Indentation cracking and deformation mechanism of sodium aluminoborosilicate glasses

Developing less brittle oxide glasses is a grand challenge in the field of glass science and technology, as it would pave the way toward new glass applications and limit the overall raw material usage and energy consumption. However, in order to achieve this goal, more insight into the correlation between the chemical composition and material properties is required. In this work, we focus on the mechanical properties of quaternary sodium aluminoborosilicate glasses, wherein systematic changes in glass chemistry yield different resistances to indentation crack initiation. We discuss the origin of the composition dependence of indentation cracking based on an evaluation of the deformation mechanism taking place during the indentation event. To this end, we use a simple metric, the extent of indent side length recovery upon annealing, to quantify the extent of reversible volume deformation. Finally, we also compare the compositional trend in crack initiation resistance to that in crack growth resistance (fracture toughness), showing no simple correlation among the two.     

Influence of copigment derived from Tasmannia pepper leaf on Davidson's plum anthocyanins

Davidson's plum (Davidsonia pruriens, F. Muell.), a native to Australian rainforests, large, crimson-red fruit, which superficially resembles plum, has been commercially cultivated in Australia since 1990s. The current production volume exceeds market demands therefore this study was designed to evaluate the suitability of Davidson's plum extract as a source of anthocyanin-based food colorant. The stability of the Davidson's plum extract towards heat treatment at 95 °C was higher than that of commercial mulberry colorant, but inferior to colorants derived from red cabbage and purple sweetpotato. An addition of a variety of phenolic acids significantly increased color intensity indicating the formation of copigmentation complexes. Commercial chlorogenic acid as well as extract from a native Australian herb rich in chlorogenic acid, Tasmannia pepper leaf (Tasmannia lanceolata, R. Br.), were both tested in model soft drink solutions subjected to light irradiation and heat treatment. In both cases, the addition of the copigment resulted in a lasting increase in color intensity. In conclusion, Davidson's plum extract can successfully be utilized as a source of natural food color. Extract from Tasmania pepper leaf can be used as a co-pigment for Davidson's plum anthocyanins. PRACTICAL APPLICATION: The color properties of an anthocyanin colorant derived from the native Australian fruit Davidson's plum are comparable to those of mulberry, which is currently applied as a food colorant in Australian food products. Utilization of Davidson's plum fruit as a source of natural color will allow the industry to increase the range of natural pigments and will create new opportunities for the emerging native food industry.     

Nonstationary Cointegration in the Fractionally Cointegrated VAR Model

We consider the fractional cointegrated vector autoregressive (CVAR) model of Johansen and Nielsen (2012a) and make two distinct contributions. First, in their consistency proof, Johansen and Nielsen (2012a) imposed moment conditions on the errors that depend on the parameter space, such that when the parameter space is larger, stronger moment conditions are required. We show that these moment conditions can be relaxed, and for consistency we require just eight moments regardless of the parameter space. Second, Johansen and Nielsen (2012a) assumed that the cointegrating vectors are stationary, and we extend the analysis to include the possibility that the cointegrating vectors are non‐stationary. Both contributions require new analysis and results for the asymptotic properties of the likelihood function of the fractional CVAR model, which we provide. Finally, our analysis follows recent research and applies a parameter space large enough that the usual (non‐fractional) CVAR model constitutes an interior point and hence can be tested against the fractional model using a Chi‐squared‐test.     

Controlled release of biocide from silica microparticles in wood paint

Porous microparticles represent an attractive encapsulation platform as they provide a feasible route to a wide range of encapsulated chemical compounds. This assures an increased lifetime of the encapsulated compound by protecting it from the surrounding environment as well as providing a way to control the release rate. Porous microparticles encapsulating the commonly used biocide for wood protection, 3-iodoprop-2-ynyl N-butylcarbamate (IPBC), have been synthesized. The microparticles are spherical with an average size distribution of roughly 1 μm as determined by scanning electron microscopy (SEM). Determination of the release rate of the biocide from microcapsules incorporated into the paint film has been performed under diluted conditions. These experiments show that a slower release of the biocide can be obtained by encapsulation. Additionally, the microparticles have been shown to prolong the biocidal effect of the fungicide under accelerated weathering tests by protecting the biocide from UV-induced chemical degradation.     

Chronic obstructive pulmonary disease in patients with end‐stage kidney disease on hemodialysis

The objectives of this study were to assess the prevalence of chronic obstructive pulmonary disease (COPD) in hemodialysis patients with spirometry and to examine the effects of fluid removal by hemodialysis on lung volumes. Patients ≥18 years at two Danish hemodialysis centers were included. Forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and FEV₁/FVC ratio were measured with spirometry before and after hemodialysis. The diagnosis of COPD was based on both the GOLD criteria and the lower limit of normal criteria. There were 372 patients in treatment at the two centers, 255 patients (69%) completed spirometry before dialysis and 242 of these (65%) repeated the test after. In the initial test, 117 subjects (46%) had airflow limitation indicative of COPD with GOLD criteria and 103 subjects (40.4%) with lower limit of normal criteria; COPD was previously diagnosed in 24 patients (9%). Mean FVC and FEV₁ decreased mildly after dialysis (FVC: 2.84 to 2.79 L, P < 0.01. FEV₁: 1.97 to 1.93 L, P < 0.01) Hemodialysis did not affect the FEV₁/FVC ratio or number of subjects with airflow limitation indicative of COPD (113 vs. 120, P = 0.324; n = 242). COPD is a frequent and underdiagnosed comorbidity in patients on chronic hemodialysis. Spirometry should be considered in all patients on dialysis in order to address dyspnea adequately. Hemodialysis induced a small fall in mean FEV₁ and FVC, which was more pronounced in patients with little or no fluid removal, but the FEV₁/FVC ratio and the number of subjects with airflow limitation indicative of COPD were not affected by dialysis.     

The Effect of Alkali Ions on the Incorporation of Aluminum in the Calcium Silicate Hydrate (C–S–H) Phase Resulting from Portland Cement Hydration Studied by 29Si MAS NMR

The incorporation of aluminum in the calcium–silicate–hydrate (C–S–H) phases formed by hydration of three different white Portland cements has been investigated by ²⁹Si MAS NMR. The principal difference between the three cements is their bulk Al₂O₃ contents and quantities of alkali (Na⁺ and K⁺) ions. ²⁹Si MAS NMR allows indirect detection of tetrahedral Al incorporated in the silicate chains of the C–S–H structure by the resonance from Q²(1Al) sites. Analysis of the relative ²⁹Si NMR intensities for this site, following the hydration for the three cements from 0.5 d to 30 weeks, clearly reveals that the alkali ions promote the incorporation of Al in the bridging sites of the dreierketten structure of SiO₄ tetrahedra in the C–S–H phase. The increased incorporation of Al in the C–S–H phase with increasing alkali content in the anhydrous cement is in accord with a proposed substitution mechanism where the charge deficit, obtained by the replacement of Si⁴⁺ by Al³⁺ ions in the bridging sites, is balanced by adsorption/binding of alkali ions in the interlayer region most likely in the near vicinity of the AlO₄ tetrahedra. This result is further supported by similar ²⁹Si MAS NMR experiments performed for the white Portland cements hydrated in 0.30M NaOH and NaAlO₂ solutions.     

Investigation and simulation of a cross-flow air classifier

Extensive experimental tests and a computational study of the performance in a cross-flow air classifier have been carried out. A computational fluid dynamics (CFD) package—Fluent—is used to first understand and explain why the cuts or the sharpness of cut of this classifier are not as sharp as they ought to be, and then to optimize the geometry and operational conditions.

Flow fields of the classifier under various set-up conditions and geometry were measured by using laser Doppler anemometry (LDA). Using sieve analyses and the HELOS-laser method, the patterns of behaviour of separation parameters such as cut size and sharpness of cut have been investigated at different boundary conditions.

Using the Fluent package, a two-dimensional computational fluid dynamics model has been developed. The model is based on the Euler–Lagrangian approach. Different turbulence models have been tested. Both Fluent 4.5, with a structured grid, and Fluent 5.1, with structured and unstructured grids, have been used.

Discussions and analyses of the experimental, as well as the computational results, are presented. The simulation with a structured grid shows good agreement with experimental data, except for the sharpness of cut. The reasons of poor performance of the classifier have been found. The geometry is optimized and other conditions were also improved. The performance of the classifier is improved. The experimental observations together with the computed results should increase the depth of understanding of the underlying mechanisms.     

Intermittency-friendly and high-efficiency cogeneration: Operational optimisation of cogeneration with compression heat pump,flue gas heat recovery,and intermediate cold storage

This paper develops, implements, and applies a mathematical model for economic unit dispatch for a novel cogeneration concept (CHP-HP-FG-CS (CHP with compression heat pump and cold storage using flue gas heat)) that increases the plant’s operational flexibility. The CHP-HP-FG-CS concept is a high-efficiency and widely applicable option in distributed cogeneration better supporting the co-existence between cogenerators and intermittent renewables in the energy system.The concept involves integrating an efficient high-temperature compression heat pump that uses only waste heat recovered from flue gases as low-temperature heat source, and an intermediate cold thermal storage allowing for non-concurrent operation of the cogeneration unit and the heat pump unit.The model is applied for a paradigmatic case study that shows how the integration of a heat pump affects the operational strategy of a cogeneration plant. It is found that CHP-HP-FG-CS offers significant reductions in fuel consumption (?8.9%) and operational production costs (?11.4%). The plant’s fuel-to-energy efficiency increases from 88.9 to 95.5%, which is state-of-the-art.The plant’s intermittency-friendliness coefficient Rc improves only marginally due to the constrained nature of the low-temperature heat source and the associated small capacity of the heat pump unit. Significant improvements in Rc are found when increasing the heat pump capacity assuming the availability of an unconstrained heat source.     

On the electrochemical migration mechanism of tin in electronics

Electrochemical migration (ECM) of tin can result in the growth of a metal deposit with a dendritic structure from cathode to anode. In electronics, such growth can lead to short circuit of biased electrodes, potentially leading to intermittent or complete failure of an electronic device. In this paper, mechanistic aspects of ECM of tin are discussed in detail, using experimental results on ECM of tin in various environments and varying potential bias. Results on the formation of local pH changes by the electrodes and experiments observations are combined with thermodynamic stability of tin species as depicted in the Pourbaix diagram.