Search results for "Acceleration"
showing 10 items of 345 documents
Positioning in a flat two-dimensional space-time: the delay master equation
2010
The basic theory on relativistic positioning systems in a two-dimensional space-time has been presented in two previous papers [Phys. Rev. D {\bf 73}, 084017 (2006); {\bf 74}, 104003 (2006)], where the possibility of making relativistic gravimetry with these systems has been analyzed by considering specific examples. Here we study generic relativistic positioning systems in the Minkowski plane. We analyze the information that can be obtained from the data received by a user of the positioning system. We show that the accelerations of the emitters and of the user along their trajectories are determined by the sole knowledge of the emitter positioning data and of the acceleration of only one …
Applications of the pulsed gas stripper technique at the GSI UNILAC
2017
Abstract In the frame of an upgrade program for the GSI UNILAC, preparing it for the use as an injector system for FAIR, a pulsed gas stripper cell was developed. It utilizes the required low duty cycle by applying a pulsed gas injection instead of a continuous gas inlet. The resulting lower gas consumption rate enables the use of low-Z gas targets over a wide range of stripper target thicknesses. The setup enables an increased flexibility for the accelerator by allowing the gas stripper to be used in time-sharing beam operation matching the capabilities of the GSI UNILAC like the acceleration of different ion beams in quasi-parallel operation. Measured charge state distributions of 238 U, …
Wavelet analysis of experimental results for coupled structural–hydraulic behavior of the EURISOL target mock-up
2009
During test runs of the The European Isotope Separation On-Line (EURISOL) target mock-up performed in December 2008, data were recorded for strain gages and for acceleration sensors. In this paper, the applicability of wavelet analysis for detecting the onset and the status of flow-induced cavitation is investigated for the first time. Even under noisy conditions, the detection of incipient cavitation was possible when combining measurements with data from structural and fluid dynamic simulations. The distribution of coefficients of suitably selected wavelets yields a quantitative measure for the extent of cavitation in the EURISOL target mock-up under representative flow conditions. Withou…
Enhanced radiation pressure-assisted acceleration by temporally tuned counter-propagating pulses
2014
Within the last decade, laser-ion acceleration has become a field of broad interest. The possibility to generate short proton- or heavy ion bunches with an energy of a few tens of MeV by table-top laser systems could open new opportunities for medical or technical applications. Nevertheless, today's laser-acceleration schemes lead mainly to a temperature-like energy distribution of the accelerated ions, a big disadvantage compared to mono-energetic beams from conventional accelerators. Recent results 111 of laser-ion acceleration using radiation-pressure appear promising to overcome this drawback. In this paper, we demonstrate the influence of a second counter-propagating laser pulse intera…
Periodic Motion for an Imperfect Solar Sail Near an Asteroid
2014
In this paper we consider the Hill 3-body problem with the extra effect of the solar radiation pressure as a model for the motion of a solar sail close to an asteroid. To model the sail’s acceleration, we include both reflectivity and absorption of the sail’s material. We describe the most relevant dynamical properties of the system for different reflectivity and absorption coefficients as well as different fixed sail orientations. We show families of periodic orbits, describe how they relate to the parameters of the sail and discuss their stability.
Lifetimes of charged and neutralD mesons
1987
We have measured the lifetimes of hadronically produced charged and neutralD mesons using silicon microstrip detectors and an active silicon target in the NA32 spectrometer at the CERN SPS. We obtainτD± = (10.9±1.51.9)·10−13s andτD(−)10 = (4.2±0.5)·10−13s based on 59 and 90 fully reconstructed decays respectively, giving a ratioτD±/τD(−)10 of 2.6 ±0.5.
Fractional Tajimi–Kanai model for simulating earthquake ground motion
2014
The ground acceleration is usually modeled as a filtered Gaussian process. The most common model is a Tajimi–Kanai (TK) filter that is a viscoelastic Kelvin–Voigt unit (a spring in parallel with a dashpot) carrying a mass excited by a white noise (acceleration at the bedrock). Based upon the observation that every real material exhibits a power law trend in the creep test, in this paper it is proposed the substitution of the purely viscous element in the Kelvin Voigt element with the so called springpot that is an element having an intermediate behavior between purely elastic (spring) and purely viscous (dashpot) behavior ruled by fractional operator. With this choice two main goals are rea…
Force-Time Characteristics and Running Velocity of Male Sprinters during the Acceleration Phase of Sprinting
1988
Abstract In an effort to investigate the force-time characteristics during the acceleration phase of the sprint start, eight male sprinters were used as subjects. Runs up to 3 m were analyzed from film, and force-time parameters were measured on a force platform. In a starting stance the reaction time of the group was .118 ± .016 s and the force production lasted .342 ± .022 s. The maximal resultant force at the moment of maximal horizontal force was 19.3 ± 2.2 N x kg1, and the direction of the force was 32 ± 7°. In the very last instant before leaving the blocks the velocity of the center of gravity was 3.46 ± .32 m x s−1. In the first contact after leaving the blocks there was a braking p…
The evolution of the large-scale emission in Fanaroff-Riley type I jets
2011
Recent observations in X-rays and gamma-rays of nearby Fanaroff-Riley type I (FR I) radio galaxies have raised the question of the origin of the emission detected in the termination structures of their jets. The study of these structures can give information on the conditions for particle acceleration and radiation at the front shocks. In addition, an evolutionary scenario can help to disentangle the origin of the detected X-ray emission in young FR I sources, like some gigahertz peaked spectrum active galactic nuclei. This work focuses on the nature and detectability of the radiation seen from the termination regions of evolving FR I jets. We use the results of a relativistic, two-dimensio…
A dynamical dark energy model with a given luminosity distance
2011
It is assumed that the current cosmic acceleration is driven by a scalar field, the Lagrangian of which is a function of the kinetic term only, and that the luminosity distance is a given function of the red-shift. Upon comparison with Baryon Acoustic Oscillations (BAOs) and Cosmic Microwave Background (CMB) data the parameters of the models are determined, and then the time evolution of the scalar field is determined by the dynamics using the cosmological equations. We find that the solution is very different than the corresponding solution when the non-relativistic matter is ignored, and that the universe enters the acceleration era at larger red-shift compared to the standard $\Lambda CD…