9,909 research outputs found
Wave conditions in the Baltic Proper and in the Gulf of Finland during windstorm Gudrun
International audienceWave conditions in the northern Baltic Proper during windstorm Erwin/Gudrun (January 2005) are analysed based on in situ measurements in three locations and output of operational wave models from the German Weather Forecast Service, the Danish Meteorological Institute and the Finnish Institute of Marine Research. The measured significant wave height reached 7.2 m in the northern Baltic Proper and 4.5 m in the Gulf of Finland. The roughest wave conditions, estimated from the comparison of the forecast and measured data, occurred remote from the sensors, off the coasts of Saaremaa and Latvia where the significant wave height was about 9.5 m. Peak periods exceeded 12 s in a large part of the northern Baltic Proper and in the central part of the Gulf of Finland
Experimental and numerical analysis of the flow behaviour of magnesium wrought alloy AZ31 for deep drawing processes at elevated temperatures
In the present paper, the flow behaviour of the magnesium wrought alloy AZ31 is analysed experimentally and numerically. Especial in deep drawing processes is the knowledge of the flow behaviour important. Depending on the type and size of the hardening and softening of a material, the process parameters such as temperature and sheet thickness must be adjusted to produce a flawless part. The material behaviour of magnesium is different compared to conventional steels, because the hardening and softening effects are changing highly with increasing temperature. For this purpose, yield curves were recorded experimentally at different temperatures by means of layer compression tests. Following the yield curves were converted based on the principle of the plastic work equivalence for finite element simulations (FEA). For validation, numerical simulations of the layer compression test at elevated temperature using the converted yield curve were carried out
Characterization of red wines aged with oak chip in the São Francisco Valley, Brazil.
This research aimed to characterize the physicochemical composition of Syrah tropical wines aged with oak chip addition
First Steps into Practical Engineering for Freshman Students Using MATLAB and LEGO Mindstorms Robots
Besides lectures on basic theoretical topics, contemporary teaching and learning concepts for first semester students give more and more consideration to practically motivated courses. In this context, a new first-year introductory course in practical engineering has been established in the first semester curriculum of Electrical Engineering at RWTH Aachen University, Germany. Based on a threefold learning concept, programming skills in MATLAB are taught to 309 students within a full-time block course laboratory. The students are encouraged to transfer known mathematical basics to program algorithms and real-world applications performed by 100 LEGO Mindstorms robots. A new MATLAB toolbox and twofold project tasks have been developed for this purpose by a small team of supervisors. The students are supervised by over 60 tutors at 23 institutes, and are encouraged to create their own robotics applications. We describe how the laboratory motivates the students to act and think like engineers and to solve real-world issues with limited resources. The evaluation results show that the proposed practical course concept successfully boosts students’ motivation, advances their programming skills, and encourages the peer learning process.
Technical design and commissioning of the KATRIN large-volume air coil system
The KATRIN experiment is a next-generation direct neutrino mass experiment
with a sensitivity of 0.2 eV (90% C.L.) to the effective mass of the electron
neutrino. It measures the tritium -decay spectrum close to its endpoint
with a spectrometer based on the MAC-E filter technique. The -decay
electrons are guided by a magnetic field that operates in the mT range in the
central spectrometer volume; it is fine-tuned by a large-volume air coil system
surrounding the spectrometer vessel. The purpose of the system is to provide
optimal transmission properties for signal electrons and to achieve efficient
magnetic shielding against background. In this paper we describe the technical
design of the air coil system, including its mechanical and electrical
properties. We outline the importance of its versatile operation modes in
background investigation and suppression techniques. We compare magnetic field
measurements in the inner spectrometer volume during system commissioning with
corresponding simulations, which allows to verify the system's functionality in
fine-tuning the magnetic field configuration. This is of major importance for a
successful neutrino mass measurement at KATRIN.Comment: 32 pages, 16 figure
Semileptonic B Decays and Determination of |Vub|
Semileptonic decays of the B mesons provide an excellent probe for the weak
and strong interactions of the bottom quark. The large data samples collected
at the B Factories have pushed the experimental studies of the semileptonic B
decays to a new height and stimulated significant theoretical developments. I
review recent progresses in this fast-evolving field, with an emphasis on the
determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element
|Vub|.Comment: 16 pages, 4 figures, accepted by Mod. Phys. Lett.
Weak Long-Ranged Casimir Attraction in Colloidal Crystals
We investigate the influence of geometric confinement on the free energy of
an idealized model for charge-stabilized colloidal suspensions. The mean-field
Poisson-Boltzmann formulation for this system predicts pure repulsion among
macroionic colloidal spheres. Fluctuations in the simple ions' distribution
provide a mechanism for the macroions to attract each other at large
separations. Although this Casimir interaction is long-ranged, it is too weak
to influence colloidal crystals' dynamics.Comment: 5 pages 2 figures ReVTe
Chirp mitigation of plasma-accelerated beams using a modulated plasma density
Plasma-based accelerators offer the possibility to drive future compact light
sources and high-energy physics applications. Achieving good beam quality,
especially a small beam energy spread, is still one of the major challenges.
For stable transport, the beam is located in the focusing region of the
wakefield which covers only the slope of the accelerating field. This, however,
imprints a longitudinal energy correlation (chirp) along the bunch. Here, we
propose an alternating focusing scheme in the plasma to mitigate the
development of this chirp and thus maintain a small energy spread
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