Thermal transport and chemical conversion in single reacting sorbent particles

The effects of particle size and carbon dioxide concentration on chemical conversion in engineered spherical particles undergoing calcium oxide looping are investigated. Particles are thermochemically cycled in a furnace under different carbon dioxide concentrations. Changes in composition due to chemical reactions are measured using thermogravimetric analysis. Gas composition at the furnace exit is evaluated with mass spectroscopy. A numerical model of thermal transport phenomena developed previously is adapted to match the physical system investigated in the present study. The model is used to elucidate effects of reacting medium characteristics on particle temperature and reaction extent. Experimental and numerical results show that (1) an increase in particle size results in a decrease in carbonation extent, and (2) the carbonation step consists of fast and slow reaction regimes. The reaction rates in the fast and slow carbonation regimes increase with increasing carbon dioxide concentration. The effect of carbon dioxide concentration and the distinction between the fast and slow regimes become more pronounced with increasing particle size.     

Formal reasoning for analyzing goal models that evolve over time

Requirements Engineering - In early-phase requirements engineering, modeling stakeholder goals and intentions helps stakeholders understand the problem context and evaluate tradeoffs, by exploring...     

Active disturbance rejection control of metal hydride hydrogen storage

Metal hydride (MH) hydrogen storage is used in both mobile and stationary applications. MH tanks can connect directly to high-pressure electrolyzers for on-demand charging, saving compression costs. To prevent high hydrogen pressure during charging, hydrogen generation needs to be controlled with consideration for unknown disturbances and time-varying dynamics. This work presents a robust control system to determine the appropriate mass flow rate of hydrogen, which the water electrolyzer should produce, to maintain the gaseous hydrogen pressure in the tank for the hydriding reaction. A control-oriented model is developed for MH hydrogen storage for control system design purposes. A proportional-integral (PI) and an active disturbance rejection control (ADRC) feedback controllers are investigated, and their performance is compared. Simulation results show that both the PI and ADRC controllers can reject both noises from the output measurements and unknown disturbances associated with the heat exchanger. ADRC excels in eliminating disturbances produced by the input mass flow rate, maintaining the pressure of the tank at the charging pressure with little oscillations. Additionally, the parameters estimated by the ADRC's extended state observer was used to predict the state-of-charge (SOC) of the MH.     

Restorative wildscapes at work: an investigation of the wellbeing benefits of greenspace at urban fringe business sites using ‘go-along’ interviews

Abstract

The potential well-being benefits associated with the use of privately owned greenspaces in working environments have received little research attention. Given the growing evidence on the restorative benefits of urban greenspace, and the fact that many people spend most of their daily hours at the workplace, the question of whether physical access to green environments from workplaces can promote well-being is a pertinent one. Person–environment relationships in peri-urban business sites were investigated in a series of semi-structured ‘go-along’ interviews with employees at Scottish science parks. Workers described a range of well-being benefits from outdoor breaks and associated these with qualities of the environment. Semi-natural and informally landscaped areas were most strongly associated with restoration during the working day. The implications of the findings for the planning and design of business sites at the urban fringe are explored.     

Aflatoxin and PAH exposure biomarkers in a U.S. population with a high incidence of hepatocellular carcinoma

The incidence of hepatocellular carcinoma (HCC) is significantly elevated in a Hispanic community in Bexar County, Texas. Chronic exposure to dietary aflatoxins (AFs) is a major risk factor for HCC; increased risk has been linked to polycyclic aromatic hydrocarbon (PAH) co-exposure and hepatitis virus infection. The aims of this study were to assess AF and PAH exposures, investigate dietary factors that may contribute to increased AF exposure, and determine the prevalence of hepatitis virus infection in Bexar Co. Blood and urine samples were collected from 184 volunteers for biomarker analyses and hepatitis screening. Serum AFB₁-lysine adduct, urinary AFM₁ and 1-hydroxypyrene (1-OHP) levels were measured using high-performance liquid chromatography. The average AFB₁-lysine adduct level detected in 20.6% of serums was 3.84 ± 3.11 pg/mg albumin (range 1.01-16.57 pg/mg). AFM₁ was detected in 11.7% of urines, averaging 223.85 ± 250.56 pg/mg creatinine (range 1.89-935.49 pg/mg). AFM₁ detection was associated with increased consumption of corn tortillas (p = 0.009), nuts (p = 0.033) and rice (p = 0.037). A significant difference was observed between mean 1-OHP values of non-smokers (0.07 ± 0.13) and smokers (0.80 ± 0.68) μmol/mol creatinine (p < 0.01). A high hepatitis C virus positivity rate (7.1%) was observed. Findings suggest that the incidence and level of AF and PAH exposure were less than those observed in a high-risk population; however, participants consuming higher amounts of foods prone to AF contamination may be more vulnerable to exposure and interactions with other environmental/biological factors (i.e., HCV).     

Rating defence major project success: The role of personal attributes and stakeholder relationships

In this paper we develop and test a model of the associations between major project managers' personal attributes and project success in the context of the Australian Defence industry. In our model, emotional intelligence, cognitive flexibility and systemic thinking were hypothesised to relate to project success, mediated by internal and external stakeholder relationships. The model was tested in an online survey with 373 major project managers. Emotional intelligence and cognitive flexibility were found to be related to the development, quality and effectiveness of major project managers' relationships with both internal and external stakeholders; and these in turn were associated with their ratings of project success. Systemic thinking, however, had no relationship with either stakeholder relationships or project success. Additional research is needed to examine the contribution of a wider range of personal attributes to stakeholder relationships and project success, and to assess whether this model is applicable in other industries and types of projects.     

Mechanosynthesis of the multiferroic cubic spinel Co2MnO4: Influence of the calcination temperature

Multiferroic materials showing magnetoelectric coupling are required in various technological applications. Many synthetical approaches can be used to improve the magnetic and/or electrical properties, in particular when the materials exhibit cationic valence fluctuations, as in the Co₂MnO₄ cubic spinel. In this compound, Co and Mn ions are in competition at the tetrahedral and octahedral positions, depending on their various oxidation states. The Co₂MnO₄ was prepared following two techniques: by a soft chemical route based on a modified polymer precursor method, and by a mechanoactivation route. Both approaches yield polycrystalline powders, but their crystallites sizes and particles morphologies differ as a function of the calcination conditions. The magnetic characterization (ZFC/FC cycles, ordering temperatures, ferromagnetic coercive fields and saturation magnetizations) showed that the synthesis procedure influenced the physical properties of Co₂MnO₄ mainly through the size of the magnetic domains, which play an important role on the magnetic interactions between the Co/Mn cations.     

Stereoselective Synthesis of Pyrroloquinolines by a Brønsted Acid Catalyzed [4+2]‐Heterocyclization of Indole‐7‐Carbaldehydes,Anilines and Electron‐Rich Alkenes

The pyrrolo[3,2,1‐ij]quinoline heterocyclic core is found in the structure of a variety of compounds with interesting applications and then, new efficient and flexible strategies to construct this skeleton are required. Here, a new diastereoselective tetrafluoroboric acid (HBF₄)‐catalyzed three‐component coupling reaction of 1H‐indole‐7‐carbaldehyde derivatives, anilines and electron‐rich alkenes to give pyrrolo[3,2,1‐ij]quinolines is described. The reaction involves an unusual [4+2]‐heterocyclization between an in situ formed imine and an alkene. The new catalytic method, where water is the only by‐product, is efficient, robust and flexible, and allows for multigram‐scale synthesis.

     

Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

Polypropylene with wider or bimodal molecular weight distribution is required for numerous applications since low molecular weight chains improve processability and high molecular weight fraction is required to get good mechanical properties. There are several routes to achieve a bimodal resin but the use of a binary catalytic system seems to be the most attractive, particularly with metallocenes combination. From a previous work two metallocenes were selected because they lead to polypropylenes with average molecular weights that differ in one order of magnitude. Two types of binary systems have been investigated, hybrid catalysts (two metallocenes loaded on the same support) and physical mixtures (two independent supported metallocenes that are introduced to the reactor and start the polymerization together), using different ratios, i.e., 25–75, 50–50, 75–25, at three reaction temperatures, i.e., 30, 50 and 70 °C. Most of the binary catalytic systems lead to bimodal molecular weight distributions. Polypropylenes produced by mixed catalysts are greatly influenced by the most active catalyst, while in PP coming from hybrid catalysts, as there is a strong interaction between both metallocenes, each one contributes according to its presence in the hybrid catalyst. Therefore, properties of obtained bimodal polypropylenes are quite influenced by the ratio between both metallocenes.