Search results for "Control system"
showing 10 items of 971 documents
Losses and depolarization of ultracold neutrons on neutron guide and storage materials
2017
At Institut Laue-Langevin (ILL) and Paul Scherrer Institute (PSI), we have measured the losses and depolarization probabilities of ultracold neutrons on various materials: (i) nickel-molybdenum alloys with weight percentages of 82/18, 85/15, 88/12, 91/9, and 94/6 and natural nickel Ni100, (ii) nickel-vanadium NiV93/7, (iii) copper, and (iv) deuterated polystyrene (dPS). For the different samples, storage-time constants up to $\ensuremath{\sim}460\phantom{\rule{0.16em}{0ex}}\mathrm{s}$ were obtained at room temperature. The corresponding loss parameters for ultracold neutrons, $\ensuremath{\eta}$, varied between $1.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $2.2\ifmmode\t…
Quantitative T 1 and proton density mapping with direct calculation of radiofrequency coil transmit and receive profiles from two-point variable flip…
2016
Quantitative T1 mapping of brain tissue is frequently based on the variable flip angle (VFA) method, acquiring spoiled gradient echo (GE) datasets at different excitation angles. However, accurate T1 calculation requires a knowledge of the sensitivity profile B1 of the radiofrequency (RF) transmit coil. For an additional derivation of proton density (PD) maps, the receive coil sensitivity profile (RP) must also be known. Mapping of B1 and RP increases the experiment duration, which may be critical when investigating patients. In this work, a method is presented for the direct calculation of B1 and RP from VFA data. Thus, quantitative maps of T1 , PD, B1 and RP can be obtained from only two …
Different acute effects of single-axis and multi-axis hand-arm vibration.
1996
Under laboratory conditions the effects of single-axis and multi-axis hand-arm vibration exposure on several strain parameters were tested in up to 20 male subjects. As parameters of these acute effects, the biodynamic vibration behavior of the hand-arm system, the electrical activity of the most affected muscle groups, the skin temperature, the vibration sensitivity of the fingertips, and the subjective vibration sensation were measured. When comparing simulated three-axis vibration exposure with single-axis vibration exposure, synergistic effects in the form of an increasing reaction could be found. It could be proven that the vector sum of the frequency-weighted acceleration in the three…
Improvement of the low energy neutrino factory
2010
The low energy neutrino factory has been proposed as a very sensitive setup for future searches for CP violation and matter effects. Here we study how its performance is affected when the experimental specifications of the setup are varied. Most notably, we have considered the addition of the "platinum'' nu(mu) -> nu(e) channel. We find that, while theoretically the extra channel provides very useful complementary information and helps to lift degeneracies, its practical usefulness is lost when considering realistic background levels. Conversely, an increase in statistics in the "golden'' nu(mu) -> nu(e) channel and, to some extent, an improvement in the energy resolution, lead to an import…
Physics Potential of the Fermilab NuMI beamline
2005
We explore the physics potential of the NuMI beamline with a detector located 10 km off-axis at a distant site (810 km). We study the sensitivity to $\sin^2 2 \theta_{13}$ and to the CP-violating parameter $\sin \delta$ as well as the determination of the neutrino mass hierarchy by exploiting the $\nu_\mu \to \nu_e$ and $\bar{\nu}_\mu \to \bar{\nu}_e$ appearance channels. The results are illustrated for three different experimental setups to quantify the benefits of increased detector sizes, proton luminosities and $\nu_e$ detection efficiencies.
Neutron-induced soft errors in advanced Flash memories
2008
Atmospheric neutrons are a known source of Soft Errors (SE), in static and dynamic CMOS memories. This paper shows for the first time that atmospheric neutrons are able to induce SE in Flash memories as well. Detailed experimental results provide an explanation linking the Floating Gate (FG) cell SE rate to the physics of the neutron-matter interaction. The neutron sensitivity is expected to increase with the number of bits per cell and the reduction of the feature size, but the SE issue is within the limit of current ECC capabilities and will remain so in the foreseeable future.
The UWB-OFDM Channel Analysis in Frequency
2009
In this paper, the ultra-wideband channel with orthogonal frequency division multiplexing (UWB-OFDM) is analyzed in the frequency domain. For UWB-OFDM channels with log-normal fading in the time domain, we show that the amplitude of each subcarrier can be approximated by a Nakagami-m random variable, where the fading parameter, the mean power and the correlation coefficient are expressed in terms of the following parameters: time arrival of the clusters, inter-arrival time of rays inside clusters, and power decay constants of rays and clusters.
Correlation effects in the total energy, the bulk modulus, and the lattice constant of a transition metal: Combined local-density approximation and d…
2009
We present an accurate implementation of total-energy calculations into the local-density approximation plus dynamical mean-field theory $(\text{LDA}+\text{DMFT})$ method. The electronic structure problem is solved through the full-potential linear muffin-tin orbital and Korringa-Kohn-Rostoker methods with a perturbative solver for the effective impurity suitable for moderately correlated systems. We have tested the method in detail for the case of Ni, and investigated the sensitivity of the results to the computational scheme and to the complete self-consistency. It is demonstrated that the $\text{LDA}+\text{DMFT}$ method can resolve a long-standing controversy between the LDA/generalized …
The <FONT FACE=Symbol>d</font> Expansion and the Principle of Minimal Sensitivity
1998
The d-expansion is a nonperturbative approach for field theoretic models wich combines the techniques of perturbation theory and the variational principle. Different ways of implemeting the principle of minimal sensitivity to the d-expansion produce in general different results for observables. For illustration we use the Nambu- Jona-Lasinio model for chiral symmetry restoration at finite density and compare results with those obtained with the Hartree-Fock approximation.
Spin-orbit torques in strained PtMnSb from first principles
2021
We compute spin-orbit torques (SOTs) in strained PtMnSb from first principles. We consider both tetragonal strain and shear strain. We find a strong linear dependence of the field-like SOTs on these strains, while the antidamping SOT is only moderately sensitive to shear strain and even insensitive to tetragonal strain. We also study the dependence of the SOT on the magnetization direction. In order to obtain analytical expressions suitable for fitting our numerical \textit{ab-initio} results we derive a general expansion of the SOT in terms of all response tensors that are allowed by crystal symmetry. Our expansion includes also higher-order terms beyond the usually considered lowest order…