Triple crystallization behavior of fractionated ethylene/α-olefin copolymers of different catalyst type

Non-isothermal crystallization processes in fractions of Ziegler-Natta (ZN) and single site (SS) based ethylene/1-butene and ethylene/1-hexene copolymers have been studied by differential scanning calorimetry (DSC). Fractionation of used copolymers was done according to molar mass (MM) and composition (comonomer content). It was observed in DSC scans that for fractions with high MM (larger than 10 kg/mol) in addition to the main high-temperature crystallization peak (HTCP), a very-low temperature crystallization peak (VLTCP) is present at temperatures in between 60–75 °C. Such peak is absent for the first fractions having very-low MM. The partial crystallinity and peak temperatures, obtained from VLTCP, increase with MM and level off at MM around 60–100 kg/mol. It was found that the crystallinity as related to the area of the VLTCP is catalyst type dependent, and is higher for the SS catalyst compared to the ZN. Peak temperature of VLTCP linearly decreases with increasing comonomer content at fixed MM while the partial crystallinity practically does not change with comonomer content.     

Parameterizing the formation rate of new particles: The effect of nuclei self-coagulation

The study is based on the work of Lehtinen et al. (2007) [Lehtinen, K. E. J., Dal Maso, M., Kulmala, M., & Kerminen, V.-M. (2007). Estimating nucleation rates from apparent particle formation rates and vice versa: Revised formulation of the Kerminen–Kulmala equation. Journal of Aerosol Science, 38, 988–994] who derived formulae connecting “real” and “apparent” nucleation rates. The parameterization neglected self-coagulation of newly formed particles and clusters, however, and here we have extended the previous work to include the effects of the self-coagulation. Our main focus was on calculating the “apparent” nucleation rate, i.e. the rate at which particles appear at sizes larger than the critical cluster size, as a function of the “real” nucleation rate. The revised parameterization was comprehensively tested against an explicit aerosol dynamic model at diverse atmospheric conditions. It was found out that nuclei self-coagulation has importance to new particle formation when J_nuc/Q>10^?2 where J_nuc is the nucleation rate and Q is the production rate of condensable vapours. This corresponds to the nucleation rates ranging from >10 cm^?3 s^?1 (free troposphere) to >10⁴ cm^?3 s^?1 (polluted boundary layer) depending on the atmospheric conditions. In terms of the particle number concentration, the calculations performed with the explicit model and the predictions of revised parameterization were generally within an order of magnitude. Several issues related to applications in large-scale models were also discussed.     

A CRITICAL REVIEW OF THE CONVENTIONAL HOT PLATEN PRESSING METHOD OF LABORATORY PRESS DRYING

The functioning of a conventional heated platen laboratory press for paper or board press dry experiments is considered analytically and in the light of experimental results from the literature. A press dry sample dries so that the evaporation zone recedes from the edges toward the center. Since the dwell time of the web within a certain moisture content range influences the resulting strength characteristics, a conventional press dry experiment will not produce a uniformly strong web. To study the possible distribution of the strength deviation, a strength development function is generated and used in computer simulation of a web being press dried. The results emphasize the importance of dwell time as a factor in press dry strength devel oprnent. Finally, basic principles are reviewed or evolving an improved press dry laboratory device, and a model is proposed.     

Emission Rates Due to Indoor Activities: Indoor Aerosol Model Development,Evaluation, and Applications

This study presents an indoor aerosol model based on size-resolved and multi-compartment approach. The current indoor aerosol model is also developed with a semi-empirical technique to estimate the emission rates due to indoor sources of aerosol particles. We present in this study a methodology to predict and estimate the best-fit input parameters for the current indoor aerosol model. The performance of the current indoor aerosol model in its single-compartment form was evaluated against previously measured indoor-outdoor aerosol data sets from an office room with mechanical ventilation and a family house with natural ventilation. The indoor aerosol model simulations show that the current methodology used to predict the best-fit input parameters to the indoor aerosol model is efficient. As expected, the penetration factor, aerosol particle deposition, and ventilation rate are the most important parameters in the indoor-outdoor relationship of aerosol particles transport. The emission rate analysis showed that fine aerosol particles production was as high as 26 particle/cm ³ s during wood burning in a fireplace. The emission rate was about eight times this value during grilling in a fireplace and sauna heating. Indoor activities take place in another room may significantly increase the aerosol particle concentrations in other rooms in the building. Therefore, it is recommended to use extra air cleaners in houses to reduce the number concentrations of emitted aerosol particles. The quantitative and qualitative results obtained by the current indoor aerosol model in this study are building and condition specific. Applying the current model to a broad range of conditions and previously measured indoor-outdoor aerosol data sets provides better understanding of aerosol particle characteristics indoors, especially regarding the aerosol particles produced during different indoor activities.     

Estimating the Viscosity Range of SOA Particles Based on Their Coalescence Time

Copyright 2014 American Association for Aerosol Research     

Effect of crosslinking on the physicochemical properties of proton conducting PVDF-g-PSSA membranes

Poly(vinylidene fluoride) (PVDF) membranes, radiation-grafted with styrene and sulfonated, were studied as a candidate material for polymer electrolyte fuel cell (PEFC). In particular the effect of the use of crosslinkers in the polymer structure was investigated using bis(vinyl phenyl)ethane (BVPE) and divinylbenzene (DVB) as reagents. Water uptake in the H+ form, proton conductivity and ion exchange capacity of the PVDF-g-PSSA membranes, as well as transport properties of oxygen and hydrogen were determined at room temperature. Crosslinking with DVB resulted in a more pronounced decrease in the properties; the use of BVPE had no significant influence. Even on the permeation of oxygen and hydrogen the BVPE had little effect: the diffusion coefficient and solubility remained at the same level as for the non-crosslinked membranes. Increasing the membrane thickness was found to be at least as effective in reducing the oxygen permeation rate as using crosslinkers.     

Landau–Zener Interferometry in a Cooper-Pair Box

In a driven system, a sequence of Landau–Zener transitions occur, and they may interfere with each other. We present experimental evidence of quantum interference effects in a superconducting charge qubit, a Cooper-pair box, where the LZ tunneling occurs at the charge degeneracy. By employing weak capacitive monitoring, we observe interference between consecutive LZ tunneling events.