中巴喀喇昆仑公路顺层岩质边坡受力分析

为了深入研究中巴喀喇昆仑公路洪扎河以北地段的顺层岩质边坡弯曲失稳机制,采用材料力学压杆稳定及刚性体平衡原理,在D.S.Cavers的基础上考虑地震力作用,分析得到岩质边坡的三种弯曲模型(平面边坡的柔性弯曲、平面边坡的三铰梁模型、曲线边坡的三绞铰模型)的失稳公式,将地震与非地震作用下平面边坡的柔性弯曲进行对比分析。研究结果表明:当内摩擦角φ_j处于0°~15°范围时,若水平地震加速度方向与岩体弯曲方向相反,平面边坡柔性弯曲模型在地震作用下不易发生弯曲变形;若水平地震加速度方向与岩体弯曲方向一致,地震作用下平面边坡柔性弯曲模型的临界状态总长度l总比非地震作用下的l小,平面边坡在此方向的地震作用下更易发生柔性弯曲变形。     

Bioaugmentation of floating treatment wetlands for the remediation of textile effluent

This pilot study evaluated the effects of bacterial augmentation on the efficiency of floating treatment wetlands (FTWs) to remediate textile wastewater. Two wetland plants, Phragmites australis and Typha domingensis, were used to develop FTWs, which were then augmented with a bacterial consortium of three strains (Acinetobacter junii, Pseudomonas indoloxydans, and Rhodococcus sp.). Results showed that both plant species removed colour, organic matter, toxicity, and heavy metals from textile wastewater and their removal efficiency was further enhanced by augmentation with bacteria. The maximum removal efficiencies of colour, COD and BOD after an 8‐day period were 97, 87 and 92%, respectively, by FTWs carrying P. australis inoculated with the bacterial consortium. Furthermore, the same combination showed 87–99% reduction of heavy metals in the textile wastewater as well. These results indicate that FTWs can be used for the treatment of textile effluent and their working efficiency can be improved by plant‐bacterial synergism.     

Influence of accelerated curing on the compressive strength of polymer-modified concrete

In recent building practice, rapid construction is one of the principal requisites. Furthermore, in designing concrete structures, compressive strength is the most significant of all parameters. While 3-d and 7-d compressive strength reflects the strengths at early phases, the ultimate strength is paramount. An effort has been made in this study to develop mathematical models for predicting compressive strength of concrete incorporating ethylene vinyl acetate (EVA) at the later phases. Kolmogorov-Smirnov (KS) goodness-of-fit test was used to examine distribution of the data. The compressive strength of EVA-modified concrete was studied by incorporating various concentrations of EVA as an admixture and by testing at ages of 28, 56, 90, 120, 210, and 365 d. An accelerated compressive strength at 3.5 hours was considered as a reference strength on the basis of which all the specified strengths were predicted by means of linear regression fit. Based on the results of KS goodness-of-fit test, it was concluded that KS test statistics value (D) in each case was lower than the critical value 0.521 for a significance level of 0.05, which demonstrated that the data was normally distributed. Based on the results of compressive strength test, it was concluded that the strength of EVA-modified specimens increased at all ages and the optimum dosage of EVA was achieved at 16% concentration. Furthermore, it was concluded that predicted compressive strength values lies within a 6% difference from the actual strength values for all the mixes, which indicates the practicability of the regression equations. This research work may help in understanding the role of EVA as a viable material in polymer-based cement composites.     

Postbuckling behaviour of stainless steel (SUS304) columns under loading-unloading cycles

Based on the equilibrium configuration paths, this study investigates the postbuckling behaviour, including the shape recovery capability, of stainless steel (SUS304) columns after a complete loading-unloading cycle. Experiments were conducted and later numerical simulation was carried out in order to analyze the observed buckling and postbuckling behaviour. Large deflection analysis is necessary for slender columns. Moreover, comparison of the experimental critical load with analytical predictions verifies the fact that physical nonlinearity should be taken into account to analyze the column’s buckling behaviour comprehensively. Thus, based on large deflection theory as well as the nonlinear stress-strain relations, the load-deformation curves of the columns during a complete loading-unloading cycle have been predicted by using the finite element modelling (FEM) code ANSYS.Precise and quantitative analyses of the results verify the fact that the material’s stress-strain properties, both in tension and compression, attribute to the column’s buckling behaviour.     

Numerical simulation of caisson installation and dissipation in kaolin clay and calcareous silt

Caissons are widely used to support fixed platforms in shallow water or moor floating platforms in deep water. Although the installation and pullout behaviours of caissons have been explored extensively, few studies are on the dissipation of excess pore pressures induced by installation of the caisson. The pull-out capacity or bearing capacity of the caisson under undrained conditions is enhanced by dissipation of excess pore pressure, given the caisson is installed in normally consolidated cohesive soil. This paper reports numerical simulations of caisson installation and the subsequent dissipation. The analyses were carried out using a coupled effective stress-pore pressure large deformation finite element (LDFE) approach incorporating the modified Cam-Clay model. The robustness of the LDFE model was validated by comparing the penetration resistance with centrifuge testing data and the guidelines. Caissons in two fine grained soils, kaolin clay and calcareous silt, were explored. The geometry of the caisson was varied to encompass the typical sizes of caissons. The dissipation responses at four locations near the caisson tip were interpreted. A normalised dissipation time around caissons is proposed, by modifying the conventional expression for a cone.     

Photo‐induced Leishmania DNA degradation by silver‐doped zinc oxide nanoparticle: an in‐vitro approach

Recently, the authors reported newly synthesised polyethylene glycol (PEG)ylated silver (9%)‐doped zinc oxide nanoparticle (doped semiconductor nanoparticle (DSN)) which has high potency for killing Leishmania tropica by producing reactive oxygen species on exposure to sunlight. The current report is focused on Leishmania DNA interaction and damage caused by the DSN. Here, we showed that the damage to Leishmania DNA was indirect, as the DSN was unable to interact with the DNA in intact Leishmania cell, indicating the incapability of PEGylated DSN to cross the nucleus barrier. The DNA damage was the result of high production of singlet oxygen on exposure to sunlight. The DNA damage was successfully prevented by singlet oxygen scavenger (sodium azide) confirming involvement of the highly energetic singlet oxygen in the DNA degradation process.Inspec keywords: silver, zinc compounds, nanoparticles, nanomedicine, DNA, microorganisms, cellular biophysics, biomedical engineeringOther keywords: photo‐induced Leishmania DNA degradation, PEGylated silver‐doped zinc oxide nanoparticle, Leishmania tropica, reactive oxygen species, sunlight, Leishmania DNA interaction, Leishmania cell, DNA damage, singlet oxygen scavenger, sodium azide, DNA degradation process, ZnO:Ag     

AC Potential-Dependent Concentration Variation and Domain Wall Pinning in Co1−x Zn x (x=0.4−0.5) Nanorods

The Co_1?x Zn _x (x=0.4?0.5) nanorods were synthesized via an AC electrochemical deposition method into anodized aluminum oxide (AAO) templates at different voltages ranging from 10 to 18 V, and nanorods of varying concentrations of Co and Zn were obtained. The characterization tools were used to examine different aspects of nanorods, e.g., shape, size, morphology, chemical composition, and magnetic behavior. Scanning electron microscope (SEM) images show that CoZn nanorods have length L=1μm and diameter d=50 nm. The grain size was calculated to be 25.4 nm using an X-ray diffraction (XRD) technique. The XRD also shows some other phases of ZnCoO. The M?H loops measured by a vibrating sample magnetometer (VSM) at room temperature show pure ferromagnetic behavior at all AC potentials. The nanorods show magnetic isotropic behavior due to strong magnetic interactions and presence of random nanorods. The potential-dependent coercivity H _c and saturation magnetization M _s show a non-linear curve which is explained on the basis of magnetic islands and domain wall pinning. This study is useful to tune the magnetic properties of nanorods by a simple and low-cost technique.     

Speckle reduction using orthogonal arrays in laser projectors

We propose using a two-level (-1 and +1 as variables) orthogonal array (OA) to generate a binary phase diffuser for speckle reduction in laser projection displays. Compared with the Hadamard matrix, the diffuser generated from OA is more flexible. The speckle contrast ratio (CR) when introducing the binary phase diffuser at an intermediate image plane within the projector is calculated, and the minimum speckle CR can be achieved by finite step change of the diffuser patterns. With Kronecker algebra, the two-dimensional diffuser can also be replaced by two one-dimensional diffusers with the same function, and it can be implemented into the laser projector electronically and easily.     

A mechanistic approach for determining plane-stress fracture toughness of polyethylene

A new mechanistic approach is used to characterize resistance of polyethylene to deformation and fracture in double-edge-notched tensile test. The new approach considers all three mechanisms involved in the fracture process, i.e. for fracture surface formation, shear plastic deformation, and necking, and can be used to determine values of specific energy consumption for each mechanism. This is different from the conventional approach, known as essential work of fracture (EWF), which does not consider the difference between shear plastic deformation and necking. Results from the new approach for a polyethylene copolymer show that specific energy density for fracture surface formation is about half of that determined from the EWF approach, and specific energy density for necking is very close to that determined from simple tensile test. The latter provides some support for validity of the new approach in characterizing fracture behaviour of polyethylene when accompanied by large deformation and necking. The paper also points out crack growth conditions that have to be met for valid application of the EWF approach and shows that such conditions are not met when deformation and necking occur in polyethylene.