Effect of moisture, charge size, and chlorine concentration on PCDD/F emissions from simulated open burning of forest biomass

Loblolly pine (Pinus taeda) was combusted at different charge sizes, fuel moisture, and chlorine content to determine the effect on emissions of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) as well as copollutants CO, PM, and total hydrocarbons. The experiments were performed in an enclosed chamber under conditions simulating open, prescribed burns of forest biomass. Burn progress was monitored through on line measurement of combustion gases and temperature while PCDD/F concentrations were determined by ambient sampling methods. PCDD/F toxic equivalency (TEQ) and total (tetra- to octa-CDD/F) emission factors were independent of charge size (1-10 kg) and moisture content (7-50%). However, the lower chlorinated, mono- to tri-CDD/F compounds were increased by poor combustion conditions: combustion efficiency lower than 0.919 was generally found when the moisture content was higher than 30%. The increase of fuel matrix chlorine from 0.04% to 0.8% using a brine bath resulted in about a 100-fold increase of PCDD/F to about 90 ng TEQ/kg of carbon burned, C(b). These emission factors were linearly dependent on Cl concentration in the biomass. PCDD 2,3,7,8-Cl-substituted congeners and homologue patterns were also influenced by the addition of chlorine resulting in emissions with a higher abundance of the most toxic congeners (TeCDD and PeCDD). When both chlorine and moisture content were increased in the fuel, a simultaneous effect of the two parameters was observed. The increased TEQ values expected from higher Cl concentrations were mitigated by the presence of water, giving MCE = 0.868, promoting formation of mono- to tri-PCDD/F, and lowering the TEQ value. Open burn simulations were used to study PCDD/F formation in different combustion conditions providing a mathematical correlation between PCDD/F emissions and chlorine and moisture content in the fuel.     

Origin of carbon in polychlorinated dioxins and furans formed during sooting combustion

The importance of solid- and gas-phase carbon precursors for the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) during sooting combustion was investigated in an entrained flow reactor (EFR). Experiments were performed at various methane (CH4) flame equivalence ratios with or without gas-phase chlorine (Cl2) and fly ash, to provide a realistic environment for carbon reactions and PCDD/DF formation. Selected experiments were conducted with labeled 13CH4 and 37Cl2 to investigate the relative roles of different carbon and chlorine species for the formation of PCDD/DF. The presence of soot and ash were the two major factors controlling the PCDD/DF yields. The 16 PCDD/DF homologues as well as other analyzed chlorinated aromatics were formed by reaction pathways that varied with degree of chlorination. The mono- and dichlorinated homologues were formed by gas-phase, catalytic, or noncatalytic flame product reactions, occurring during soot formation in the near flame zone and/or at lower reaction temperatures (<650 degrees C) in the postcombustion zone. Meanwhile, the higher (tri- to octa-) chlorinated homologues were mainly formed in the postcombustion zone (<650 degrees C) by fly ash-catalyzed de novo synthesis of the soot. Of these, the PCDD/DFs were formed from high carbon number (>C12) fragments in the solid soot structure, while the PCDDs, at least in part, were also formed by reaction of two C6 fragments. The tri- to hexachlorinated DD/DF homologues were formed via a relatively fast de novo synthesis occurring during the first minutes of reactions on the continuously formed soot particles, whereas de novo synthesis on an aged soot matrix was the major pathway for the hepta- and octachlorinated congeners.     

Structural feature-based evaluation method of binarization techniques for word retrieval in the degraded Arabic document images

One of the most important and necessary steps in the process of document analysis and recognition is the binarization, which allows extracting the foreground from the background. Several binarization techniques have been proposed in the literature, but none of them was reliable for all image types. This makes the selection of one method to apply in a given application very difficult. Thus, performance evaluation of binarization algorithms becomes therefore vital. In this paper, we are interested in the evaluation of binarization techniques for the purpose of retrieving words from the images of degraded Arabic documents. A new evaluation methodology is proposed. The proposed evaluation methodology is based on the comparison of the visual features extracted from the binarized document images with ground truth features instead of comparing images between themselves. The most appropriate thresholding method for each image is the one for which the visual features of the identified words in the image are “closer” to the features of the reference words. The proposed technique was used here to assess the performances of eleven algorithms based on different approaches on a collection of real and synthetic images.     

Symbolic Test-generation in HOL-TESTGEN/CirTA A Case Study

HOL-TestGen/CirTA is a theorem-prover based test generation environment for speci cations written in Circus, a process-algebraic speci cation language in the tradition of CSP. HOL-TestGen/CirTA is based on a formal embedding of its semantics in Isabelle/HOL, allowing to derive rules over speci cation constructs in a logically safe way. Beyond the derivation of algebraic laws and calculi for process re nement, the originality of HOL-TestGen/ CirTA consists in an entire derived theory for the generation of symbolic test-traces, including optimized rules for test-generation as well as rules for symbolic execution. The deduction process is automated by Isabelle tactics, allowing to protract the state-space explosion resulting from blind enumeration of data. The implementation of test-generation procedures in CirTA is completed by an integrated tool chain that transforms the initial Circus speci cation of a system into a set of equivalence classes (or "symbolic tests"), which were compiled to conventional JUnit test-drivers. This paper describes the novel tool-chain based on prior theoretical work on semantics and test-theory and attempts an evaluation via a medium-sized case study performed on a component of a real-world safety-critical medical monitoring system written in Java. We provide experimental measurements of the kill-capacity of implementation mutants.     

Impact of organoclays on the phase morphology and the compatibilization efficiency of immiscible poly(ethylene terephthalate)/poly(ε-caprolactone) blends

Adding nanofillers Cloisite 30B (C30B) and Cloisite 15A (C15A) to poly(ethylene terephthalate) (PET)/poly(ε-caprolactone) (PCL) (70/30, wt/wt) blends via melt blending can improve their phase morphology and change their interface properties. The effects of the different selective localization of clay on the structure and the morphologies are studied and evaluated by theoretical and experimental methods. It is found that C30B is selectively localized in PET and at the PET-PCL interface, whereas C15A is mainly localized at the interface. Moreover, the changes in the rheological behavior of the blends are attributed to the formation of clay network-like structures. X-ray diffraction, scanning electron microscope, and transmission electron micrograph observations also evidenced an exfoliated and/or intercalated structure of C30B, and intercalated structure of C15A in the blend, together with significant morphology changes of the initially immiscible blend. The relative permeability to PET/PCL of the nanocomposites decreased with the increasing of nanoclays content. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48812.     

PCDD and PCDF emissions from simulated sugarcane field burning

The emissions from simulated sugarcane (Saccharum officinarum) field burns were sampled and analyzed for polychlorinated dibenzodioxins and dibenzofurans (PCDDs and PCDFs). Sugarcane leaves from Hawaii and Florida were burned in a manner simulating the natural physical dimensions and biomass density found during the practice of preharvest field burning. Eight composite burn tests consisting of 3-33 kg of biomass were conducted, some with replicate samplers. Emission factor calculations using sampled concentration and measured mass loss compared well to rigorous carbon balance methods commonly used in field sampling. The two sources of sugarcane had distinctive emission levels, as did tests on separate seasonal gatherings of the Florida sugarcane. The average emission factor for two tests of Hawaii sugarcane was 253 ng toxic equivalents (TEQ)/kg of carbon burned (ng TEQ/kg(Cb)) (rsd = 16%) and for two gatherings of Florida sugarcane was 25 ng TEQ/kg(Cb) (N = 4, rsd = 50%) and 5 ng TEQ/kg(Cb) (N = 2, rsd = 91%). The Hawaii sugarcane, as well as most of the Florida sugarcane, had emission values which were well above the value of 5 ng TEQ/kg(Cb) commonly attributed to biomass combustion. Application of this emission factor range to the amount of U.S. sugarcane fields burned suggests that this practice may be a relatively minor source of PCDDs and PCDFs in the U.S. national inventory, but the limited sample size and range of results make this conclusion tenuous.     

A design of a tunable hybrid Solc filter for 40-Gbps DWDM optical systems

In this paper, a contribution for enhancing the performance of a hybrid tunable Solc filter for 40-Gbps DWDM systems is presented. By using liquid crystal cells with variable birefringence, we have achieved a wavelength tuning of 33 ITU channels, for a 100-GHz frequency spacing, from 1564.69 to 1530.32 nm via a 10-stage hybrid Solc filter. The designed device presents a tuning step of 0.1 nm by applying a voltage difference of 0.2 V. The optical cancelling technique is used to make a 3-dB bandwidth tuning between 0.31 and 1.4 nm. The channel’s bandwidth is adjusted for different kinds of 40-Gbps modulated channels spectra. The 10-stage hybrid Solc filter provides theoretically an insertion loss of 4.6 dB, by using polarizers and birefringent plates characterized by high anti-reflection coatings, while its crosstalk approximates 14 dB. The proposed filter provides very low polarization-dependent loss through the incorporation of a polarization beam splitter and a polarization beam combiner.     

Gravity direction-based ultra-fast intraprediction algorithm for H.264/AVC video coding

The H.264/AVC video coding standard uses in intraprediction, 9 directional modes for 4 × 4 and 8 × 8 luma blocks, and 4 directional modes for 16 × 16 luma macroblocks, and 8 × 8 chroma blocks. The use of the variable block size and multiple modes in intraprediction makes the intracoding of H.264/AVC very efficient compared with other compression standards; however, computational complexity is increased significantly. In this paper, we propose a fast mode selection algorithm for intracoding. This algorithm is based on the vector of the block’s gravity center whose direction is used to select the best candidate prediction mode for intracoding. On this basis, only a small number of intraprediction modes are chosen for rate distortion optimization (RDO) calculation. Different video sequences are used to test the performance of proposed method. The simulation results show that the proposed algorithm increases significantly the speed of intracoding with negligible loss of peak signal-to-noise ratio quality.     

ECDGP: extended cluster‐based data gathering protocol for vehicular networks

An important application in wireless networks is data collection. It aims to gather and deliver specific data for concerned authorities. Many researchers invest in vehicular ad hoc networks for that purpose to acquire data from different sources on the roads as from its vicinity. A vehicle is considered as a mobile data collector, it gathers real‐time or delay‐tolerant data such as road traffic, environmental information, and event advertisements. In a previous work, we have proposed a novel clustered data gathering protocol (CDGP) for vehicular ad hoc network, which improves the collection performance by implementing a new space division multiple access technique called dynamic space division multiple access and a retransmission mechanism in case of errors. However, CDGP supports only delay‐tolerant data as it does not use any aggregation technique. In this paper, we propose an enhancement of this protocol by extending it to support: (i) both real‐time and delay‐tolerant applications; (ii) multiple types of data; and (iii) aggregation of collected data prior to sending them to the initiator. We present the plausible analytical complexity of the extended CDGP, as we illustrate the superiority of its performance throughout the results obtained from simulation experiments, using a Freeway mobility model. Copyright © 2015 John Wiley & Sons, Ltd.     

Metamodel-assisted Kalai-Smorodinsky equilibria to solve a multicriteria optimization problem

Structural and Multidisciplinary Optimization - The main idea of solving a multicriteria optimization problem (MOP) is to find non-dominated solutions belonging to the Pareto frontier (e.g., a...