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.     

Chemical Modeling of Acid-Base Properties of Soluble Biopolymers Derived from Municipal Waste Treatment Materials

This work reports a study of the proton-binding capacity of biopolymers obtained from different materials supplied by a municipal biowaste treatment plant located in Northern Italy. One material was the anaerobic fermentation digestate of the urban wastes organic humid fraction. The others were the compost of home and public gardening residues and the compost of the mix of the above residues, digestate and sewage sludge. These materials were hydrolyzed under alkaline conditions to yield the biopolymers by saponification. The biopolymers were characterized by ¹³C NMR spectroscopy, elemental analysis and potentiometric titration. The titration data were elaborated to attain chemical models for interpretation of the proton-binding capacity of the biopolymers obtaining the acidic sites concentrations and their protonation constants. The results obtained with the models and by NMR spectroscopy were elaborated together in order to better characterize the nature of the macromolecules. The chemical nature of the biopolymers was found dependent upon the nature of the sourcing materials.     

A level set topology optimization method for the buckling of shell structures

Structural and Multidisciplinary Optimization - Shell structures are some of the most widely used in engineering applications. Flat plates, stiffened panels, and wing ribs are each examples of...     

Analysis of the Content of Fatty Acid Methyl Esters in Biodiesel by Fourier-Transform Infrared Spectroscopy: Method and Comparison with Gas Chromatography

The increasing importance of sustainability in energy production has led to a global commitment to the use of fuels derived from renewable biological sources, such as biodiesel produced from plant crops or biomass residues, that do not compete with human food for their production. For a biofuel to be considered biodiesel, it must satisfy the specifications described in the UNE 14214, with the UNE-EN 14103 referring to the determination of fatty acid methyl ester content. This standard applies gas chromatography as an analytical technique. Gas chromatography is a widely used technique in the analysis of methyl ester although it has a number of drawbacks such as: long analysis times, a high consumption of high-quality gases and internal standards, does not allow the analysis of different compounds with the same column, etc. From an industrial production point of view, is necessary to know the fatty acid methyl ester content in biodiesel samples quickly. This paper studies the development of an analytical method using Fourier transform infrared spectroscopy (FTIR) as alternative to gas chromatography (GC), since it is a simple, rapid, and precise analytical technique to quantify fatty acid methyl ester content in biofuel samples.     

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.     

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.

     

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).     

Applicability of the geological strength index (GSI) classification for very weak and sheared rock masses. The case of the Athens Schist Formation

 The Athens Schist Formation includes a wide variety of metasedimentary rocks, varying from strong or medium strong rocks such as sericite metasandstone, limestone, greywacke, sericite schist through to weak rocks such as metasiltstone, clayey and silty shale and phyllite. The overall rock mass is highly heterogeneous and anisotropic owing to the combined effect of advanced weathering and severe tectonic stressing that gave rise to intense folding and shearing followed by extensional faulting, which resulted in highly weathered rock masses and numerous shear and/or mylonite zones with distinct downgraded engineering properties. This paper is focused on the applicability of the GSI classification system to these highly heterogeneous rock masses and proposes an extension of the GSI system to account for the foliated or laminated weak rocks in the lower range of its applicability. Received: 5 March 1998 · Accepted: 13 July 1998