining words. A specific directed graph is proposed to model this transformation: words are stored in vertices, whereas edges represent word transitions. Thus, the word net has a text representation which reflects the natural word order in the text, so it can be used directly for encoding purposes. A specific coding scheme is described at the top of the word net. It regards a text as a sequence of word transitions, in such a way that each word is encoded by traversing a specific edge from the vertex which stores the preceding word. This accomplishes a 1-order text preprocessing whose output is an intermediate byte representation that can be effectively encoded with universal techniques. This technique is called E-G₁ and performs on some variants.This experience is used to revisit the concept of word net. It is used to identify significative 2-word symbols by performing a specific transformation on frequent edges. The resultant transformed word net appends these 2-word symbols to the original word vocabulary, and allows a specific hierarchical relationship between them and their component words. The transformed approach also enhances the original coding scheme to handle these new features. A new technique, called E-G₂, approximates a 2-order model on words that also support specific variants.Both techniques are studied from empirical and experimental perspectives. Some compressors are also used to analyze the preprocessing ability of E-G with respect to different compression approaches. Competitive space/time trade-offs are achieved when our approaches are used to compress medium-large size texts. The best results are achieved when E-G preprocessing is coupled with high-order compressors such as Prediction by Partial Matching (PPM).     

Optimization of polytetrafluoroethylene content in cathode gas diffusion layer by the evaluation of compression effect on the performance of a proton exchange membrane fuel cell

This research investigates the optimal polytetrafluoroethylene (PTFE) content in the cathode gas diffusion layer (GDL) by evaluating the effect of compression on the performance of a proton exchange membrane (PEM) fuel cell. A special test fixture is designed to control the compression ratio, and thus the effect of compression on cell performance can be measured in situ. GDLs with and without a microporous layer (MPL) coating are considered. Electrochemical impedance spectroscopy (EIS) is used to diagnose the variations in ohmic resistance, charge transfer resistance and mass transport resistance with compression ratio. The results show that the optimal PTFE content, at which the maximum peak power density occurs, is about 5 wt% with a compression ratio of 30% for a GDL without an MPL coating. For a GDL with an MPL coating, the optimal PTFE content in the MPL is found to be 30% at a compression ratio of 30%.