A new application of functionalized platinum nanoparticles as chemiresistor coating

Chemiresistor sensor based on Pt nanoparticles stabilized with 11-mercaptoundecanoic acid was developed for detection of some volatile organic compounds (VOCs). This sensor was prepared by drop coating technique onto interdigitated microelectrode. This film displayed linear current–voltage (I–V) characteristics and decrease the resistance at room temperature. The chemiresistive sensing properties were measured over a concentration range of 1.4–400 mg L⁻¹ for methanol, ethanol, ethyl acetate and acetone vapors. The results showed good sensitivity to methanol vapors and low detection limits for all examined vapors.     

Assessment of Phosphate Limestone Wastes as a Component of a Store-and-Release Cover in a Semiarid Climate

In a semiarid climate where the annual precipitation is low and the evaporation rate is high, contaminated drainage production from mine tailings can be controlled by reducing water infiltration. Store-and-release covers that use capillary barrier effects can prevent water percolation by storage and evaporation (or evapotranspiration) during wet and dry climatic periods. In Morocco, sedimentary phosphate mines are located close to contaminated sites, which includes the abandoned Kettara mine. This mine site generates highly contaminated acid rock drainage (ARD) with negative impacts on its surrounding area. In order to validate if phosphate mine wastes can be used as cover material to reclaim the Kettara site, instrumented test columns were exposed to field conditions and tested for a period of one and a half years. Under natural conditions, more than 94 % of the total net infiltration (246.5 mm) was released to the atmosphere by evaporation. Preliminary tests showed that the studied scenarios can limit deep water infiltration even during extreme simulated rainfall (155 mm/d) and could be used to efficiently control contaminated drainage in a semiarid climate.     

Thermal stability and mechanical properties of nanocrystalline Fe–Ni–Zr alloys prepared by mechanical alloying

The thermal stability of nanostructured Fe_100?x?y Ni _x Zr _y alloys with Zr additions up to 4 at.% was investigated. This expands upon our previous results for Fe–Ni base alloys that were limited to 1 at.% Zr addition. Emphasis was placed on understanding the effects of composition and microstructural evolution on grain growth and mechanical properties after annealing at temperatures near and above the bcc-to-fcc transformation. Results reveal that microstructural stability can be lost due to the bcc-to-fcc transformation (occurring at 700 °C) by the sudden appearance of abnormally grown fcc grains. However, it was determined that grain growth can be suppressed kinetically at higher temperatures for high Zr content alloys due to the precipitation of intermetallic compounds. Eventually, at higher temperatures and regardless of composition, the retention of nanocrystallinity was lost, leaving behind fine micron grains filled with nanoscale intermetallic precipitates. Despite the increase in grain size, the in situ formed precipitates were found to induce an Orowan hardening effect rivaling that predicted by Hall–Petch hardening for the smallest grain sizes. The transition from grain size strengthening to precipitation strengthening is reported for these alloys. The large grain size and high precipitation hardening result in a material that exhibits high strength and significant plastic straining capacity.     

A Koiter‐Newton approach for nonlinear structural analysis

A new approach termed the Koiter‐Newton is presented for the numerical solution of a class of elastic nonlinear structural response problems. It is a combination of a reduction method inspired by Koiter's post‐buckling analysis and Newton arc‐length method so that it is accurate over the entire equilibrium path and also computationally efficient in the presence of buckling. Finite element implementation based on element independent co‐rotational formulation is used. Various numerical examples of buckling sensitive structures are presented to evaluate the performance of the method. The examples demonstrate that the method is robust and completely automatic and that it outperforms traditional path‐following techniques. This improved efficiency will open the door for the direct use of detailed nonlinear finite element models in the design optimization of next generation flight and launch vehicles. Copyright © 2013 John Wiley & Sons, Ltd.     

Solving the facility and layout and location problem by ant-colony optimization-meta heuristic

This paper describes a heuristic algorithm for solving the plant/facility location problem by applying ant-colony optimization meta-heuristic. The facility location problem is discussed, and a mathematical formulation is presented. The problem is then modelled as a quadratic assignment problem. An ant algorithm is developed to solve the problem. The results reveal that the proposed algorithm can be adaptively constructed to solve discrete plant location problems. This has been applied to a set of known test problems and appears to be able to compete with other current solutions with encouraging results.     

Analytical computation of support characteristic curve for circumferential yielding lining in tunnel design

Circumferential yielding lining is able to tolerate controlled displacements without failure,which has been proven to be an effective solution to large deformation problem in squeezing tunnels.However,up to now,there has not been a well-established design method for it.This paper aims to present a detailed analytical computation of support characteristic curve(SCC)for circumferential yielding lining,which is a significant aspect of the implementation of convergence-confinement method(CCM)in tunnel support design.Circumferential yielding lining consists of segmental shotcrete linings and highly deformable elements,and its superior performance mainly depends on the mechanical characteristic of highly deformable element.The deformation behavior of highly deformable element is firstly investigated.Its whole deforming process can be divided into three stages including elastic,yielding and compaction stages.Especially in the compaction stage of highly deformable element,a nonlinear stress-strain relationship can be observed.For mathematical convenience,the stress-strain curve in this period is processed as several linear sub-curves.Then,the reasons for closure of circumferential yielding lining in different stages are explained,and the corresponding accurate equations required for constructing the SCC are provided.Furthermore,this paper carries out two case studies illustrating the application of all equations needed to construct the SCC for circumferential yielding lining,where the reliability and feasibility of theoretical derivation are also well verified.Finally,this paper discusses the sensitivity of sub-division in element compaction stage and the influence of element length on SCC.The outcome of this paper could be used in the design of proper circumferential yielding lining.     

Evaluating the ductility and shear behaviour of carbon fibre reinforced polymer and glass fibre reinforced polymer reinforced concrete columns

Brittle shear failure in short reinforced concrete (RC) columns has been identified as one of the most dangerous failure modes that may cause collapse of bridges, based on research findings and damage reconnaissance of past earthquakes. Using ABAQUS software, the effect of carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) on retrofitting of existing circular RC columns, and also enhancing of shear strength have been studied. Five types of concrete columns were studied in the ‘as built’ condition to investigate the shear failure mode of columns. These columns were assessed again after being retrofitted by using CFRP and GFRP. Based on findings of this research, the effect of CFRP jackets on improving the shear behaviour of column is more than that of GFRP jackets, while GFRP jackets are more effective than CFRP jackets, regarding their contribution in increasing the column ductility. Therefore, these FRP composites can be utilized in different conditions, according to column demand for increasing the ductility or shear strength. Copyright © 2010 John Wiley & Sons, Ltd.     

Modelling of solid-phase tea waste extraction for the removal of manganese from food samples by using artificial neural network approach

In this study, a three-layer artificial neural network (ANN) model was employed to develop prediction model for removal of manganese from food samples using tea waste as a low cost adsorbent. After removal of manganese from food samples with acetic acid (5 mol L⁻¹), manganese was adsorbed to a small amount of tea waste, desorbed with nitric acid as a eluent solvent, and determined by flame atomic absorption spectrometry. The input parameters chosen of the model was pH, amount of tea waste, extraction time and eluent concentration. After backpropagation (BP) training, the ANN model was able to predict extraction efficiency of manganese with a tangent sigmoid transfer function at hidden layer and a linear transfer function at output layer. Under the optimum conditions, the detection limit was 0.6 ng g⁻¹. The method was applied to the separation, pre-concentration and determination of manganese in food samples and one reference material.     

Photoconductive Hybrid Films via Directional Self‐Assembly of C60 on Aligned Carbon Nanotubes

Hybrid nanostructured materials can exhibit different properties than their constituent components, and can enable decoupled engineering of energy conversion and transport functions. Novel means of building hybrid assemblies of crystalline C₆₀ and carbon nanotubes (CNTs) are presented, wherein aligned CNT films direct the crystallization and orientation of C₆₀ rods from solution. In these hybrid films, the C₆₀ rods are oriented parallel to the direction of the CNTs throughout the thickness of the film. High‐resolution imaging shows that the crystals incorporate CNTs during growth, yet grazing‐incidence X‐ray diffraction (GIXD) shows that the crystal structure of the C₆₀ rods is not perturbed by the CNTs. Growth kinetics of the C₆₀ rods are enhanced 8‐fold on CNTs compared to bare Si, emphasizing the importance of the aligned, porous morphology of the CNT films as well as the selective surface interactions between C₆₀ and CNTs. Finally, it is shown how hybrid C₆₀–CNT films can be integrated electrically and employed as UV detectors with a high photoconductive gain and a responsivity of 10⁵ A W^?1 at low biases (± 0.5 V). The finding that CNTs can induce rapid, directional crystallization of molecules from solution may have broader implications to the science and applications of crystal growth, such as for inorganic nanocrystals, proteins, and synthetic polymers.