2,401 research outputs found
Analysis of ring laser gyroscopes including laser dynamics
Inertial sensors stimulate very large interest, not only for their
application but also for fundamental physics tests. Ring laser gyros, which
measure angular rotation rate, are certainly among the most sensitive inertial
sensors, with excellent dynamic range and bandwidth. Large area ring laser
gyros are routinely able to measure fractions of prad/s, with high duty cycle
and bandwidth, providing fast, direct and local measurement of relevant
geodetic and geophysical signals. Improvements of a factor would open
the windows for general relativity tests, as the GINGER project, an Earth based
experiment aiming at the Lense-Thirring test at level. However, it is
well known that the dynamics of the laser induces non-linearities, and those
effects are more evident in small scale instruments. Sensitivity and accuracy
improvements are always worthwhile, and in general there is demand for high
sensitivity environmental study and development of inertial platforms, where
small scale transportable instruments should be used. We discuss a novel
technique to analyse the data, aiming at studying and removing those
non-linearity. The analysis is applied to the two ring laser prototypes GP2 and
GINGERINO, and angular rotation rate evaluated with the new and standard
methods are compared. The improvement is evident, it shows that the
back-scatter problem of the ring laser gyros is negligible with a proper
analysis of the data, improving the performances of large scale ring laser
gyros, but also indicating that small scale instruments with sensitivity of
nrad/s are feasible.Comment: 9 pages and 7 figure
Anomalous resilient to decoherence macroscopic quantum superpositions generated by universally covariant optimal quantum cloning
We show that the quantum states generated by universal optimal quantum
cloning of a single photon represent an universal set of quantum superpositions
resilient to decoherence. We adopt Bures distance as a tool to investigate the
persistence ofquantum coherence of these quantum states. According to this
analysis, the process of universal cloning realizes a class of quantum
superpositions that exhibits a covariance property in lossy configuration over
the complete set of polarization states in the Bloch sphere.Comment: 8 pages, 6 figure
Local and Global Analytic Solutions for a Class of Characteristic Problems of the Einstein Vacuum Equations in the "Double Null Foliation Gauge"
The main goal of this work consists in showing that the analytic solutions
for a class of characteristic problems for the Einstein vacuum equations have
an existence region larger than the one provided by the Cauchy-Kowalevski
theorem due to the intrinsic hyperbolicity of the Einstein equations. To prove
this result we first describe a geometric way of writing the vacuum Einstein
equations for the characteristic problems we are considering, in a gauge
characterized by the introduction of a double null cone foliation of the
spacetime. Then we prove that the existence region for the analytic solutions
can be extended to a larger region which depends only on the validity of the
apriori estimates for the Weyl equations, associated to the "Bel-Robinson
norms". In particular if the initial data are sufficiently small we show that
the analytic solution is global. Before showing how to extend the existence
region we describe the same result in the case of the Burger equation, which,
even if much simpler, nevertheless requires analogous logical steps required
for the general proof. Due to length of this work, in this paper we mainly
concentrate on the definition of the gauge we use and on writing in a
"geometric" way the Einstein equations, then we show how the Cauchy-Kowalevski
theorem is adapted to the characteristic problem for the Einstein equations and
we describe how the existence region can be extended in the case of the Burger
equation. Finally we describe the structure of the extension proof in the case
of the Einstein equations. The technical parts of this last result is the
content of a second paper.Comment: 68 page
Relationship between lactation curve function and phenotypic variance in random regression Test Day models
In Random Regression models (RRM), the most updated version of Test Day (TD) models, the lactation curve is split into a fixed average curve and a random animal specific part (deviation from the average curve) (Schaeffer, 2004). The variance component of the RR coefficients determines the (co) variance function of each pair of days in milk (DIM) (Pool and Meuwissen, 2000). Very different patterns of variance functions have been reported in literature, and several authors pointed out a possible rule of the type of function chosen as RR sub-model and data structure (Kettunen et al., 2000; Meyer, 1998). Aim of this work is to investigate some possible reasons for such results, in particular the effects of the mathematical function and of the possible occurrence of different shapes of lactation curve (regular and atypical)
Engineering copper nanoparticle electrodes for tunable electrochemical reduction of carbon dioxide
The electrochemical conversion of CO2 catalyzed by copper (Cu)-based materials is widely reported to produce different valuable molecules, and the selectivity for a specific product can be achieved by tuning the characteristics of catalytic materials. Differing from these studies on materials, the present work focuses on the engineering of gas diffusion electrodes in order to properly modify the selectivity, particularly by changing the Cu nanoparticle catalyst loading of the electrodes. Low catalyst loadings (≤ 0.25 mg cm−2) favor CH4 production, and intermediate (∼ 1.0 mg cm−2) loadings shift the selectivity toward C2H4. Eventually, larger values (≥ 2.0 mg cm−2) promote CO production. Detailed analyses reveal that both bulk and local CO generation rates, and charge transfer mechanism are responsible for the observed loading-dependent selectivity. The present work provides a new strategy for steering the CO2RR selectivity by simple electrode engineering beyond material development
LCA assessment related to the evolution of the earthquake performance of a strategic structure
Several buildings and infrastructures, located in urban areas, are identified as strategic in the case of an earthquake event. This is the case of a water treatment plant which is currently built in Genoa, Italy, and which has been assessed for the scope of this research. Since the structure has been designed following the seismic design prescriptions, this work aims to provide a preliminary assessment of how the degradation mechanisms do affect its earthquake response. To this purpose, both chloride attack and carbonation are taken into account as main degradation mechanisms. Moreover, due to the importance of the water treatment plant, to develop a realistic Life Cycle Assessment (LCA) analysis, the earthquake resistance of the structure and its evolution over time as a function of the aforesaid degradation mechanisms, have been accounted as Serviceability Limit State to estimate the frequency of the maintenance activities needed in a timeframe of 100 years
Horizontal rotation signals detected by "G-Pisa" ring laser for the Mw=9.0, March 2011, Japan earthquake
We report the observation of the ground rotation induced by the Mw=9.0, 11th
of March 2011, Japan earthquake. The rotation measurements have been conducted
with a ring laser gyroscope operating in a vertical plane, thus detecting
rotations around the horizontal axis. Comparison of ground rotations with
vertical accelerations from a co-located force-balance accelerometer shows
excellent ring laser coupling at periods longer than 100s. Under the plane wave
assumption, we derive a theoretical relationship between horizontal rotation
and vertical acceleration for Rayleigh waves. Due to the oblique mounting of
the gyroscope with respect to the wave direction-of-arrival, apparent
velocities derived from the acceleration / rotation rate ratio are expected to
be always larger than, or equal to the true wave propagation velocity. This
hypothesis is confirmed through comparison with fundamental-mode, Rayleigh wave
phase velocities predicted for a standard Earth model.Comment: Accepted for publication in Journal of Seismolog
Commissioning of the MEG II tracker system
The MEG experiment at the Paul Scherrer Institut (PSI) represents the state
of the art in the search for the charged Lepton Flavour Violating (cLFV) decay. With the phase 1, MEG set the new world best
upper limit on the \mbox{BR}(\mu^+ \rightarrow e^+ \gamma) < 4.2 \times
10^{-13} (90% C.L.). With the phase 2, MEG II, the experiment aims at reaching
a sensitivity enhancement of about one order of magnitude compared to the
previous MEG result. The new Cylindrical Drift CHamber (CDCH) is a key detector
for MEG II. CDCH is a low-mass single volume detector with high granularity: 9
layers of 192 drift cells, few mm wide, defined by wires in a
stereo configuration for longitudinal hit localization. The filling gas mixture
is Helium:Isobutane (90:10). The total radiation length is
\mbox{X}_0, thus minimizing the Multiple Coulomb Scattering (MCS)
contribution and allowing for a single-hit resolution m and an
angular and momentum resolutions of 6 mrad and 90 keV/c respectively. This
article presents the CDCH commissioning activities at PSI after the wiring
phase at INFN Lecce and the assembly phase at INFN Pisa. The endcaps
preparation, HV tests and conditioning of the chamber are described, aiming at
reaching the final stable working point. The integration into the MEG II
experimental apparatus is described, in view of the first data taking with
cosmic rays and beam during the 2018 and 2019 engineering runs. The
first gas gain results are also shown. A full engineering run with all the
upgraded detectors and the complete DAQ electronics is expected to start in
2020, followed by three years of physics data taking.Comment: 10 pages, 12 figures, 1 table, proceeding at INSTR'20 conference,
accepted for publication in JINS
Comparative analysis of local angular rotation between the Ring Laser Gyroscope GINGERINO and GNSS stations
The study of local deformations is a hot topic in geodesy. Local rotations of
the crust around the vertical axis can be caused by deformations. In the Gran
Sasso area the ring laser prototype GINGERINO and the GNSS array are operative.
One year of data of GINGERINO is compared with the ones from the GNSS stations,
homogeneously selected around the position of GINGERINO, aiming at looking for
rotational signals with period of days common to both systems. At that purpose
the rotational component of the area circumscribed by the GNSS stations has
been evaluated and compared with the GINGERINO data. The coherences between the
signals show structures that even exceed 60 coherence over the 6-60 days
period; to validate this unprecedented analysis two different methods have been
used to evaluate the local rotation using the GNSS stations. The analysis
reveals that the shared rotational signal's amplitude in both instruments is
approximately , an order of magnitude lower than the amplitudes
of the signals examined using the coherence method. The ring laser array GINGER
is at present under construction, and the confrontation of the ring laser data
with GNSS antennas provides evidence of the fruibility and validity of the ring
laser data for very low frequency investigation
Single-hit resolution measurement with MEG II drift chamber prototypes
Drift chambers operated with helium-based gas mixtures represent a common
solution for tracking charged particles keeping the material budget in the
sensitive volume to a minimum. The drawback of this solution is the worsening
of the spatial resolution due to primary ionisation fluctuations, which is a
limiting factor for high granularity drift chambers like the MEG II tracker. We
report on the measurements performed on three different prototypes of the MEG
II drift chamber aimed at determining the achievable single-hit resolution. The
prototypes were operated with helium/isobutane gas mixtures and exposed to
cosmic rays, electron beams and radioactive sources. Direct measurements of the
single hit resolution performed with an external tracker returned a value of
110 m, consistent with the values obtained with indirect measurements
performed with the other prototypes.Comment: 18 pages, 18 figure
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