Production of hot rolled dual-phase steel strip by coiling below martensite start temperature

The laboratory tests showed that a dual-phase steel can be produced on the basis of the chemical composition given here, providing the coiling temperature is below the martensite start temperature. It is then possible to dispense with an additional air cooling period on the runout table, which is mandatory with production concepts known up to now. The best mechanical properties are attained at a coiling temperature of 200°C. The final rolling temperature should be around A_r3 to avoid a heavy ferrite deformation without softening and, on the other hand, to reduce the yield stress increase caused by aging. Nitrogen aging can be suppressed by the addition of small amounts of titanium to bind nitrogen, forming a dispersion of titanium nitrides. The feasibility of this concept under production conditions was confirmed by means of hot rolling tests on a hot wide strip mill.     

Assigning Electronic States in Carbon Nanodots

Luminescent carbon nanodots exhibit enormous potential to be used as functional building blocks in energy conversion devices. Their intrinsic heterogeneity, however, hinders a thorough characterization and subsequently their applicability. In this work, the spectroscopic and electrochemical properties of prototype carbon nanodots were thoroughly studied in solution. Spectro‐electrochemical experiments revealed information on the spectral features of several oxidized and reduced species of our carbon nanodots. Therefore, these experiments were complemented with pulse radiolysis where the spectral signature of the one‐electron oxidized and reduced forms were identified. Both, electrochemically and radiolytically reduced and oxidized products show high reactivity in solution which correlates with an open‐shell character, detected by paramagnetic resonance spectroscopy. The herein presented studies help to understand the complex nature of carbon nanodots and serve to overcome difficulties in device fabrication.     

NMR Studies on Li+, Na+ and K+ Complexes of Orthoester Cryptand o-Me2-1.1.1

Cryptands, a class of three-dimensional macrobicyclic hosts ideally suited for accommodating small guest ions, have played an important role in the early development of supramolecular chemistry. In contrast to related two-dimensional crown ethers, cryptands have so far only found limited applications, owing in large part to their relatively inefficient multistep synthesis. We have recently described a convenient one-pot, template synthesis of cryptands based on O,O,O-orthoesters acting as bridgeheads. Here we report variable-temperature, ¹H-1D EXSY and titration NMR studies on lithium, sodium, and potassium complexes of one such cryptand (o-Me₂-1.1.1). Our results indicate that lithium and sodium ions fit into the central cavity of the cryptand, resulting in a comparably high binding affinity and slow exchange with the bulk. The potassium ion binds instead in an exo fashion, resulting in relatively weak binding, associated with fast exchange kinetics. Collectively, these results indicate that orthoester cryptands such as o-Me₂-1.1.1 exhibit thermodynamic and kinetic properties in between those typically found for classical crown ethers and cryptands and that future efforts should be directed towards increasing the binding constants.     

Comment on “Modeling and Validation of Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger”

We propose a significant correction to be applied on the modeling that appears in the article “Modeling and Validation of Nanoparticle Charging Efficiency of a Single-Wire Corona Unipolar Charger” by Chien et al., published in Aerosol Science and Technology 45(12), pages 1146–1179. It concerns the boundary condition based on Peek’s law, because the geometry of the main component of the corona charger is a needle and not a wire. The effects of adopting a more realistic modeling could be very important. Boundary conditions are a key factor in the resolution of the present problem, because they affect the results a lot. This could explain why the modeling results in that article do not fit very well the experimental ones. Our proposed modification could improve them.

Copyright 2014 American Association for Aerosol Research     

Design features of the Botlek rail tunnel in the Betuweroute

In this paper, the westernmost of the three bored tunnels in the Betuweroute is outlined: the twin bored Botlek Rail Tunnel. This paper deals with the specific local boundaries and the characteristic design features. Special emphasis is placed on the design of the shield tunnel boring machine. This evolved from a special proposal from the bidding contractors group BTC—a combination of Ballast Nedam, HBW, Strukton, Van Hattum en Blankevoort and Wayss & Freytag—which included an Earth pressure balanced shield (EPB-shield) instead of the slurry balanced shield that was foreseen in the reference design of the Client NS-RIB (Dutch Railways).