The Shifted Box Scheme for Scalar Transport Problems

When solving certain scalar transport problems, it is important to use fast methods that do not produce any parasitic oscillating solutions, but still have good energy conservation properties. The well known box scheme has these properties, but the use is restricted by severe conditions on the sign of the coefficients. In order to avoid this restriction, we introduce a modified method, that we call the shifted box scheme. It is very efficient for initial-boundary value problems, since it does not require more work per time step than an explicit scheme, while still being unconditionally stable.Dedicated to David Gottlieb on the occasion of his 60th anniversary.     

Free transverse vibrations of cracked nanobeams with surface effects

The flexural vibrations of cracked micro- and nanobeams in the presence of surface effects are studied. The cracked-beam model is set up by dividing the classical cracked beam element into two segments connected by a rotational spring located at the cracked section. This model promotes a discontinuity in bending slope, which is proportional to the second derivative of the displacements. Numerical examples demonstrate the effects of beam length, and crack position and severity on the calculated values of natural frequencies of an anodic alumina nanowire in the presence of surface effects. Limiting cases are considered and good agreements with the data available in the literature are obtained.     

Synthesis,structure, and mechanical properties of castor oil‐based polyamidoamines toughened epoxy coatings

A series of toughened epoxy systems was prepared via crosslinking of diglycidyl ether of bisphenol A with castor oil‐based polyamidoamines as curing agents. To this aim two series of polyamidoamines were synthesized in two steps from the reaction of castor oil with triethylenetetramine and then reaction of these products with dissolved salicylic acid in dimethyl formamide (DMF). The structure of the compounds was confirmed by FTIR spectra, GC‐Mass and ¹H‐NMR spectroscopy. The mechanical properties, adhesion and water resistance of polyamine and polyamidoamines cured epoxy systems were studied. It was found that significant improvement in toughness and adhesion of the epoxy films was achieved by using polyamidoamines as curing agents. The results showed a great enhancement in toughness and adhesion properties of the epoxy coats proportional to increasing castor oil weight ratio, and/ or using salicylic acid and DMF. Furthermore, polyamidoamines cured samples showed higher water resistance and less degradation in hot water immersion tests than polyamine cured samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A robust control chart for simple linear profiles in two‐stage processes

In many manufacturing systems, the final product is the result of several dependent stages. In particular, in multistage processes, the quality characteristics of downstream stages are influenced by those in the earlier stages (upstream). This property is referred to as the cascade property, which, if disregarded in process monitoring, may bring about misleading results for the subsequent fault diagnosis. Considering the relationships among consecutive stages of the process, the U statistic is the most widely used method for monitoring multistage processes. Using this method, our paper deals with monitoring a two‐stage process where quality characteristics are represented as simple linear profiles. To guard against the detrimental effect of contaminated data in the phase I of statistical process control, two well‐known robust M‐estimators, including Huber's and bi‐square, are employed for estimation of the process parameters. Under different degrees of autocorrelation across stages of the process and also for different contamination rates, the performances of the proposed methods are compared with that of the conventional least‐square method. From the viewpoint of estimation performance measures, including unbiasedness and efficiency, along with the capability of the control chart in identifying the true source of variation, extensive simulation results reveal that robust estimators outperform the traditional method in a two‐stage process. Meanwhile, it should be noted when there is contamination only in the first stage of the process, the least‐square method performs slightly better.     

Predictive model for seismic sliding displacement of slopes subjected to pulse-like motions

Bulletin of Engineering Geology and the Environment - This paper employs pulse-like ground motions (PLGMs) and presents a predictive model to estimate the earthquake-triggered displacement of...     

Coefficient Diagram Method Based Load Frequency Control for a Modern Power System

With the increasing penetration of renewable energy sources with a wide range of operating conditions causing power system uncertainties,conventional controllers are incapable of providing proper performance to keep the system stable.However,controllable or dispatchable loads such as electric vehicles(EVs) and heat pumps(HPs) can be utilized for supplementary frequency control.This paper shows the ability of plug-in hybrid EVs,HPs,and batteries(BTs)to contribute in the frequency control of an isolated power system.Moreover,we propose a new online intelligent approach by using a coefficient diagram method(CDM) to enhance the system performance and robustness against uncertainties.The performance of the proposed intelligent CDM control has been compared with the proportional-integral(PI) controller and the superiority of the proposed scheme has been verified in Matlab/Simulink programs.     

Aging of membranes prepared from PVA and cellulose nanocrystals by use of thermal compression

Novel membranes consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs), nanosilica (NS), glutaraldehyde (GLA) and glycerine (G) were prepared using a compression moulding process. Rice husk is selected to isolate pure cellulose nanocrystals via mechanical and chemical treatment. The biodegradability of the membranes has been evaluated using UV accelerated weathering as well as a soil burial test. The chemical structure of the membranes were characterised by Fourier-Transformation Infrared (FTIR) spectroscopy. The microstructure of the membranes was characterised by using Scanning Electron Microscope (SEM). The mechanical properties of the membranes were evaluated using standard techniques. The swelling and weight loss resulting from biodegradation were also evaluated. The results showed that the developed membranes can be used as food packaging bags owing to biodegradability (weight loss) under irradiation and during soil burial. The membranes are environmentally friendly.     

Prediction of strain energy-based liquefaction resistance of sand-silt mixtures: An evolutionary approach

Liquefaction is a catastrophic type of ground failure, which usually occurs in loose saturated soil deposits under earthquake excitations. A new predictive model is presented in this study to estimate the amount of strain energy density, which is required for the liquefaction triggering of sand-silt mixtures. A wide-ranging database containing the results of cyclic tests on sand-silt mixtures was first gathered from previously published studies. Input variables of the model were chosen from the available understandings evolved from the previous studies on the strain energy-based liquefaction potential assessment. In order to avoid overtraining, two sets of validation data were employed and a particular monitoring was made on the behavior of the evolved models. Results of a comprehensive parametric study on the proposed model are in accord with the previously published experimental observations. Accordingly, the amount of strain energy required for liquefaction onset increases with increase in initial effective overburden pressure, relative density, and mean grain size. The effect of nonplastic fines on strain energy-based liquefaction resistance shows a more complicated behavior. Accordingly, liquefaction resistance increases with increase in fines up to about 10-15% and then starts to decline for a higher increase in fines content. Further verifications of the model were carried out using the valuable results of some downhole array data as well as centrifuge model tests. These verifications confirm that the proposed model, which was derived from laboratory data, can be successfully utilized under field conditions.     

Characterisation and swelling–deswelling properties of superabsorbent membranes made of PVA and cellulose nanocrystals

Novel superabsorbent membranes (SMs) consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) originated from rice husk (RH), glutaraldehyde (GLA) and glycerine (G) were manufactured by a compression moulding process. RHs were used to isolate pure CNCs via mechanical and chemical treatments. RHs were used to improve water-retention. Glycerine was used to increase the elasticity of the SMs. These SMs were characterised by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical testing and differential scanning calorimetry (DSC). SMs showed a greater equilibrium swelling capacity than neat cross-linked PVA. Moreover, the water transport mechanism of all SMs was found to follow Fickian diffusion. SMs exhibited good pH-dependent swelling reversibility and high-water retention capacity, making them more efficient water-retention materials. The biodegradability of the SMs was evaluated against environmental changes. The SM was also investigated for antimicrobial activity against pathogenic bacteria such as Candida Albicans (fungus), Bacillus subtilis (G+ Ve), Staphylococcus aureus (G+ Ve), Proteus Vulgaris (G-Ve) and Erwinia Carotovora (G-Ve). The hydrogel membrane has been found to act as a useful water reservoir, which may make it useful in agricultural applications.     

Flow Upstream of Orifices and Sluice Gates

Potential flow solutions of a point/line sink are extended to study the velocity field upstream of a finite-size orifice and sluice gate. It is found that, in the “near field” zones, the iso-velocity surfaces appear to be semiellipsoidal; while in the “far field” zones they become hemispheres. The shape and size of the orifice/sluice gate were found to be of no effect on the flow behavior beyond a certain distance. The development of velocity profile away from the orifice and sluice gate is examined, and the effects of water depth are studied. The results of this study compare very well with other numerical and experimental studies, and provide a general understanding of the flow field upstream of orifices and sluice gates.