Design and analysis of a new wave energy converter based on a point absorber and a hydraulic system harvesting energy from waves near the shore in calm seas

The aim of this paper is to illustrate the design of a new wave energy converter, composed of a point absorber and a hydraulic system (power take off) and sized for recovering energy in calm seas from waves near the shore. The point absorber is consisting of a rectangular shaped buoy integrating a piston pump. The set buoy‐pump oscillates under the waves action and moves natural water in a closed circuit hydraulic system (power take off) composed of a piping connecting the piston pump itself, a pressurized reservoir, a hydraulic turbine and a discharge tank. The methodology adopted for designing the main constituents involves a 1D mathematical model, settled for understanding the motion of the buoy under the hypothesis of regular waves and fully developed sea, and a sizing procedure applied for the design of all the components of the hydraulic system. The project related to the Calabrian site of Cetraro (Mediterranean Sea—south Italy) led to designing a system with a 4 m large buoy, associated with a small 13 cm diameter micro Pelton turbine, so that more than 22 000 kWh could be recovered in a year.     

Effect of pH,co-monomer content,and surfactant structure on the swelling behavior of microgel-azobenzene-containing surfactant complex

The contraction/swelling transition of anionic PNIPAM-co-AAA particles can be manipulated by light using interactions with cationic azobenzene-containing surfactant. In this study the influence of pH-buffers and their concentrations, the charge density (AAA content) in microgel particles as well as the spacer length of the surfactant on the complex formation between the microgel and surfactant is investigated. It is shown that the presence of pH buffer can lead to complete blocking of the interactions in such complexes and the resulting microgel contraction/swelling response. There is a clear competition between the buffer ions and the surfactant molecules interacting with microgel particles. When working in pure water solutions with fixed concentration (charge density) of microgel, the contraction/swelling of the particles is controlled only by relative concentration (charge ratio) of the surfactant and AAA groups of the microgel. Furthermore, the particle contraction is more efficient for shorter spacer length of the surfactant. The onset point of the contraction process is not affected by the surfactant hydrophobicity. This work provides new insight into the interaction between microgel particles and photo-sensitive surfactants, which offers high potential in new sensor systems.     

Asthma‐related outcomes associated with indoor air pollutants among schoolchildren from four informal settlements in two municipalities in the Western Cape Province of South Africa

The health impact of indoor air pollution in informal settlement households has not been extensively studied in South Africa. This cross‐sectional study investigated the association between asthma and common indoor exposures among schoolchildren from four informal settlements located in two municipalities in the Western Cape Province. A total of 590 children, aged 9‐11 years, were recruited. The International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire was administered to caregivers. Pulmonary function assessment included spirometry and fractional exhaled nitric oxide (FeNO). Phadiatop test for atopy was done. The prevalence of doctor‐diagnosed asthma was 3.4% (n = 20) among whom only 50% were on treatment. The prevalence of current wheeze was 12.9%, and 17.6% had airway obstruction (FEV₁ < lower limit of normal), while 10.2% had airway inflammation (FeNO > 35 ppb). In adjusted logistic regression models, dampness, visible mold growth, paraffin use for cooking, and passive smoking were associated with a twofold to threefold increased risk in upper and lower airway outcomes. The strongest association was that of visible mold growth with rhinitis (adjusted odds ratio—aOR 3.37, 95% CI: 1.69‐6.71). Thus, there is a need for improved diagnosis of childhood asthma and Indoor Air Quality in informal settlement households.     

Solvent-deficient synthesis of cerium oxide: Characterization and kinetics

The reaction mechanism and kinetics of CeO₂ synthesis using a solvent-deficient method are investigated by simultaneous thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The decomposition process of the cerium(III) nitrate hexahydrate and ammonium bicarbonate precursor mixture with four observed stages is monitored using TGA/DSC measurements in a nonisothermal regime with heating rates of 5, 10, 15 and 20?°C min^?1. The proposed mechanism indicates a complex synthesis with several parallel reactions, some of which occur at room temperature. A detailed kinetic analysis is performed using isoconversional (expanded Friedman, modified Coats-Redfern and Kissinger) and model fitting (N^th order and nucleation and growth models) methods. The first three stages are best described by the N^th order model with activation energy values of 21, 53 and 90?kJ?mol^?1. The last stage, during which ammonium nitrate decomposition occurs, is best fit by the nucleation and growth model and has an activation energy of 129?kJ?mol^?1. The proposed mechanism, supported by the kinetic analysis in our study, indicates that CeO₂ has already formed before the reaction reaches 200?°C. The average crystallite size of CeO₂ synthesized at 300?°C, which was calculated from the XRD measurements and observed in the SEM and TEM data, is between 10 and 20?nm.     

Combined Experimental and Computational Methods Reveal the Evolution of Buried Interfaces during Synthesis of Ferroelectric Thin Films

Understanding interfaces between dissimilar materials is crucial to the development of modern technologies, for example, semiconductor–dielectric and thermoelectric–semiconductor interfaces in emerging electronic devices. However, the structural characterization of buried interfaces is challenging because many measurement techniques are surface sensitive by design. When interested in interface evolution during synthesis, the experimental challenges multiply and often necessitate in situ techniques. For solution‐derived lead zirconate titanate (PZT) ferroelectric thin films, the evolution of buried interfaces during synthesis (including dielectric–metal and metal–metal) is thought to dramatically influence the resultant dielectric and ferroelectric properties. In the present work, multiple experimental and computational methods are combined to characterize interface evolution during synthesis of ferroelectric PZT films on platinized Si wafers—including in situ X‐ray diffraction during thermal treatment, aberration‐corrected scanning transmission electron microscopy of samples quenched from various synthesis states, and calculations using density functional theory. Substantial interactions at buried interfaces in the PZT/Pt/Ti/SiO _x /Si heterostructure are observed and discussed relative to their role(s) in the synthesis process. The results prove that perovskite PZT nucleates directly from the platinum (111)‐oriented bottom electrode and reveal the roles of Pb and O diffusion and intermetallic Pt₃Pb and Pt₃Ti phases.     

Flow Field Analysis in a Ventilated Large Enclosure Subject to Non-Homogeneous Boundary Conditions

Non-homogeneous thermal boundary conditions may play a relevant role in flow fields within ventilated enclosures. One such large-scale (23 m 3 ) test enclosure has been set in operation by termination jets under a combination of thermal unbalances in order to describe the dependence of secondary flow patterns on the bulk airflow. An integrated approach has therefore been attempted that features both measurements and calculations. An extensive and painstaking set of flow field measurements has been performed first, relative to different thermal and fluid dynamic working conditions, by means of a custom Laser Doppler Velocimetry apparatus. A commercial CFD software was then employed to perform the related calculations. A transitional regime is present (Re , 2000, based on grille diffuser equivalent diameter) at the given forcing inlet flow, as well as the competition between natural and forced convection. Some qualitative comparisons with respective experimental data are presented to delineate the role of thermal disturbances.     

Proton-conducting barium stannates: Doping strategies and transport properties

High temperature proton conductors (HTPCs) find their applications in steam electrolysis, gas sensing, and most importantly, fuel cells. In this work, proton conductivities and transport properties of doped BaSnO₃ are investigated. Samples of BaSn_0.9D_0.1O_2.95 (D = In, Lu, Er, Y, and Gd) were prepared by solid-state reaction and relative densities >93% were achieved after sintering at 1600 °C or lower. Although Y doping is commonly known to yield the highest conductivities for BaCeO₃ and BaZrO₃, In-doped BaSnO₃ exhibits the highest conductivity and conductivities decrease in the order In > Lu > Er > Y > Gd. Ionic radius and electronegativity matching between dopants and host Sn⁴⁺ is shown to be an important doping strategy for enhancing conductivities of BaSnO₃. Measurements of H/D isotope effect and electromotive force (EMF) were performed on BaSnO₃ to give direct evidence for proton conduction and to examine transport properties. The ratio between conductivities in H- and D-atmosphere (σ_H/σ_D) is 2.62 in reducing conditions, indicating protons transfer via the Grötthus mechanism. Proton transport numbers reached above 0.75 at 450 °C, and n- and p-type electronic conduction is identified to be secondary in reducing and oxidizing atmospheres, respectively. Electronic contribution to conductivity is found to increase with temperatures. Conductivities of BaSnO₃ are seen to be comparable to Y-doped BaZrO₃ (e.g., grain conductivities for both Y-doped BaSnO₃ and BaZrO₃ are ∼1.5 × 10⁻⁴ S cm⁻¹ at 350 °C), and are much higher than other common HTPCs, such as LaPO₄ and LaNbO₄. The high conductivity and good sinterability make BaSnO₃ a promising HTPC.     

Dissolution behavior of MgO-pyrochlore composites in acidic solutions

The dissolution behavior of sintered MgO-pyrochlore (Nd₂Zr₂O₇ was chosen for this study) composites in HNO₃ and H₂SO₄ solutions has been studied. The dissolution in 11 M HNO₃ and 7.9 M H₂SO₄ at 60 °C resulted in a selective dissolution of MgO. It was found that initially the fraction of dissolved MgO increases linearly with dissolution time. Magnetic bar stirring enhanced the mass transfer rate and resulted in a higher dissolution rate of MgO compared with the static and ultrasonic dissolution. It also provided mechanical forces to completely disintegrate the undissolved Nd₂Zr₂O₇ porous matrix into residual powder. Both MgO and Nd₂Zr₂O₇ can be dissolved in boiling concentrated (18 M) H₂SO₄, and Nd₂Zr₂O₇ dissolves incongruently. The dissolution of Mg²⁺ and Nd³⁺ followed first order kinetics, but Zr⁴⁺ precipitated out due to low solubility in concentrated H₂SO₄.     

The Efficiency of Application Nanosilver in Technological Processes of Making Red Wine

The efficiency of using nanostructured silver in technological processes of making red wine has been studied with the purpose of substituting sulfur dioxide. For preparation of research objects, we used dry wine material of red grape variety ＂Saperavi＂. After completion of malolactic fermentation, the second racking the wine material off the lees and its treatment with antiseptics were carried out. Sulfur dioxide （Kadifit） and different doses of nanostructured silver were used. Microbiological investigation was performed on the presence of lactic bacteria after completion of malolactic fermentation and racking off the lees. The investigation of phenolic compounds was conducted at the following stages of technological processes： （1） after completion of alcoholic fermentation and racking off the lees; （2） after completion of malolactic fermentation; （3） after the second racking off the lees and treatment with antiseptics. By means of the HPLC analysis, the amounts ofcatechins, phenolcarbonic acids and flavonols were determined. It has been established that after conduction of malolactic fermentation in the process of racking the wine material off the lees and storage, the application of 0.6 mg/L of nano-silver for blocking of lactic-acid bacteria and inhibition of oxidation of phenolic compounds has the same effect as sulfitization with 50 mg/L of Kadifit.