Advances in reduction of NOx and N2O1 emission formation in an oxy-fired fluidized bed boiler

Fossil fuel combustion is one of the major means to meet the mounting global energy demand. However, the increasing NO_x and N₂O emissions arising from fossil fuel combustion process have hazardous effects. Thus, mitigating these gases is vital to attain a sustainable environment. Interestingly, oxy-fuel combustion in fluidized bed for carbon capture and minimized NO_x emissions is strongly sustainable compare to the other approaches. It was assessed that NO_x formation and fuel-N conversion have significant limitation under oxy-fluidized bed compared to air mode and the mechanism of NO_x formation is still deficient and requires further development. In addition, this review paper discussed the potential of primary measure as low emission process with others supplementary techniques for feasible NO_x reduction. The influences of combustion mode, operating parameters, and reduction techniques such as flue gas recirculation, oxygen staging, biomass co-firing, catalyst, influence of fluidized bed design and structure, decoupling combustion and their merges are respectively evaluated. Findings show that significant minimization of NO_x emission can be achieved through combination of primary and secondary reduction techniques.     

Enhancement of electromechanical properties of natural rubber by adding barium titanate filler: An electro-mechanical study

Natural rubber is one of the most potential electro-active polymers for sensors, actuators, and energy harvesting applications. Enhancing the characteristic properties of polymers by reinforcing with fillers that possess multifunctional attributes have attracted considerable attention. In the present study, barium titanate reinforced natural rubber composite is prepared by using two-roll mill mixing. Afterwards, mechanical, electrical, and electromechanical properties of the composites are extensively analyzed by reinforcing different amounts of barium titanate into the matrix of natural rubber. The fabricated dielectric composite shows excellent properties such as high dielectric constant, low dielectric losses, high dielectric breakdown strength, and extreme stretchability. It is observed that as the filler loading reaches the value of 11 parts per hundred rubber (phr), maximum agglomeration of the particles occurs. Maximum stretchability and highest ratio of dielectric constant to elastic modulus are obtained at 8 phr of barium titanate fillers and at the loading, a maximum actuation strain of 11.24% is achieved. This study provides a simple, economical, and effective method for preparing enhanced mechanical, electrical, and electromechanical properties of natural rubber composites, facilitating the wide applications of dielectric materials as actuators and generators.     

Cellular Disulfide Bond Formation in Bioactive Peptides and Proteins

Bioactive peptides play important roles in metabolic regulation and modulation and many are used as therapeutics. These peptides often possess disulfide bonds, which are important for their structure, function and stability. A systematic network of enzymes—a disulfide bond generating enzyme, a disulfide bond donor enzyme and a redox cofactor—that function inside the cell dictates the formation and maintenance of disulfide bonds. The main pathways that catalyze disulfide bond formation in peptides and proteins in prokaryotes and eukaryotes are remarkably similar and share several mechanistic features. This review summarizes the formation of disulfide bonds in peptides and proteins by cellular and recombinant machinery.     

Effect of different titania phases on the hydrogen gas sensing features of polyaniline/TiO2 nanocomposite

This paper presents a resistance-based hydrogen gas sensor using polyaniline (emeraldine)/TiO₂ nanocomposite (PT–NC) thin film. It is demonstrated that different gas sensing features can arise when various TiO₂ phases (anatase and rutile) are applied. The different wt% of TiO₂ phases were dispersed into an acidic solution of aniline monomers and PT–NCs were synthesized by an in-situ self-assembly chemical oxidative polymerization method of aniline. PT–NCs deposited on an epoxy glass substrate having Cu-interdigited electrodes for hydrogen gas sensing at air pressure and room temperature. Our results show that the better sensitivity of the sensor strongly depends on the sensor surface morphology and its components. Furthermore, hydrogen gas sensing mechanism of the sensor based contact areas between Pani chains and TiO₂ grains was studied.     

Investigation of the Metal–Oxide Buried Interfacial Zone with Linear Sweep Voltammetry

Interest in copper as a technologically important material needs to be met with greater understanding of the fundamental chemical reactions of copper. In particular, there is still a lack of universal agreement on the oxidation process of bulk copper and thin copper films. In this study, the authors demonstrate the use of linear sweep voltammetry (LSV) to study buried structures in the oxide layers on copper. In particular, LSV can be used to detect reactions at buried interfaces. It is also emphasized that surface scientists should recognize Cu₃O₂ and the decomposition of copper oxides at the metal–oxide interface in new studies on copper oxidation and in interpreting already existing copper oxidation data. The two key parameters that drive oxide growth and decomposition are demonstrated to be oxygen activity and the free energies of formation of the oxides (per mole of oxide ion). The complex nature of the oxidation of copper, as well as other metals and alloys, can be described qualitatively using the Modified Cabrera–Mott (C–M) Model. Surface studies of oxidation of metals and alloys need to be supported and complemented by other techniques such as chemical or electrochemical methods.     

Physical and Mathematical Modeling of Inert Gas-Shrouded Ladle Nozzles and Their Role on Slag Behavior and Fluid Flow Patterns in a Delta-Shaped, Four-Strand Tundish

Inert gas shrouding practices were simulated using a full-scale, four-strand water model of a 12-tone, delta-shaped tundish. Compressed air was aspirated into the ladle shroud to model volumetric flow rates that range between 2 and 10 pct of steel entry flows. Bubble trajectories, slag layer movements, and flow fields, were visualized. Flow fields were visualized using particle image velocimetry (PIV). A numerical model also was developed using discrete phase modeling (DPM) along with the standard k-ε turbulence model with two-way turbulence coupling. Predicted flow fields and bubble trajectories corresponded with the water model experiments.     

Kinetic analysis of magnesium aluminate spinel formation: Effect of MgO:Al2O3 ratio and titania dopant

The mechanistic pathway of MgO-Al₂O₃ reaction in solid state to form MgAl₂O₄ spinel was investigated to correlate the kinetic parameters with ratio of reactants (MgO:Al₂O₃) and with the presence of a doping agent, TiO₂. The time-temperature-expansion data of oxide compacts was analyzed using several model free analyses and model based (linear and non-linear) kinetic algorithms. These indicated that spinel formation process can be best described by single step with n-dimensional Avrami equation for every MgO:Al₂O₃ ratio, irrespective of titania dopant. The activation energy (E_a) of the process was proportional to % spinel formed in each system and validated with quantitative XRD analysis. The higher value of Avrami coefficient (n) in 90 wt% Al₂O₃ compositions has been explained with geometric considerations of powder packing. Incorporations of 1% TiO₂ in the MgO: Al₂O₃ oxide compact did not markedly affect the reaction model, frequency factor and Activation energy.     

Subband entropy-based features for clothing invariant human gait recognition

This paper presents a wavelet-based feature extraction method for human gait recognition. The selection of features with most discriminative information is the key to improve recognition performance. The frequency domain representation of the gait image is obtained by using fast Fourier transforms. Next, a discrete wavelet transform is applied to the obtained spectrum. With single-level wavelet decomposition, four coefficients are generated. The sum of the entropy of these four wavelet coefficients is computed yielding the wavelet Entropy Image (wEnI) which is used here as the potential feature for human gait recognition. A template matching-based approach is used as the classification. The performance of the proposed wEnI feature is evaluated using whole-based and part-based methods. The experimental results show that the wEnI feature performs better compared to state-of-the-art gait features in common use.     

An efficient hybrid multicast transport protocol for collaborative virtual environment with networked haptic

In recent years, we have witnessed a growing interest in the synchronous collaboration based class of applications. Several techniques for collaborative virtual environments (CVE), haptic, audio and visual environments (C-HAVE) have been designed. However, several challenging issues remain to be resolved before CVE and C-HAVE become a common place. In this paper, we focus on applications that are based on closely coupled and highly synchronized haptic tasks that require a high-level of coordination among the participants. Four main protocols have been designed to resolve the synchronization issues in such environments: the synchronous collaboration transport protocol, the selective reliable transmission protocol, the reliable multicast transport protocol and the scalable reliable multicast. While these four protocols have shown good performance for CVE and C-HAVE class of applications, none of these protocols has been able to meet all of the basic CVE requirements, i.e., scalability, reliability, synchronization, and minimum delay. In this paper, we present a hybrid protocol that is able to satisfy all of the CVE and C-HAVE requirements and discuss its implementation and results in two tele-surgery applications. This work is partially supported by Grants from Canada Research Chair Program, NSERC, OIT/Ontario Distinguished Researcher Award, Early Research Award and ORNEC Research Grant.