Size distribution of polydispersed aerosols during condensation in the continuum regime: Analytic approach using the lognormal moment method

An analytic solution for polydispersed aerosol condensation was obtained in the continuum regime. In this new approach, lower order moments, as compared to a previous study, were used to the log-normal aerosol size distribution, in order to obtain an analytical solution. The resultant analytic solution based on the lognormal size distribution was compared with the exact solution and proved to be in good agreement. The obtained solution was also found to be consistent to a greater degree with the exact solution was the previous analytic moment solution for the polydispersed aerosol condensation process. This is particularly true for cases in which broad size distributions exist.     

Simulation of sulfide buildup in wastewater and atmosphere of sewer networks.

A model concept for prediction of sulfide buildup in sewer networks is presented. The model concept is an extension to--and a further development of--the WATS model (Wastewater Aerobic-anaerobic Transformations in Sewers), which has been developed by Hvitved-Jacobsen and co-workers at Aalborg University. In addition to the sulfur cycle, the WATS model simulates changes in dissolved oxygen and carbon fractions of different biodegradability. The sulfur cycle was introduced via six processes: 1. sulfide production taking place in the biofilm covering the permanently wetted sewer walls; 2. biological sulfide oxidation in the permanently wetted biofilm; 3. chemical and biological sulfide oxidation in the water phase; 4. sulfide precipitation with metals present in the wastewater; 5. emission of hydrogen sulfide to the sewer atmosphere and 6. adsorption and oxidation of hydrogen sulfide on the moist sewer walls where concrete corrosion may take place.     

Small volume PCR in PDMS biochips with integrated fluid control and vapour barrier

In this paper we demonstrate a new method for microfabricating PDMS devices that controls vapour diffusion, thereby reducing water loss at elevated temperatures and greatly increasing the reliability of the PCR. In the past, the vapour and liquid diffusion properties of the PDMS material in microfluidic devices have impaired performance. We show that this water loss is primarily due to vapour diffusion from the PDMS biochip and by implanting a polyethylene vapour barrier layer in the PDMS, the overall fluid loss was almost eliminated (reduced by a factor of 3). We have also developed a procedure to ensure irreversible bonding between the PDMS and the implant. With this improved microfabrication method we demonstrate the feasibility and advantages of performing small volume PCR genetic amplification (i.e. with less than 2 μl of PCR sample) within a PDMS–glass hybrid biochip. Diaphragm pumps and pinch-off valves were integrated in the system and these enabled fluid retention during the amplification stage and will facilitate higher levels of on-chip automation.     

Response kinetics of temperature-independent resistive oxygen sensor formulations: a comparative study

This contribution compares the response kinetics of two temperature-independent resistive oxygen sensor formulations: LaCu_0.3Fe_0.7O_3−δ (LCF) and La_0.05Sr_0.95Ti_0.65Fe_0.35O_3−δ (LSTF). Screen-printed thick film sensor specimens were prepared. Sensor characteristics towards oxygen were determined, and additional measurements in the frequency domain were realized: the former indicate a fast and nearly temperature-independent response of LCF and LSTF compositions in the temperature range between 750 and 900 °C. The latter allow conclusions on the underlying sensing mechanism. Whereas oxygen sensitivity of LSTF is exclusively controlled by a reaction step, response of LCF is governed by reaction only at lower temperatures. At higher temperatures, a diffusion process becomes limiting. This different behavior is attributed to different microstructures of the sensitive films.     

Elastic and optical properties of BeS,BeSe and BeTe under pressure

We have performed the first principles full-potential linearized augmented plane wave calculations (FP-LAPW) with density functional theory in local density approximations (LDA), in aim to determine and to predict the pressure dependence of structural and optical properties of zinc-blende BeS, BeSe and BeTe compounds. The elastic constant, refractive index and its variation with hydrostatic pressure are well described.     

Study of fuel insolubles: Formation conditions and characterization of copper compounds

The solids formed in the systems containing copper in different oxidation states, in the presence and absence of hexanoic acid and dodecanethiol, together and separately, at room temperature, were studied. The experiments were performed in a mineral oil matrix, free of sulfur compounds and metals; a diesel oil matrix; and the reagents alone, without any matrix. The deposits formed were analyzed by elemental analysis (EA), infrared spectroscopy (IR), thermogravimetric analysis (TGA) and total copper by inductively coupled plasma-optical emission spectrometry (ICP-OES), for their identification and determination of the probable structures. In samples containing both hexanoic acid and dodecanethiol, when there is copper(I), anhydrous copper(II) hexanoate is preferentially formed, but in samples of copper(II), copper(II) mercaptate is formed first. In samples of metallic copper in mineral oil matrix, no deposit formations occur. In all cases in which deposits were formed, they were the same as in diesel oil matrix.     

Modelling of aluminium scrap melting in a rotary furnace

In a typical secondary aluminium process, the scrap feed is charged into a rotary furnace, melting and mixing under a salt layer in the furnace. The complexity in such a pyrometallurgical process is due not only to the high temperature effect and the complex chemical reactions, but also to the highly complex scrap feed with a distributed nature of aluminium types, compositions, sizes, shapes, paintings and other contaminations. In this study, user sub-models, which represent the distributed nature of the scrap feed, were developed and integrated into a computational fluid dynamics (CFD) based process model of a rotary furnace. Aluminium scrap was classified into several groups depending on their properties, e.g., size, establishing a discretized population balance model (PBM). The melting behaviour of aluminium scrap was simulated with the exchange of information between the melting sub-model and the CFD calculations. In addition, the sub-model for scrap burn-off was also developed and integrated in the CFD framework providing distributed burn-off rates. Simulations of the melting process were made to model the flow and thermal phenomena in such a furnace, and the influence of the scrap size, shape and quality, as well as burn-off rate were studied.