Prediction of hydrate formation conditions based on the vdWP‐type models at high pressures

Prediction of phase boundaries of gas hydrates has been done for several decades based on the vdWP (van der Waals and Platteeuw) hydrate equation and the classical thermodynamic equations for describing the water fugacities in water or ice phase. This procedure gives a reasonable prediction at low pressures, but when the pressure increases, above 10⁵ kPa, it shows a significant error. In the conventional vdWP‐type models it has been assumed that the volume difference between the empty hydrate lattice and pure liquid water is independent of the system pressure and temperature. In this work, different approaches for describing the volume dependency of pure liquid water and the empty hydrate lattice on the system pressure have been used to predict the hydrate equilibria based on the vdWP‐type model. Also, an expression is introduced to estimate the volume of methane hydrate lattice as a function of pressure and temperature. Finally, this method is extended to other hydrate formers, that is, ethane, carbon dioxide, xenon, and nitrogen. The predicted values are in good agreement with the experimental data both for L_w–H–V and L_w–H–L_hf phase boundaries.     

Treatment of laundry waste‐water by electrocoagulation

BACKGROUND: The present study describes an electrocoagulation process for treating laundry waste‐water using aluminum plates. The effect of various parameters such pH, voltage, hydraulic retention time (HRT), and number of aluminum plates between the anode and cathode on efficiency of treatment are investigated. RESULTS: Experimental results showed that by increasing HRT, treatment efficiency increases but beyond 45 min changes are negligible. Among the results for chemical oxygen demand (COD), phosphorus, detergent, colour and turbidity, the lowest decrease was found for phosphorus. The larger the HRT, the greater the electrical current needed to achieve constant voltage and temperature in the system. The pH of the influent is a very significant variable which affects the treatment of laundry waste‐water considerably, the optimal range being 6.0–8.0. In addition, it was found that the pH increases from 8.3 to more than 10 over the first hour of treatment after which the pH remains relatively constant. Finally, kinetic analysis indicates that the adsorption system obeys a second‐order kinetic model. CONCLUSION: The aluminum hydroxide generated in the cell decreases the concentration of pollutants in laundry waste‐water to a permissible level. It is concluded that, compared with other treatment processes, electrocoagulation is more effective in treating laundry waste‐water under appropriate conditions. Copyright © 2011 Society of Chemical Industry     

Enhancing the mechanical properties of an epoxy coating with rice husk ash, a green product

In this research, rice husk ash (RHA) —a carbon neutral waste product that is an abundant source of silica—was chosen as an innovative filler for epoxy paint. The influence of the RHA on different mechanical properties of the cured coatings (wear, hardness, and elongation) was investigated. Wear tests in pin-on-disc mode were carried out and followed by scanning electron microscopic observations to determine the wear mechanism for specimens with different values of carbon and silica according to their different colors as fillers for epoxy paint. Pencil hardness tests and bending tests were performed according to ASTM D3363 and ASTM D522 standards, respectively. Adding RHA (heat treated at 700°C) at two levels—10 and 20% weight fraction—to the unfilled epoxy paint increased the wear resistance, scratch resistance, and elongation of the filled coating compared to the unfilled epoxy coating.     

Solution combustion synthesis of FeCr2O4:Zn,Al pigment powders

FeCr₂O₄:Zn,Al pigment powders were prepared via a solution combustion synthesis method. Effects of Zn and Al dopants and less/extra Fe content on the structure, molecular bonds, and optical properties of powders were studied. Results showed that addition of dopants as well as extra/less content of Fe led to weaker combustion and consequently lower X-ray diffraction peak intensities, lattice parameters, and differential thermal analysis peak intensities. Moreover, Fourier transform infrared analysis illustrated that the band position of Cr–O and Fe–O bonds were shifted to higher frequencies with moving away from stoichiometry. In addition, scanning electron micrographs showed that in all samples, porous spongy microstructures were formed with highly flake-like agglomerated particles. Furthermore, there was a significant difference between the powder samples and the tiles colored with in glaze powders due to the partial dissolution of pigments in contact with the molten glaze of tiles. In comparison to the tile colored with the stoichiometric FeCr₂O₄ pigments without dopants, the color difference (ΔE) in the tiles colored by the iron chromite pigments doped with Zn and Al dopants and less/extra Fe content reached the high values as large as ΔE = 36.19. The solar reflectance values (R_s) in near-infrared region were above 50% in all samples. Near 80% R_s in the tile colored by the iron chromite pigment doped with 3 mol% Zn and the yellowish brown appearance (L* = 43.44, a* = 6.77, b* = 18.38, c* = 19.59, h = 69.79) showed that the sample was a good candidate for cool building materials such as roof tiles.     

Enhanced degradation of reactive dyes using a novel carbon ceramic electrode based on copper nanoparticles and multiwall carbon nanotubes

A novel carbon ceramic electrode consisting of CuNPs and MWCNT was developed to treat reactive orange 84 (RO84) wastewater using ultrasound-assisted electrochemical degradation. The proposed electrode generated more hydroxyl radicals than non-nanoparticle electrodes did. In addition, a new electrochemical sensor was applied to determine residue RO84 in an aqueous medium during discoloration. This sensor is based on a glassy carbon electrode modified with gold nanourchins and graphene oxide and can detect RO84 concentration in the range of 1.0-1200 μmol·L^-1 with the detection limit of 0.03 μmol·L^-1. The degradation effects of the modified electrode on RO84 were evaluated systematically with different initial pH values, time durations, and amounts of CuNPs and MWCNT. The results suggested that the removal efficiency of RO84 was approximately 83% after 120 min of electrolysis in a phosphate buffer with pH 8.0 using a carbon ceramic electrode made with 4.0 wt% CuNPs and 4.0 wt% MWCNT. The possible mechanism of RO84 degradation was monitored by gas chromatography-mass spectrometry, and degradation pathways were proposed.     

Optimal Design Experiment of Ageing Time and Temperature in Inconel-713C Superalloy Based on Hardness Objective

This study consists of assessing the influence of ageing heat treatments on characteristics of the microstructure and the hardness in the Inconel-713C nickel-based superalloy. The ageing process including the time and the temperature was modified based on the material hardness, by the design of experiments (DOE). For this objective, ageing treatments consisted of heating at 850, 890 and 930 °C for 8 and 16 h, after a solutioning treatment. Experimental results showed that the mean hardness reached the highest value (as 43.2 RC) in the sample that was age-hardened at 890 °C for 8 h, without requiring usual double ageing heat treatments. Besides, the DOE also predicted the highest hardness, which would be related to the specimen, hardened at 896.1 °C for 8 h and also 895.3 °C for 16 h, based on vertical and parallel lines, respectively. The highest hardness was associated with the optimum volume fraction (as 64%) of approximately fine size (as 500 nm) of \(\gamma '\) precipitates. Besides, M₂₃C₆-type carbides plus NbC had a positive effect to enhance the hardness value. X-ray diffraction (XRD) results indicated various phases created in different ageing heat treatments that affected the hardness.     

Factors affecting terrestrial invertebrate diversity in bioretention basins in an Australian urban environment

Biodiversity conservation is a significant challenge for urban planning and management. When new urban development strategies are introduced, their effects on urban biodiversity are often unknown and may have serious consequences for conservation. A relatively new urban development strategy for sustainable urban water cycle management is Water Sensitive Urban Design (WSUD). While this strategy has been implemented in Australia over the past decade, little is known about the impacts on biodiversity from its application.A field investigation was conducted on 12 bioretention basins, which are a type of vegetated WSUD system. The study used invertebrates captured through pitfall trapping as biodiversity indicators and was conducted in the Melbourne area during the summer of 2006–2007. It investigated the effect of ten habitat factors separately and as group factors on biodiversity of the systems. It also examined how invertebrates were distributed within these WSUD systems.The results suggested that greater leaf/plant litter depth or a combination of greater leaf/plant litter depth and larger number of plant taxa is a significant contributor to biodiversity in bioretention basins. Therefore, the design and management of bioretention basins should consider increasing these habitat factors as key elements to promote biodiversity. The distribution pattern of invertebrates within the systems increased from the edges towards the centre suggesting that designing the sites should consider shape and size to create larger interior habitats for enhancing biodiversity.The results of this study are important for the design and management of bioretention basins to improve biodiversity conservation in urban environments.     

Experimental investigation on freeze−thaw durability of polymer concrete

Assessing the durability of concrete is of prime importance to provide an adequate service life and reduce the repairing cost of structures. Freeze–thaw is one such test that indicates the ability of concrete to last a long time without a significant loss in its performance. In this study, the freeze–thaw resistance of polymer concrete containing different polymer contents was explored and compared to various conventional cement concretes. Concretes’ fresh and hardened properties were assessed for their workability, air content, and compressive strength. The mass loss, length change, dynamic modulus of elasticity, and residual compressive strength were determined for all types of concretes subjected to freeze–thaw cycles according to ASTM C666-procedure A. Results showed that polymer concrete (PC) specimens prepared with higher dosages of polymer contents possessed better freeze–thaw durability compared to other specimens. This high durability performance of PCs is mainly due to their impermeable microstructures, absence of water in their structure, and the high bond strength between aggregates and a polymer binder. It is also indicated that the performance of high-strength concrete containing air-entraining admixture is comparable with PC having optimum polymer content in terms of residual compressive strength, dynamic modulus of elasticity, mass loss, and length change.     

Nonlinear model identification of a frictional contact support

Accurate predictions of a structure dynamics require precise modeling of its boundary conditions including any nonlinear effects. This paper investigates the behavior of frictional supports that are examples of boundary conditions exhibiting nonlinear effects, such as stiction and slip phenomena, depending on the structure vibration amplitudes. The dependency of restoring forces in a frictional contact to the vibration amplitude level is identified in this study using experimental observations. In an experimental case study measured responses of a beam fixed at one end and frictionally supported at the other end were expanded using corresponding nonlinear normal modes of the structure and a reduced order model of the continuous system containing dominant nonlinear effects of the contact was obtained. The obtained discrete model constitutes bases for identification of restoring forces in the contact interface using force state mapping. The identified nonlinear restoring forces are then employed to specify parameters of a predictive contact model for the boundary support. The obtained contact model is capable of predicting damping and softening effects due to micro/macro-slippage and accurately regenerates the experimental results at various response levels.     

Lead time control in multi-server multi-stage assembly system

In this paper, two multi-objective models to optimally control the lead time in multi-server multi-stage assembly system by considering server allocation problem (SAP) and also service rate control problem (SCP) are presented, where new product orders, including all their operations, are entered to the system according to a Poisson process, only one type of products also is produced by the production system, and multi-servers can be settled in each service station. Each operation of any work is operated at a devoted service station with only one of the servers located at a node of the network based on a first-come-first-serve discipline, while the processing times are independent random variables with exponential distributions. Furthermore, it is also assumed that the transport times between each pair of service stations are independent random variable with generalized Erlang distributions. Such system can be modeled as a queueing network, where the system is in the steady state and the lead time is controllable. For modeling of multi-server multi-stage assembly system, initially the network of queues is transformed into an appropriate stochastic network with exponentially distributed arc lengths. A differential equations system is organized to solve and obtain approximate lead time distribution for any particular wok by applying a proper finite-state continuous-time Markov model. Then, two multi-objective models including four conflicted objectives are presented to optimally control the servers allocated to the service stations in SAP and also service rate of service stations in SCP. For solving a discrete-time approximation of the primary multi-objective problems, the goal attainment technique is employed. In this research, reactive controlling in a multi-server multi-stage assembly system also is discussed.