1,615 research outputs found
Dilatancy relation for overconsolidated clay
A distinct feature of overconsolidated (OC) clays is that their dilatancy behavior is dependent on the degree of overconsolidation. Typically, a heavily OC clay shows volume expansion, whereas a lightly OC clay exhibits volume contraction when subjected to shear. Proper characterization of the stress-dilatancy behavior proves to be important for constitutive modeling of OC clays. This paper presents a dilatancy relation in conjunction with a bounding surface or subloading surface model to simulate the behavior of OC clays. At the same stress ratio, the proposed relation can reasonably capture the relatively more dilative response for clay with a higher overconsolidation ratio (OCR). It may recover to the dilatancy relation of a modified Cam-clay (MCC) model when the soil becomes normally consolidated (NC). A demonstrative example is shown by integrating the dilatancy relation into a bounding surface model. With only three extra parameters in addition to those in the MCC model, the new model and the proposed dilatancy relation provide good predictions on the behavior of OC clay compared with experimental data
A workflow for building surface-based reservoir models using NURBS curves, coons patches, unstructured tetrahedral meshes and open-source libraries
Tidal capture of an asteroid by a magnetar: FRB-like bursts, glitch and anti-glitch
Recently, remarkable anti-glitch and glitch accompanied by bright radio
bursts of the Galactic magnetar SGR J1935+2154 were discovered. These two
infrequent temporal coincidences between the glitch/anti-glitch and the fast
radio burst (FRB)-like bursts reveal their physical connection of them. Here we
propose that the anti-glitch/glitch and FRB-like bursts can be well understood
by an asteroid tidally captured by a magnetar. In this model, an asteroid is
tidally captured and disrupted by a magnetar. Then, the disrupted asteroid will
transfer the angular momentum to the magnetar producing a sudden change in the
magnetar rotational frequency at the magnetosphere radius. If the orbital
angular momentum of the asteroid is parallel (or anti-parallel) to that of the
spinning magnetar, a glitch (or anti-glitch) will occur. Subsequently, the
bound asteroid materials fall back to the pericenter and eventually are
accreted to the surface of the magnetar. Massive fragments of the asteroid
cross magnetic field lines and produce bright radio bursts through coherent
curvature radiation. Our model can explain the sudden magnetar spin changes and
FRB-like bursts in a unified way.Comment: 6 pages, 1 figure, published by MNRAS
https://doi.org/10.1093/mnras/stad158
Decoy State Quantum Key Distribution With Modified Coherent State
To beat PNS attack, decoy state quantum key distribution (QKD) based on
coherent state has been studied widely. We present a decoy state QKD protocol
with modified coherent state (MCS). By destruction quantum interference, MCS
with fewer multi-photon events can be get, which may improve key bit rate and
security distance of QKD. Through numerical simulation, we show about 2-dB
increment on security distance for BB84 protocol.Comment: 4 pages, 4 figure
Malicious Agent Detection for Robust Multi-Agent Collaborative Perception
Recently, multi-agent collaborative (MAC) perception has been proposed and
outperformed the traditional single-agent perception in many applications, such
as autonomous driving. However, MAC perception is more vulnerable to
adversarial attacks than single-agent perception due to the information
exchange. The attacker can easily degrade the performance of a victim agent by
sending harmful information from a malicious agent nearby. In this paper, we
extend adversarial attacks to an important perception task -- MAC object
detection, where generic defenses such as adversarial training are no longer
effective against these attacks. More importantly, we propose Malicious Agent
Detection (MADE), a reactive defense specific to MAC perception that can be
deployed by each agent to accurately detect and then remove any potential
malicious agent in its local collaboration network. In particular, MADE
inspects each agent in the network independently using a semi-supervised
anomaly detector based on a double-hypothesis test with the Benjamini-Hochberg
procedure to control the false positive rate of the inference. For the two
hypothesis tests, we propose a match loss statistic and a collaborative
reconstruction loss statistic, respectively, both based on the consistency
between the agent to be inspected and the ego agent where our detector is
deployed. We conduct comprehensive evaluations on a benchmark 3D dataset
V2X-sim and a real-road dataset DAIR-V2X and show that with the protection of
MADE, the drops in the average precision compared with the best-case "oracle"
defender against our attack are merely 1.28% and 0.34%, respectively, much
lower than 8.92% and 10.00% for adversarial training, respectively
Temporal evolution of depolarization and magnetic field of FRB 20201124A
Fast radio bursts (FRBs) are energetic millisecond phenomena in radio band.
Polarimetric studies of repeating FRBs indicate that many of these sources
occupy extreme and complex magneto-ionized environments. Recently, a
frequency-dependent depolarization has been discovered in several repeating
FRBs. However, the temporal evolution of polarization properties is limited by
the burst rate and observational cadence of telescopes. In this letter, the
temporal evolution of depolarization in repeating FRB 20201124A is explored.
Using the simultaneous variation of rotation measure and dispersion measure, we
also measure the strength of a magnetic field parallel to the line-of-sight.
The strength ranges from a few to . In
addition, we find that the evolution of depolarization and magnetic field
traces the evolution of rotation measure. Our result supports that the
variation of depolarization, rotation measure and the magnetic field are
determined by the same complex magneto-ionized screen surrounding the FRB
source. The derived properties of the screen are consistent with the wind and
the decretion disk of a massive star.Comment: 9 pages, 3 figures, 1 table, accept for publication in ApJ
The physical origin of the periodic activity for FRB 20180916B
Fast radio bursts (FRBs) are transient radio signals with
millisecond-duration, large dispersion measure (DM) and extremely high
brightness temperature. Among them, FRB 20180916B has been found to have a
16-day periodic activity. However, the physical origin of the periodicity is
still a mystery. Here, we utilize the comprehensive observational data to
diagnose the periodic models. We find that the ultra-long rotation model is the
most probable one for the periodic activity. However, this model cannot
reproduce the observed rotation measure (RM) variations. We propose a
self-consistent model, i.e., a massive binary containing a slowly rotational
neutron star and a massive star with large mass loss, which can naturally
accommodate the wealth of observational features for FRB 20180916B. In this
model, the RM variation is periodic, which can be tested by future
observations.Comment: 12 pages, 8 figure
Quantum repeaters free of polarization disturbance and phase noise
Original quantum repeater protocols based on single-photon interference
suffer from phase noise of the channel, which makes the long-distance quantum
communication infeasible. Fortunately, two-photon interference type quantum
repeaters can be immune to phase noise of the channel. However, this type
quantum repeaters may still suffer from polarization disturbance of the
channel. Here we propose a quantum repeaters protocol which is free of
polarization disturbance of the channel based on the invariance of the
anti-symmetric Bell state under collective
noise. Our protocol is also immune to phase noise with the Sagnac
interferometer configuration. Through single-atom cavity-QED technology and
linear optics, this scheme can be implemented easily.Comment: 5 pages, 2 figure
Characterization and identification of in vitro metabolites of (-)-epicatechin using ultra-high performance liquid chromatography-mass spectrometry
Purpose: To characterize and identify metabolites of (-)-epicatechin in microsomal fraction of rat hepatocytes (MFRHs). Methods: A single incubation of (-)-epicatechin (1 mL, 50 µg/mL) in MFRH (0.5 mg/mL) was used for the generation of metabolites. Thereafter, the sample was subjected to protein precipitation prior to analysis with ultra-high performance liquid chromatography coupled to linear ion-trap orbitrap mass spectrometry (UHPLC-LTQ-Orbitap MS). Results: Nine metabolites of (-)-epicatechin were characterized on the basis of high resolution mass measurement, MS spectra and literature data. Based on their structures, the major metabolic routes of (-)-epicatechin in MFRHs were identified as hydroxylation, dihydroxylation and glycosylation. Conclusion: This is the first report on metabolites of (-)-epicatechin in MFRHs, and it is helpful in gaining deeper insight into the metabolism of (-)-epicatechin in vivo. The results will also provide guidance in research on the pharmacokinetics of new drugs. Keywords: (-)-Epicatechin, Metabolites, Hydroxylation, Dihydroxylation, Glycosylation, Rat liver microsomes, Pharmacokinetic studie
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