Technical University of Berlin

About: Technical University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Quantum dot & Laser. The organization has 27292 authors who have published 59342 publications receiving 1414623 citations. The organization is also known as: Technische Universität Berlin & TU Berlin.

Comparison of 2.3-kV Medium-Voltage Multilevel Converters for Industrial Medium-Voltage Drives

Abstract: This paper compares the expense of power semiconductors and passive components of a (2.3 kV, 2.4 MVA) two-level, three-level neutral-point-clamped, three-level flying-capacitor, four-level flying-capacitor, and five-level series-connected H-bridge voltage source converter on the basis of the state-of-the-art 6.5-, 3.3-, 2.5-, and 1.7-kV insulated gate bipolar transistors for industrial medium-voltage drives. The power semiconductor losses, the loss distribution, the installed switch power, the design of flying capacitors, and the components of an sine filter for retrofit applications are considered.

Quantum and Information Thermodynamics: A Unifying Framework Based on Repeated Interactions

Abstract: Nanomachines are subject to random thermal and quantum fluctuations that are not captured by traditional thermodynamic theory. A new theoretical investigation offers a step toward a unified nanoscale theory by showing how externally prepared systems (e.g., atoms in an optical cavity or DNA bases in an enzyme reaction) that interact with a nanoscopic device can be a source of nonequilbrium free energy.

Power-efficient rendez-vous schemes for dense wireless sensor networks

Abstract: We propose two generic rendez-vous schemes for dense wireless sensor networks, including the transmitter- and receiver-initiated cycled receiver schemes. Our studies include the analyses and comparisons of their power efficiencies, especially under a fading channel as a realistic physical layer. We believe our modeling strategies as well as the results are applicable to any rendez-vous scheme of the cycled- receiver nature. The paper further proposes precise guidelines and optimization strategies for synchronization in wireless sensor networks.

Zone-boundary phonons in hexagonal and cubic GaN

Abstract: We present results of second-order Raman-scattering experiments on hexagonal and cubic GaN covering the acoustic and the optical overtone spectral region. Based on a comparison of the experimental scattering data with the calculated phonon-dispersion curves as well as the group-theoretically derived selection rules, we were able to assign the observed structures to particular phonon branches and determined the points in the Brillouin zone from which the scattering originates. Our measurements reveal the energies of acoustic zone-boundary phonons in hexagonal GaN.

Mechanism for the formation of elemental sulfur from aqueous sulfide in chemical and microbiological desulfurization processes

Abstract: A detailed reaction mechanism is proposed for the formation of crystalline elemental sulfur from aqueous sulfide by oxidation with transition-metal ions like VV, FeIII, CuII, etc. The first step is the formation of HS• radicals by one-electron oxidation of HS- ions. These radicals exist at pH values near 7 mainly as S•-. Their spontaneous decay results in the formation of the disulfide ion S22-. The further oxidation of disulfide either by S•- radicals or by the transition-metal ions yields higher polysulfide ions from which the homocyclic sulfur molecules S6, S7, and S8 are formed. In water these hydrophobic molecules form clusters which grow to droplets of liquid sulfur (sulfur sol). Depending on the composition of the aqueous phase, crystallization of the liquid sulfur as either α- or β-S8 is rapid or delayed. Surfactants delay this solidification, while certain cations promote it. All these reactions are proposed to take place in desulfurization plants working by the Stretford, Sulfolin, Lo-Cat, SulFe...