2,539 research outputs found
Conservative (failed)-tail effects at the fifth post-Newtonian order
This work deals with the tail and ``failed'' tail sectors of the conservative
dynamics for compact binary systems at the 5PN order. We employ the Fokker
Lagrangian method with dimensional regularization, and our results for the tail
sector are perfectly consistent with the previous EFT computations. As for the
``failed'' tail sector, we have good hopes that this new computation will help
solving the current discrepancy in the literature.Comment: 8 pages. v2: local report number added, harmless typo corrected in
Eq. (3.8
Electromagnetic fields in compact binaries: post-Newtonian wave generation and application to double white dwarfs systems
The aim of this work is twofold: (i) to properly define a wave-generation
formalism for compact-supported sources embedded in Einstein-Maxwell theory,
relying on matched post-Newtonian and multipolar-post-Minkowskian expansions;
(ii) to apply this formalism (which is valid for any type of post-Newtonian
sources) to the case of two stars with constant and aligned magnetic dipoles,
by computing the fluxes of energy and angular momentum to the next-to-leading
order, as well as the gravitational amplitude modes. Assuming eccentric orbits,
we derive the evolution of orbital parameters, as well as the observables of
the system, notably the gravitational phase for quasi-circular orbits. Finally,
we give some numerical estimates for the contribution of the magnetic dipoles
for some realistic systems.Comment: 44 page
Electromagnetic fields in compact binaries: a post-Newtonian approach
Galactic binaries, and notably double white dwarfs systems, will be a
prominent source for the future LISA and Einstein Telescope detectors.
Contrarily to the black holes observed by the current LIGO-Virgo-KAGRA network,
such objects bear intense magnetic fields, that are naturally expected to leave
some imprints on the gravitational wave emission. The purpose of this work is
thus to study those imprints within the post-Newtonian (PN) framework,
particularly adapted to double white dwarfs systems. To this end, we construct
an effective action that takes into account the whole electromagnetic structure
of a star, and then specify it to dipolar order. With this action at hand, we
compute the acceleration and Noetherian quantities for generic electric and
magnetic dipoles, at a relative 2PN order. Finally, focusing on physically
relevant systems, we show that the magnetic effects on the orbital frequency,
energy and angular momentum is significant, confirming previous works
conclusions.Comment: 23 pages, no figure, supplementary material attached v2: references
and acknowledgments update
Gravitational Wave Flux and Quadrupole Modes from Quasi-Circular Non-Spinning Compact Binaries to the Fourth Post-Newtonian Order
This article provides the details on the technical derivation of the
gravitational waveform and total gravitational-wave energy flux of non-spinning
compact binary systems to the 4PN (fourth post-Newtonian) order beyond the
Einstein quadrupole formula. In particular: (i) we overview the link between
the radiative multipole moments measured at infinity and the source moments in
the framework of dimensional regularization; (ii) we compute special
corrections to the source moments due to "infrared" commutators arising at the
4PN order; (iii) we derive a "post-adiabatic" correction needed to evaluate the
tail integral with 2.5PN relative precision; (iv) we discuss the relation
between the binary's orbital frequency in quasi-circular orbit and the
gravitational-wave frequency measured at infinity; (v) we compute the
hereditary effects at the 4PN order, including those coming from the recently
derived tails-of-memory; and (vi) we describe the various tests we have
performed to ensure the correctness of the results. Those results are collected
in an ancillary file.Comment: 32 pages, no figure. v2: reference of the companion letter updated.
v3: post-referee versio
Gravitational-Wave Phasing of Quasi-Circular Compact Binary Systems to the Fourth-and-a-Half post-Newtonian Order
The inspiral phase of gravitational waves emitted by spinless compact binary
systems is derived through the fourth-and-a-half post-Newtonian (4.5PN) order
beyond quadrupole radiation, and the leading amplitude mode (, m) = (2,
2) is obtained at 4PN order. We also provide the radiated flux, as well as the
phase in the stationary phase approximation. Rough numerical estimates for the
contribution of each PN order are provided for typical systems observed by
current and future gravitational wave detectors.Comment: 9 pages, 1 table. v2: reference of the companion paper updated. v3:
post-referee version, typo corrected in Eq. (9
A new understanding of the early behaviour of roller compacted concrete in large dams
In respect of autogenous and drying shrinkage and the effects of relaxation creep during the hydration cycle, roller compacted concrete in dams has to date been universally assumed to behave in the same manner as conventional mass concrete, despite notional evidence to the contrary on prototype dam structures, particularly in respect of high-paste RCC. While the results of laboratory materials testing and associated early behaviour analyses for RCC have been published, no conclusive example exists in the public domain whereby predicted behaviour is confirmed through measured behaviour on a comprehensively-instrumented prototype dam structure. In his PhD thesis, Quentin Shaw presents evidence to indicate that the early behaviour of RCC, and particularly high quality, high-paste RCC in dams, is quite different to that of CVC. Referring to instrumentation records from Wolwedans and Knellpoort dams in South Africa, Çine Dam in Turkey, Wadi Dayqah Dam in Oman and Changuinola 1 Dam in Panama, indications of less than expected shrinkage and stress relaxation creep during the hydration cycle in the constituent RCC are documented. Taking the comprehensively-instrumented and monitored Wolwedans Dam, the actual materials behaviour of the constituent RCC is evaluated through the replication of the prototype behaviour on a finite element model. Through this analysis, it is clearly demonstrated that the level of shrinkage and stress relaxation creep that would be traditionally assumed in RCC simply did not occur. In fact, the analyses suggested that no shrinkage, or creep was apparent. The reasons for the different behaviour of high-paste RCC compared to CVC are subsequently explored. With Wadi Dayqah Dam as the only example evaluated where some drying shrinkage and/or stress relaxation creep was obviously apparent, the evident susceptibility of this lean RCC mix, with a high w/c ratio, a high content of non-cementitious fines, natural gravel aggregates, a high aggregate water absorption and placement in a very dry environment, is noted. However, it is considered to be the combination of a strong aggregate skeletal structure developed through roller compaction and a low w/c ratio that results in a particularly resilience in high-paste RCC to early shrinkage and creep. It is also recognised that temperature and gravity effects in an arch dam structure will tend to limit, or even eliminate containment stresses in the critical load-carrying upper section and that this will reduce the risk and impact of stress relaxation creep. Consequently, a new understanding of the early behaviour of RCC in large dams is presented, suggesting that a high quality RCC mix in an arch dam can be designed for a cumulative shrinkage and stress relaxation creep under the hydration cycle of approximately 20 microstrain, compared with a more traditionally accepted value of between 125 and 200 microstrain. The implications of these findings on the design of large RCC dams are demonstrated to be significant, particularly in respect of RCC arch dams. In addition, suggestions are made for the requirements in respect of RCC mix design for negligible shrinkage and creep, while an approach to combine the use of field measurement with structural modelling to predict and demonstrate actual RCC behaviour is briefly discussed.Thesis (PhD)--University of Pretoria, 2011.Civil Engineeringunrestricte
Prise en compte de l’occupant dans une démarche interdisciplinaire de réhabilitation durable
Une approche interdisciplinaire avec une entrée relevant des sciences humaines et sociales peut conduire à une meilleure prise en compte de l’occupant dans les opérations de réhabilitation. Celle décrite ici s’appuie sur l’analyse du processus informationnel et communicationnel qui s’instaure entre l’usager et son cadre de vie. La satisfaction des usagers est au cœur de la démarche, qui intègre la perception du confort par l’usager sans pour autant chercher à changer son comportement. L’objectif est de proposer des scénarios de réhabilitation qui intègrent à la fois la dimension mesurable du confort et la dimension perçue par l’occupant. Pour illustrer nos propos, nous avons choisi d’expliciter un exemple : celui du confort thermique.An interdisciplinary approach based human and social sciences can lead to a better understanding of the householder concerning the process of rehabilitation. The one described here insists on the informative and communicative analysis established between the user and his environment. Users' satisfaction is at the core of the procedure. It includes the user’s perception of comfort without trying to change his behaviour. The aim is to offer different scenarios of rehabilitation that include at the same time the measurement of comfort and the measurement perceived by the householder. To illustrate this point, we have chosen to work on the thermal comfort example
Experimental and numerical investigations of nanoindentation properties at the sub- grain level in Ni-based and Ti-based polycrystalline alloys
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A biology-driven deep generative model for cell-type annotation in cytometry
Cytometry enables precise single-cell phenotyping within heterogeneous
populations. These cell types are traditionally annotated via manual gating,
but this method suffers from a lack of reproducibility and sensitivity to
batch-effect. Also, the most recent cytometers - spectral flow or mass
cytometers - create rich and high-dimensional data whose analysis via manual
gating becomes challenging and time-consuming. To tackle these limitations, we
introduce Scyan (https://github.com/MICS-Lab/scyan), a Single-cell Cytometry
Annotation Network that automatically annotates cell types using only prior
expert knowledge about the cytometry panel. We demonstrate that Scyan
significantly outperforms the related state-of-the-art models on multiple
public datasets while being faster and interpretable. In addition, Scyan
overcomes several complementary tasks such as batch-effect removal,
debarcoding, and population discovery. Overall, this model accelerates and
eases cell population characterisation, quantification, and discovery in
cytometry
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