Predicting potential deadlocks in multithreaded programs

In a multithreaded program, competition of threads for shared resources raises the deadlock possibility, which narrows the system liveness. Because such errors appear in specific schedules of concurrent executions of threads, runtime verification of threads behavior is a significant concern. In this study, we extended our previous approach for prediction of runtime behavior of threads may lead to an impasse. Such a prediction is of importance because of the nondeterministic manner of competing threads. The prediction process tries to forecast future behavior of threads based on their observed behavior. To this end, we map observed behavior of threads into time‐series data sets and use statistical and artificial intelligence methods for forecasting subsequent members of the sets as future behavior of the threads. The deadlock prediction is carried out based on probing the allocation graph obtained from actual and predicted allocation of resources to threads. In our approach, we use an artificial neural network (ANN) because ANNs enjoy the applicable performance and flexibility in predicting complex behavior. Using three case studies, we contrasted results of the current and our previous approaches to demonstrate results. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of soft‐storey mechanism caused by infill elimination on displacement demand in nonlinear static procedure using coefficient method

In recent earthquakes, many buildings have been damaged due to the soft‐storey mechanism failure. The seismic design codes for buildings do not contain enough criteria to predict the real displacement of such buildings. This paper focuses on evaluating the nonlinear displacement of buildings that fail in soft‐storey mechanism form. Results show that the nonlinear static procedure with coefficient method, which is described in Chapter 3 of ASCE/SEI 41‐06, does not have sufficient accuracy for estimation of structure displacement demand in such buildings. In this paper, the coefficient methodology is used for evaluating the target displacement for 5‐storey, 8‐storey and 15‐storey special moment resisting steel frames. For this purpose, dynamic nonlinear time‐history analysis has been applied for the mentioned structures having a soft‐storey mechanism failure form. The numerical results of storey displacement and interstorey drift were compared with those values obtained from the coefficient method described in Chapter 3 of ASCE/SEI 41‐06. Copyright © 2012 John Wiley & Sons, Ltd.     

Simultaneous multi-objective optimization of a new promoted ethylene dimerization catalyst using grey relational analysis and entropy measurement

A hybrid approach between the Taguchi method and grey relational analysis (GRA) with entropy measurement was applied to determine a single optimum setting for reaction factors of the proposed ethylene dimerization catalyst having overall selectivity to 1-butene (S_1-btn (%)) and turnover frequency (TOF (h^-1)) as multiple quality characteristics. Titanium tetrabutoxide (Ti(OC₄H₉)₄) catalyst precursor in combination with triethyl aluminum (TEA) activator, 1,4-dioxane as a suitable modifier, and ethylene dichloride (EDC) as a novel promoter were used in the catalysis. Control factors of temperature, pressure, Al/Ti, 1,4-dioxane/Ti, and EDC/Ti mol ratios were investigated on three levels and their main effects were discussed. The effect of the binary interaction between temperature, pressure, and Al/Ti mol ratio was also examined. Weight of the responses was determined using entropy. Analysis of variance (ANOVA) for data obtained from GRA indicated that EDC/Ti mol ratio with 27.64% contribution had the most profound effect on the multiple quality characteristics. Development of the weighted Grey-Taguchi method used the Taguchi method as its basic structure, adopted GRA to deal with multiple responses, and entropy to enhance the reasonability of the comprehensive index produced by GRA to make the results more objective and accurate. Overall, these combined mathematical techniques improved catalytic performance for 1-butene production.     

The morphology and gas‐separation performance of membranes comprising multiwalled carbon nanotubes/polysulfone–Kapton

The development of desirable chemical structures and properties in nanocomposite membranes involve steps that need to be carefully designed and controlled. This study investigates the effect of adding multiwalled nanotubes (MWNT) on a Kapton–polysulfone composite membrane on the separation of various gas pairs. Data from Fourier transform infrared spectroscopy and scanning electron microscopy confirm that some studies on the Kapton–polysulfone blends are miscible on the molecular level. In fact, the results indicate that the chemical structure of the blend components, the Kapton–polysulfone blend compositions, and the carbon nanotubes play important roles in the transport properties of the resulting membranes. The results of gas permeability tests for the synthesized membranes specify that using a higher percentage of polysulfone (PSF) in blends resulted in membranes with higher ideal selectivity and permeability. Although the addition of nanotubes can increase the permeability of gases, it decreases gas pair selectivity. Furthermore, these outcomes suggest that Kapton–PSF membranes with higher PSF are special candidates for CO₂/CH₄ separation compared to CO₂/N₂ and O₂/N₂ separation. High CH₄, CO₂, N₂, and O₂ permeabilities of 0.35, 6.2, 0.34, and 1.15 bar, respectively, are obtained for the developed Kapton–PSF membranes (25/75%) with the highest percentage of carbon nanotubes (8%), whose values are the highest among all the resultant membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43839.     

Carbon nanotubes growth on sub-surface catalyst layer of Cu–Ni nanoparticles thin film

Cu–Ni nanoparticles (NPs) thin films were prepared by Direct Current (DC) magnetron sputtering with Cu and Ni targets. The products were used as catalysts for Thermal CVD (TCVD) growing of carbon nanotubes (CNTs) from acetylene gas at 825°C. In order to characterize the nano catalysts, X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM) and to study the synthesized CNTs Scanning Electron Microscopy (SEM) and Raman Spectroscopy were applied. A remarkable CNT grown on the sub-surface of catalyst layer compared to its top is deduced from SEM images. Despite the poor catalytic activity of the top-surface, these considerations led us to conclude more catalytic activity of the sub-surface.     

Synthesis of biocompatible and degradable microspheres based on 2‐hydroxyethyl methacrylate via microfluidic method

Monodisperse poly(2‐hydroxyethyl methacrylate), p‐HEMA, microspheres in size ranging from 16 to 340 (μm) were synthesized by in situ emulsion photopolymerization of HEMA monomer with polyethylene glycol diacrylate (p‐EGDA) by means of a three‐dimensional microfluidic flow‐focusing device. An aqueous solution of HEMA, p‐EGDA as chain extender and UV‐photoinitiator serving as dispersed phase formed microdroplets in a continuous oil phase mainly consisting of n‐heptane. A downward coaxial orifices design in the device led to confinement of the reaction admixtures thread to central axis of the microchannels. This design strategy could solve the wetting problem of dispersed phase with the microchannels leading to a successful production of monodisperse microspheres with size variation of less than 4%. The effects of concentration of p‐EGDA, surfactant, and flow rate ratios on microsphere size were examined. It was observed that increasing the concentration of p‐EGDA slightly increases the size whereas increasing the flow rate ratios of continuous to dispersed phase effectively decreases the size of microspheres. The rapid continuous synthesis of p‐HEMA based microspheres via the microfluidic route with reliable control over size, size distribution, and composition opens new doors for mass production of biocompatible and degradable polymeric microspheres for enormous biotechnological applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40925.     

Air-breathing microbial fuel cell with enhanced performance using nanocomposite proton exchange membranes

This work aims to improve the performance of air-breathing microbial fuel cells (MFCs) through using hydrocarbon polymer based nanocomposite proton exchange membranes. Accordingly, nanocomposite membranes based on sulfonated poly(ether ether ketone) (SPEEK) and montmorillonite (MMT) were investigated for such an application. Although the incorporation of MMT into SPEEK membranes resulted in reduced oxygen permeability as well as proton conductivity, but the overall selectivity was found to be improved. MFC tests revealed that using the optimized nanocomposite membrane (SPEEK-70/MMT-3 wt%) results in a considerably higher open circuit voltage (OCV) compared to the corresponding neat membrane. Moreover, it was found that the SPEEK-70/MMT-3 wt% membrane is able to provide about 40% more power output than Nafion^®117. On the account of high proton conductivity, low oxygen permeability, high electrochemical performance, ease of preparation and low cost, hydrocarbon based nanocomposite PEMs could be considered as promising electrolytes to enhance the performance of MFCs.     

Rheological,crystal structure,barrier, and mechanical properties of PA6 and MXD6 nanocomposite films

In this study, rheological, crystal structure, barrier, and mechanical properties of polyamide 6 (PA6), poly(m‐xylene adipamide) (MXD6) and their in situ polymerized nanocomposites with 4 wt % clay were studied. The extent of intercalation and exfoliation as well as type of crystals, crystallinity, and thermal transitions were investigated using X‐ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. Dynamic rheological measurements revealed that incorporation of nanoclay significantly increases complex viscosity of MXD6 nanocomposites at low frequencies, which was related to the formation of a nanoclay network and exchange reaction between MXD6 chains. The comparative study of dynamic characteristics (G′ (ω) and G″ (ω)) for aliphatic and aromatic polyamide nanocomposites with their neat resins as well as the relaxation spectra for both polymer systems confirmed the possibility of the aforementioned phenomena. Although, the crystallinity of MXD6 films was lower as compared to PA6 films, the permeability to oxygen was more than 5 times better for the former. Incorporating 4 wt% clay enhanced the barrier property, tensile modulus, and yield stress of PA6 and MXD6 nanocomposite films in both machine and transverse directions without sacrificing much puncture and tear resistances. The PA6‐based films showed higher tear and puncture strength as compared to MXD6 films. POLYM. ENG. SCI., 54:2617–2631, 2014. © 2013 Society of Plastics Engineers     

Direct synthesis of bi-modal porous structure MCM-41 and its application in CO2 capturing through amine-grafting

A bi-modal porous structure MCM-41 (BPS-MCM-41) was synthesized and functionalized by 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane (TRI); also, its performance in amine grafting and CO₂ capturing was compared with that of pore-expanded MCM-41 [1]. To create larger pores beside the mesoporous structure of MCM-41, carbon black nanoparticles were used as the solid template. Characterizing the BPS-MCM-41 using the BET and BJH techniques resulted in the surface reduction of 29.3 percent and volume increase of 68.46 percent. The pore size distribution showed two peaks: a narrow peak at 2.24 nm diameter, which belonged to micelles, and a wide one at about 50 nm due to the presence of used nanoparticles. The functionalization confirmed that BPS-MCM-41 is capable of accommodating a large quantity of amine groups. The CO₂ adsorption measurement indicated that internal volume of the adsorbent was a critical factor affecting the adsorption capacity of the amine grafted adsorbents.