4,868 research outputs found
Constraining CP violation in neutral meson mixing with theory input
There has been a lot of recent interest in the experimental hints of CP
violation in B_{d,s}^0 mixing, which would be a clear signal of beyond the
standard model physics (with higher significance). We derive a new relation for
the mixing parameters, which allows clearer interpretation of the data in
models in which new physics enters in M_12 and/or \Gamma_12. Our results imply
that the central value of the D\O\ measurement of the semileptonic CP asymmetry
in B_{d,s}^0 decay is not only in conflict with the standard model, but in a
stronger tension with data on \Delta\Gamma_s than previously appreciated. This
result can be used to improve the constraint on \Delta\Gamma or A_SL, whichever
is less precisely measured.Comment: 5 pages, 2 figures, informed of prior derivation of eq. (21), title
modifie
Can Effective Policy Implementation Alter Political Selection? Evidence from Female Legislators in India
Impact of the First Powering Cycles on the LHC Superconducting Dipole Coil Geometry
The impact of the first powering cycles on the LHC superconducting dipoles coil geometry has been investigated. Dedicated magnetic measurements have been performed to estimate the changes in the geometric component of the harmonics, caused by the last highest Lorentz force the coil has ever experienced. Several magnets have been powered at increasing current steps while the field quality has been measured to quantify the changes in geometry. The effect of the thermal cycles has been also considered as well as the systematic differences between measurements before and after the quench training. The reconstruction of the coil geometry variations is discussed in terms of continuous modes of deformation as well as single block displacements
Design and validation of a hardware-in-the-loop test bench for evaluating the performance of an active mass damper
The purpose of this study is to propose an innovative solution for evaluating the performance of a full-scale Active Mass Damper (AMD). The AMD adopted is a custom hydraulic actuator, developed for active control of existing buildings against earthquakes. For vibration control, a sky-hook algorithm was implemented. Its characteristics ensure good robustness, which is fundamental in structural engineering since buildings are subjected to significant variation in dynamic properties in presence of damage or ambient conditions. A Hardware-In-the-Loop (HIL) test bench was specifically designed to simulate the actual working condition of the anti-seismic system. The HIL setup consists of a shaking table moved by a hydraulic actuator in accordance with the roof's displacement, evaluated using a structural numerical model of the building to which the AMD is fixed. The presence of two distinct active systems (HIL and AMD) could generate control issues; therefore, a Triple Variable Control logic was introduced to reduce the interaction delay. The effectiveness of the proposed AMD is validated comparing the roof's displacement in an uncontrolled structure with that in a controlled one. Also, the robustness of the control algorithm was verified using a non-linear structural model and applying seismic excitation at different intensities
DESIGN AND ANALYSIS OF AN INNOVATIVE CUBESAT THERMAL CONTROL SYSTEM FOR BIOLOGICAL EXPERIMENT IN LUNAR ENVIRONMENT
After about 50 years since the Apollo missions, Space Agencies are planning new manned missions beyond LEO,
aiming to full functional Lunar and Martian outposts. Leaving the protection of Earth’s magnetic field, human body
will be exposed by a huge amount of harmful radiations coming from both solar wind and cosmic rays, which represent
a risk for the astronauts. In order to prepare for future manned exploration missions, many biological experiments have
been conducted inside and outside the International Space Station (ISS). From these experiments, engineers and
scientists gained knowledge about biological degradation after a long period of exposure to space radiations. Similar
experiments were also carried out in small free-flyers. For example, the O/OREOS mission is built with a 3U CubeSat
that is evaluating how microorganisms can survive and can adapt to the harsh orbit environment. Small platforms, such
as CubeSats, are gaining interest for many applications including science experiments. Biological payloads require
very stable environmental conditions, implying that environment requirements are very stringent and that existing
passive thermal control systems may not be sufficient to support these class of experiments. The goal of this paper is
to describe and discuss the design of an active environmental control system suitable for supporting biological payloads
hosted onboard nanosatellites. In particular, we focused the attention on the case of a payload constituted by a bacterial
culture that needs oxygen supply for growing up. The rate of growth and vitality are measured through bacteria
metabolic parameters. The reference mission is built with a 6U CubeSat in Lunar Polar Orbit, with the main scientific
objective of measuring the effect of the lunar radiation environment on a culture of “Bacterium Deinococcus
Radiodurans”. This kind of bacteria exhibits significant resistance to ionising radiation and the survival temperature
range is 30°C ± 10°C. The thermal control system (TCS) is constituted by Stirling cryocooler, Peltier cells and heaters.
The aforementioned pieces of equipment operate on the oxygen tank and test chamber in order to control temperature
of the oxygen necessary for the growth of the bacteria. To verify the temperature requirements, two kinds of analysis
are performed: radiative analysis, to have information about the heat fluxes from space environment; and lastly, a
thermo-fluid dynamics analysis, to gather data about temperature in the test chamber. As result, it is possible to confirm
that, with the chosen TCS, the temperature requirement is verified during the mission
Design and development of a reduced form-factor high accuracy three-axis teslameter
Acknowledgments: The authors would like to thank Reuben Debono for his useful guidance and help in the
PCB assembly of the instruments at the Electronic Systems Lab at the Faculty of Engineering at University of
Malta. The authors would like to thank R. Ganter, project leader of the Athos undulator beamline and H-H.
Braun, SwissFEL machine director, for their constant support throughout the entire project. The authors would
like to thank Sasa Spasic and his team at Sentronis facilities for their fruitful discussions and their guidance
during testing.A novel three-axis teslameter and other similar machines have been designed and developed for SwissFEL at the Paul Scherrer Institute (PSI). The developed instrument will be used for high fidelity characterisation and optimisation of the undulators for the ATHOS soft X-ray beamline. The teslameter incorporates analogue signal conditioning for the three-axes interface to a SENIS Hall probe, an interface to a Heidenhain linear absolute encoder and an on-board high-resolution 24-bit analogue-to-digital conversion. This is in contrast to the old instrumentation setup used, which only comprises the analogue circuitry with digitization being done externally to the instrument. The new instrument fits in a volumetric space of 150 mm × 50 mm × 45 mm, being very compact in size and also compatible with the in-vacuum undulators. This paper describes the design and the development of the different components of the teslameter. Performance results are presented that demonstrate offset fluctuation and drift (0.1–10 Hz) with a standard deviation of 0.78 µT and a broadband noise (10–500 Hz) of 2.05 µT with an acquisition frequency of 2 kHz.peer-reviewe
Fast and efficient critical state modelling of field-cooled bulk high-temperature superconductors using a backward computation method
Abstract: A backward computation method has been developed to accelerate modelling of the critical state magnetization current in a staggered-array bulk high-temperature superconducting (HTS) undulator. The key concept is as follows: (i) a large magnetization current is first generated on the surface of the HTS bulks after rapid field-cooling (FC) magnetization; (ii) the magnetization current then relaxes inwards step-by-step obeying the critical state model; (iii) after tens of backward iterations the magnetization current reaches a steady state. The simulation results show excellent agreement with the H -formulation method for both the electromagnetic and electromagnetic-mechanical coupled analyses, but with significantly faster computation speed. The simulation results using the backward computation method are further validated by the recent experimental results of a five-period Gd–Ba–Cu–O (GdBCO) bulk undulator. Solving the finite element analysis (FEA) model with 1.8 million degrees of freedom (DOFs), the backward computation method takes less than 1.4 h, an order of magnitude or higher faster than other state-of-the-art numerical methods. Finally, the models are used to investigate the influence of the mechanical stress on the distribution of the critical state magnetization current and the undulator field along the central axis
RooHammerModel: interfacing the HAMMER software tool with the HistFactory package
Recent -physics results have sparkled great interest in the search for
beyond-the-Standard-Model (BSM) physics in transitions.
The need to analyse in a consistent manner big datasets for these searches,
using high-statistics Monte-Carlo (MC) samples, led to the development of
HAMMER, a software tool which enables to perform a fast morphing of MC-derived
templates to include BSM effects and/or alternative parameterisations of
long-distance effects, avoiding the need to re-generate simulated samples. This
note describes the development of RooHammerModel, an interface between this
tool and the commonly-used data-fitting framework HistFactory. The code is
written in C++ and admits an alternative usage in standalone RooFit analyses.
In this document, the structure and functionality of the user interface are
explained. Information of a public repository where it can be accessed is
provided, as well as validation and performance studies of the interface. The
methods developed in the construction of RooHammerModel can provide specific
information for alternative future attempts to interface HAMMER with other
data-fitting frameworks
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