Utilization of polyethylene terephthalate waste as a carbon filler in polypropylene matrix: Investigation of mechanical,rheological, and thermal properties

Polyethylene terephthalate (PET) waste was converted into carbon and the feasibility of utilizing it as a reinforcing filler material in a polypropylene (PP) matrix was investigated. The carbon produced by the pyrolysis of waste PET at 900°C in nitrogen atmosphere contains high carbon content (>70 wt%). PP/carbon composites were produced by melt blending process at varying loading concentrations. Scanning electron microscopy images at the fractured surface revealed that the carbon filler has better compatibility with the PP matrix. The mechanical, thermal, and rheological properties and surface morphology of the prepared composites were studied. The thermogravimetric analysis studies showed that the thermal stability of the PP/carbon composites was enhanced from 300 to 370°C with 20 wt% of carbon. At lower angular frequency (0.01 rad/s), the storage modulus (G′) of PP was 0.27 Pa and those of PP with 10 and 20 wt% carbon was 4.06 and 7.25 Pa, respectively. Among the PP/carbon composite prepared, PP with 5 wt% carbon showed the highest tensile strength of 38 MPa, greater than that of neat PP (35 MPa). The tensile modulus was enhanced from 0.9 to 1.2 GPa when the carbon content was increased from 0 to 20 wt%.     

Unification of Common Cause Failures’ Parametric Models Using a Generic Markovian Model

The main objective of this paper is to provide a unified Markov model which could implement any parametric models devoted to the treatment of common cause failures (CCFs), namely: beta factor, multiple greek letter, alpha factor, multiple beta factor, and binomial failure rate. The choice of the Markovian representation is motivated by the fact that classical reliability approaches (e.g., Fault trees) are not able to catch the dynamic aspect induced by CCF events. The proposed Markovian model is also capable of dealing with any M-out-of-N configuration. It is illustrated on the basis of a system made up of four identical components (N = 4) in order to quantitatively examine the differences between the first four mentioned parametric models. For that purpose, the considered performance indicators are the average unavailability (U _avg) and the average unconditional failure intensity (i.e., failure frequency) (w _avg).     

Enhancement of wear resistance and impact toughness of as cast hypoeutectic high chromium cast iron using niobium

The effect of niobium additions on the as-cast microstructure of a hypoeutectic high-Cr cast iron containing 2.2 wt.% C and 16.5 wt.% Cr was investigated. With increasing niobium content, the eutectic M₇C₃ carbides were refined and became less elongated as well as its volume fraction was decreased gradually. The first precipitated NbC particles could be act as heterogeneous substrate of proeutectic austenite and a barrier to M₇C₃ grain growth. The morphology of NbC carbides changed with increasing niobium content. Such NbC particles were increased with increasing Nb content and subsequently contributed to increased hardness. Optimum toughness was obtained for the irons alloyed with 2.14% Nb. The effects of applied load and Nb-additions on wear resistance of high chromium cast iron have been studied. The results showed that wear resistance increases with increasing Nb addition. Furthermore, the effectiveness of the NbC particles on the weight loss was more evident at higher loads.     

Estimation of atmospheric emissions of six semivolatile polycyclic aromatic hydrocarbons in southern canada and the United States by use of an emissions processing system

Polycyclic aromatic hydrocarbons (PAHs) are toxic compounds that are ubiquitous in the atmospheric environment. The input for an emissions processing system that was originally configured forthe study of criteria air pollutants was updated to calculate emissions of six semivolatile PAHs. The goal of the work was to produce emissions estimates with the spatial and temporal resolution needed to serve as input to a regional air quality model for southern Canada and the U.S. Such modeling is helpful in determining reductions in PAH emissions that may be necessary to protect human and ecosystem health. The total annual emission of the six PAHs (sigma6PAH) for both countries was estimated at 18 273 Mg/year. A total of 90% of these emissions arise from U.S. sources. The top six source types account for 73% of emissions and are related to metal production, open burning, incineration, and forest fires. The emission factors used in this study were derived from published compilations. Although this approach has the advantage of quality control during the compilation process, some compilations include factors from older studies that may overestimate emissions since they do not account for recent improvements in emission control technology. When compared to estimates published in the National Emissions Inventory (NEI) for 2002, the U.S. emissions in this study are higher by a factor of 4 (16 424 vs 4102 Mg/year). The cause of this difference has been investigated, and much of it is likely due to our use of data unavailable in the 2002 NEI but inferred here on the basis of the PAH emissions literature. Augmenting the 2002 NEI with this additional information would bring its reported annual emissions to 8213 Mg/year, which is within a factor of 2 of the estimates herein. The results presented for southern Canada are the first published values for all known PAH sources in that country.     

Efficient Use of UAVs for Public Safety in Disaster and Crisis Management

In the case of crisis and disaster situations, Public Safety Organization (PSO) experience situations where most of the telecommunication infrastructure becomes unavailable or not reliable. Thus, an effective disaster assessment of the situation becomes a challenging task for the PSO. UAV is considered as the most suitable solution to address these scenarios where a maximal radio coverage of the target area is crucial. In this work, a square area is considered which mathematical approximation to ensure a maximal coverage based on “covering a square with equal circles” is investigated. The proposed approach outperforms the existing ones as it reduces effectively the total difference delay time to cover the target area. Furthermore, it allows time-saving to achieve more stops at the target area compared to existing schemes leading to better PSO activity performance.

     

Integral Diffusion Model of the Kinetics of Growth of Nitrided Layer in Gas Nitriding of Armco Iron

Metal Science and Heat Treatment - The kinetics of gas nitriding of Armco iron is studied using an integral diffusion model. A system of differential equations is used to calculate the thickness of...     

Lagrangian bounds for large‐scale multicommodity network design: a comparison between Volume and Bundle methods

The Bundle Method and the Volume Algorithm are among the most efficient techniques to obtain accurate Lagrangian dual bounds for hard combinatorial optimization problems. We propose here to compare their performance on very large scale Fixed‐Charge Multicommodity Capacitated Network Design problems. The motivation is not only the quality of the approximation of these bounds as a function of the computational time but also the ability to produce feasible primal solutions and thus to reduce the gap for very large instances for which optimal solutions are out of reach. Feasible solutions are obtained through the use of Lagrangian information in constructive and improving heuristic schemes. We show in particular that, if the Bundle implementation has provided great quality bounds in fewer iterations, the Volume Algorithm is able to reduce the gaps of the largest instances, taking profit of the low computational cost per iteration compared to the Bundle Method.