NP-completeness of chromatic orthogonal art gallery problem

The Journal of Supercomputing - The chromatic orthogonal art gallery problem is a well-known problem in the computational geometry. Two points in an orthogonal polygon P see each other if there is...     

Common pool water resources management considering a regulator interference: A game theory approach to derive managerial policies for Urmia lake,Iran

An increased need for water, combined with a scarcity of water resources, has resulted in serious challenges regarding water resource management. Those issues have always been a major concern of most research regarding the management and operation of water resources. Various qualitative and quantitative methods, Game Theory (GT) being an example, have been proposed for managing common pool water resources. This study adopts GT to address a case of common pool water resource management, including consideration of the interference of a regulator. Urmia lake in north‐western Iran was chosen as an illustration of a common source of water shared between two provinces acting as littoral stakeholders to the lake. Due to a non‐cooperative behaviour of the stakeholders, the lake is most likely to dry up. To change the game situation, a regulator was inserted into the game as a third player. The game among players is investigated in terms of two static and dynamic game methods. Two strategies are defined for each player. The equilibrium point will be achieved according to the strategies adopted by the players. For static games, a low‐level equilibrium under non‐cooperation conditions is obtained. Dynamic games among players are more likely to occur, rather than static games. The equilibrium of high‐level productivity will be obtained under cooperative conditions among the players.     

Quantum decoherence of Dirac fields in non-inertial frames beyond the single-mode approximation

The effects of Quantum decoherence on Dirac fields in an accelerated frame are studied beyond the single-mode approximation. The decoherence phenomena are investigated through the quantum channel approach using the amplitude damping channel and the dephasing one. The entanglement and purity are two distinct quantum features which are investigated. We have assumed that only the non-inertial observer experiences decoherence phenomena. The associated effects of the acceleration, damping rate, and dephasing rate are considered. It is found that acceleration and decoherence rates will decrease the degree of entanglement and purity. It turns out that beyond the single-mode approximation, the maximal entangled state cannot be achieved. Moreover, a comparison between the damping and dephasing processes is done which reveals the fact that damping effects on the entanglement are stronger than dephasing effects, whereas dephasing has stronger effects on the purity.     

Characterization of the particle–matrix interface in rubber-modified epoxy by atomic force microscopy

Atomic force microscopy (AFM) was used to study the interphase regions in rubber-toughened epoxy polymers. The nature of the interphase region was varied by either the adducting of reactive oligomers or by crosslinking the shell polymer on core/shell latex particles. The adducted reactive oligomers were comprised of carboxyl-terminated, butadiene-actrylonitrile copolymers (CTBN) prereacted with either (1) a low molecular weight diglycidyl ether of bisphenol A-based epoxy, which results in an interphase with increased crosslink density, or (2) a high molecular weight epoxy based on the diglycidyl ether of propylene glycol (DEGP), which results in an interphase with decreased crosslink density. The second type of rubber particles is custom-made submicron core/shell latex particles of a poly(butadiene-co-styrene)[P(BS)] core with an acrylate shell. Two acrylate shells were (1) PMMA/AN shell containing 25% acrylonitile and (2) a similar PMMA/AN with 5% divinyl benzene. The toughness of these blends was characterized using linear elastic fracture mechanics. The features on the fracture surfaces were examined using both AFM and FESEM (field emission scanning electron microscopy). AFM was able to detect features not observed in SEM and also to quantify all of the fracture surface features. In particular, the height-to-width ratio of the rim surrounding cavitated particles provided a useful means for determining the ductility of the interphase region. Attempts were made to determine the size of the interphase region using the frictional mode and the tip-adhesion forces. Unfortunately, the results of both approaches are inconclusive at the present time; this is most likely due to the deformation surrounding the rubber particles detected in the fast fracture regions. © 1995 John Wiley & Sons, Inc.     

Creep analysis of an earth embankment on soft soil deposit with and without PVD improvement

In this paper, an anisotropic creep constitutive model, namely Creep-SCLAY1S is employed to study the installation effects of prefabricated vertical drains (PVDs) on the behavior of a full scale test embankment, namely Haarajoki embankment in Finland. The embankment was constructed on a natural soft soil with PVD installed to improve the drainage under one half of it. The Creep constitutive model used in this study, incorporates the effects of fabric anisotropy, structure and time within a critical state based framework. For comparison, the isotropic modified Cam clay (MCC) model and the rate-independent anisotropic S-CLAY1S model are also used for the analyses. The numerical predictions are compared with field measurements and the results indicate that the creep model provides an improved approximation of field settlements, and excess pore pressure build-up and dissipations. In addition, the application of two commonly used permeability matching techniques for two dimensional (2D) plane-strain analysis of the PVD problem is studied and the results are discussed highlighting their limitations and advantages.     

Nanoindentation of isotactic polypropylene: Correlations between hardness,yield stress,and modulus on the local and global scales

The correlations between the hardness, yield stress, and modulus of elasticity of isotactic polypropylene (iPP) were evaluated on the local and global scales. Nanoindentation and traditional macromechanical tests were incorporated for this purpose. Thus, local and global mechanical properties were measured at various temperatures and strain rates. A certain relation was found between the local and global mechanical properties. Moreover, Johnson's model (developed according to the expanding cavity model) was also evaluated at various temperatures and strain rates. The Johnson model was valid only for the yield stresses obtained by nanoindentation and compressive tests and also the elastic modulus obtained via nanoindentation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The influence of different preparation methods on the aggregation status of pyrogenic nanosilicas used in concrete

Investigation of the effects of nanosilica materials in cementitious mixtures has attracted considerable research attention due to the very high specific surfaces of these materials. However, high surface area leads to aggregation of these materials due to high surface attraction forces, which could seriously reduce their nano filler effect. In this research the dispersion of pyrogenic nanosilicas in water and parameters influencing it were investigated. The results show that serious aggregation of pyrogenic nanosilicas in water occurs. Increasing the amount of applied forces, particularly the use of ultrasonic waves, has considerable effect in breaking aggregates into smaller aggregates with maximum size up to 0.9 μm. Increasing the pH was found to be very effective in improving dispersion of nanosilicas and through combined use of high pH and applying high levels of energy such as ultrasonic method it is possible to break all the aggregates into primary aggregates with maximum size of about 0.06 μm.     

Removal of Gas Pollutants of a Thermal Oxidizer with a Dynamic Scrubber

The absorption of gas pollutants including CO₂, CO, NO, NO₂, SO₂, and H₂S from the exhaust of a paint recuperative oxidizer into NaOH solution has been studied using an industrial scale dynamic scrubber. Experimental results show the influence of the absorbent concentration on the pollutant removal efficiency. The best removal efficiencies of CO₂, CO, NO, NO₂, SO₂, and H₂S were 79, 80, 80, 100, 75 and 88 %, respectively, with 2 % NaOH as the absorbent. A comparison of these results with previous studies shows that the liquid‐to‐gas flow rate ratio (F_L/F_G) in this dynamic scrubber is much smaller than for traditional NaOH scrubbers and spray dryers.     

Whisker Formation Induced by Component and Assembly Ionic Contamination

This paper describes the results of an intensive whisker formation study on Pb-free assemblies with different levels of cleanliness. Thirteen types of as-received surface-mount and pin-through-hole components were cleaned and intentionally contaminated with solutions containing chloride, sulfate, bromide, and nitrate. Then the parts were assembled on double-sided boards that were also cleaned or intentionally contaminated with three fluxes having different halide contents. The assemblies were subjected to high-temperature/high-humidity testing (85°C/85% RH). Periodic examination found that contamination triggered whisker formation on both exposed tin and solder fillets. Whisker occurrence and parameters depending on the type and level of contamination are discussed. Cross-sections were used to assess the metallurgical aspects of whisker formation and the microstructural changes occurring during corrosion.     

A novel MLP approach for estimating asphaltene content of crude oil

ABSTRACT

Asphaltene is considering to be the most problematic part of oil that causes pipe plugging, permeability reduction, and ultimately loss of production through its separation process from oil body as result of any thermodynamic change. Its weight fraction is one of key inputs to any asphaltene related modeling, which requires an expensive and time consuming experimental procedure. In this research, for the first time a novel MLP-ANN structure is proposed to predict this critical parameter at wide range of operational conditions, with satisfactory precision. A dataset of over 300 experimental data was gathered from open literature and used to train and test the proposed construct. The results show network great performance and therefore, can be used as a universal tool to provide input for any asphaltene-related modeling, with assurance.