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Search Results: 1 - 10 of 654665 matches for " A. J. Franke "
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Full dynamic resolution low lower DA-Converters for flat panel displays
C. Saas,J. Franke,J. A. Nossek
Advances in Radio Science : Kleinheubacher Berichte , 2006,
Abstract: It has been shown that stepwise charging can reduce the power dissipated in the source drivers of a flat panel display. However the solution presented only provided a dynamic resolution of 3 bits which is not sufficient for obtaining a full color resolution display. In this work a further development of the basic idea is presented. The stepwise charging is increased to 4 bits and supplemented by a current source to provide an output signal which represents an 8 bit value with sufficient accuracy. Within this work the application is an AM-OLED flat panel display, but the concept can easily be applied to other display technologies like TFT-LCD as well.
Modeling variations of marine reservoir ages during the last 45 000 years
J. Franke, A. Paul,M. Schulz
Climate of the Past (CP) & Discussions (CPD) , 2008,
Abstract: When dating marine samples with 14C, the reservoir-age effect is usually assumed to be constant, although atmospheric 14C production rate and ocean circulation changes cause temporal and spatial reservoir-age variations. These lead to dating errors, which can limit the interpretation of cause and effect in paleoclimate data. We used a global ocean circulation model forced by transient atmospheric Δ14C variations to calculate reservoir ages for the last 45 000 years for a present day-like and a last glacial maximum-like ocean circulation. A ~30% reduced Atlantic meridonal overturning circulation leads to increased reservoir ages by up to ~500 years in high latitudes. Temporal variations are proportional to the absolute value of the reservoir age; regions with large reservoir age also show large variation. Temporal variations range between ~300 years in parts of the subtropics and ~1000 years in the Southern Ocean. For tropical regions, which are generally assumed to have nearly stable reservoir ages, the model suggests variations of several hundred years.
Modeling variations of marine reservoir ages during the last 45 000 years
J. Franke,A. Paul,M. Schulz
Climate of the Past Discussions , 2008,
Abstract: When dating marine samples with 14C, the reservoir-age effect is usually assumed to be constant, although atmospheric 14C production rate and ocean circulation changes cause temporal and spatial reservoir-age variations. These lead to dating errors, which can limit the interpretation of cause and effect in paleoclimate data. We used a global ocean circulation model forced by transient atmospheric Δ14C variations to calculate reservoir ages for the last 45 000 years for a present day-like and a last glacial maximum-like ocean circulation. A ~30% reduced Atlantic meridonal overturning circulation leads to increased reservoir ages by up to ~500 years in high latitudes. Temporal variations are proportional to the absolute value of the reservoir age; regions with large reservoir age also show large variation. Temporal variations range between ~300 years in parts of the subtropics and ~1000 years in the Southern Ocean. For tropical regions, which are generally assumed to have nearly stable reservoir ages, the model suggests variations of several hundred years.
Size Dependence of Domain Pattern Transfer in Multiferroic Heterostructures
Kévin J. A. Franke,Sebastiaan van Dijken
Physics , 2013, DOI: 10.1103/PhysRevLett.112.017201
Abstract: Magnetoelectric coupling in multiferroic heterostructures can produce large lateral modulations of magnetic anisotropy enabling the imprinting of ferroelectric domains into ferromagnetic films. Exchange and magnetostatic interactions within ferromagnetic films oppose the formation of such domains. Using micromagnetic simulations and a 1-D model, we demonstrate that competing energies lead to the breakdown of domain pattern transfer below a critical domain width. Moreover, rotation of the magnetic field results in abrupt transitions between two scaling regimes with different magnetic anisotropy.
Ship emitted NO2 in the Indian Ocean: comparison of model results with satellite data
K. Franke, A. Richter, H. Bovensmann, V. Eyring, P. J ckel, P. Hoor,J. P. Burrows
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2009,
Abstract: The inventory of NOx emission from international shipping has been evaluated by comparing NO2 tropospheric columns derived from the satellite instruments SCIAMACHY (January 2003 to February 2008), GOME (January 1996 to June 2003), and GOME-2 (March 2007 to February 2008) to NO2 columns calculated with the atmospheric chemistry general circulation model ECHAM5/MESSy1 (January 2000 to October 2005). For both measurements and model consistently the tropospheric excess method was used to obtain mean NO2 columns over the shipping lane from India to Indonesia, and over two ship free regions, the Bay of Bengal and the central Indian Ocean. The long-term data set from SCIAMACHY yields the first monthly analysis of ship induced NO2 enhancements in the Indian Ocean. Comparison of data from the three instruments and in addition OMI reveals differences between the datasets which are discussed with respect to the diurnal cycle of NO2 and the increase in shipping traffic over the time period studied. In general, the model simulates the differences between the regions affected by ship pollution and ship free regions reasonably well. Minor discrepancies between model results and satellite data were identified during biomass burning seasons in March to May over India and the Indochinese Peninsula and August to October over Indonesia. We conclude that the NOx ship emission inventory used in this study is a good approximation of NOx ship emissions in the Indian Ocean for the years 2002 to 2007. It assumes that around 6 Tg(N) yr 1 are emitted by international shipping globally, resulting in 90 Gg(N) yr 1 in the region of interest when using Automated Mutual Assistance Vessel Rescue System (AMVER) as spatial proxy. A second model run using lower ship emissions estimates of 3–4 Tg(N) yr 1 globally results in poorer agreement with the satellite data.
Dynamic Jahn-Teller effect in electron transport through single C60 molecules
T. Frederiksen,K. J. Franke,A. Arnau,G. Schulze,J. I. Pascual,N. Lorente
Physics , 2008, DOI: 10.1103/PhysRevB.78.233401
Abstract: Scanning tunneling spectra on single C60 molecules that are sufficiently decoupled from the substrate exhibit a characteristic fine structure, which is explained as due to the dynamic Jahn-Teller effect. Using electron-phonon couplings extracted from density functional theory we calculate the tunneling spectrum through the C60- anionic state and find excellent agreement with measured data.
Unoccupied states of individual silver clusters and chains on Ag(111)
A. Sperl,J. Kroeger,N. Neel,H. Jensen,R. Berndt,A. Franke,E. Pehlke
Physics , 2007, DOI: 10.1103/PhysRevB.77.085422
Abstract: Size-selected silver clusters on Ag(111) were fabricated with the tip of a scanning tunneling microscope. Unoccupied electron resonances give rise to image contrast and spectral features which shift toward the Fermi level with increasing cluster size. Linear assemblies exhibit higher resonance energies than equally sized compact assemblies. Density functional theory calculations reproduce the observed energies and enable an assignment of the resonances to hybridized atomic 5s and 5p orbitals with silver substrate states.
Quantum Fields on the Light Front, Formulation in Coordinates close to the Light Front, Lattice Approximation
E. -M. Ilgenfritz,S. A. Paston,H. -J. Pirner,E. V. Prokhvatilov,V. A. Franke
Mathematics , 2006, DOI: 10.1007/s11232-006-0091-8
Abstract: We review the fundamental ideas of quantizing a theory on a Light Front including the Hamiltonian approach to the problem of bound states on the Light Front and the limiting transition from formulating a theory in Lorentzian coordinates (where the quantization occurs on spacelike hyperplanes) to the theory on the Light Front, which demonstrates the equivalence of these variants of the theory. We describe attempts to find such a form of the limiting transition for gauge theories on the Wilson lattice.
Experimental studies on particle emissions from cruising ship, their characteristic properties, transformation and atmospheric lifetime in the marine boundary layer
A. Petzold, J. Hasselbach, P. Lauer, R. Baumann, K. Franke, C. Gurk, H. Schlager,E. Weingartner
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: Particle emissions from ship engines and their atmospheric transformation in the marine boundary layer (MBL) were investigated in engine test bed studies and in airborne measurements of expanding ship plumes. During the test rig studies, detailed aerosol microphysical and chemical properties were measured in the exhaust gas of a serial MAN B&W seven-cylinder four-stroke marine diesel engine under various load conditions. The emission studies were complemented by airborne aerosol transformation studies in the plume of a large container ship in the English Channel using the DLR aircraft Falcon 20 E-5. Observations from emission studies and plume studies combined with a Gaussian plume dispersion model yield a consistent picture of particle transformation processes from emission to atmospheric processing during plume expansion. Particulate matter emission indices obtained from plume measurements are 8.8±1.0×1015(kg fuel) 1 by number for non-volatile particles and 174±43 mg (kg fuel) 1 by mass for Black Carbon (BC). Values determined for test rig conditions between 85 and 110% engine load are of similar magnitude. For the total particle number including volatile compounds no emission index can be derived since the volatile aerosol fraction is subject to rapid transformation processes in the plume. Ship exhaust particles occur in the size range Dp<0.3 μm, showing a bi-modal structure. The combustion particle mode is centred at modal diameters of 0.05 μm for raw emissions to 0.10 μm at a plume age of 1 h. The smaller-sized volatile particle mode is centred at Dp≤0.02 μm. From the decay of ship exhaust particle number concentrations in an expanding plume, a maximum plume life time of approx. 24 h is estimated for a well-mixed marine boundary layer.
Electric-field control of magnetic domain wall motion and local magnetization reversal
Tuomas H. E. Lahtinen,Kévin J. A. Franke,Sebastiaan van Dijken
Physics , 2011, DOI: 10.1038/srep00258
Abstract: Spintronic devices currently rely on magnetic switching or controlled motion of domain walls by an external magnetic field or spin-polarized current. Achieving the same degree of magnetic controllability using an electric field has potential advantages including enhanced functionality and low power consumption. Here, we report on an approach to electrically control local magnetic properties, including the writing and erasure of regular ferromagnetic domain patterns and the motion of magnetic domain walls, in multiferroic CoFe-BaTiO3 heterostructures. Our method is based on recurrent strain transfer from ferroelastic domains in ferroelectric media to continuous magnetostrictive films with negligible magnetocrystalline anisotropy. Optical polarization microscopy of both ferromagnetic and ferroelectric domain structures reveals that domain correlations and strong inter-ferroic domain wall pinning persist in an applied electric field. This leads to an unprecedented electric controllability over the ferromagnetic microstructure, an accomplishment that produces giant magnetoelectric coupling effects and opens the way to multiferroic spintronic devices.
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