Energy storage capacity investigation of pulsed current formed nano-structured lead dioxide

An electro-deposition method was used for the preparation of nano-structured lead dioxide. The lead dioxide films prepared were used as positive electrodes of lead acid batteries. Different parameters such as pulse time (t_on), pulse height, and relaxation time (t_off) were optimized to obtain higher capacity. Depend on the pulse conditions, a range of different morphologies of various porosities and connectivity was obtained. The resulting batteries were discharged to a cut off voltage of 1.75 V by a pulsed current method. The energy storage ability of the prepared lead acid batteries shows a close relation with the morphology of cathode materials. Maximum capacity was observed when pulse and relaxation time was equal to 0.1 and 5 s, respectively, at a current density of 25 mA cm⁻². A change in morphology of lead dioxide from aggregated globular structure to nanofiber was occurred. It was found that the high surface area as well as high connectivity between particles resulted in increased discharge capacity. Analysis of electrochemical impedance spectroscopy (EIS) data revealed that the charge transfer resistance is decreased by a change in morphology from bulk globular to nanofiber as the energy storage test showed. The time dependence of impedance behavior of a sample prepared at t_on = 0.1 s and t_off = 5 s at 25 mA cm⁻² was investigated and the results are discussed.     

A web-based high-performance multicriteria decision support system for medical diagnosis

Multicriteria decision making (MCDM) methods can be powerful aids for evaluating patients' medical information in medical diagnostic systems. Technique ordered preference by similarity to the ideal solution (TOPSIS) is one of the more widely used MCDM methods in decision support systems. For the purpose of this work, the TOPSIS method is modified into a more suitable form and used for the implementation of a web-based medical diagnostic system. In our modified TOPSIS method, we have utilized fuzzy logic so that users can more accurately describe their symptoms. The data given to the modified TOPSIS method are often massive in proportions and may take a considerable amount of time to generate a ranking of alternatives. TOPSIS lends itself to parallel computation because it is virtually a combination of matrix computations. Therefore, computer parallelism is implemented so that a large amount of input data can be handled simultaneously, hence decreasing overall execution time. In addition, to make our MCDM system more accessible, we have designed our system to be web based. The web-based medical diagnosis system includes a dynamically generated web-based user interface, while the parallel implementation of the modified TOPSIS component, in conjunction with the Common Gateway Interface, forms the back end of the system. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 1083–1099, 2007.     

Thickness and scratch resistance of adsorbed film formed by triblock symmetrical copolymer solutions

The thickness and scratch resistance of adsorbed films formed on mild steel samples (MS1020), which have been immersed in water copolymer solutions, are reported. The effects of bulk temperature and the copolymer structures, normal, poly(ethylene oxide)_m‐poly(propylene oxide)_n‐poly(ethylene oxide)_m, and reverse, poly(propylene oxide)_n‐poly(ethylene oxide)_m‐poly(propylene oxide)_n, are elucidated. The films' thicknesses are independent of structure but not of temperature. The adsorbed films of above cloud point solutions are thicker than below cloud point. However, nanoscratch experiments carried out to measure the scratch resistance of the films reveal that despite of thicker film formed by above cloud point solutions, it is relatively more prone to being detached than the thinner films of below cloud point solutions. The effect of extreme pressure additive, alkyl phosphate ester (APE), is also investigated suggesting the normal copolymer has comparable scratch resistance with APE when used at below the cloud point. Copyright © 2016 John Wiley & Sons, Ltd.     

A fuzzy approach for the earned value management

The Earned Value technique is a crucial technique in analyzing and controlling the performance of a project which allows a more accurate measurement of both the performance and the progress of a project. This paper presents a new fuzzy-based earned value model with the advantage of developing and analyzing the earned value indices, and the time and the cost estimates at completion under uncertainty. As the uncertainty is inherent in real-life activities, the developed model is very useful in evaluating the progress of a project where uncertainty arises. A small example illustrates how the new model can be implemented in reality.     

Speed limit reduction in urban areas: A before–after study using Bayesian generalized mixed linear models

In fall 2009, a new speed limit of 40 km/h was introduced on local streets in Montreal (previous speed limit: 50 km/h). This paper proposes a methodology to efficiently estimate the effect of such reduction on speeding behaviors. We employ a full Bayes before–after approach, which overcomes the limitations of the empirical Bayes method. The proposed methodology allows for the analysis of speed data using hourly observations. Therefore, the entire daily profile of speed is considered. Furthermore, it accounts for the entire distribution of speed in contrast to the traditional approach of considering only a point estimate such as 85th percentile speed. Different reference speeds were used to examine variations in the treatment effectiveness in terms of speeding rate and frequency. In addition to comparing rates of vehicles exceeding reference speeds of 40 km/h and 50 km/h (speeding), we verified how the implemented treatment affected “excessive speeding” behaviors (exceeding 80 km/h). To model operating speeds, two Bayesian generalized mixed linear models were utilized. These models have the advantage of addressing the heterogeneity problem in observations and efficiently capturing potential intra-site correlations. A variety of site characteristics, temporal variables, and environmental factors were considered. The analyses indicated that variables such as lane width and night hour had an increasing effect on speeding. Conversely, roadside parking had a decreasing effect on speeding. One-way and lane width had an increasing effect on excessive speeding, whereas evening hour had a decreasing effect. This study concluded that although the treatment was effective with respect to speed references of 40 km/h and 50 km/h, its effectiveness was not significant with respect to excessive speeding-which carries a great risk to pedestrians and cyclists in urban areas. Therefore, caution must be taken in drawing conclusions about the effectiveness of speed limit reduction. This study also points out the importance of using a comparison group to capture underlying trends caused by unknown factors.     

Reaction sintering of nano-sized ZnO–Nb2O5 powder mixture: sintering,microstructure and microwave dielectric properties

Sintering behavior, microstructures and microwave dielectric properties of ZnNb₂O₆ (ZN) ceramics prepared by reaction-sintering method were investigated. The X-ray diffraction patterns of the sintered samples revealed single-phase formation with a columbite structure after 1–5 h sintering at 1,025–1,125 °C. After sintering at 1,125 °C for 5 h, the ZN ceramics with the density of 5.56 g/cm³ (98.9 % of the theoretical density) and good microwave dielectric properties of ε_r = 23.9, Q × f = 51,000 and τ_f = ?62 ppm/°C were obtained. The obtained results demonstrated that the reaction-sintering process is a simple and effective method to prepare the ZN ceramics for applications on microwave dielectric resonators.     

Hot tensile properties and microstructural evolution of as cast NiTi and NiTiCu shape memory alloys

Hot tensile properties of as cast NiTi and NiTiCu shape memory alloys were investigated by hot tensile test at temperature range of 700–1100 °C using the strain rate of 0.1 s⁻¹. The NiTi alloy exhibited a maximum hot ductility at temperature range of 750–1000 °C, while the NiTiCu alloy showed it at temperature range of 800–1000 °C. It was found that at temperatures less than 750 °C, diffusion-assisted deformation mechanism was inactive leading to semi-brittle type of failure and limited ductility in both alloys. Also it was found that at temperature range of 800–1000 °C, dynamic recrystallization is dominant leading to high ductility. Likewise, the fracture surface of the specimens presenting the maximum hot ductility showed an ideal type of ductile rupture in which they gradually pulled out to a fine point. On the other hand, the decline in ductility occurred at the temperatures above 1000 °C was attributed to the liquid phase formation leading to interdendritic and intergranular type of fracture.     

Tensile behaviour of patch-repaired CFRP laminates

The present study examines the tensile behaviour of composite structures repaired by bonding external patches. Various patches of different stacking sequences placed on both sides of the parent plate were considered. Damage development and the failure process of the repaired plates were analyzed and a parent plate fracture model has been proposed. Optimised patch repairs were calculated by finite element modelling. It was found that high stress concentration along the longitudinal edges of circular patches and/or at the transverse edges of the hole leads to early damage initiation in the parent plate. However, the position of damage initiation and the process of damage progression depend particularly on the properties of repair patches. In order to optimise patch repairs, finite element modelling was used and it was founded possible to attain over 90% of the strength of an unnotched specimen. The optimised patch design can be characterised by an optimal strength ratio R^*, which should be minimized when selecting repair parameters.     

Highly efficient dye-sensitized solar cell prepared by electrophoretic deposition method: the effect of TiO<Subscript>2</Subscript> films thickness on the performance of cells

In this work, nanocrystalline P25 TiO₂ films with different thicknesses were deposited on FTO coated glass substrates by an electrophoretic deposition technique (EPD) and applied as the work electrode for dye-sensitized solar cells (DSSC) using cis-bis(isothiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylato)(4,4'di-nonyl-2'-bipyridyl) ruthenium(II) (Z907, Dyesol) as sensitizing dye.The results showed that the increasing the thickness of TiO₂ films lead to increase the adsorption of the dye on the TiO₂ layers which in turns improved the short-circuit photocurrent (J_sc) and open-circuit voltage (V_oc), respectively. Furthermore, it was found that the effects of the surface states on the recombination of the photo-injected electrons (electron–hole pairs) in the TiO₂ films strongly depend on theTiO₂ electrode annealing temperature. Finally, a DSSC with a 32.82 μm thickness for TiO₂ film annealed at 600°C produced the highest conversion efficiency with an incident solar energy of 100 mW/cm² (η = 8.23%, J_sc = 15.98, V_oc = 0.73, FF = 0.7).     

Ductile crack growth and constraint in pipelines subject to combined loadings

An important failure mode of offshore pipelines is ductile fracture of the pipe wall triggered by a hypothetical welding defect. In this study, pipelines having an external part-through semi-circumferential crack of various sizes, subject to combined internal pressure and inelastic bending are considered. This is done to assess the response of pipelines during both their installation and operational conditions. Detailed 3D nonlinear finite element (FE) models of pipelines are developed. A row of elements ahead of the initial crack front are modeled using a voided plasticity material model, which enables simulation of crack growth and the subsequent fracture failure mode (denoted by the critical curvature, κ_crit). After discussing the typical response characteristics of such pipelines, the FE model is used to parametrically investigate the influence of varying pipe and crack dimensions, and also the internal pressure levels, on κ_crit. In the second part of this paper, the crack tip constraint ahead of a growing crack in such pipes is evaluated and systematically compared to the crack tip constraint of both the traditionally used deeply cracked Single Edge Notch Bend (SENB) specimens and the constraint-matched Single Edge Notch Tensile (SENT) specimens. This is achieved by comparing the crack resistance curves (R-curves) along with stress triaxiality and equivalent plastic strain fields evaluated ahead of a growing crack of the three systems. The results present grounds for justification of usage of SENT specimens in fracture assessment of such pipes as an alternative to the traditional overly conservative SENB specimens.